hybridfree/eevblog-posts huggingface dataset:
Electronics, storage, and "power them up every couple of years" - Page 1
Forum section: electronics / repair

author: CkRtech
author_rank: Regular Contributor
timestamp: May 29, 2017, 08:40:30 pm
content: I'm going to come clean on this - I enjoy repairing stuff, and I certainly have a lot of "stuff" - but I haven't really stuck by the idea of consciously powering stuff up every few years. I'll pull OLD stuff from an estate sale, garage sale, etc., do some spot checks and various other things before powering it on to save a possible boom...and sometimes it is so cheap and time is limited - so I just plug my ears and do a smoke test. If something fails, fix it.For some guys that collect and treasure these old electronics (and don't really do repairs, themselves), they say to power them up and run them a bit every so often - most notably stating that they should be powered up as frequent as once a year to prevent caps from going bad faster than they should.I mostly just try to keep my stuff in good environment where I can and address future problems as they happen.I'll just open this up:1: What sort of truth is there to powering up something every few years for preservation of components?2: Is it worth it?I have a few pieces that store settings and use rechargeable batteries/super capacitors - and those are the only ones I bother to power every so often.

author: tautech
author_rank: Super Contributor
timestamp: May 29, 2017, 09:13:40 pm
content: 1. Yes2. YesThe most susceptible components to aging are electrolytics but there are options if powering up unused equipment.Variac, and gently ramp up the supply to give the electrolytics time to reform or a simple dim bulb tester.

author: CkRtech
author_rank: Regular Contributor
timestamp: May 29, 2017, 09:34:48 pm
content: Quote from: tautech on May 29, 2017, 09:13:40 pmI take back what I said - I have waited until picking up variac/building a dim bulb tester prior to servicing a late 70s/early 80s stereo.Addendum - What about powering up something (say - early 80s IBM computer) with a number of tantalums after it has been sitting for a few decades? This is an initial approach question in addition to a maintain question (after initial service).

author: tautech
author_rank: Super Contributor
timestamp: May 29, 2017, 09:48:19 pm
content: IMO Tants are another issue, yes somewhat related as they're susceptible to surges especially if they haven't been downrated WRT working voltages.If the rest of the circuit is not behaving as designed (old dry caps) then tants can be at risk.
Tek 465B X-axis beam problem - Page 1
Forum section: electronics / repair

author: tipex
author_rank: Newbie
timestamp: May 27, 2017, 02:43:02 pm
content: Hi all!I'm new to this forum. I was searching information about an oscilloscope and just found this amaizingly big community. I hope someone can help meI have an old Tektronix 465B oscilloscope. Suddenly, the X axis is not displayed correctly anymore. The beam stops in the middle of the CRT screen. It's compressing all the X axis (temporal) information in almost a half of the screen, and the timespace is distorted (not linear) when the dot approaches the end of the beam (almost in the middle of the screen).The Y axis is working correctly.I'm attaching you a photo of the scope with a 1kHz signal in it. With the TIME/DIV set at 1ms, I should see one period/cycle of the signal in every division; however, as you can see, I'm seeing more than 2 cycles in one division. You can see also that the waveform is distorted at the end of the beam and is no longer lineal.Do you have any idea of what can be happening?Can it be the X-axis (horizontal) amplifier? Or the CRT circuit?Where should I start looking?Any help would be really appreciated

author: David Hess
author_rank: Super Contributor
timestamp: May 27, 2017, 04:22:00 pm
content: The problem is probably the output stage of the horizontal CRT amplifier but:1. Check the low voltage power supply outputs for level and ripple.2. Visually inspect the neck of the CRT to see if one of the horizontal deflection leads fell off. These leads will be on the top or bottom.

author: james_s
author_rank: Super Contributor
timestamp: May 27, 2017, 04:25:31 pm
content: I had that happen once on mine, one of the wires came off the deflection pins and it had exactly the same symptom.
Search: Casio power cord connector - Page 1
Forum section: electronics / repair

author: NottheDan
author_rank: Frequent Contributor
timestamp: May 20, 2017, 08:48:56 pm
content: I just got a Casio AS-L desk calculator (from the very early 70s), unfortunately without power cord and it uses a connector I'm not familiar with. Does anybody know where I can come by plug for it?

author: Nusa
author_rank: Super Contributor
timestamp: May 20, 2017, 09:42:54 pm
content: A straight-on picture of the connector and a height and width measurement would be helpful.Also confirmation on the input voltage printed on the case, so we know if we're looking for a mains cord or an AC or DC adapter.

author: NottheDan
author_rank: Frequent Contributor
timestamp: May 20, 2017, 10:00:41 pm
content: Quote from: Nusa on May 20, 2017, 09:42:54 pmIt's a mains cord.

author: helius
author_rank: Super Contributor
timestamp: May 20, 2017, 10:00:51 pm
content: Some old Roland keyboards used that connector type.

