CMU200 repair attempt - shipping damage (oh those post monkeys...) - Page 1
Forum section: electronics / rf-microwave

author: Yansi
author_rank: Super Contributor
timestamp: September 19, 2020, 09:19:28 am
content: Hello,I have finally decided to get a CMU200, at least as an upgrade for my oooold spectrum analyzer. So I have found a good deal, unit seemingly in a very good shape... only to find a month later, post monkeys played football with it.Long story short: Unit was dropped hard on a corner (near the power switch), does not even power on. Chassis is deformed on the left side.After further inspection and disassembly, I have found a sheared PCB in the computer module. And lot of other stuff one doesn't want to see: electrolytic cap(s?) that spilled their guts, overheated BGA chips and fans seized so hard you can barely spin them by hand - even though there seems to be little to no dust inside the unit.See photos below of the damage. Main PCB of the computer module has sheared near the mounting point, inner layer traces more than likely severed. I do not think this would be an easy to repair if possible at all.The question now is, can one get anywhere just the PC module to replace? I have searched ebay for these, found none for sale. Not sure if my search buzzwords were weak, or they are simply not available. I have tried even searching the part number printed on it, which I think is 1090.9244.24.Can anyone point me please to where I could probably get a replacement PC for it? (Hoping the only electrical damage so far is just the PC).Many thanks,Yansi

author: Qw3rtzuiop
author_rank: Frequent Contributor
timestamp: September 19, 2020, 06:46:53 pm
content: The CPU board is called FMR. They are used in several instruments built in "Bauweise 2000" (Translation: Architecture 2000).They are several generations of these boards FMR5, FMR6.... . But i dont know if they are flashed for a specific model and if you can use a board of an FSV spectrum analyzer in an CMU200 even if it would be the same FMR generation.

author: Yansi
author_rank: Super Contributor
timestamp: September 19, 2020, 07:39:38 pm
content: Yup, I have already found out it is called as such, in my case the board is "FMR6+T5" respectively. Thanks for confirming. They are probably interchangeable, as the whole FW sits on an externally connected HDD. But there maybe other firmware (such as the BIOS) specialized for the instrument. I have found that at least the FMR boards of different versions can be swapped for the same instrument.Unfortunately, I can't find any board on sale. Searching ebay I have found only two boards from Israel, both of which are some pretty old types with the price of way more than I have payed for the whole CMU. What a bummer!//Hoping some will show up on ebay, or that someone will offer a spare one, if he happens to have one. Is anyone willing to offer one, if you happen to have a spare?I would prefer replacing it, rather trying to repair it. The shear line on the PCB goes under the connector on the other side, so almost impossible to repair the traces (not even trying to count internal signal layers, as the PCB is more than likely 6+ layer, would guess even 8 layer.) Repair attempt would need to start with X-raying the PCB first (which I could manage to do) to get an idea of the internal damage and how many traces has been severed.

author: Qw3rtzuiop
author_rank: Frequent Contributor
timestamp: September 19, 2020, 08:07:51 pm
content: Based on my experiments the serial number (and therefore the instrument type and sub type) is stored somewhere on the FMR.I wish you good luck on your search for an affordable replacement FMR. But that will certainly take a lot of time.Until then you can try to repair your damaged FMR.Is the orange standby led illuminated? Maybe your keyboard foil is broken too.

author: richnormand
author_rank: Unknown
timestamp: September 19, 2020, 08:11:15 pm
content: Just looking at your photos for input so I might be totally wrong.1)On my CMU200 the small fan was seized. I was able to remove it and disassemble the unit. After a bit of motor oil it has been humming for the past 4 years.2)Electrolytic cap. If you do not want to remove the pcb it can be gutted and replaced from the top with flying wires (Kluge warning,,, but it works).3)Overheating sticker. Mine had that too. Still working well.4)The crack on the pcb might be repairable assuming there are no internal fine traces in the inside layers. I have seen worse and only had to bridge the top trace.Might be worth a close inspection after removing the unit under a binocular and a bright light before getting a replacement.look at the battery while in there. Mine was dead.Also, a shock like that might have dislodged a connector to the pcb. Might be a good idea to nudge all of them.Best of luck with it.

