Rohde & Schwarz Universal Radio Communication Tester CMU200: PSU problem - Page 1
Forum section: electronics / repair

author: richnormand
author_rank: Unknown
timestamp: May 26, 2016, 08:08:28 pm
content: Rohde & Schwarz Universal Radio Communication TesterModel CMU200Issue: Front power button Standby (orange) goes to Run (green) but nothing else happens. The unit is totally dead otherwise.Followed the “service” manual flow chart but this does not fit with the diagnostics. The orange light indicates the PSU supplies the 12V standby voltage. This checks out with the LED at the back of the motherboard. The green light is supposed to indicate that the 5V line is OK. This is not the case since all the LEDs for the 3.3 v, 5.2v, 6v, 8v, 12v, 12v Fan, etc…. are all OFF. The so called “service” manual is not very useful for this and does not treat that particular case. Either way, it says to replace PSU or replace front module.Suspect the PSU third stage or the front module controller. Removed all modules separately to see if there was a shorted/faulty plugin unit that could inhibit the “power good” signal and shut down the PSU, but no luck.Removed the PSU and operated it outside the unit. Getting a good 280V from the line primary and the 12V standby voltage is present. Third stage with the inverter transformer for all the other voltages does not seem to be active. It goes to board 2 that has a slew of control circuitry.Checked the electrolytics MOSFETs and IGBTs etc.. as a first pass, before digging in further.Other possibility could be the front module controller that never sends the signal to “turn on” to the PSU or some “power good” handshake, much like in computers.Any history of PSU failure for the CMU200? Only found one mention on this forum, no details. Nothing else on the web either.Anyone with the schematics or the plug pinouts to the motherboard? That would save me a lot of tracing signals and reverse engineering. As you can see from the photo this is not a simple straightforward inverter supply! I do have the “operating” and “service” manuals for it but did not find more detailed information.Help appreciated!Cheers and thanks.UPDATE:Reassembled the PSU. Removed all plugins and anything attached to the motherboard except the front control panel. No luck. Same issue.Took apart the front control module (a custom PC basically). Checked all the smd fuses and all is OK. Changed the 3V lithium memory backup battery while in there.Only suspicious item is what seems to be a temperature indicator as shown in the photo attached.

author: ZL1CVD
author_rank: Regular Contributor
timestamp: May 31, 2016, 01:49:03 am
content: I haven't had a faulty CMU200 supply but have repaired many HP 8924 & E8285A supplies. I had put aside an E8285A supply for a couple of years because it got the better of me until a ham radio contact told me to read thishttp://www.repairfaq.org/sam/smpsfaq.htm- It didn't specifically help fix the supply but put my mind into SMPSU repair mode which enabled me to nut it out. I also have read somewhere that CMU200 supplies also fail from dry electrolytic's & opern circuit inductor.73s om de chris zl1cvd

author: richnormand
author_rank: Unknown
timestamp: May 31, 2016, 05:37:23 pm
content: Quote from: ZL1CVD on May 31, 2016, 01:49:03 amThanks ZL1CVD,This is a nice reference/link, in particular the several cases presented and the supplementary material near the end. I printed most of it and will go to the various references given in there.I tested pretty much the board three for shorts and the ESR of the various big caps. All is OK. I still have to remove some of the power devices off circuit to test them properly without the low impedance of the second inverter transformer winding across. Nothing obvious either on power resistors, no sign of over heating. Also board twu is a maze of opamps, opto-isolators and the control chips for the dozen of voltages supplied by this PSU.Your comment about open inductors is an excellent one. I'll do that tonight.Next thing to do, since I can power the unit on the bench and get the 12V "standby" voltage, will be to locate the "power on" pin as well as the "power good" pin on the bloody connector. Its a future buss type connector with a zillion pins. A proper pinout for the plug would be so useful here to locate the temps limits and control lines!This might be the only way to see if the fault might be located on the front module not sending the "power on" command to start the PSU secondary. That scenario would be similar to an ATX computer PSU when you ground the green wire to get it to start. I repaired some ATX PSUs in the past with shorted power MOSFETS and bad caps, but the complexity of this particular R&S supply is pretty awesome.Thanks again for the info, will chime back when I go though the information you linked me to.

author: richnormand
author_rank: Unknown
timestamp: June 03, 2016, 09:29:00 pm
content: Looked at inductors and such, no luck. It's really starting to look like the PSU is not getting the command to start compared to "start and collapse" due to a short (no click noise) .Looks like I have to identify the "power good" line and the "main start" line at the connectors and scope any activity on these.Link from ZL1CVD is really worth the read. 73s

author: PartialDischarge
author_rank: Super Contributor
timestamp: June 11, 2016, 10:16:16 am
content: Hello Richtoday I opened my CRTU which I guess has the same PS (PULS SN250) and 'probably' the same connectors at the control side. I believe at least the former is true, so here's what I did:1) check voltages at PSU connector with unit turned OFF (but powered)2) check voltages at PSU connector with unit turned ON3) identify possible "power on" lines at PSU connector3) turn off and disconnect unit, find those 'candidate' lines at control side (X12 connector in my unit)See attached pictures and PDF. Pins pictured in green, output some voltage even in the OFF state.So, I'd say B1, C1 and D1 are pretty good candidates, especially B1 given that the ON logic could be negative.If i were you I'd measure the voltage at B1 with the PSU disconnected from the equipment, and if you get some voltage, drive it to zero with a10K to 100Kohm resistor

author: richnormand
author_rank: Unknown
timestamp: June 11, 2016, 03:32:49 pm
content: Quote from: MasterTech on June 11, 2016, 10:16:16 amHi MasterTech,thanks for the response and the work you put into this.It would be nice to have the voltages on the pins while it is working and while it is in standby.Looks like the same connector alright, may even be the same motherboard too.Here is a sketch of the connector I did last week. At the lower left and at the far lower right are the pins I had marked "to check" up to the front CPU module. Much like you suggested.As you can see B1 C1 and D1 are on the list. Also are A2 A3 D3 A24 B24 and D24 that need to be traced on the MB.Also is a pix of the PSU label with the type number. Looks like it is the same PSU. Not a surprise considering the lineage of the two units.There is also another separate connector that goes to the first plug-in. It looks like and old pc hard drive connector.I have the PSU powered on the bench with the standby 12V line active.I'll try a 10k resistor to drive the B1 line to zero as you suggested and try other combinations.Cheers and thanks. This is an on-going saga......UPDATE:Just measured the voltages. PSU on the bench (not connected to the motherboard but under power):(pin#, voltage)a1 10.7Vb1 11.1c1 0d1 0a2 0.1a3 0d3 0.5a24 1.0b24 0d24 12.4UPDATE2:Drove a1 and b1 to near ground with a current limit resistor (about 1k). No effect. They are high internal resistance lines as 10k brought them to about 5V.Also d24 is a solid 12V. Probably the 12V standby.I used two voltmeters to look at the two major set of pins that look like high current output, most likely the system 5V and such. I would have noticed if the PSU came to life.So does not look like a1 or b1 are negative logic to start it. Perhaps some other pin are positive logic and require the 12V to start the PSU?Would be nice to take a full readings on a good unit while in "standby" and then "on" and see what are the difference on these lines indeed.

author: PartialDischarge
author_rank: Super Contributor
timestamp: June 11, 2016, 10:25:01 pm
content: I think you missed the PDF I posted earlier. there are the voltages at standbby and power on.from what i see your unit looks good in standby state. Can you look into the logical circuitry inside the PC that drives the signals I refer to in the X12 coonector? If at least we knew if those signals are inputs or outputs to,the psu

author: richnormand
author_rank: Unknown
timestamp: June 12, 2016, 12:22:25 am
content: Quote from: MasterTech on June 11, 2016, 10:25:01 pmWOW! You are right. I totally missed the PDF in your original post.Sorry about that MasterTech, my faultNice job too.I'll plug the PSU back on the motherboard and move to looking at the PC X12 connector side.Thanks again. Hope we meet some day, I owe you a beer!

author: PartialDischarge
author_rank: Super Contributor
timestamp: June 12, 2016, 06:30:41 am
content: Good news, just decided to test the B1 pin by myself. While the CRTU was in standby I drove that line low with an 820ohm resistor (just to go a bit farther than you...) using the grounded screw next to it and voila it turns onI was confident about B1 because the 0.2V present when the unit is on, resembles the saturation voltage of a transistor driving that line low.So next thing you'll have to test the same, and you'll know if its the PSU or the control unitCheers

author: msraya
author_rank: Unknown
timestamp: June 12, 2016, 08:07:33 am
content: Very Interesting Information.I my CMU power supply dies suddenly.. I will need that information...Thanks All!!Manuel

author: richnormand
author_rank: Unknown
timestamp: June 12, 2016, 02:52:37 pm
content: Quote from: MasterTech on June 12, 2016, 06:30:41 amThanks for the feedback MasterTech, much appreciated.Just did that with a 820 ohms and even went to a near dead short (10 ohms) with no luck. The PSU does not start.Only other factor I can think of is the fact that my PSU is on the bench. Once plugged in the motherboard/PC it would have a load and perhaps another control signal ("service" manual mentions things like over temperature and power good signals for example)?Was yours on the bench unloaded or in circuit when you did the test??At any rate it looks like you are right and that B1 is the start signal.I'll trace it in the PSU before reassembling the whole thing and bring B1 low while in the CMU200.