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: May 23, 2017, 09:52:06 am
content: There are some HP cords that might be compatible on Sphere's new arrivals page. Don't know if they're the same but might be worth ahttp://www.sphere.bc.ca/test/new.html#catalog

author: NottheDan
author_rank: Frequent Contributor
timestamp: May 23, 2017, 08:09:17 pm
content: Quote from: Lorenzo_1 on May 23, 2017, 09:52:06 amI don't think they are the same. Very similar but not the same. But thanks to your hint I think I found the correct one:https://web.archive.org/web/20160802081036/http://www.cs.ubc.ca/~hilpert/e/powerConn/index.html#jCalcAnd I don't think I'll have much luck getting one. Bit of a shame really.

author: Nusa
author_rank: Super Contributor
timestamp: May 23, 2017, 10:29:35 pm
content: If you can find individual pin sockets that fit those pins snugly, you may be able to create a one-off solution with either silicone rubber or a non-conductive epoxy. I bet you can use the receptacle itself as a partial mold. Experiment on something else as a proof of concept, of course.

author: mgraves235
author_rank: Newbie
timestamp: May 26, 2017, 06:20:01 am
content: is replacing that socket with a standard iec out of the question?

author: NottheDan
author_rank: Frequent Contributor
timestamp: May 26, 2017, 11:50:54 am
content: Quote from: mgraves235 on May 26, 2017, 06:20:01 amNo, it is not. But I'm trying to keep it in as original a condition as possible. Also, it is a 115V device and line voltage here is 240V. I'm a little bit worried that, if I put a standard IEC socket I'll do something stupid and thoughtless with it and a standard power cord.
GW Instek GDS 2102 scope - searching for power supply schematic - service manual - Page 1
Forum section: electronics / repair

author: ciccio
author_rank: Frequent Contributor
timestamp: March 18, 2017, 09:29:21 am
content: I have this 9 years old GDS 2102 scope, with a faulty power supply.I'vr discovered (did not remember) that the PS is always connected to mains, the rear switch is for optional battery operation.I've checked major parts, replaced a shorted MOSFET in the primary side, a broken NTC and open fuses, but no results: new fuses do not burn, a loud thump () but no smoke or flames, power supply dead.Need a more accurate examination-Does anybody have a schematic or a service manual, or a source for a spare?Thank you for any help-Best regards

author: ciccio
author_rank: Frequent Contributor
timestamp: March 23, 2017, 09:37:18 am
content: Update:contacted GW Instek on their website.Got a reply from Netherland, where they have a service center.The scope is obviously out of warranry, but they ask me to send there the scope for repair, or offer to sell a replacement PS board.I'm waiting for a quote for the second option: I understand it must come from Taiwan.The do not give schematics and/or service manuals to the end user.I fear that the cost (including EU paperwork for imporing from Netherland and delivery) will be very high.It's time for buying a new scope.In the meantime I'm going to retry to repair the board myself...Hope in better results.

author: ciccio
author_rank: Frequent Contributor
timestamp: May 26, 2017, 06:55:13 pm
content: Update:EDIT : The scope's model is GDS-2120, not GDS-2102.I tried to repair the PS board but, without a schematic, it was a very hard task... I hate switching power suppliesIn the meantime Instek (Good Will Instrument Euro B.V) has sent me a quote for:one power supply board plus one new LCD module with LED backlighting (they do not stock anymore the power supply board with CFL backligh supply, so a new display is required).Price for the two modules plus delivery is 85.00 Euros.There will be some delay because the spares will come from Taiwan, but the price is honest and the guy in Holland was very cooperative.In about two weeks I'll have my scope working again.Best regards
Help me find the firmware for Weller WMRS soldering station - Page 1
Forum section: electronics / repair

author: easa
author_rank: Newbie
timestamp: May 24, 2017, 01:20:22 pm
content: In the Weller WMRS soldering station, suddenly died the PIC16F876 controller. Seekeng firmware...

author: Andy Watson
author_rank: Super Contributor
timestamp: May 26, 2017, 06:10:14 pm
content: How dead is processor? Have you tried read out the code?

author: easa
author_rank: Newbie
timestamp: May 26, 2017, 06:51:48 pm
content: No. Just once the PSU unit did not turn on. The 1st pin of the chip sat on the ground with a resistance of 3.6 ohm.
Tektronix 465B Power Supply Problems - Page 1
Forum section: electronics / repair

author: mwgiesbrecht
author_rank: Newbie
timestamp: May 29, 2017, 11:34:13 pm
content: Hello. I suppose since this is my first post I better introduce myself before asking any questions. I'm Matt, from near Winnipeg, Canada. I was a professional archaeologist but now I am going back to school to study electromechanical maintenance. I have a decent, basic electronics knowledge and I have fixed a lot of stuff, but I am definitely better at mechanical repairs than I am at electrical/electronics. For now, anyways. I do want to learn more.I recently received a Tek 465B scope complete with a DM44 and a scope mobile, effectively for free. The scope powered up and I had shapes on the screen, but the unit would not read out a proper waveform.By reading through previous posts on this forum, and the service manual, I tracked down the problem (at least A problem) to the -8v supply. The voltage was high and the bridge was malfunctioning, I replaced it as well as the filter cap. I also replaced the bridges for the +15v and +5v rails while I was there, as well as the capacitor for the +5v rail.To make some of this work easier, I removed the transformer. When it came time to reinstall it, I noticed a wire had come loose from somewhere. This wire (Grey and White) connected to the Main Power Switch, but I was not sure where the other end of it connected to previously. From the schematics (and logic?) it seems like it should connect to the blue mains input wire at the blue stand off on the board, but when I did this, the main external fuse went boom.It also seems like a wire has broken off of the input voltage selector switch, so maybe that is where the loose wire from the power switch came from. However, then something else must be missing, because the blue wire surely can not just terminate at the blue stand off? There would be no circuit then.Long story short, if anyone can explain (words and pictures if possible) what the connections on the main power switch, line voltage selector switch, and at the blue stand off should be, I would be very grateful. The schematics are helpful but I wish they would have labelled more of the wire colours.Thanks for now,M
Viable to refurbish Whaledent UC1-110 ultrasonic cleaner?? - Page 1
Forum section: electronics / repair