author: Yansi
author_rank: Super Contributor
timestamp: September 19, 2020, 08:38:45 pm
content: The unit was working before it was handed over to the post monkeys. Even though it had seized fan, blown cap and overheated BGA chip. But the PCB crack finally done it.The PCB seems to have two signal layers on outer sides (I can clearly see traces on the first inner layer).If you look at the photo, but zoomed in, you can see the inner layer traces too (sorry, photo not the best, can make a better one). There is at least a dozen of them broken on the layers I can see, not sure if there are any internal signal layer in between the outer most power planes.

author: TheMG
author_rank: Frequent Contributor
timestamp: September 19, 2020, 08:39:07 pm
content: Quote from: Yansi on September 19, 2020, 09:19:28 amThus the importance of proper packaging, something that unfortunately too many eBay sellers fail to do properly.How was the unit packaged? Large heavy items like this really should have at minimum 15cm of foam on all sides, and a double-wall box or nested boxes. All too often I see people use newspaper or bubble wrap, neither of which are any good for heavier items as it compresses too easily. Packing peanuts are also no good as the peanuts move around and the item ends up sinking to the bottom of the box while in transit.Tip: before and during unpacking, always take pictures, so if you find the packaging was inadequate resulting in the item getting damaged, you will have evidence to file a claim for a refund.

author: Yansi
author_rank: Super Contributor
timestamp: September 19, 2020, 09:00:29 pm
content: Packaging was definitely inadequate. I got refunded half the price I have payed for it: the unit cost was about $500 (just the basic model without any interesting options), so if not counting the shipping and VAT, I got a $250 boat anchor now (shipping and VAT excluded).This refund problem is already solved, but the boat anchor needs a new PC board to become a CMU200 back again.

author: TheMG
author_rank: Frequent Contributor
timestamp: September 19, 2020, 11:48:33 pm
content: I would attempt a repair, maybe you'll get lucky and repairing any visible traces (including the ones on lower layers that you can see through the board) will make it work again. At this point, you've got nothing to lose. Worst case is you've put time and effort into it and it still doesn't work.Looks like most of the traces lead to vias, so visually follow the traces to a via or solder pad, and use those as points to solder mod wire to.

author: Yansi
author_rank: Super Contributor
timestamp: September 20, 2020, 08:59:22 am
content: I could attempt repairing it, but I think that the damage it got is way in the BER region. The crack is much longer (after inspecting closely - see photo) and I can count 20+ severed traces in there. The crack is right under the connector, so not much access to the other side of board to at least see where the traces go.//EDIT: Inspected more closely: There is 8+2 traces on the component sides broken and likely 5 on the other. But I still need the Xray to determine the connections of like half the traces.If the Xray attempt will be successful, I think that bodging 15 traces shouldn't be as that bad, they seem to be only quite short links. I'll try to get an Xray of the board now.

author: ogden
author_rank: Super Contributor
timestamp: September 20, 2020, 09:34:27 am
content: Close to humanly impossible repair unless you have schematic *and* gerbers. I would start to look for spare board or buyer of this unit as it is (for parts or repair).

author: Yansi
author_rank: Super Contributor
timestamp: September 20, 2020, 10:04:02 am
content: Of course no schematic and no gerbers, the only think I can try is to get the Xray image of the board. If not, then to trash with it.After seeing the availability of replacement boards (little to none), it would make sense to sell it as trash for parts. But I would rather wait selling it, until I get another unit - I may need other replacement part for it too.Also, I have asked two persons specifically, that could have the replacement computer, we'll see if I succeed there.

author: ogden
author_rank: Super Contributor
timestamp: September 20, 2020, 01:56:11 pm
content: Quote from: Yansi on September 20, 2020, 10:04:02 amThat looks like 6 layer board to me, traces could be shadowing one another all over the board. Single image won't help, rather 1 or more hours of "live" 3D X-ray tracing. There's catch - even one trace buried under BGA and you have problem bodge-wiring it.In case of few inner-layer breaks one could try using dremel to carefully dig in, but in your 20 traces case it seems like hopeless 0.1% success rate idea.