author: PartialDischarge
author_rank: Super Contributor
timestamp: June 12, 2016, 03:05:11 pm
content: Quote from: richnormand on June 12, 2016, 02:52:37 pmIt was inside the crtu, it may have another signals that need to be connected before power up.... so all is not lost for you

author: richnormand
author_rank: Unknown
timestamp: June 12, 2016, 09:13:45 pm
content: Quote from: MasterTech on June 12, 2016, 03:05:11 pmOK I reinstalled the PSU in the unit. When I go from "standby" to "run" the B1 line goes from 11.0 volts down to 0.2 volts as it should. But "no cigar"...So either there is something else preventing the startup or the problem is inside the PSU....

author: PartialDischarge
author_rank: Super Contributor
timestamp: June 13, 2016, 03:14:09 am
content: Theres one more test you should do. put a scope probe at b21 and see whether the line is driven low by pressing the power up button or not. I suspect it will, and you have a faulty PSU.I recall from another eevblog thread about the cmu or crtu ( cant remember) that a guy fixed his psu by changing a switched regulator. It was something like TOP2000Y or TOPY2000, at the time I looked at ebay and it was available for sale. Besides trying to 'debug' that psu Id suggest you change that chip too....Keep it up, that unit deserves to be repaired!EDIT: it was a TOP200YN...let me know if you identify that part in your unit

author: richnormand
author_rank: Unknown
timestamp: June 15, 2016, 02:18:30 am
content: Quote from: MasterTech on June 13, 2016, 03:14:09 amThanks again.Status: PSU is plugged to the motherboard with all units. The front button is initially amber (standby) and then green (on) when pressedThe b21 is of course the whole line abcd21.voltages are first in standby mode and then in on mode.A1 10.8 then 0.77 NOTE: did not change with PSU on bench and in your measurements it was 10.6V off and 11.3 on... TO DO CHECK!B1 11.8 then 0.23, seems OKB21 0.33 then 0.33 Note: see scope trace laterD3 0.4 then 0.4 Note: same as on benchD1 0 then 0C1 0 then 0Scope traces. Low speed Tek 7D20 with direct probe.B21 line: initial is 0. Then plug probe in standby, then push on button. NOTE: initial rise in voltage and then a shutdown. Remove probe. Voltage consistent with previous measurements. The other outputs react the same...A1 line : initial 0, plug probe in standby 10.8V, then push on button drops to 0.77V. Remove probe.Voltages not consistent with previous measurements on bench. Note vertical v/div, same horz.At my first tear-down of the PSU I noticed the TOP200YN and got the spec-sheet. The one I noticed was on the primary at the 120 and 220V first inverter. The initial 280VDC stage was ok, as well as the 12V standby. On the other hand I did not check if there are others for the third supply. I will check for that.

author: PartialDischarge
author_rank: Super Contributor
timestamp: June 15, 2016, 05:16:39 am
content: At this point all you have to do is find the faulty item within the PSU, otherwise the signals look ok. If I were you I'd find a substitute TOP200YN...Meanwhile keep looking and see whether you can test and identify any other broken parts

author: PartialDischarge
author_rank: Super Contributor
timestamp: June 15, 2016, 06:08:50 am
content: Its actually fairly easy to test that top200, see attached pictures from the PowerIntegrations specs...

author: richnormand
author_rank: Unknown
timestamp: June 15, 2016, 09:23:00 pm
content: Quote from: MasterTech on June 15, 2016, 05:16:39 amI'll do the test in the spec sheet. The first one on the primary side is most likely OK as I have the full voltage on the cap and the 12V standby and it takes care of the switch between 110 and 220AC as a preregulator, but I'll look at all the other boards too.Looked at Mouser, Allied, Digikey and Gervais (here in Canada) and a few other places for the TOP200YN. All non stock and obsolete. Life cycle seems to have been short for this product. I'll look to see if there is a replacement for it that is compatible. Several TOP200YN are on Ebay and Alibaba from china....most likely counterfeit or recycled, but if they work, for a while OK.In the meantime I'll finish doing all the measurements I can think of while the PSU in still plugged in. The most different reading from your "standby" and "on" list (apart from the obvious lack of main supply) is the A1 line. Looks like perhaps the "power good" signal sent back from the PC front end?Cheers

author: PartialDischarge
author_rank: Super Contributor
timestamp: June 16, 2016, 01:37:59 am
content: Yes, c1 d1 are probably power good outputs, and maybe a1 tooThe direct replacement, with only a tiny difference from the original is the 3 pin top222yn available from Mouser:

author: richnormand
author_rank: Unknown
timestamp: June 16, 2016, 11:03:27 pm
content: Quote from: MasterTech on June 16, 2016, 01:37:59 amOrdered from Mouser this afternoon in case I need them.

author: PartialDischarge
author_rank: Super Contributor
timestamp: June 22, 2016, 05:25:40 pm
content: Quote from: RF_fanatic on June 22, 2016, 08:27:19 amHi, the button does not go directly to the psu, there is some logic on the pc board side. I know this because when you power it down, a message appears on then screen and then it shuts down. So the button is sending a message to the pc, and I guess the logic turns off the psu when the pc replies "ok, its safe to turn off now"...

author: PartialDischarge
author_rank: Super Contributor
timestamp: June 22, 2016, 07:07:25 pm
content: Quote from: RF_fanatic on June 22, 2016, 06:59:01 pmlol, I think you also missed the PDF i posted earlier, I found that connection too!

author: richnormand
author_rank: Unknown
timestamp: June 22, 2016, 09:42:20 pm
content: Quote from: RF_fanatic on June 22, 2016, 08:47:32 pmIndeed MasterTech did a good jobThe 12V standby is working well and all the primary side of the PSU checks out. The front will go from amber to green. The B1 line goes down as expected.In my case there is no difference in standby voltages out of the PSU without the front PC or any of the modules.Enabling the PSU from the front or on the bench does not show any difference. Dead in both cases. But I can see a situation where the front PC could prevent the PSU from starting. Real test would be to force a good PSU to start while on the bench and see if it goes. There is probably more than one signal required, such as over temp, pc logic shutdown etc...I am waiting for a TOP222YN to replace the TOP200YN. Off-bench test of the TOP200YN seem OK however. By the way out of three boards (not counting the smallish one attached on board one) I only found one TOP device but there are two other switching supplies here I think. I have not totally figured out the control board.Finished mapping two of the boards, tested all caps and inductors (small resistor types for open in particular) All OK for now.As I go to each board I remove the clips on the heatsink and note the device numbers for future reference.Progress will be slow over the next week as other stuff is piling up.EDIT: just got the TOP222YN and put it in.

author: PartialDischarge
author_rank: Super Contributor
timestamp: June 23, 2016, 03:14:42 am
content: Nice job Rich, eventually youll get the faulty part. Dont forget to post your notes on the psu (ie part numbers, schematics...) as it may help others in the future!

author: richnormand
author_rank: Unknown
timestamp: June 23, 2016, 07:01:13 pm
content: Quote from: MasterTech on June 23, 2016, 03:14:42 amWill do. Mostly part locations and part numbers. Don't get your hope too high for complete and detailed schematics however. I'll trace what I need for a repair and understanding the problem.

author: richnormand
author_rank: Unknown
timestamp: June 23, 2016, 09:29:59 pm
content: Ok just a quick update. Replaced the TOP200YN with the new(er) TOP222YN. Fast and easy, so why not.Same behaviour as before.Considering the TOP can handle about 25W max and is switching the full primary current, it reinforce my comment in the first post that it most likely only handles the standby 12V. The person that fixed their PSU changing the TOP most likely did not have the 12V standby to start with. I just sent him/her a pm to confirm.Back to the bench it goes.

author: Ericmax
author_rank: Contributor
timestamp: July 14, 2016, 08:04:54 am
content: Hello everybody.I'm Eric from France.I bought a CMU200 on E-bay UK that I received yesterday.Very happy with my purchase, I unwrapped my package.the unit appears in good condition, so I plugged it to see all its possibilities.The unit has started and the screen displayed the boot with the message "" CMOS checksum error - Defaults loaded "I decided to take pictures to indicate the problem to the vendor and ask if we had to change the battery.Unfortunately I only had time to take two photos that CMU is off by itself. all lights are turned off before the Panel.I unplugged the CMU, handled the power button and reconnected but no lights are on and the CMU looks dead.Retried this morning always the same, no light and no reaction at CMU.Do you think my problem is the PSU ?

author: PartialDischarge
author_rank: Super Contributor
timestamp: July 14, 2016, 10:20:22 am
content: At least an orange led should be on when you plug the unit. There is a 12V standby voltage generated by the PSU.If not present, then yes, the psu is dead and most probably is the top200 which handles that voltage.

author: Ericmax
author_rank: Contributor
timestamp: July 14, 2016, 02:53:32 pm
content: Thank you MasterTech.It is the symptom, no LED lit when pluggedyou know where is this component in the psu ?

author: richnormand
author_rank: Unknown
timestamp: July 14, 2016, 04:45:17 pm
content: Quote from: Ericmax on July 14, 2016, 02:53:32 pmONE:The TOP200 is on the board 2 that connect between the two main boards. as shown in the two photos here.Unfortunately you have to take apart the whole psu to get at it. It provides the 12V standby supply. This shows as the amber light at the front on the on/off switch. This is a good time to also check the electrolitic capacitors and small inductors while you are in there. Near the psu connector on the motherboard is a series of LED that gives the status of each power rail. You can have a quick look to see if the 12V stanby is on. If not you can measure it at the connector using the info in previous posts here.The initial TOP200 was susceptible to line transient and at the suggestion of MasterTech I replaced it with a TOP222YN from Mouser. Unfortunately, in my case, the psu issues are much deeper than just the standby supply. I hope you will be lucky and that this is the only issue you have.Also check the two small fuses at the power-line entrance of the main board.TWO:The errors you mentioned in your previous post might be a weak Li bios backup battery. Mine was almost dead. It is a regular button battery as used in computers but getting at it requires removing the whole front module and screen. A real pain. See photo attached.Best of luck with it and don't forget to have fun!