author: rbm
author_rank: Regular Contributor
timestamp: May 26, 2017, 11:36:40 am
content: Hi,I have an older Whaledent UC1-110 ultrasonic cleaner that appears to function but also appears to be weak in its action even though it is rated at 110 Watts. I'm attributing that to the piezo elements wearing out over time. I tried a foil test on the machine and it was only able to puncture the foil in a few spots leading me to that conclusion. The UC1 has an operating frequency of 55KHz and finding aftermarket transducers at that frequency is difficult. It is very easy to purchase 50W 40KHz ceramic transducers from many online suppliers so one option I have is to refurbish the cleaner by replacing the two OEM transducers and OEM driver card with modern equivalents. I'm not an expert in ultrasonics so I don't know if this plan is viable. Would I be able to do this change and end up with a functioning device?Foil test results:OEM Piezo transducers:
Tek 475 fade in from left at 0.2,0.1,0.05us time/div - Page 1
Forum section: electronics / repair

author: rz
author_rank: Contributor
timestamp: May 26, 2017, 08:48:26 am
content: I bought a tek 475 scope. All works fine except the trace fade in from the left about 1-2 grids when the time/div is at 0.2, 0.1, 0.05us. I have read the troubleshooting manual, but no exact problem in the manual.I suspect the problem is in the Z-axis circuits. In the service manual, Q680 is used to ensure proper early turn-off CRT at faster sweep rates.

author: Andy Watson
author_rank: Super Contributor
timestamp: May 26, 2017, 09:03:37 am
content: Mine does that. I think it is normal.

author: tggzzz
author_rank: Super Contributor
timestamp: May 26, 2017, 10:06:24 am
content: There is a tweak in the service manual.What you need to be able to see is >10 divisions of visible sweep, plus, for a square wave signal used as a trigger, the leading/triggering edge of the square wave.If you can see both those, there's nothing to be concerned about.

author: rz
author_rank: Contributor
timestamp: May 26, 2017, 10:41:13 am
content: Quote from: Andy Watson on May 26, 2017, 09:03:37 amThank you for the reply. Hope it is normal.

author: rz
author_rank: Contributor
timestamp: May 26, 2017, 10:42:25 am
content: Quote from: tggzzz on May 26, 2017, 10:06:24 amThe trace are fade in. If the time/div > 0.1us, the trace can start from the left edge of the CRT.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 26, 2017, 11:14:26 am
content: Maybe stupid question, does your position pots works ? If you use the beam finder, are you able to put the dot / line in the screen center ??

author: rz
author_rank: Contributor
timestamp: May 26, 2017, 11:19:25 am
content: Quote from: coromonadalix on May 26, 2017, 11:14:26 amThank you. I can see the whole trace by adjust the position pot. I just wonder is this a malfunction of the scope.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 26, 2017, 12:27:20 pm
content: Mine does that, too. I think there's something wrong with the Z axis, but I never looked into it.It is a problem, because fully the left half of the trace is invisible at maximum sweep. Trace intensity has to be turned up all the way so that retrace is visible (i.e., defeating blanking altogether -- probably not healthy), to see it.Tim

author: tombi
author_rank: Regular Contributor
timestamp: May 26, 2017, 01:37:52 pm
content: Ha!I spent a good long while debugging this problem on mine before I discovered it was normal.One thing you can do is to run through the Display and Z Axis Calibration procedure (3-10 in my manual) and in particular the Grid Bias and Z Axis compensation. This should help to brighten the trace on the left side.Just make sure its warm before you begin. Oh and be careful about what you touch!Tom

author: whitevamp
author_rank: Regular Contributor
timestamp: May 26, 2017, 02:13:07 pm
content: mine is visable with the position knob at half way " center position. " and dose not change till i hit about 3/4 of the way to left or right.
Fluke 117 problem with 6 and 60 MOhm scales - FIXED ! - Page 1
Forum section: electronics / repair

author: Original
author_rank: Contributor
timestamp: May 24, 2017, 10:34:56 pm
content: Hello,I have recently salvaged a badly abused fluke 117 multimeter. All scales seem to be working pretty well within spec except the 6 and 60MOhms.The 6MOhms is off about 5% compared to my Fluke 189.The 60Mohms range (and idle in autorange) stops at about 13.57MOhms (fluctuating).The PCB is very clean and nothing appears blown.The voltage on the terminals for 6MOhms is 0.6V and for 60Mohms is 0.375V.In circuit, with the meter off the movs and thermistors etc measure:RV1 7 MOhmRV3 4.70 MOhmRV2 3.77 MOhmFusible resistor 1045 OhmRT1 1103 OhmRT2 983 OhmPlease be kind enough to help me repair this meter.Thanks,Chris

author: retiredcaps
author_rank: Super Contributor
timestamp: May 24, 2017, 11:48:47 pm
content: Quote from: Original on May 24, 2017, 10:34:56 pmAll three MOVs, R1, R2, and R3 are bad. You can remove them from the 117 for test purposes and the 6 and 60M ohm readings should be within spec. All three MOVs, out of circuit, should read 0L resistance with another working meter.The fusible resistor and two PTCs, RT1 and RT2, are fine.Report your findings and if the removal of the MOVs fixes the problems, then we can suggest replacements from mouser/digikey.

author: Original
author_rank: Contributor
timestamp: May 25, 2017, 12:13:42 am
content: And of course you are absolutely right! the movs are blown...Can you please suggest alternatives? Any source is good.Thanks againedit: I have just foundhttps://www.eevblog.com/forum/testgear/fixing-a-fluke-87v/are there any better alternatives?

author: retiredcaps
author_rank: Super Contributor
timestamp: May 25, 2017, 06:23:54 am
content: Quote from: Original on May 25, 2017, 12:13:42 amIn your original picture, I could see a bit of black on the MOV so I suspected they were bad and your in circuit measurements confirmed so.QuoteThe above thread has the suggested one.