author: Yansi
author_rank: Super Contributor
timestamp: September 22, 2020, 06:20:48 pm
content: Bad news everyone,the röntgen maschine brekken ist. So I am not able to let my friends do an Xray of the board on a proper electronics inspection machine. Fuuu***ck.So the only option is to get a replacement board. Anyone willing to sell one?

author: richnormand
author_rank: Unknown
timestamp: September 22, 2020, 09:00:45 pm
content: possible interest?FMR5 and front for CMU200 for sale:https://www.eevblog.com/forum/buysellwanted/fs-(eu)-cmu200-front-panel/

author: Yansi
author_rank: Super Contributor
timestamp: September 22, 2020, 10:04:21 pm
content: By no means I am an expert CMU200 rebuilder, can somebody explain, if an older computer (FMR5) can be fitted into a machine where FMR6 was originally? And when/how I can obtain the firmware that will work both with the old board and the newer rest of the instrument?From what I have learnt so far, there should be some kind of a "version manager" that will rebuild firmware from scratch for the HW detected, but it requires to have a suitable image to put on a fresh HDD drive (or CF card, if one wants). Where to obtain a workable image of the drive is still a mystery to me. Although this thread also reveals a lot of interesting info about the CMU:https://www.eevblog.com/forum/testgear/enabling-options-for-rs-test-equipment/50/

author: Qw3rtzuiop
author_rank: Frequent Contributor
timestamp: September 23, 2020, 08:56:59 am
content: I dont think the initial firmware is needed. The offered FMR was already initialized and is taken from a CMU200. Im just not sure if you will get a new serial number. And after change you should start the "firmware update after board change" to be sure. You dont need a fresh installation for that.The service manual contains a hint that there seems to be different connectors of the FMR. But the model 04 is the unit with the FMR4 board an model 12 with FMR5. I would assume that the later versions share the same connector. But you can check that. The service manual wasnt updated after they changed to FMR6 (or i dint have the lastet version avaiable).BTW. The price offered is pretty good if you consider that there is also the keyboard and the lcd included. The keyboard is another main source of failures.

author: Yansi
author_rank: Super Contributor
timestamp: September 23, 2020, 11:48:03 am
content: Connectors may be compatible, sure, but the PC software is not, is it? I have already a likely working HDD drive with the original FW for FMR6, but I would likely need a different firmware for FMR5. Or will FMR5 run from the FMR6 HDD drive? That's what I am asking. If someone can confirm, I will buy the FMR5 right away.

author: Qw3rtzuiop
author_rank: Frequent Contributor
timestamp: September 23, 2020, 01:34:52 pm
content: The main difference between the FMR versions are the CPUs. But it is just a PC with some IO. I dont see any reason why it shouldnt work. Upgrades from FMR5 to FMR6 are prooven to work. But you can ask the seller if he can give you an image of his hdd.

author: Yansi
author_rank: Super Contributor
timestamp: September 23, 2020, 02:02:02 pm
content: Just thinking about the compatibility - you sure FMR5 can be plugged into a FMR6 backplane? Just noticed CMUs with FMR5 computer boards have only 5pin DIN keyboard connections, while the FMR6 equipped CMUs have USB ports on the back (although I have learned they are only emulated USB ports for KB/Mouse and nothing else). But I think there is no electronics on the backplane, so the USBs must be interfaced directly to the FMR - hence thinking, there may be an compatibility issue between FMR5 and 6? Am I right or.. ?

author: Qw3rtzuiop
author_rank: Frequent Contributor
timestamp: September 23, 2020, 02:13:56 pm
content: The CMU200 I used to have was equipped with an FMR6 and a motherboard with PS2 connector on the backside. The serial number on the back was different to the one that was displayed in the menu. It worked but had some input level issues caused by a broken DIG board.