author: Ericmax
author_rank: Contributor
timestamp: July 14, 2016, 05:22:18 pm
content: Hi Richnormand and thank you for all that information.I opened the CMU to display the control LED power supplies.Of course. no LED is lit but I noticed that the LED +12V STB flashes once per second, which suggests that it is this part that is down.It's really unlucky, the device functioned only 2 minutes after unpacking, just time to see the boot and BIOS problem.I am negotiating with the seller to have a functional PSU but I think this problem of PSU is the weak point of all CMUand CRTU-RUThank you all for your help.

author: PartialDischarge
author_rank: Super Contributor
timestamp: July 14, 2016, 05:35:43 pm
content: Quote from: Ericmax on July 14, 2016, 05:22:18 pmIf the led 12STB lights once per second then "maybe" the TOP200 is ok and it is activating its self-protection circuit for whatever reason, youll have to investigage

author: richnormand
author_rank: Unknown
timestamp: July 14, 2016, 05:36:04 pm
content: Quote from: Ericmax on July 14, 2016, 05:22:18 pmIf the 12V standby LED flashes once a second it might indicate the supply is trying to start and then shuts down due to a malfunction and repeats the cycle.This could be a short on the rail or a fault in the psu itself. You could remove the psu completely and see if the 12V standby works OK by itself (no load). If it does, the problem is in one of the plugin units or the motherboard or the front screen/computer module or other stuff such as an over-temperature sensor.You could remove each modules one by one to try to isolate which one is faulty.But first I would remove and operate the psu by itself and see if the 12V STB is OK without any load on it.

author: Ericmax
author_rank: Contributor
timestamp: July 16, 2016, 03:54:57 am
content: Hello everybody.Did not test my CMU200 on arrival, coming back to you who seem to know well the device.For information this is a CMU200 WCDMA FDD 1100.0008.30 sold on Ebay UK theoretically with the following options:CMU200 WCDMA FDDIntel CPU 256MB MemoryThe Unit Has the Following OptionsK21, K22, K23, K24, K65 + PCMCIA U65, U99Following my problem PSU, so I opened the CMU and I am surprised to find so few modules. I attached a picture of the open device without PSUIf one of you just tell me if the device is complete for the given configuration for I am a bit lost in all these options.thank you beforehand.wekkend good to you all.

author: Pieh0
author_rank: Contributor
timestamp: July 16, 2016, 03:58:37 am
content: Yes, that's complete.The K options are software, and the U options are variations of standard modules.U65 is obviously the PCMCIA slots, and U99 means RF1 can only take 2 watts, where as the other version can take up to 50w.

author: Ericmax
author_rank: Contributor
timestamp: July 16, 2016, 04:05:37 am
content: Hi Pieh0.thanks for these informations.it remains only to find a functional PSU me to finally have fun.The option B41, B17 and B12 interest me if I can turn it on again.

author: richnormand
author_rank: Unknown
timestamp: July 18, 2016, 09:24:59 pm
content: Quote from: richnormand on June 23, 2016, 07:01:13 pm********ERRATA**********See reply #59 and 62 later in this thread.There should be FIVE one ohm resistors and ONE diode in the lot.I did not change the text below so that the other responses still make sense in that context.This is what happens when you work way past your bedtime*************************First: I will post part placements of two of the boards as soon as I get a chance to scan my notes.Second: the PSU is now back in action. On board 3 there are two series of 1.0 ohm resistors in parallel. The marked one is going to a comparator. ALL the resistances were in the 100 to 200k rangeThey looked pristine and the markings was for 1 ohm.... No sign of heating, looked perfect.I removed a couple resistances from the second set and they, indeed, measured 1 ohm each. Guess they are measuring current draw on the 400V main storage capacitor for each of the supply rails.Plugged back the PSU in the unit expecting some magic smoke but all the supplies were according to MasterTech's table (Thanks again). But apart from a few beeps the front display was dead. However I could see some activity with a strong flashlight. Must be a dead fluorescent tube or the inverter board.Fortunately it is a TDK board (doc on google) and it was the 2.0A smd fuse that was gone. I can post info if someone needs it.A small detail that I should have given more attention to was one missing screw on the PSU outer casing when I first took it apart. With my luck I assume I ended up with the lab unit that was reassembled from various broken parts until they go rid of it.Many thanks to all the people that contributed to this thread. I owe a beer to MasterTech in particular....

author: tautech
author_rank: Super Contributor
timestamp: July 18, 2016, 10:22:49 pm
content: Quote from: richnormand on July 18, 2016, 09:24:59 pmThe thread wouldn't be complete unless you did.These are easily overlooked, I've seen it in Philips monitors and have wondered if it's a symptom of failing caps in the backlight HV converter.

author: Pieh0
author_rank: Contributor
timestamp: July 18, 2016, 11:00:50 pm
content: So just to be clear, the thing that killed a piece of test gear that cost tens of thousands of dollars (brand new), with a top quality power supply from PULS, was kicked in the nuts by some 1 ohm resistors?I've got 2 CMU200's with 1 dead psu and the other looking like it's also on the way out, so it would be nice if this is the fix.

author: richnormand
author_rank: Unknown
timestamp: July 19, 2016, 12:49:29 am
content: Quote from: Pieh0 on July 18, 2016, 11:00:50 pm*****ERRATA, actually 5 one ohm resistors and one diode********Actually it was 6 one ohm resistors in parallel. It was 1/6 ohm initially monitoring the current taken from the main 400V cap via the comparator IC for that rail. I guess if one failed it gets worse and the next one goes and so on, but none showed any sign of external failure. Each was over 100k in resistance when I measured them. Keep in mind the other set (bottom of pix) of 1 ohm resistor were all OK. That would limit the possibility this was a bad batch as the others are OK.Overall it's kind of weird. Took me a while since no schematics are available and it is a pretty sophisticated PSU.Good luck with fixing yours. If I can help, let me know.My next issue is to fix the small fan to the front panel that is seizing up. Time to take it apart for the nth time again.

author: PartialDischarge
author_rank: Super Contributor
timestamp: July 19, 2016, 09:27:04 am
content: Thats very good news!, definitively seems like a design flaw, hope many more broken psus of the same type can be fixed with this info.

author: richnormand
author_rank: Unknown
timestamp: July 19, 2016, 06:57:49 pm
content: Quote from: richnormand on July 19, 2016, 12:49:29 amDismantled the front panel again and oiled the small fan that feeds the CPU. Did the same to the main fan in the rear. All quiet now.Here are my notes. Most power devices on two of the boards have been identified. The third one is not complete as found the issue while going through the process.Also is a diagram of the PSU motherboard connector. And don't forget the attachment from MasterTech with all the voltages.

author: valgamaa
author_rank: Contributor
timestamp: July 19, 2016, 07:06:52 pm
content: It's interesting that all the resistors on the PCB, other than the ones that failed, are MELF. The PCB pads also look like they are intended for MELF resistors, so the missing screw suggests you may have been the victim of a low-quality previous repair.The 0805 (guessed size) resistors may not have the same heat dissipation capabilities, so they may well have cooked slowly, leading to the failure.All in all a rather tricky one to fix.

author: richnormand
author_rank: Unknown
timestamp: July 19, 2016, 08:38:02 pm
content: Quote from: valgamaa on July 19, 2016, 07:06:52 pmThe failed resistors were all MELF just like the ones at the bottom of the photo. The photo is after my repair, with what I had on hand that would fit in the space. Sorry, I should have been more precise in the description. I figured if it does not last I'll simply coil a length of wire that amounts to 1/6 ohm around the board or wire a remote resistor where space permits. So far so good as the unit has been working nonstop for two days now. But, yes, I do expect to get back in there eventually as this was a quick and dirty fix to see if that was the root issue. As stated in my previous post, I was expecting some magic smokebut it is still running.....I also used my Seek Thermal to check for heating but that was with the PSU operating alone (ie. no load). I have not put the outer case back together either..... Playing the waiting game

author: valgamaa
author_rank: Contributor
timestamp: July 20, 2016, 05:02:18 pm
content: Quote from: richnormand on July 19, 2016, 08:38:02 pmAh, sorry, I assumed it was a 'before' picture.... with such a low resistance the resistors are unlikely to dissipate anything close to their rated power, so the repair is unlikely to need modifying.