author: retiredcaps
author_rank: Super Contributor
timestamp: May 25, 2017, 06:25:45 am
content: Just curious, did you get this for free from a recycle bin? Or from a colleague?

author: Original
author_rank: Contributor
timestamp: May 25, 2017, 07:27:35 am
content: It was used onboard a ship. The chief engineer no longer trusted it because of the above issue.Also the faceplate has completely faded away.Any ideas where i could find a replacement top cover?

author: retiredcaps
author_rank: Super Contributor
timestamp: May 25, 2017, 06:14:09 pm
content: Quote from: Original on May 25, 2017, 07:27:35 amThat is reasonable.QuoteYou can try Fluke. The top cover is part number 2525553 as per Fluke 11x calibration manual page 18.Alternatively, I have seen replacement top covers on ebay.com from time to time.Keep in mind that it might be very expensive. If this were my meter, a white sharpie or a label maker would suffice.
Rigol DP832 power supply faulty out of the box - Page 1
Forum section: electronics / repair

author: hazmoment
author_rank: Contributor
timestamp: May 24, 2017, 08:54:15 am
content: So Im in the market for a variable power supply and thought I'd spend the extra dollars and get the rigol DP832 over some other more basic cheaper units I was looking at. It arrived yesterday and switched it on, no loads connected, channel 2 & 3 seem to work sweet, channel 1 however does not output the preset voltage. The actual voltage at the terminals should be displayed on the LCD screen, but reads 0V no matter what the preset voltage is set to, and displays UR (unregulated) where the other channels display CV, or CC. It seems there is a fault preventing channel one from supplying any voltage/current whatsoever. The place i bought it from are suggesting I fix it and they reimburse me for it. Has anyone experienced this same problem with these power supplies? I understand they are a goodpower supply whilst they are working but have heard of a few faults with blowing series pass transistors etc when shorting the terminals (even though they should be current limiting) I dont want to be having toopen and fix a brand new lab grade power supply i payed good money for, especially because itll void my warranty. Interested to hear peoples thoughts on what the issue could be.

author: CJay
author_rank: Super Contributor
timestamp: May 24, 2017, 09:13:41 am
content: There is no issue, don't dick about with it, just contact the seller and send it back for replacement.Simple.

author: Simon
author_rank: Unknown
timestamp: May 25, 2017, 06:51:17 am
content: Please do not double post, it is very disrespectful of members trying to help you when you have 2 simultaneous discussions going on for exactly the same post.
REQ: Glassman Europe Limited LV300-10 Schematic / Service Manual - Page 1
Forum section: electronics / repair

author: Mad Professor
author_rank: Regular Contributor
timestamp: May 26, 2017, 08:28:19 pm
content: Hi All.As per the topic title I am trying to locate the Schematic and or Service Manual for a Glassman Europe Limited LV300-10 DC Power Supply.I have picked this unit up for free from work, as they are saying it is faulty.The unit powers up, but will not output a voltage.It seems like the unit is stuck in remote and not local mode.There is a switch on the front of the unit to select REM/LOC, does not seem to affect the unit, and the REM led above the switch stays lit.None of the error leds are lit.Thanks for your time.
Please help me identify what this component is and its datasheet. - Page 1
Forum section: electronics / repair

author: waynebonc
author_rank: Newbie
timestamp: May 24, 2017, 05:30:41 pm
content: HelloDoes anyone know what this SMD component is and it's datasheet? I've been looking for quite a long time and I can't seem to get hang of it. It looks like a 5 pin SOT package and has "61 Y" inscribed on it. Other than that I do not know. It's commonly used in Chinese equipment as it's not the first time I came across it however I never cared to look into what it actually is. I don't have a donor board so I can't take one off something else. Beneath it exactly is a SIM tray.Thanks!

author: Armadillo
author_rank: Super Contributor
timestamp: May 24, 2017, 05:50:30 pm
content: Likely is a LDO linear regulartor 3.25voltsSearch for Ricoh RP 102 N datasheet.

author: DaJMasta
author_rank: Super Contributor
timestamp: May 24, 2017, 05:56:20 pm
content: My search came up with a XC9206A1L6M, a 600kHz step down switching converter.... though I don't see an inductor there, so maybe not.

author: waynebonc
author_rank: Newbie
timestamp: May 24, 2017, 07:29:37 pm
content: I pulled one out and took some readings with the cable plugged into a supply. This is what I got. On the bottom that is a charging/sync cable. One pin feeds directly off USB Vcc.

author: waynebonc
author_rank: Newbie
timestamp: May 24, 2017, 07:32:57 pm
content: There is only a coil nearby

author: Fisher77
author_rank: Regular Contributor
timestamp: May 24, 2017, 09:02:54 pm
content: I agree with Armadillo.Here is a link for the data shett that came from, page 29:http://www.mouser.com/ds/2/792/rp102-e-844503.pdf

author: JFJ
author_rank: Regular Contributor
timestamp: May 24, 2017, 11:47:33 pm
content: Looking at the RP102x datasheet, the SOT23-5 package pin-out doesn't appear to match the "61 Y" devices pictured above:Pin 4 is labelled as "No Connection" in the datasheet, but each of the pictured "61 Y" devices has pin 4 connected to a passive component.Pin 5 is labelled as "Output Pin", but its solder pad is marked as "USB Vcc" in the second picture (the highest output voltage for the RP102x series is only 3.3V, so couldn't be the source for the USB Vcc).