author: richnormand
author_rank: Unknown
timestamp: September 25, 2020, 02:37:38 pm
content: Another FMR5 board:https://www.ebay.ca/itm/184462065687?ul_noapp=true

author: Yansi
author_rank: Super Contributor
timestamp: September 27, 2020, 08:34:56 am
content: That board is unfortunately an economical nonsense. I can buy almost a whole unit for that kind of price.(one needs to add all the import fees and VAT to that to see where I see the issue, as a poor european)And yup, I have bought another unit for parts. Got extremely lucky to buy it very cheap. Or maybe I can repair this one if not the first one? Seller stated that "it does not turn on". So I pretty much hope it is a PSU issue, as SMPS is what I can deal with, should I repair one.All repair attempts currently on hold, waiting for all the parts and stuff or people getting out of quarantine.

author: Yansi
author_rank: Super Contributor
timestamp: October 09, 2020, 10:08:44 am
content: Little update on where we are at:I have received another boat anchor from Israel: Yet another non functioning CMU200. This time it is the most basic configuration, likely with FMR5 or older computer, almost without any additional SW options. Just some GSM stuff - at least according to the stickers I see through the cover on the side.I do not have the unit at home yet, need to move it another 40 km to my lab. The described issue is "does not turn on". Well, I have tried to bravely plugg it to mains, it turned on instantly upon flipping the switch at the back. But the display remained black. Once I pressed the front soft power button, it instantly turned off and I couldn't turn it on any more. (I did not try any further).Does this problem looks like any of the typical ones with these units?I bought this unit very cheaply, almost for scrap price (shipping was more expensive than the unit itself). Wanted it especially for two things: It may have a functional computer and also importantly it has the 50W rated input module! I hope I can salvage it as a downgrade for my unit (as the 50W is the base configuration and my more recent unit has the 2W input option).Is there any argument why the 2W option is better, than the 50W? Is the 2W option better in anything? I could not find out.It would be nice to have both units repaired in the end. But I still don't have any other spare PC yet. But one spare FMR5 will be on the way shortly, including the whole front assembly with LCD any keyboard.Still need to negotiate the FMR6 (supports USB ports) for my main unit.Also meanwhile I have received another upgrade module for my main unit, the B17 (Analog IQ/IF interface).So, thats where I am at now.

author: Bicurico
author_rank: Super Contributor
timestamp: October 09, 2020, 10:55:10 am
content: Let me give you my advice:Sell your boat ancors on eBay for the best price possible and get yourself a fully working and stuffed CMU200.Otherwise you will end up like me: I know own a total of 3xCRTU and 2xCMU200!It started when I bought two broken CRTU in hope of building one working unit from it. I ended up buying some missing components (some from Israel) and managed to get BOTH working.Then I stumbled on a great deal for two broken CMU200. So I bought another broken CRTU to get the required parts to make both CMU200 working. The last CRTU is actually working, too, but without any option at all.Looking back, I might have spent the same money as 1-2 working units are currently sold on eBay.Was it worth it? For fun yes, but perhaps it would have been better to just get one fully loaded CMU200 (option wise) in fully immaculate state. None of my 5 devices pass the self-test 100%. And that is the sad reality of these devices: if the RX/TX self tests fail, you will in most cases not be able to correct the out of spec parameters.Is this a big issue? Not really - except you need immaculate measurments at exactly the failing frequency range.Another option is to get the Siglent SSA3021Plus...Regards,Vitor

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 09, 2020, 11:47:39 am
content: Quote from: Yansi on October 09, 2020, 10:08:44 amAs far as I know the 2W comes with the CMU-B96 additional RF generator option.

author: Yansi
author_rank: Super Contributor
timestamp: October 09, 2020, 02:20:20 pm
content: How does B96 module look like? I do not think there is any module added. Couldn't find any photo of the module on the web.Above the input assembly, which normally has the huge heatsink, there is a small module, marked as 1100.2600.02 - which acording to quick google search is some kind of "reference board". Not sure what it does, but the unit is fitted with an OCXO. Maybe something to do with it? Part of the OCXO option?

author: Yansi
author_rank: Super Contributor
timestamp: October 09, 2020, 02:29:15 pm
content: @Bicurico: All I bought originally was a fully working unit. But received bashed junk instead, so just trying to repair it now. RX/TX module should be fine in that one. But I now know that these modules tend to fail, due to components drifting out of spec, so some of the selftests may not pass by a few tenths of a dB. (Or so I read somewhere).Selling on ebay - no, not worth the hassle. Selling locally? Likely impossible to find a buyer. Worst case, unit/s (hopefully one at most) will be gutted for parts. Already heard from a few people interested in buying some parts.But don't try to change my mind please, I am still optimistic... so far.