author: PartialDischarge
author_rank: Super Contributor
timestamp: July 20, 2016, 05:09:48 pm
content: Quote from: valgamaa on July 20, 2016, 05:02:18 pmWell, not so fast, resistors can get damaged by power OR voltage. Paralleling them doesnt lower the peak voltage they suffer, and in circuits like this where a cap is charged through them from mains strange things can happen with overshoot voltages especially if an inductance is somehow present... Most probably this is how those resistors failed

author: Ericmax
author_rank: Contributor
timestamp: July 23, 2016, 04:13:41 am
content: Hello everybody.I received my TOP222YN. after replacing the TOP, PSU on the table I finally have my 12V STB (12,23Vdc exactly).When the PSU is mounted in the CMU, the 12V STB LED on the motherboard flashes as before.I removed the front Panel CMU and 12V STB LED lights normally.When I connect the CPU board only (no keyboard, no screen, no PCMCIA) LED 12V STB flashes again.I changed most of 820?f 6,3V on the CPU but the problem is still there.PSU mounted in the CMU without front panel, I put b1 to GND, the CMU starts and all control power supplies LEDs are on and the fans turn.to be continued

author: PartialDischarge
author_rank: Super Contributor
timestamp: July 23, 2016, 09:09:27 am
content: Quote from: Ericmax on July 23, 2016, 04:13:41 amThe 12VSTB goes directly to the CPU, see my previous post with a PDF that describes where that signal goes (exact connector pin also). You could attach a lab power supply to that exact pin, inputting 12V with a current limit to see if its drawing more than 100-200mA

author: Ericmax
author_rank: Contributor
timestamp: July 23, 2016, 09:25:06 am
content: Hello.yes I have now.I limit 250mA and U drops to 0.6 V on my lab power supply.I thought of a chemical capacitor or SMD tantalum or diode.I look for a component with a high temperature but would be much simpler with the thermal camera.

author: PartialDischarge
author_rank: Super Contributor
timestamp: July 23, 2016, 11:05:52 am
content: Quote from: Ericmax on July 23, 2016, 09:25:06 amtheres a trick, if you dont have a thermal camera use a small amount of clear flux, it will evaporate quickly on the hot part

author: Ericmax
author_rank: Contributor
timestamp: July 23, 2016, 03:49:10 pm
content: If I trace the 12V STB properly, I arrive on 2651MTC-ADJ regulator circled in red in the picture.I tested all the capacitors around and i disconnected the diodes to isolate the input and output of the regulator.after measurements between the input (Vin) and output (SW) I feel that the Internal MOSFET is dead but this remains to be confirmed.

author: richnormand
author_rank: Unknown
timestamp: July 24, 2016, 04:30:40 am
content: Quote from: Ericmax on July 23, 2016, 03:49:10 pmLooking at the spec sheet for that chip, assuming the circuit here is similar.a)Power off.Can you measure the resistance of Vin, AVin (the chip internal power supply), SW, PB and PGND with respect to the 12V STB ground pin?Only the PGND should be a short.b)Power off.Also from your comment I assume the two zeners nor the input and output caps (found in the "typical application" section in the spec sheet) are shorted.c)Power off.Can you measure resistance between SW and FB as well as FB and PGND to find if the mosfets are shorted.Power on.Finally if these two mosfet are driven to turn on both at the same time and stay on it would also look like a short to load the line, but not with the power off. Any voltage on these pairs of pins?d)Could it be that the problem is on the output side of the 2651 and the chip is trying to drive a short elsewhere? Particularly if test a) and b) are OK should the output side look like a short? That could overdrive the 12V standby psu before it 2651 cutoff protection happens?Hopefully that chip is still available if needed.Unfortunately my unit is fully back together so I could not take a quick look at the circuit, unlike the last time. However, if you need it I am willing to dismantle the front module again.OK it is past midnight here. I'll chime in tomorrow morning if I think of anything else.

author: Ericmax
author_rank: Contributor
timestamp: July 24, 2016, 05:08:10 am
content: Hi richnormand.Thank you for your help and your proposal but do not disassemble your unit now works againThe LM2651 is available from Mouser, I'll order it tomorrow, will be easier.all capacitors, inductors, and diodes are correct.I made all feasible measures on inputs outputs by disconnecting peripherals that maximum components and regulator appears short circuit V in, SW and PGND on.at different power with old TOP200, I measured on a 12V STB a 18Vdc briefly.the maximum for the LM2651 is 14V, I think he's burning at that time.I have confirmation when I replaced the LM2651.I would tell you if it can help other members to troubleshoot their front panel.

author: richnormand
author_rank: Unknown
timestamp: July 24, 2016, 03:47:25 pm
content: Quote from: Ericmax on July 24, 2016, 05:08:10 amThat is an interesting observation Ericmax. You would think that such a gross over-voltage would not happen, even in a no load situation. The PSU should have such a protection via a crowbar zener or limiter of some sort. It might be worthwhile to investigate the PSU behavior with the new TOP222 to make sure this does not happen before installing the new 2651.

author: Ericmax
author_rank: Contributor
timestamp: July 24, 2016, 04:20:29 pm
content: since replacing the TOP200 by the 222, did I do many measurement with and without front panel.of course, with the front panel, impossible to measure because it is safe mode. but without the CPU board I have always had a very stable U around 12,23V.may be there is there you had other causes of the destruction of the LM2651.Above all I have to replace to confirm my observations.

author: Pieh0
author_rank: Contributor
timestamp: July 24, 2016, 11:26:23 pm
content: Just had a look in one of the PSU's i've got, and the 6 1ohm resistors you have are different to mine, cause one of them is a diode.I'll have to have a look at the other psu later, just in case it's a difference in the versions.

author: Ericmax
author_rank: Contributor
timestamp: July 25, 2016, 02:44:16 am
content: if you have several PSU to compare, look at the date code and PCB revisions, this may give indications of eventual corrections.

author: Pieh0
author_rank: Contributor
timestamp: July 25, 2016, 03:12:08 am
content: Can't see anything on the labels to show there's a revision number, everything looks the same apart from the serial number, and what might be a yy-mm-dd date code.Had a poke around with the multimeter, and it looks like B1 is hits 10v, then dies, which takes A1 with it.Also the quick check leds show that 5.2v and 3.3v aren't there, it did start up once or twice, but it quickly clapped out.It's 4am here so i'll have a look at it later on.Picshttp://imgur.com/a/IHBNy

author: richnormand
author_rank: Unknown
timestamp: July 25, 2016, 03:22:25 pm
content: Quote from: Pieh0 on July 24, 2016, 11:26:23 pmWell...I took the PSU off the CMU200 and, just like you found out, I could not find an indication of revision. The rest of the markings are identical to your unit except for the serial number and manufacturing date.I started to work on a different theory and spent an hour sifting through my bench garbage bin.Guess what I found. Five failed one ohm resistors and one failed (open) diode..... That is what happens when you work late at nigh. So I probably went away to see what I had in smd resistors, duplicated the batch seen at the bottom of the picture and completely forgot about the diode!Since the PSU started to work perfectly I never gave it a second thought. Looks like its a pretty generic diode similar to the others on the board. If it was a zener or a special diode there is no way to find out now anyway.Any markings on the diode on your board? I could no see any on the failed one. I'll measure the voltage across the resistors and try to figure the diode polarity (OK from your photo) and see if it is forward or back biased.I'll put an errata on my original post not to lead people astray.EDIT: using Pieh0's photo as reference I replaced the bottom resistor with a general purpose diode. From the photo I assumed the cathode band is on the right and that would make it back biased as I get a positive voltage on that side. Comparator protection of some sort?Thanks for posting the photo Pieh0.

author: Pieh0
author_rank: Contributor
timestamp: July 25, 2016, 05:11:17 pm
content: Just poked the outputs with the scope to see what was happening, and here's the result.Started with the mains turned off, mains on, then B1 to ground, and then mains off in 10 ish second chunks, and like i said, 3.3v and 5.2v are dead, and A1 starts up, then dies, what i found interesting was the 12v line going to where it is, then crashing to ~8v.Ignore the little wobble on the 12v just as it went high, fat fingers and tiny wires don't work well.3rd picture is the same test, but with a working psu.So at least from that we know that the 12v dying isn't due to a fault, but something is stopping the psu causing 12v to drop like it does on the working psu.Time for a cold drink and a think.**edit**Well i've checked the resistors, and they're 1ohm each, so time to try and find the 5 and 3v lines.

author: richnormand
author_rank: Unknown
timestamp: July 25, 2016, 09:06:27 pm
content: Quote from: Pieh0 on July 25, 2016, 05:11:17 pmA1 I think is the "power good" line. Its high with the 12V standby (power off) and it looks like it goes down a few seconds later indicating a problem on the bad supply and stays up on the good one when you power up.B1 is the soft start.There are three 12V rails I think. 12V standby generated by the TOP200, 12V for the unit and a 12V for the fan.Can you monitor what the 12V standby (D24 should be on all the time) does on the bad/good supply. Perhaps the 12V standby goes down and takes the rest. (Unlikely)Can you follow up the "signal good" line to see where it takes its inputs? that might give you an indication of where the control circuit for the 5V is (intermediate board 2 perhaps)Can you see voltage on the transformer for the 5V line? The 3V might be derived from it on board 1?There are two wires connected to a quick disconnect on board 3 going to the big transformer on the opposite board. I think that might be the 5V circuit drive if memory serves.I assume all measurements were done with the PSU out and without any load? Mine worked OK in that situation (not always true of all PSUs).

author: Pieh0
author_rank: Contributor
timestamp: July 25, 2016, 09:27:25 pm
content: The 12v trace was from D24, just checked all 3 12v lines and here's what i got.The standby is ok, stays up even when A1 drops to 0v.I'll have a look at the other bits later, the psu is too crowded to be poking around at the momentAnd yes, no load.Also probed abcd 1, c&d1 don't goto ~5v, so i think it's clear it's that side of things. I'll have a poke around later.Thanks,Pieh0.**edit**Followed the "signal good" line until it went into a CD4093BC on board 2.So now the fun begins trying to find where 5v comes from on board 1.**edit2**5v is totally dead, it's not even switching. There doesn't appear to be a 5v tap on the transformer, but basically every other voltage is there (28v & +/-12v).Traced it back to that little add on board on board 1, it has a UC3843AN smps controller on it, and it's close to where the 5v seems to be coming out of on the working psu.