author: waynebonc
author_rank: Newbie
timestamp: May 25, 2017, 12:15:37 am
content: JFJ, that is what I said after saying that he was correct. However I assumed that since these PCBs are designed and manufactured in China, someone made a "knock off" of theirs. But this can't be the case. As you already said, Pin 5 is an OUTPUT pin when in fact it should be INPUT (USB Vcc).
[Repair] Cyberpower CP1500PFCLCD UPS display - Page 1
Forum section: electronics / repair

author: usagi
author_rank: Frequent Contributor
timestamp: May 24, 2017, 12:47:11 am
content: The display on one of my CP1500PFCLCD is super dim and needs repair.Looks like an edgelit LED backlight. Voltage across K-A reads 3.9V.I really have no idea how to go about repairing this!

author: bktemp
author_rank: Super Contributor
timestamp: May 24, 2017, 06:28:43 am
content: Verify if the current is correct: 3.9V sounds wrong for two blue LEDs. If they are in series I would expect more like 6V, while a single LED would be around 3V-3.3V.If the current is ok, the LEDs are probably dead and you need to replace them. Most edgelit backlights use LED chips mounted directly on the pcb. They are almost impossible to replace, so you need to bodge some other LEDs to the display.

author: CJay
author_rank: Super Contributor
timestamp: May 24, 2017, 08:51:46 am
content: Ah, cute, it's got a backlight strip.You may be able to replace the strip with something harvested from an LED backlit laptop panel, ask your local PC repair place if they have a smashed panel you could have?
Power filter testing - Page 1
Forum section: electronics / repair

author: FrankT
author_rank: Regular Contributor
timestamp: May 26, 2017, 06:04:10 am
content: At least I think it's a power noise filter.The coffee machine at work has stopped. It doesn't power up. I can measure 240VAC going into the filter, but only about 80-90v AC coming out.It is this device...http://www.ebay.com/itm/Kondensator-Capacitor-Entstorfilter-F55-047-406-Saeco-Crema-Incanto-Magic-Royal-/300886391803Does the low voltage indicate a problem, or is that ok when not under load?

author: bktemp
author_rank: Super Contributor
timestamp: May 26, 2017, 06:13:25 am
content: It is a typical mains input filter consisting of a common mode choke and some capacitors.The resistance between input and output should be very low, between the input or output terminals it should be around 680k because of the built in discharge resistor.If the resistance between input and output is much higher, the common mode choke is probably damaged (overheated because of too much current?).

author: FrankT
author_rank: Regular Contributor
timestamp: May 26, 2017, 08:22:52 am
content: Thank you for the detailed reply.I measured terminals and they matched everything you said they would beIt turns out the wire end that I was measuring also had the power switch and a micro switch in series. It turns out the power switch has died. (480k when closed)A big thank you from everyone in the office; I will be safe working environment again when the caffeine starts flow!
HP 3611A - wrong current set pot and raised cap - Page 1
Forum section: electronics / repair

author: JustSquareEnough
author_rank: Unknown
timestamp: March 17, 2017, 12:58:22 am
content: Hello,I picked up an HP 3611A off ebay. when testing the voltage control was within spec but found that the current would only adjust to about half of spec for both the .85A and 1.5A ranges. upon further investigation it looks like r19, which should be a 10k 5 turn pot, was replaced with a single turn pot, I did not check its value! So, I'll be ordering a new pot for this unit and that should clear that up, very strange.my question though, I also see a capacitor with a raised vent, should I go ahead and replace it or should I replace the pot only and see if measurements are in spec under load?Thanks!

author: singapol
author_rank: Frequent Contributor
timestamp: March 17, 2017, 01:55:16 am
content: The cap should be replaced as it's not normal...something changed.

author: JustSquareEnough
author_rank: Unknown
timestamp: May 23, 2017, 01:05:36 am
content: I finally got around to repairing this. Turns out the pot was the right value, 10k but was not a 10 turn as it should be. So the raised and by repair time leaking capacitor was causing the issues with not getting the upper limit on the current limit control. I recorded a video and put a few pictures on my blog if any one cares to watchalthough it was pretty easy diagnostic it was still a fun repair, and it was my firstwebsite:http://justsquareenough.com/Electronics/HPE3611ARepair

author: anotherlin
author_rank: Frequent Contributor
timestamp: May 23, 2017, 08:46:12 pm
content: Hey, I just watch the video, nice !As for your question about the 35V vs. 50V rated capacitors on the schematic vs. the actual device.My guess is that when the schematic was drawn, the 470uF wasn't available at 35V or rather, they've just made a mistake, drawing 470uF instead of 330uF. For the design at hand, 330uF is probably more than sufficient, not much current is to be drawn from the +/-12 rails. Also, the AC voltage shouldn't be higher than 20VAC, so a 35V is perfectly adequate with much than enough safety margin.As for testing the current limiting, why don't you just short your DMM in ampmeter "mode" ?

author: bitseeker
author_rank: Super Contributor
timestamp: May 23, 2017, 11:01:11 pm
content: Congrats on your first repair, JustSquareEnough. Warning, it can be addictive.
Data Precision 8200 Calibrator  - Display board getting hot - Page 1
Forum section: electronics / repair

author: MatteoX
author_rank: Regular Contributor
timestamp: May 23, 2017, 03:19:37 pm
content: I would appreciate if somebody who has Data Precision 8200 voltage calibrator could check if the power transistors on the display PWB get hot. There is no need to remove the display, just touch it on the back side where the transistors are located (big tinned dots).I have recently purchased DP 8200. It had problem with few segments on the display but otherwise seems to be operational. I removed the display PWB to replace the bad driver, 74C374, and I noticed that the PCB areas around each of the power transistors that are driving anodes of the 7-segment display are brown. I powered the unit after the chip replacement (I used 74HC374 that I had in stock). Everything worked fine but these transistors get very hot - 78C if all 7 segments are on, little bit cooler (around 65C) when only 2 segments are on. When box is closed, things will get even hotter - there are no ventilation holes.I did a few quick measurements and results are shown on the attached schematics. Supply voltage on the collectors of Q201-207 is about 8.8V. Voltage drop on these darlingtons is about 4.5V. Voltage drop on 10 Ohm resistor connected to individual segments (R201-R208) is about 1.7V, that means current through each segment is 170 mA. So, the max. power dissipated on these transistors when all 7 segments are on is about 0.75W ( 4.5V * 170mA * 7 segments * 1/7 duty cycle)!10 Ohm resistors are also dissipating lot of power, 0.29W in the worst case (1.7V ^ 2 / 10 Ohm) and get very hot too.I feel uncomfortable that things are running this hot. Everything seems to be working properly but I don't understand why it was designed to stress these components so much. Any thoughts?
stern pinball Logic repair - Page 1
Forum section: electronics / repair