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 09, 2020, 05:16:33 pm
content: Quote from: Yansi on October 09, 2020, 02:20:20 pmI'm not sure how the B96 looks like, but the CMU200 is very good at modules in modules in modules, so a good chance that it's hiding somewhere.About the reference board, let me quote the service manual:Quote

author: Yansi
author_rank: Super Contributor
timestamp: October 09, 2020, 06:18:07 pm
content: OOokay so that board definitely does not have anything to do with the B96. So how can I tell whether the "2W input only" CMU has the second generator fitted, without actually turning it on (I am not able to, yet)?Meanwhile I'll try to move home the second boat anchor to be able to better diagnose the power-up issue.

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 09, 2020, 06:27:12 pm
content: I just checked my CMU200 that also has the 2W limit and it has the B95 option which is also an additional RF generator (no idea what the differences are).

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 09, 2020, 06:37:19 pm
content: A bit more info here:https://www.eevblog.com/forum/testgear/rohde-schwarz-cmu200-cmu-b95-additional-rf-generator-removal/

author: Yansi
author_rank: Super Contributor
timestamp: October 12, 2020, 07:42:28 pm
content: Hello,so another update. I have brought home the other unit, described as "does not turn on". Turns out, it turns on pretty damn well. But the LCD has a failed backlight and it is failing with some error.After disassembling the unit, to my big surprise, I have found an audio analyzer (B41) installed! Yaaaay! Definitely a keeper.To not make a mess in this thread to not to mix repairs of two units together, I have created another separate thread for the other unit. I hope you will understand, why splitting the thread may be a good idea.Link to repair thread of the other unit:will be edited in here in a moment.

author: Yansi
author_rank: Super Contributor
timestamp: October 22, 2020, 07:59:58 pm
content: Update: Back at my home lab, with two great packages!Many thanks to usersIce-Teaandeb4eqafor kindly providing me these needed spare parts!Hopefully I will now be able to make this unit work back again.

author: Yansi
author_rank: Super Contributor
timestamp: October 22, 2020, 10:05:08 pm
content: As I couldn't help myself, I needed to try the new computer NOW. So I have assembled the computer chassis with the FMR6+T5 from Ice-Tea. Replaced fan with a good one from the computer assembly from eb4eqa and plugged the whole into the unit, flipped the switch on the back and...... the unit started, ran for about 3 seconds, then turned off. So I pressed the front soft power button and voila, it's booting! Then halfway through the boot, screen went black. Guess what, the CFL inverter just decided to die on me!Unit otherwise seems to boot up properly, I got to the spectrum analyzer screen successfully, while holding a strong flashlight against the LCD screen to see at least something in there.So it seems a lot of work for tomorrow:- Likely replace the encoder wheel. The one in the unit seems not responding well. It seems to skip pulses.- Look what happened with the CFL inverter. Again, the stupid SMD fuse? (Interestingly enough, this inverter has a 3A fuse placed, the one I have repaired in the other unit got a 2A fuse, also blown).- Maybe replace the LCD with the one from eb4eq, as that one was modified with a LED backlight (need to ask how to wire it)- Source suitable replacement electrolytics for the computer board (at least one is an obvious toast)- Dismantle the unit down to bare chassis and then pound it back to shape with a hammer- Mount everything back, while praying it'll still work- Try installing the B17 option board into it- Make some haccs to the firmwareAgain - many thanks Ice-Tea and eb4eqa for the parts.