author: Pieh0
author_rank: Contributor
timestamp: July 26, 2016, 03:55:53 pm
content: Found it!It seems to be the UC3843AN on the add on board, or something else on it (op amps), cause when i swapped them around, the working psu dies the same way the broken psu did.So, off to RS to order a pack of them, just in case.Wonder what caused it to die.Going to compare the signals going in and out of both psu's so hopeful everyone else can just shove a probe on pin x to determine if that's the board that's died, seeing as it's buried deep inside the psu.https://www.fairchildsemi.com/datasheets/uc/uc3843.pdfThere's the comparison of the traces of both board.

author: richnormand
author_rank: Unknown
timestamp: July 26, 2016, 05:41:41 pm
content: Quote from: Pieh0 on July 26, 2016, 03:55:53 pmNice to have a comparison between the good and bad unit! I'll be intriged to find out what RS wants for it.

author: Pieh0
author_rank: Contributor
timestamp: July 26, 2016, 05:50:34 pm
content: Quote from: richnormand on July 26, 2016, 05:41:41 pmI mean RS Components for the UC3843AN, £5 for 5.

author: richnormand
author_rank: Unknown
timestamp: July 26, 2016, 06:50:05 pm
content: Quote from: Pieh0 on July 26, 2016, 05:50:34 pmHa! that makes more sense now. Not being familiar with RS Components my only two options for RS were Rohde and Schwarz or Radio ShackHopefully you will get that PSU back in the game.Interesting, reading the whole thread, is that at least three different issues were identified in what does look to be a well designed PSU, with quality components no less.My next task will be to make a copy of the hard drive, just in case the software is coded for a particular unit and options!

author: tautech
author_rank: Super Contributor
timestamp: July 27, 2016, 12:23:43 am
content: Quote from: Pieh0 on July 26, 2016, 03:55:53 pmDon't jump to hasty conclusions.These are a common SMPS IC, yes they do occasionally fail but more often it's componentry around them.The datasheet you linked for it is probably the worst I've seen for lack of application detail.Here's a better one:http://www.ti.com/lit/ds/symlink/uc3843.pdfP8 list a typical application, similar is often used by manufacturers.Depending on the exact topography used in your application, normal points of failure include:HV dropper resistor/s (startup supply)IC supply bulk cap (IC V+ supply smoothing)Flyback diodes (run supply)Check each of the above.Here's TI's documents page too, with a heap of application notes that may help too.http://www.ti.com/product/UC3843/technicaldocuments

author: Pieh0
author_rank: Contributor
timestamp: July 27, 2016, 03:12:04 am
content: I swapped the board's around with the chip on and the faulty supply worked, so it most likely something on the board its self, or something further up the line killed it, only one way to find out.Putting in a new chip will be able to confirm that or not, but if it isn't that, then it will be something else on the board, that's when the fun will start cause i'll have to trail wires out of the psu to feed it while i probe around.Thankfully there's no mains voltage going into there.http://imgur.com/a/G5liHpictures of the board.

author: PartialDischarge
author_rank: Super Contributor
timestamp: July 27, 2016, 05:08:13 am
content: Hi Pieh,if for future reference you could measure and post a table with the correct voltages at that connector with the unit in standby and turned on that would be of great help to other users of CMUs/CRTUs whose psus turn faulty

author: Pieh0
author_rank: Contributor
timestamp: July 27, 2016, 09:16:12 am
content: Well i replaced the UC3843AN, and that didn't do it, but 1 board works and the other doesn't, as before.So, the other chips on that board are an LM393M, a CD4001BCM and a TLE2022c.If it wasn't for the fact that swapping out this mini board made the psu work, i'd be looking further up the line. Hopefully it isn't one of the many transistors on that board.**edit**Well it isn't any of them, so not sure what else to look at. Time for a think

author: richnormand
author_rank: Unknown
timestamp: July 27, 2016, 06:31:05 pm
content: Quote from: Pieh0 on July 27, 2016, 09:16:12 amSince you know which one is bad I would be tempted to put both beside each other, in the same orientation.Use the DMM on the diode ohm scale and systematically probe each transistor and diode looking for a difference between the two. Reverse polarity if you don't find a difference and repeat.Similarly on the input, output and Vcc of the opamps. Just finding a difference may be of help.Finally do a board to board comparison of resistors and other components.I realise these are still in circuit so its not really a test of the component at this stage but there "should" be a difference between the two boards somewhere lest the flaw is hidden deep in one of the ICs.

author: Pieh0
author_rank: Contributor
timestamp: July 27, 2016, 06:33:48 pm
content: Will do, knowing my luck i wont find any problems, then the head scratching will start

author: Ericmax
author_rank: Contributor
timestamp: July 27, 2016, 07:01:31 pm
content: Good evening.small post to confirm my troubleshooting CMU200.Probleme: abrupt shutdown of CMU, as if a fuse had burned.1: Troubleshooting PSU: 12V STB LED flash on backplane> replacing TOP200YN by TOP222YN. ( look on Mouser )Testing the PSU removed CMU: B1 shunt to GND> PSU works well.test the PSU in the CMU> 12V LED flash STB> problem on CPU board.The 12V STB enters directly on a LM2651MTC-ADJ regulator.http://www.ti.com.cn/cn/lit/ds/symlink/lm2651.pdfThis regulator is short circuit.2: Replacing LM2651MTC-ADJ (Mouser or Digikey)Testing the CPU directly connected to the CMU ( Without LCD, PCMCIA and keyboard ) > CMU works well. ( motherboard post boot BIP)reassembly of the front panel and replaced on the CMU.everything is Ok my CMU working again.If it helps users CMU200 or CRTU, hoping to be useful.

author: richnormand
author_rank: Unknown
timestamp: July 27, 2016, 09:11:22 pm
content: Quote from: Ericmax on July 27, 2016, 07:01:31 pmThat is great news.Enjoy.On my unit I also had to oil the small fan in the CPU enclosure.You might want to check it before closing the box.

author: Pieh0
author_rank: Contributor
timestamp: July 28, 2016, 04:53:18 am
content: Quote from: richnormand on July 27, 2016, 06:31:05 pmHad a probe around like you said, and found a transistor and 2 diodes giving different readings, so i swapped the transistors around, and while it doesn't stay on, it does pulse some voltage through the 5v/3v3 line.Doesn't help that the diode's aren't marked, and the transistors are in code, but they're simple npn/pnp transistors, nothing special. The one that seems to be dead is marked with 1Bs (), which seems to be a BC846B.are the locations of parts.Looks like the diodes are simple switching diodes, so a bunch of BAQ34's should do it.

author: msraya
author_rank: Unknown
timestamp: July 28, 2016, 10:12:00 am
content: I would put simple LL4148http://www.marsport.org.uk/smd/sod80.htmManuel

author: Pieh0
author_rank: Contributor
timestamp: July 28, 2016, 10:15:56 pm
content: Just ordered "a few" of them, could only get 100 as a MOQ, so at least i'll have spares

author: Pieh0
author_rank: Contributor
timestamp: July 30, 2016, 12:26:31 am
content: Well it's fixed, for the moment.Changed that transistor and the diodes, and it's started up!Seems like what ever killed the PSU also killed the DSP module :/.Thanks for the help

author: richnormand
author_rank: Unknown
timestamp: July 30, 2016, 12:42:51 am
content: Quote from: Pieh0 on July 30, 2016, 12:26:31 amWell that is good news indeed.So you now have two CMUs.

author: Pieh0
author_rank: Contributor
timestamp: July 30, 2016, 01:49:59 am
content: Quote from: richnormand on July 30, 2016, 12:42:51 am1 Working and 1 working apart from the DSP. Swapped the boards inside around and it's the main processing board that's died, so maybe it's a voltage reg or something, but trying to probe in there will be a pain.Something to work on later.Here's the board that died.http://imgur.com/a/V5HIP

author: richnormand
author_rank: Unknown
timestamp: July 30, 2016, 03:28:48 am
content: Quote from: Pieh0 on July 30, 2016, 01:49:59 amThat could be a difficult one.Anything on the board that looks like it would have taken the blunt of it, like a tantalum decoupling cap or voltage regulator or such?

author: hafrse
author_rank: Regular Contributor
timestamp: September 11, 2016, 10:20:32 pm
content: Hello Ericmax ,Just curious, what is the type of the power supply in your CMU200, is it a SN230 or SN250.ThanksQuote from: Ericmax on July 27, 2016, 07:01:31 pm

author: hafrse
author_rank: Regular Contributor
timestamp: September 11, 2016, 10:26:18 pm
content: Hello,I have a CMU200 with a bad power supply, the type is SN230 1091.2320.00 . I can get the SN250 1091.1982.00 type instead, are they compatible? the only thing I find on the SN250 type is that it has an extra orange socket with 4 pins near the main socket. Bothy are for the CMU200. According to the seller of the SN250 , the orange socket goes to a power cable to feed the signaling module which I don not have in my CMU200.Many thanks in advance!

author: richnormand
author_rank: Unknown
timestamp: September 11, 2016, 10:49:38 pm
content: Quote from: hafrse on September 11, 2016, 10:26:18 pmMy CMU200 has the SN250. From what I could see inside the PSU the extra plug for the signalling module just connected to the regular outputs. My guess (could be wrong here) is they are the same supply apart from the extra plug and perhaps more current output for the extra module? If you do not get better feedback I could take my PSU off the unit and have a look for you, post some photos, if time is not an issue. Also the plug looked like a regular old style hard drive plug....