author: salviador
author_rank: Regular Contributor
timestamp: May 22, 2017, 12:28:41 pm
content: Hi, I'm fixing a stern pinball Of the 90's.The pinball work but I have a problem, The cpu resets.I connected my logic analyzer in the bus I noticed that the D2 is sometimes dirty, I've changed some 74 ttl logic but But I did not notice any improvementsWhy the D2 databus is dirty?

author: Andy Watson
author_rank: Super Contributor
timestamp: May 22, 2017, 12:42:25 pm
content: Are the power supplies clean?I have seen similar "random" logic changes due failing ground connections - due to poor vias and sometimes cold-joints. Check the power on the actual pins of the ICs.

author: salviador
author_rank: Regular Contributor
timestamp: May 22, 2017, 01:24:15 pm
content: Thank you Andy!My question is why only Data2 and not in other Data bit.

author: Andy Watson
author_rank: Super Contributor
timestamp: May 22, 2017, 01:48:32 pm
content: Quote from: salviador on May 22, 2017, 01:24:15 pmI think my earlier answer is still valid. However, consider also: Your logic analyzer is telling you either 1 or 0 - it may be that the signal is at an indeterminate logic level - either because it is tri-state or because it is conflicting with an output that is not properly releasing the bus.

author: stj
author_rank: Super Contributor
timestamp: May 22, 2017, 02:36:45 pm
content: so what board is it?got any photo's?most problems like this are caused by bad chip sockets.

author: salviador
author_rank: Regular Contributor
timestamp: May 22, 2017, 03:05:06 pm
content: send photo

author: Pinkus
author_rank: Frequent Contributor
timestamp: May 22, 2017, 03:47:16 pm
content: looks like you are using an Intronix Logicport. Did you try to raise or lower the logic threshold a bit? Maybe you are juuuust out of the valid range.

author: salviador
author_rank: Regular Contributor
timestamp: May 22, 2017, 05:09:02 pm
content: Quote from: Pinkus on May 22, 2017, 03:47:16 pmYer I try:3.00v2.50v2.30v2.00v

author: grumpydoc
author_rank: Super Contributor
timestamp: May 22, 2017, 07:17:54 pm
content: Some notes herehttp://www.pinballsupernova.com/images/Sega_Stern%20White%20Star%20Repair%20-%20PinWiki.pdfI presume you have schematicsAs ever, start with the PSU rails

author: DaJMasta
author_rank: Super Contributor
timestamp: May 22, 2017, 07:54:57 pm
content: Do you have an oscilloscope as well? Hook up a probe to the dirty line and a few to ones that seem to be good and see if there's a visual difference (or another working line and a rail or two). Could tell you a lot about the source of the problem.

author: edavid
author_rank: Super Contributor
timestamp: May 22, 2017, 07:59:33 pm
content: Did you try swapping the CPU?

author: Pinkus
author_rank: Frequent Contributor
timestamp: May 23, 2017, 08:37:35 am
content: Quote from: DaJMasta on May 22, 2017, 07:54:57 pmthat is probably the best way to proceed

author: salviador
author_rank: Regular Contributor
timestamp: May 23, 2017, 09:40:57 am
content: I changed 80% logic, worked for 10 minutes and then as before
[Repair] Keithley 2015 THD - THD not working - Page 1
Forum section: electronics / repair

author: usagi
author_rank: Frequent Contributor
timestamp: May 22, 2017, 11:17:59 pm
content: Picked up a used Keithley 2015 THD, everything works except the THD measurement - it never shows anything, just shows a blank.All other DMM functionality passes full calibration, and functions perfectly.The OCD in me wants to get the THD working. Sadly there does not appear to be any schematics or service manual for the THD module. Also the 2015 THD has basically zero self test functionality.Anyone with a 2015 THD have suggestions where to start? Or maybe pointers to 2015 THD module schematics or 2015 THD service manual?

author: MadTux
author_rank: Frequent Contributor
timestamp: May 22, 2017, 11:43:23 pm
content: K2015 THD board usually isn't too difficult to fix, I fixed a couple of broken ebay cheapies some time ago.Find the data sheet for all chips (AD9850, OPA275 and a couple more, follow the signal from AD9850 towards the BNC, the area with the analog switches is a bit confusing, those 2x4 opamps on the bottom are used to buffer the signal on each BNC, each opamp has 200Ohms on output to get 50Ohms on BNC).One of mine had a bad OPA275 and another magically fixed itself after swapping a couple of chips. It's also very helpful to have another working K2015 next to broken one, so you can compare signals, exchange those 17AT65 EPROMs to confirm data integrity and swap suspect chips, so you don't have to buy them only to realize the problem is somewhere else ;-)I have uploaded 17AT65 firmware here on forum, in case you need it.
Is this a fuse (from a projector lamp power supply) - Page 1
Forum section: electronics / repair

author: ElektroQuark
author_rank: Unknown
timestamp: May 21, 2017, 10:15:16 am
content: Hi,My projector stopped working in the middle of a movie. It's an Optoma HD80.If I try to start it, it tries to boot starting fans but i have a second fans stop and system powers off without any fault LED lighted.The HVPS of the lamp has this:As the label, it looks like a fuse. It's open.In the back of the PCB the pins of the fuse are conected by a series of 2.2M resistors:Is it really a fuse?If so, any advice at buying/changing it?