author: Yansi
author_rank: Super Contributor
timestamp: October 23, 2020, 05:17:22 pm
content: So, today's update: I have stripped the chassis completely and hammered in into its original shape. Then put everything back and tested, all working again. Great!Now on to the upgrade task: I have a CRTU-B7 module, that as far as I can tell is identical as CMU-B17 module, the IQ/IF interface. What I am struggling with now, is how to wire it all correctly. I have a hard time understanding the drawing on the cover of the cards.I have already tried to wire it, but I don't think I have it correctly connected. There are wires left I don't know where to plug.First, let me photograph the cover drawing in detail - see attachments. I have had some option boards already installed, just need to add the B17. The drawing is also available in the service manual,http://gotroot.ca/cmu200/CMU_Service.pdfpage 199. I hope these drawings are the same.I have added the required 4 BNCs to the back of the unit and connected them to the respective connectors X514, X515, X520, X521. Easy.Then I have unplugged W33 from the "A7" board (unplugged X703) and plugged it in the B17 module, into X501.A jumper link was then used to join X502 from B17 back to X703 on A7 board. That also seems quite clear.But where the hell should X37, X38 and X39 from the RxTx board go?How to wire the "A7 slot board" back with the B17 in between and what to do with the other option boards I have there?I find it quite confusing and the lack of any detailed signal diagrams of the modules does not make it any easier.But how to wire the rest, remains a mystery :-O

author: Yansi
author_rank: Super Contributor
timestamp: October 23, 2020, 05:19:08 pm
content: Okay, I may start to understand what is what. But I may have some cables missing then! O_o I came up with this:The RxTx module should be connected as following:X37 to X522X38 - no connectionX39 to X513From the B17 module to the "A7" card then:X518 to X708X516 to X706The A7 card also needs likely some reference frequency, originaly port X703, now loops through the B17 module goes into X501 then loops back from X502 to A7-X703.This way, it seems the instrument is working. Both basic Tx and Rx.What I am still missing are the connections from X923, X924, X925 of the B68 module.Looking and thinking more in detail, if the option B68 is installed, the signal should go from A5-X518 to A9-X923, then loop through and back from A9-X924 to A7-X708.Now I have it wired directly A5-X518 to A7-X708. Which works, but without the B68 option. Huh.To reduce confusion and make things clear, I made an image. Image is worth thousand words.This is how it is wired now. Rest of the connections are in their original state, as they were before.Wiring may be finished, or it seems now I seem to understand what should go where. .. apart from those 4 BNCs I have added on the back - the wires to them are too short for some of the connections, will need to fix that.Now I have a few questions I would like to get help with; if anybode knows, please leave a comment below!1) What type of connector are those small ones on the modules? Seems like MCX, but smaller? I would like to make some custom cables to tidy up the mess in there, currently hacked from random lengths of jumpers.2) How to access any settings related to the B17 module? Do I need to put in just the right license keys to enable it, or do I need a whole software install madness?3) Is it normal, that the auxiliary generator (B95) is capable of only up to -60dBm and only through ports RF1 and RF2?//EDIT: those small connectors seem to be MMCX?

author: _Wim_
author_rank: Super Contributor
timestamp: October 23, 2020, 05:45:46 pm
content: Here is the "Module and Cable Exchange manual", with has some basic interconnection circuit diagrams. Maybe this can help (never really had a close look at this manual, but archived it for when I would need it...)

author: _Wim_
author_rank: Super Contributor
timestamp: October 23, 2020, 05:56:52 pm
content: Page 121 of this CRTU service manual also has some instructions on replacing a B7 module

author: _Wim_
author_rank: Super Contributor
timestamp: October 23, 2020, 06:05:14 pm
content: I forgot my CMU200 also has a B17 optionHere is a picture I took when a received the unit. I can have a closer look maybe this weekend and open my unit up, but maybe this can help already.