author: hafrse
author_rank: Regular Contributor
timestamp: September 12, 2016, 06:12:59 am
content: Thanks to let me know/confirm that it only feeds the signaling module, I have pictures of the SN250 no need to take your power supply out. I will try the SN250 when I get it and test it in my CMU200.Many thanks!Quote from: richnormand on September 11, 2016, 10:49:38 pm

author: Brainbox
author_rank: Contributor
timestamp: September 12, 2016, 03:01:43 pm
content: If You do not intend to use the signalling unit, just pull them out and run the hardware change utility.For normal RF measurements they are of no use and only pull a lot of unneeded power from Your supply.Besides that the CMU becomes much quicker during startup.

author: richnormand
author_rank: Unknown
timestamp: September 12, 2016, 04:14:52 pm
content: Quote from: hafrse on September 11, 2016, 10:26:18 pmLooks like it only feeds that one module on the outside, as you suspected. And if I remember correctly inside the PSU it just tapped the regular output rails, nothing special. My guess is you should be OK.

author: hafrse
author_rank: Regular Contributor
timestamp: September 24, 2016, 07:04:12 pm
content: Quote from: richnormand on September 12, 2016, 04:14:52 pmMany thanks for the pictures!

author: RF_fanatic
author_rank: Regular Contributor
timestamp: September 24, 2016, 09:15:39 pm
content: I can confirm the SN250 will work as replacement for the SN230

author: hafrse
author_rank: Regular Contributor
timestamp: October 04, 2016, 07:28:59 pm
content: Hello,Now I have a working power supply, to the next problem, the CMU starts and boots direectly when I press the main power on the back, the cmu200 boots ok but I can not shut it down from the front soft button to standby mode. No message when I press that says the system is shutting down. I replaced the power supply with the one from my other working cmu, same problem , replaced the keyboard pcb, same problem.Has anyone information about this start/standby soft botton "logic" ? is it on the CPU board ? any keyboard chip involved ?Thanks for any info

author: Brainbox
author_rank: Contributor
timestamp: October 05, 2016, 12:52:17 pm
content: Did you mount the front panel firmly in place?I had problems with the "on" button too.It went out that the front panel was not exactly in place and the connectors from the front panel to the motherboard did not mate complete.I did not fit the little screws which hold the front panel in place and that causes a mismatch.

author: richnormand
author_rank: Unknown
timestamp: October 05, 2016, 04:35:29 pm
content: Quote from: hafrse on October 04, 2016, 07:28:59 pmIf the suggestion from Brainbox does not pan out for you I would suggest looking at pin B1 on the PSU plug. That is the "soft start/off" pin that should go from 12V to 0 when switching. It then goes via the motherboard to the front panel plug. Also pin A1 looks like the "power good" line. You might want to check these signals.Their locations and pinouts are shown in the first pages of this thread.

author: eriklidgren
author_rank: Newbie
timestamp: October 10, 2016, 06:25:42 pm
content: Thank you all who contributed to this thread. It helped me troubleshoot my CMU200. At the beginning I suspected the power supply. It would start to power up and then die a few seconds into the boot sequence. This would loop continuously. I found that I could get it to boot successfully when I reinserted the keypad connector. But It would die and restart when I pressed any button on the frontpanel. I ordered a replacement keypad and now it works. The old keypad silver plating looks tarnished.

author: hafrse
author_rank: Regular Contributor
timestamp: October 11, 2016, 07:44:41 pm
content: Quote from: hafrse on October 04, 2016, 07:28:59 pmHello,Problem is solved now, it was the standby circuit which was not working (can be a controller chip, etc...) , I replaced the CPU board and now it works as it should.

author: hafrse
author_rank: Regular Contributor
timestamp: October 11, 2016, 07:47:49 pm
content: Quote from: richnormand on October 05, 2016, 04:35:29 pmThanks for the information, the pin is always logically 0 . when I press standby, no message on the display appears saying that the system is shutting down, I suspected the standby circuit (controller chip, etc...), replaced the CPU card and now it works fine.Thanks again

author: EB5AGV
author_rank: Contributor
timestamp: October 13, 2016, 09:25:27 am
content: Hi all,As I have commented on a sepparate thread, I am also working on a faulty PSU. Mine is a PULS SN250I have a doubt regarding a couple wires coming from the main PCB to the upper one. Wires are GREEN and BLACK in colour and come from a transformer. I think they should go to the BL and SW connections respectively on the upper board, as I guess the GREEN one could be close to BLUE (BLAU in GERMAN) and the BLACK one in German is SCHWARZ, so the SW. But of course this is just a guess. I take pictures of everyting but didn't picture that onePlease, could you help me?Thanks!JosePS: I have used a previous picture of this thread to show what I mean

author: hafrse
author_rank: Regular Contributor
timestamp: October 13, 2016, 11:19:45 am
content: Hello,You are correct, the Black goes to SW.My power supply died yesterday when I was uninstalling/ installing the CPU card..., no standby voltage and TOP222 is ok.it seems that these power supplies are very sensitive.What is wrong with yours?George

author: EB5AGV
author_rank: Contributor
timestamp: October 13, 2016, 11:29:54 am
content: OK, thanks!Well, mine did not generate 5.2V and 3.3V. So, following a previous post on this thread, I analyzed the small plug-in board. And, yes, exactly the same transistor was bad!. In my unit there were some corrosion signs on it. I will post some pictures.I replaced it and powered it out of the unit, and yes, the PSU came back to life.But, this morning, I have assembled it and put it back into the CMU200. And then, just switching the PSU switch, something has exploded inside!I have looked and it is very uncommon: the dual hole ferrite just close to the main bridge, on the red and black cables, was cracked in two and there were signs of an spark among the positive and negative cables, just below the ferrite. I guess it was due to my cleaning work which perhaps had left some residue just below the ferrite. But, anyway, it was quite uncommon and has scared meBoth fuses were also gone. So I have put new ones but, as I was unsure of the cabling, I had not yet powered it, just in case.So, after lunch, I will try it again. Let's close fingers!Jose

author: EB5AGV
author_rank: Contributor
timestamp: October 13, 2016, 02:45:52 pm
content: Well, I have good and not so good news.The good ones is that the PSU is working fine. So I have been able to boot the unit for first timeAnd then the fun stops... It takes a lot of time on the startup window, showing onProcessBaseDiscoverOptionsBeginAfter several minutes, it continues, shows all the installed options and even the serial number. Once, it has shown a "non-volatile RAM empty error" after that, but the next time it has not.Then you can continue, but no function really works and, when trying to do something (as activate the spectrum analyzer), all of them end with a red framedSystem Errrorwindow.Installed software is V 4.51. I have tried to change to V 4.53 (as it is already on the hard disk), but it kept doing the same, so I have reverted back to 4.51UPDATE: after the N-th attempt, after the red error window and a power down sequence, now it does not boot up!. When you connect the power supply, the GREEN light on the front panel lights immediately after just a blink of the YELLOW one. And that is all!. No fan running, nothing. I have waited for some time, with the PSU disconnected but, so far, it keeps doing the same. The only LED that shines is the 12V Standby (besides the front panel green one!)Any idea?Thanks!Jose

author: EB5AGV
author_rank: Contributor
timestamp: October 13, 2016, 04:43:11 pm
content: Well, I would say that these PSUs are crapWhat happens now is that the PSU does not start up!. It has the right voltage on the POWER ON pin (B1), but when the unit sets it low or when you do it with a resistor, the PSU does not start.So it has lasted for about one hour!I am about to open it again...Regards,Jose

author: richnormand
author_rank: Unknown
timestamp: October 13, 2016, 09:11:19 pm
content: Quote from: EB5AGV on October 13, 2016, 04:43:11 pmOk probably means the first cap from the line and the first stepdown converter should work.To make sure measure the 350V and 280V for the following stepdown trans.across these to make sure. Just to make sure you still have a full bridge, not one with two open diodes. The fact that both fuses were gone, ouch!Then since the original TOP222 seems to be fragile, measure the 12V standby output at the output connector, in addition to the 5V soft on/off.If OK, short circuit the soft on/off and see if any output voltage rail has a short "blip" and then shutdowns. See previous posts in this thread. If it does, the little board has to be looked at again.Each of the main supply rails have their own rectifier, regulator, over current and voltage. If any of those has an over current or short it will cause a shutdown and the transformer with all the taps.PSU works fine out of the unit without a load (not always true for this type of PSU). First order of the day then is to get the PSU going. But you need to figure out if there are issues with modules on the motherboard that could have caused this also.Other comment: RAM, I also got a similar messages and inconsistent boots on my unit. Changed the coin cell on the front board and ran the tool utility on bootup to refresh the configuration.