author: PA0PBZ
author_rank: Super Contributor
timestamp: May 21, 2017, 10:29:00 am
content: Looks like a spark gap to me.

author: cowana
author_rank: Frequent Contributor
timestamp: May 21, 2017, 10:50:22 am
content: I'd go with an 800V GDT (Gas Discharge Tube)

author: ElektroQuark
author_rank: Unknown
timestamp: May 21, 2017, 11:03:55 am
content: Can it be a TVS?

author: wraper
author_rank: Unknown
timestamp: May 21, 2017, 11:15:50 am
content: Quote from: EdoNork on May 21, 2017, 11:03:55 amno

author: Gyro
author_rank: Super Contributor
timestamp: May 21, 2017, 11:17:37 am
content: TVSs are semiconductor devices. That one is specifically a gas discharge tube, it will have much higher peak current capability (arc discharge).

author: ElektroQuark
author_rank: Unknown
timestamp: May 21, 2017, 11:47:18 am
content: So it's OK to see it as an open circuit with the meter.

author: Gyro
author_rank: Super Contributor
timestamp: May 21, 2017, 12:25:29 pm
content: Yes, if out of circuit. Your meter probably can't resolve the 22Meg resistor chain on the back, although there should be other circuit elements too.

author: bktemp
author_rank: Super Contributor
timestamp: May 21, 2017, 12:27:18 pm
content: The spark gaps in projectors are used for igniting the lamp:A capacitor gets charged until the threshold voltage is reached and the sparkgap fires, discharging the capacitor into the ignition transformer for generating many kV for igniting the HID lamp.That's why it is called a switching spark gap (unlike other spark gaps, designed for overvoltage protection).When the projector stopped working while it was on, I doubt the spark gap is the problem, because it is only necessary for starting the lamp.Did you check for other faults?I had a projector that didn't power up. After debugging the power supply without success I found the lamp door interlock switch broken off its mounting bracket, therefore it disabled the lamp power supply.
Search: Rotary encoder knobs used in Keysight InviniiVision Scopes ... - Page 1
Forum section: electronics / repair

author: _Harry_
author_rank: Contributor
timestamp: May 17, 2017, 07:05:11 pm
content: Hi guys,for repair I'm searching the OEM brand/type of that 24 pulses/360° rotary encoder with pushbutton switch, what's used as e.g. trigger knob, channel offset knob, ...The encoder shaft diameter is 6mm, length of the visible part of that black plastik shaft is 9mm (7mm flattened for the knob), no detent.One more detail:The shaft has a "groove" on the top end and sidewards on the flatten side. Almost every encoder of that kind out there has no groove on the flattened side. Seems like Keysight is using a special manufacturer ... could not find exactly that looking encoder somewhere.Any ideas?

author: carl_lab
author_rank: Frequent Contributor
timestamp: May 17, 2017, 07:44:40 pm
content: http://bfy.tw/BqnVhttp://www.alps.com/prod/info/E/HTML/Encoder/Incremental/EC12E/EC12E_list.html

author: _Harry_
author_rank: Contributor
timestamp: May 17, 2017, 08:06:19 pm
content: Thanks carl for your fast reply.First - I'm already googling since many hoursYes, the ALPS encoders of that kind look very similar.But when looking into the data sheets of ALPS EC12 series encoders I can't find one with the groove on the flatten insulated plastic shaft.(have my description above little more specified)

author: stj
author_rank: Super Contributor
timestamp: May 17, 2017, 08:24:09 pm
content: if it was Alps it would say it on it.

author: Jwalling
author_rank: Unknown
timestamp: May 17, 2017, 09:46:13 pm
content: Does the knob have a matching "bump" to fit in the slot?

author: carl_lab
author_rank: Frequent Contributor
timestamp: May 20, 2017, 10:48:42 am
content: Quote from: _Harry_ on May 17, 2017, 08:06:19 pmMaybe Bourns fits better?http://uk.rs-online.com/web/p/mechanical-rotary-encoders/7816811/https://www.google.de/search?tbm=isch&q=alps+rotary+encoder&gws_rd=cr&ei=Ph4gWZDkCsz3aJX5iKgH#tbm=isch&q=bourns+rotary+encoder&imgrc=_Does the axle look similar to that Alps?http://www.minikits.com.au/components/electromechanical/rotary-encoders/EC12E-2420801If the missing slit is the only problem, why not slit it using a hacksaw?

author: _Harry_
author_rank: Contributor
timestamp: May 20, 2017, 02:04:44 pm
content: @Jwalling: No@Carl: Yeah ... I found many encoders like that.But I'm searching for the exactly OEM one (won't risk that something doesn't work well / quality reasons)

author: Armadillo
author_rank: Super Contributor
timestamp: May 21, 2017, 06:41:50 am
content: I once dismantled and teardown a HP encoder. There are active chips with wire bonding inside much more complex than simple IR or mechanical encoder.I ended up fixing a priced encoder to a priced instrument without spending time to decipher the encodes.
Tektronix A6302 Current Probe Slide - Page 1
Forum section: electronics / repair