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 23, 2020, 06:05:25 pm
content: It's covered in great detail here:https://www.mikrocontroller.net/topic/433164?page=singleI hope your German is sufficient, and it's a long thread so searching for B7 could help.

author: Yansi
author_rank: Super Contributor
timestamp: October 23, 2020, 06:41:17 pm
content: Quote from: _Wim_ on October 23, 2020, 06:05:14 pmThank you for the photo. It seems I have it wired the same way, even though I loop the RX and TX paths through yet another option module. I have there a huge double-width module "B68+B21+B54+B56"I have already run the "firmware update after board change". That has run successfully. I meant more like where is the control menu to access the setting of the IF/IQ paths, that the B17 module does.

author: _Wim_
author_rank: Super Contributor
timestamp: October 23, 2020, 06:51:32 pm
content: Quote from: Yansi on October 23, 2020, 06:41:17 pmI am not in the lab right now, but if I remember correctly, it is in the same screen where you select the input and output channels, but on the 2nd page (so you need to switch pages with the button bottom right)

author: _Wim_
author_rank: Super Contributor
timestamp: October 23, 2020, 06:56:36 pm
content: Quote from: Yansi on October 23, 2020, 06:41:17 pmThis manual describes the operation (from page 191). Zipped to 3 parts because is was to big to attach here

author: _Wim_
author_rank: Super Contributor
timestamp: October 23, 2020, 06:58:29 pm
content: Quote from: _Wim_ on October 23, 2020, 06:56:36 pmpart 2 (rename to *.z01)

author: _Wim_
author_rank: Super Contributor
timestamp: October 23, 2020, 06:59:32 pm
content: Quote from: _Wim_ on October 23, 2020, 06:56:36 pmpart 3 (rename to *.z02)

author: _Wim_
author_rank: Super Contributor
timestamp: October 23, 2020, 07:01:57 pm
content: Quote from: _Wim_ on October 23, 2020, 06:51:32 pmThis is how it should look like

author: Yansi
author_rank: Super Contributor
timestamp: October 23, 2020, 07:17:02 pm
content: Aaarrgh!!! There is a second screen. Sure, B17 settings are right there.But I have hard time understanding the diagram with a dozen of switches. Where do the signals go?I would like to know what exactly the B17 module does inside. The HW diagram of the interconnection inside the unit looks like this (in my unit). But how to correlate between the menu settings and what happens in reality?I was mostly interested in the B17 module, because I understood it can provide the I and Q baseband signals both for TX and/or RX. That would mean I could, possibly, utilize the CMU200 as a universal transmitter/receiver, with IQ interface I could use for truckload of interesting things.//By the way, the LCD backlight is repeatedly crapping out on me, but the fault is not in the CFL inverter board, but somewhere on the LCD breakout board, where the big ribbon cable is terminated to. Taping the board fixes the backlight. But it does not seem to be a problem with the ribbon cable connector itself. Power supply is randomly missing for the CFL inverter. Shouldn't the CMU be able to drive an external VGA monitor? //

author: Yansi
author_rank: Super Contributor
timestamp: October 23, 2020, 07:25:02 pm
content: Now looking at it the second time, isn't this it?It would make sense. But the I/Q ports are not available then anywhere outside the unit. Just the IF signals.(will download the manual, just a moment pls)//EDIT: Guessed correctly. See picture from manual. But that also means there are no IQ signals available. The option B17 provides only the four IF3 TX/RX IN/OUT BNC connectors and not really any I/Q signals.

author: _Wim_
author_rank: Super Contributor
timestamp: October 23, 2020, 07:36:43 pm
content: I never really used that option in mine, so I cant really help with that, but will be reading along if you figure it out

author: Yansi
author_rank: Super Contributor
timestamp: October 23, 2020, 07:40:38 pm
content: I guess the IQ interfaces are really hiding somewhere in between the 13 unused connectors on the B17 module.If there are really two IQ mods and two demods, there must be 8 unused connectors on the B17 dedicated to these.If I would just have a piece of a pigtail cable with MMCX on the end, would be quite easy to probe the B17 module to find what all the connectors do. But, I have to somehow fix the damn backlight, its starting to piss me off.