author: EB5AGV
author_rank: Contributor
timestamp: October 13, 2016, 09:32:06 pm
content: Quote from: richnormand on October 13, 2016, 09:11:19 pmYes, maybe the bridge has been damaged. I will replace it, as it has suffered a big overload. Thanks for the hint!Regarding the battery replacement, it is what I have done before, thinking that the non-power issue could be related with the CPU. The battery measured only 2.4V. I have replaced it and will reset configuration as soon as I get the PSU back to work!I will let you know what I find.Thanks!Jose

author: EB5AGV
author_rank: Contributor
timestamp: October 13, 2016, 10:51:33 pm
content: Quote from: EB5AGV on October 13, 2016, 09:32:06 pmSome more information... The bridge is OK. I get about 270V on the RED and BLUE wires, just after the bridge and then close to 400V on C215 (220uF/400V cap) on the top PCB.The 12V STANDBY is present and stable. The POWER ON line is as shown on the document, close to 11V on STANDBY. But when I put it to GND, nothing happens. There is no glitch on any output. It is as if the unit did not notice the ON signal. I have checked and it goes to the vertical PCB among top and bottom ones. There are some ICs there and the first one is a CD4093BCM NAND,Schmitt Trigger. The bad thing is that it is located on the inner side, so checking how it operates is not easy.Regards,Jose

author: hafrse
author_rank: Regular Contributor
timestamp: October 14, 2016, 08:53:52 pm
content: Quote from: EB5AGV on October 13, 2016, 04:43:11 pmI agree, I have now 2 dead power supplies, no 12v standbuy output. One of them was working before 3 days ago, it just stopped after I reinstalled the front frame, something is killing them and they do not tolerate any thing...Will check the TOP200, I have ordered 5 of them.Regards,George

author: richnormand
author_rank: Unknown
timestamp: October 15, 2016, 01:38:04 am
content: Quote from: EB5AGV on October 13, 2016, 10:51:33 pmYa, I found the same problem for testing mine. I ended up soldering several wirewrap wires to about five or six points I wanted to check and labeling them. Then I reassembled the whole PSU and did the measurements. You might notice it took me quite a while to find the open resistors and diode (front end of this thread). I don't really know of another method to do this, unless someone comes up with a better suggestionBy the way my symptoms did look pretty much like yours too.One of the most complicated PSU I ever dealt with. As Scotty would say " The more complicated the plumbing the easier it is to clog the system"....

author: EB5AGV
author_rank: Contributor
timestamp: November 15, 2016, 08:36:59 pm
content: Well, I have managed to get the CMU200 running again. I got a faulty PSU and have fixed itBut then the problem it had before remains. I have already replaced the CMOS battery and run the BIOS CMU Default configuration. But, on powering up, the unit hangs onBaseDiscoverOptionsBeginProcess, showing on Info window justSW: V 4.51, withModelandSerial#blank. And inOptionsthere is nothing shown for some long time.After about 5-10 minutes, theOptionswindows is filled with the unit configuration and the boot up continues. But then, if you select for example RF Spectrum, when you press ON, there is s System Error (Filename: R nl-page in u-mode, Line 615) and tells you to power cycle the unit.Any idea of what could be happening?Thanks!Jose

author: richnormand
author_rank: Unknown
timestamp: November 15, 2016, 08:50:30 pm
content: 1)What was the root cause of the failure with your PSU EB5AGV ?2)My first reaction would be to recheck all the connectors from the motherboard and the front computer and the HDD. Then suspect corrupted data transfer from the old HDD.check that the small fan in the front module is running (mine was not, seized)3) make a full bit copy image of the hard drive (procedure mentioned on this forum before, using HDD-Raw-Copy tool by user _Wim_) These hdd are getting old and near failure.4) Once you are sure your disk image is OK, go to DOS (attach usb keyboard and Alt-F4) and chkdisk and defrag the HDD.This would give you a backup to change disk drive if needed. I used a compact flash (bootable type) with a converter to mimic the HDD and transferred the disk image to it. Mine used to lock up randomly during boot up and it stopped doing it since I am not using the original HDD. I suspect some corrupted software data until the drive warmed up as I also had issues reading it with my HDD to USB converter while setting up for the transfer.Even if that does not solve your issue at least you will have a proper backup of the OS.Good luck with it.

author: RF_fanatic
author_rank: Regular Contributor
timestamp: November 15, 2016, 10:19:27 pm
content: This problem is most likely caused by a dead DIG unit. I've seen it with multiple units.The dead DIG unit gives the typical very long waiting time without showing serial number.

author: EB5AGV
author_rank: Contributor
timestamp: November 15, 2016, 10:51:38 pm
content: Quote from: RF_fanatic on November 15, 2016, 10:19:27 pmWhen you say dead, you mean not fixable?Jose

author: RF_fanatic
author_rank: Regular Contributor
timestamp: November 16, 2016, 01:43:32 pm
content: It might be fixable but inside the dig module there are multiple boards.I have some defective dig boards myself and also working dig boards so minimizing the problem to board level would be the next step for me.But i have limited time..But perhaps it would help others to pick it up after i identified it on board level. In that case i can give it higher priority. (At the moment im focussing on calibration of deviations of the cmu)

author: EB5AGV
author_rank: Contributor
timestamp: November 16, 2016, 03:27:27 pm
content: Quote from: RF_fanatic on November 16, 2016, 01:43:32 pmYesterday I opened the DIGITAL BOARD module... Yes, it had four plug-in boards, two larger and two smaller, and there was plenty of dark dust and some signs of slight corrosion. But even after a careful cleaning, the unit does the same.It would be great to have known-good boards to swap. I offer myself to work on this if I can get an spare DIG board.Regards,Jose

author: RF_fanatic
author_rank: Regular Contributor
timestamp: November 16, 2016, 10:16:34 pm
content: I will try if I can trace back the fault to internal plug-in module level of the DIG board tomorrow evening or otherwise this weekend.I have a special CMU setup in which I can easily do checks on module level for a quick assesment of faulty units. Uptill now I've used it on module level but can be easily be altered for plugin level.It would be wise to open a separate topic for this.

author: richnormand
author_rank: Unknown
timestamp: November 16, 2016, 10:39:33 pm
content: Quote from: RF_fanatic on November 16, 2016, 10:16:34 pmIf you do open a new topic please leave a note here too, so the rest of us with dodgy CMUs can follow it. BTW thanks for all your efforts on these topics RF_fanatic, much appreciated.

author: RF_fanatic
author_rank: Regular Contributor
timestamp: November 17, 2016, 10:16:19 pm
content: As requested :https://www.eevblog.com/forum/repair/cmu200-rohde-schwarz-hangs-during-basediscoveroptionsbegin/

author: msraya
author_rank: Unknown
timestamp: October 25, 2018, 08:01:15 am
content: Hello!!Same problem here with LM2651MTC-ADJ regulator. Only I put a LM2651MTC-3.3 and burned something elseI will try to put another LM2651 to see if it works, but I think i burned something..Someone with a spare main board FRM6 to exchange??ManuelEA7EE

author: RF_fanatic
author_rank: Regular Contributor
timestamp: October 26, 2018, 08:49:16 pm
content: I do have a couple of FMR5 units if that would help. Only problem is that the display iterface is totally different..

author: wiredwrx
author_rank: Contributor
timestamp: March 30, 2020, 01:06:48 am
content: Sorry to resurrect an old thread, but just obtained a non-working CMU200, and all my searching revealed this thread as really the only resource for a resolution. So, here goes:Pulled off the cover, and noticed that the standby led was lit constantly, which I guess is good. However, the power button on the front of the unit doesn't light up at all. I removed the PSU, but can't seem to get any voltage out of the PSU on the bench...not even the standby voltage, which surprises me.Put the PSU back in the unit, LED shows standby voltage, and grounded pin B1 through 200K resistor, but nothing happened. None of the LEDs lit, and the unit is just dead. Monitored B1 with a scope, and there is no voltage present with the PSU installed and powered on, and of course, no ground/low signal when the front panel button is pressed.I tried to initiate turn on by grounding B1 through the 200K resistor with the PSU removed, and no go.Really confused by all this, and my electronics knowledge just isn't great enough to figure this out alone.Any direction or help would be greatly appreciated.UPDATE: So, with the PSU installed and connected, I grounded, without a resister, B1, and lo and behold, the PSU started, all the LEDs went green, and got some beeps, and the HD was definitely spinning and doing its thing, but no lights came up on the front panel, and the LCD stayed dark. Gonna pull all the option slices out, and see if I can get it to boot, but at this point, I am leaning towards something wrong on the front panel or motherboard. "Hopefully" I'll find something that burnt, or a misaligned or damaged cable, or something.UPDATE 2: Got some beeps out of the unit, and with a flashlight, I am able to see something on the screen. So, perhaps the invertor is not operating. But still, no lights on the front panel, so still hoping/thinking there might be an easy solution once I get the front assembly off.Kindly,Michael

author: richnormand
author_rank: Unknown
timestamp: March 30, 2020, 03:37:47 am
content: I used much less than 800 ohms on B1 to start it if I remember correctly. You also should get the standby power even when the PSU is alone.Unlike some PSU this one is fully functional when no load is applied. So there is no need to have it connected to the motherboard until all the proper voltages are present when it gets the "power good" signal.You might want to read the whole thread at this point.The initial posts in this thread will give you several things to check and include several pinouts.In mine it ended up being a row of resistors that were defective (all open) in the current monitoring loop, but along the thread you will find other issues that people have identified and things to check.I'll monitor this thread to follow your progress and see if I can help if you post more details.Best of luck with it.