author: Yansi
author_rank: Super Contributor
timestamp: October 23, 2020, 07:53:15 pm
content: Wait a minute...There is already a dedicated 15pin dsub on the rear panel. All signals therefore must travel through the backplane. Wondering, what the bandwidth of the baseband is.//EDIT: The pinout of that conenctor is yummy. (not)//EDIT2: Tried to look up in the manuals, what the IF frequencies are: Seems 10.7 MHz for RX and 13.85 for TX. See "Option R&S CMU-B17 IQ AND IF INTERFACE Technical Information"http://www.usedsite.co.kr/pds/file/CMU_Rev10_e.pdf, Annex 4: Specification on page TI.12Baseband BW is 2.5 MHz.

author: Yansi
author_rank: Super Contributor
timestamp: October 23, 2020, 08:53:01 pm
content: Okay, B17 solved so far. On to some next steps:Repair the damn intermittent LCD backlight.Why the rear "MONITOR" VGA output connector does not work? On either of the two CMUs I have, the monitor output provides no signal. Or so does a connected monitor tell me. And I know my monitor is good and has working VGA input. Even tried a different monitor on there, still "no signal". Needs to investigate, as having a big external screen is a big plus.Has any of you sucessfully used the rear MONITOR output on the CMU?//EDIT: Faulty VGA cable. F!!!!!!ck. Now I have obliterated the offending cable, so it can no more.

author: Yansi
author_rank: Super Contributor
timestamp: October 24, 2020, 12:04:20 pm
content: Continuing the story:CMU-B17: I almost thought all is well, until I found it ain't. There is a problem in the TX PATH, I get really shite output whenever I enable the main TX generator. Noisefloor goes significantly up and the TX level is incorrect, very much lower. (Whats even more weird, is switching on FM modulation, it starts to work OK.)To be able to troubleshoot any further, I have tried to investigate, what is what port on some of the cards.First, I have updated my "whats in the B17" picture with what some of the ports do, while showing how the default "bypass all" path looks like. What rest of the used ports do should be obvious from the manualOption R&S CMU-B17 IQ AND IF INTERFACE Technical InformationThen, the analysis began, just with closed modules as they are plugged in the unit. I don't want to open them and risk damaging something. But it would certainly help reverse engineering the CMU.RXTX board:X39 is the IF3 RX output (10.7 MHz)X38 is yet another IF3 RX output, but few dB less signal there (10.7 MHz).X37 is the IF3 TX input (13.85 MHz)X36 is the transmitter's IF2 output (487.5 MHz, see it there, very low but constant level about -60 dBm)X35 is the receiver's IF2 output (487.5 MHz, see random stuff as the analyzer is sweeping and LO2 leakage)The digital card A7:X701 reference input 78.000 MHz (funny, even when unplugged, everything is working like nothing happened)X702 reference input 80.000 MHz (when unplugged, analyzer stops working. Plug back and it continues)X703 reference input 110.800 MHz (Beware, when unplugged, firmware crashes and locks up)X704 something something to B41 audio analyzer or the big B66/68/76/78 card. What may it be?X705 reference output REF2 (BNC on the back, configurable frequency, +6 dBm. Quite surprised this ain't function of the REF board.)X706 is a receive input CH1 (10.7 MHz)X707 is not populated, but very likely receive input CH2X708 is a transmit output CH1 (13.85 MHz, about -5 dBm)X709 is populated, unused, guessing transmit CH2. Would be nice to confirm with a CRTU unit that has two RXTX cards.Reference board:X102 unused, likely another ref inputX103 reference input EXT 10 MHz (BNC on the back)X104 reference output of 10 MHz (BNC on the back)X105 outputs 27.7 MHz (for the audio B41 option)X106 outputs 110.800 MHz (for RXTX board and B95/96 option)X107 outputs 110.800 MHz (unused)X108 outputs 110.800 MHz (for digiboard A7 and B17 option)X109 outputs 80.000 MHz (for digiboard A7)X110 outputs 78.000 MHz (for digiboard A7)That is what I have so far.Still don't know, why chaining the B68 option into the TX path (loop through X924 in, X923 out) causes the TX signal from A7 to be significantly attenuated and noisefloor noticably higher. Anyone any ideas? The TX generator is unusable with the B68 in the path. (Only starts working correctly when FM mod is selected)