author: wiredwrx
author_rank: Contributor
timestamp: March 30, 2020, 04:19:37 am
content: Thanks for the reply. I have been through the thread several times, though nothing has been exactly like what I am experiencing.Also, don't forget that you also changed a diode along with those other resistorsGonna trace the front power button LEDs and the power button, and see what happens.As an aside, I replugged in all the cards, and booted the unit by grounding B1. It booted up properly, and then the led on RF3 lit showing input. And, with a flashlight, it looks like the unit is at the SA screen, its hard to tell, but it definitely appears to be booting properly.Next step is to get the front off, and look for obvious damage, and see what I can find.UPDATE: Attached an Monitor to the VGA out, and kinda as expected, got a good signal, and was able to watch the unit post and boot. But, none of the front panel buttons appear to do anything. Leads me to believe that there is some sort of major issue with the front panel. Time to delve in and see what I find. ***Does anyone by chance have a pin out of the various connectors between the front panel and the other boards?***ThanksMichael

author: richnormand
author_rank: Unknown
timestamp: March 30, 2020, 07:59:00 pm
content: My unit also had a dead display but seemed to try to boot. I could see some action with a flashlight.Here is a link to the inverter board and how I removed the front panel:https://www.eevblog.com/forum/repair/rs-crtu-need-help-removing-the-front-panel/msg1127200/#msg1127200Turned out to be a bad smd fuse.While you are there you should consider replacing the battery and checking the small cooling fan (mine was seized and the temperature monitors were indicating past high temps)Another thing I did while in there was to bit copy and replace the hard drive. I kept the original as a backup copy and replaced it with a flashcard memory.But first you have to find out why the command to the PSU is not getting there. There are several connectors between the front unit and the motherboard to check for proper connections.

author: wiredwrx
author_rank: Contributor
timestamp: March 30, 2020, 08:28:27 pm
content: Well, the plot thickens, or perhaps, I have figured it out. Got everything apart, and started focusing on the green membrane behind the keys. The membrane connects with a thin flat cable to J3 on the FMR5 board behind the display. The flat cable definitely (well, to me, maybe no one else, please let me know) seems to have shorted and/or taken some sort of voltage/amperage it was not meant to.See the streaking/?burning? running up the cable in pic 1?Also, it looks like something "delaminated" from the cable in pic 2-4? Interestingly, I wonder if that was a fuse of some sort. When flattened, there is a metal film of sorts on the "top" that shows continuity to ground. Any one remember seeing something like that on their green membrane before?Finally, I am hoping that nothing else took a hit. A quick look around doesn't show any burnt parts, and the board looks pristine. I am hoping that nothing blew, or, that these little chips in pic 5 are fuses, but will need a tweezer probe to check. I can't see any markings with my aging eyes.Thoughts?P.S. And, the fuse on the back light inverter blew, so have to deal with that. I really hope they are related, because if not, then I may have more issues than I think.Thanks,Michael

author: wiredwrx
author_rank: Contributor
timestamp: March 30, 2020, 08:33:21 pm
content: Quote from: richnormand on March 30, 2020, 07:59:00 pmThanks for the advice and direction. I did just backup the HD, and will likely be putting in an SSD, if I can get it to work properly first. I will also change the backup battery, and check the fan while I am at it, but mine doesn't appear to have a temp sticker.Thanks,Michael

author: Qw3rtzuiop
author_rank: Frequent Contributor
timestamp: March 31, 2020, 11:29:44 am
content: I recommend an IDE to CF adapter. An ssd is overkill for the task and the OS wont use TRIM etc.This adapter is in use for 1 year in my CMU200:https://www.aliexpress.com/item/32575994548.html?spm=a2g0s.9042311.0.0.27424c4doOdtrAMy unit suffered from a broken keyboard foil to. There was similar damage on that flatflex cable.You can buy cloned keyboard foils on Taobao for appr. 40$.But i dont see burnmarks on your pics. It looks like corosion of the silver plating.Edit:This is the taobao link for the keyboard pcbs:https://item.taobao.com/item.htm?id=544961277461By this time they are also available on ebay but much more expensive.

author: Ice-Tea
author_rank: Super Contributor
timestamp: March 31, 2020, 11:53:48 am
content: * The keypad membrane often looks black. Just the silver oxidizing, afaik* They can often be repaired. Main cause of trouble is the delamination. If you look closely, you'll see a piece of tape connects the two layers. You'll need to replace that with copper tape or something. Don't try to solder it, doest work.* If not: I can probably dig up a spare.* Backlight: the inverters are prone to failure. You can find replacements but they are expensive. Easiest is just to get a LED replacement strip. Watch out: afaik, it runs of 5V, many of the LED inverter boards out there need 9V at least.

author: wiredwrx
author_rank: Contributor
timestamp: March 31, 2020, 05:28:50 pm
content: Quote from: Ice-Tea on March 31, 2020, 11:53:48 amThanks for your responses. ICE, if you have a spare membrane, that would be awesome. I'll try and PM you.I haven't decided about going LED or just repair the inverter just yet. I assume the stock back light can be adjusted, and I may want to stick with that.Qw3rtzuiop, I was also thinking about using a CF adapter, and will likely do that instead of an SSD. Thanks for confirming it will work, and for the link.Thanks,Michael

author: richnormand
author_rank: Unknown
timestamp: March 31, 2020, 10:52:58 pm
content: About using a CF card. It will work, as this is what I have setup, with the adaptor previously mentioned. That is what I meant about using a flashcard instead of the original HD.If you do that make sure you use the card type that is bootable (not all of them are. The bootable ones tend to be also more expensive I found out). There is a thread somewhere on this forum about that. I'll post the link when I find it.The other thing to be aware of is the CF cards do wear out over time with this type of usage, so make sure you have a good bit copy of the original disk.Before considering the switch to LED for the display I would try just changing the inverter fuse (cheap and easy) and look at the state of the fluos before. If they are still good you might still get a long service time out of them.It will be interesting to find out what is the reason the PSU signal does not work from the front panel.have fun!

author: richnormand
author_rank: Unknown
timestamp: April 02, 2020, 09:22:19 pm
content: "There is a thread somewhere on this forum about that. I'll post the link when I find it."Well the thread was about making a bit copy of the HDD but I relocated where I found the CF flash information from my notes.https://lowendmac.com/2015/the-lowdown-on-using-compactflash-to-replace-an-ide-hard-drive/Note the "You should be sure you’re using a UDMA CF card, as non-UDMA cards are not generally bootable when used with an IDE adapter." in the article.This is exactly what I found the hard way and after getting a UMDA card from eBay it all worked perfectly. Keep in mind that CF cards will deteriorate with the number of read/write but mine has been working for a couple of years. I burned a backup copy on CD and also kept the original HDD (belt and suspenders) in my CMU200 three-ring binder.Booting the OS is a tad faster but most of the time is taken initialising all the modules.Also with the adapter double check the ribbon cable polarity as my cable allowed plugging it in two different positions.

author: wiredwrx
author_rank: Contributor
timestamp: April 02, 2020, 09:36:50 pm
content: Quote from: richnormand on April 02, 2020, 09:22:19 pmThanks for the info once again. I will keep that all in mind. First, need to get the unit working, then I can get to improving it.

author: Rollin Hand
author_rank: Regular Contributor
timestamp: April 04, 2020, 01:57:42 pm
content: i try the cf with one Chinese adapter didn't work ,did not boot.

author: wiredwrx
author_rank: Contributor
timestamp: April 23, 2020, 06:04:20 pm
content: An update, which I hope will be helpful to others.Sourced a replacement membrane, and now she works as she should. Also replaced the SMD fuse on the inverter board, and it works also. I was able to de-solder the old fuse, and solder in a replacement (I usedhttps://tinyurl.com/ycdcxm9p) with a regular iron with a pointed tip and a tweezer. It really wasn't too hard, and if I can do, likely anyone can do it. Only thing is, It is dimmer than the other CMU200 I have, so I think the reflector has curled around the tube as has been suggested elsewhere, or perhaps the glass is discoloring along with the curled tube. Gonna consider using LEDs.Now, for the askI know I have several options and cards that I don't need. Anyone know of a list, and perhaps a how to/diy on what can be removed, and how? I know I have B83, because when the unit boots, I get a message about initializing B83, which lengthens the bootup significantly. So, I wouldn't mind paring down the un-eeded/un-useful options and cards.Thanks for all the suggestions and help,Michael

author: ZL1CVD
author_rank: Regular Contributor
timestamp: July 24, 2020, 02:54:04 am
content: Picture shows bare minimum hardware for basic RF (spec analyser, RF generator, RF power meters).

author: wiredwrx
author_rank: Contributor
timestamp: July 24, 2020, 03:30:33 am
content: Thanks for that. Do you know if the OS/Software will throw a fit if I remove the modules? Also, if you are able, do you mind taking pics of the coax between the modules, because I think I will need to move many connections if I remove the modules.Thanks again,Michael

author: ZL1CVD
author_rank: Regular Contributor
timestamp: July 29, 2020, 10:27:58 am
content: Sorry, that is the only picture I have of bare minimum. I sold that over year ago now. You can look closely to work it out. There are service manuals around and top plate show interconnections.When you remove module/s, you must blank of the air duct so other modules get correct cooling. I use aluminium roofing tape because I have it and it has EMI shielding properties. But you can use other tape you have.Once you finished removing everything, start up version manager and rung 'firmware update after module change' - this is from memory, it may be slightly different wording but means same. This procedure takes some time - maybe 15 minutes or more. It updates everything to make sure all path attenuation's and firmware is correct for what is left installed.If you need more information, look at the service manuals that are around. There is allot of information in those.

author: ZL1CVD
author_rank: Regular Contributor
timestamp: July 29, 2020, 10:33:30 am
content: Here is another internal bare minimum picture..

author: Ice-Tea
author_rank: Super Contributor
timestamp: July 29, 2020, 10:38:16 am
content: Quote from: wiredwrx on July 24, 2020, 03:30:33 amThe wiring diagram is printed on the cover of the modules.