author: mtdoc
author_rank: Super Contributor
timestamp: May 21, 2017, 05:33:15 am
content: I recently picked up a Tek A6302 on eBay. It is in good shape overall and seems to work just fine. The only issue is that the small black plastic thumb slide comes off easily if pressure is not applied downward while sliding the probe between open and closed positions. If you look on eBay for these probes you'll see plenty for sale with this piece missing or broken. I'm hoping to avoid that fate.Any advice on how to best secure this plastic piece to the metal slide it slots into? I suspect that when new it snapped firmly into place but over time the fit loosened. It's a bit tricky to glue it without interfering with the sliding action. I already tried with a small amount of cyanoacrylate without success. The metal slide looks like it may be copper but I'm not certain.
tektronix oscilloscope MSO2024 firmware update crashed - Page 1
Forum section: electronics / repair

author: alarm
author_rank: Newbie
timestamp: May 20, 2017, 09:06:09 am
content: Hi,I have a tektronix oscilloscope MSO2024. I did the firmware update and it crashed, I have a white screen. I was advised to reinject the firmware.img file with a JTAG adapter. I have two JTAG adapter:Altera USB blaster (Chinese)Olimex ARM-USB-TINY-HCan I use one of 2 JTAG adapters?How do I proceed?Thank you
Power supply failure - Page 1
Forum section: electronics / repair

author: Gip-Gip
author_rank: Contributor
timestamp: May 19, 2017, 04:01:09 am
content: I shorted two pins on an OS-245(P)/U's power supply with my probe (on accident) and it won't power on anymore. Fuses are good, and I honestly have no clue except maybe one of the many transistors have died, or worse. Pins are P998

author: Armadillo
author_rank: Super Contributor
timestamp: May 19, 2017, 05:33:46 am
content: Is there any DC voltages at P890? +/- 25 volts. ?

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: May 19, 2017, 05:39:02 am
content: There looks to be a full service manual here with schematic for the LV supply at about p.268 in the pdf.https://ia801304.us.archive.org/20/items/tektronix_OS-245_P_U/OS-245_P_U.pdfMight help if you don't already have it.

author: Gip-Gip
author_rank: Contributor
timestamp: May 19, 2017, 12:28:55 pm
content: Yes. The problem is definitely the regulator.

author: Gip-Gip
author_rank: Contributor
timestamp: May 20, 2017, 02:31:36 am
content: All the removable transistors on the regulator test good. Should I go about testing the diodes first or the soldered transistors?

author: Armadillo
author_rank: Super Contributor
timestamp: May 20, 2017, 03:20:46 am
content: Please fix the components back. Just measure these voltages, and will be sufficient; see attached.
Tek 2440 PSU repair. - Page 1
Forum section: electronics / repair

author: grtyvr
author_rank: Newbie
timestamp: May 20, 2017, 02:44:31 am
content: A couple of weeks ago got a dead Tek 2440. I am trying to figure out what is wrong with the PSU. When I try injecting voltage at the diode in front of the primary supply the output follows the voltage. There is no threshold of 18 volts to trigger the 12v output. That case does not seem to be covered in the troubleshooting flowchart. Anyone able to point me in the right direction?
Tektronix 2465A Test 06 Fail 01 - Page 1
Forum section: electronics / repair

author: branadic
author_rank: Super Contributor
timestamp: May 19, 2017, 09:38:09 pm
content: Hi folks,after a while I wanted to use my analog scope 2465A to take some measurements. The scope was unpowered for a while.After turning on the scope the selftest stopped with test 06 fail 01. After a while of search in the web I found, that this indicates a low or high voltage level of the internal memory backup battery. I've never opened the scope and never touched the battery, so potentially an under voltage was causing this error during selftest because of the batteries age.The original 3.5V 750mAh Keeper LTC-7P lithium cell seemed to be unobtanium. However I found LTC-7PN Lithium EVE EF651625 3.6V 750mAh and ordered it immediately:LTC-7PNToday was the day of operation. After unwrapping the scope and extracting the board I was able to measure the voltage of the backup battery. It measured ~1.9V so high time to replace it.Since the memory needs to be powered during the replacement I used a 2x Mignon AA battery holder with 2x AA 1.2V rechargeable battery giving 2.4V in total and soldered the battery holder as described on:Tektronix 2465A DV Oscilloscope Memory Backup Battery Replacementto the board, before I started to desolder the original backup battery.A few careful ten minutes later the original backup battery was removed. Soldering the new battery to its place was easy going. After putting everything together and powering the scope everything worked fine without any errors. So the memory content is save for the next years. Brilliant.-branadic-
Help - Fluke 8200A - Page 1
Forum section: electronics / repair

author: Rafael
author_rank: Regular Contributor
timestamp: May 17, 2017, 12:54:46 am
content: Hello,Please, can anyone share any documentation of the Fluke 8200A? I have one, I can power on and light the tubes but read no measurements. Stuck in zeros...Or any tips on where to start?Thanks!

author: ElektronikLabor
author_rank: Regular Contributor
timestamp: May 18, 2017, 05:53:47 am
content: It's an old meter; maybe checking for broken solder joints could help?

author: dundee
author_rank: Regular Contributor
timestamp: May 18, 2017, 07:23:44 am
content: Try to clean the switches.They are often coroded.

author: Rafael
author_rank: Regular Contributor
timestamp: May 18, 2017, 11:01:02 pm
content: Well guys, thanks a lot for the tips...The switches and joints were cleaned. I have -15999 in VDC, MVC shows a blink digit, VAC don´t show any digit, OHMs switches are keeping the digits in -15999 too... When pressed AUTO, all digits are off now...For me, RIP voltmeter...Hard to find a good one...Thanks!
Help - Agilent HP 6627A - Page 1
Forum section: electronics / repair

author: Marco_Mar
author_rank: Contributor
timestamp: May 18, 2017, 08:49:15 am
content: Hi everybody, my name is Marco and I am a newcomer in this forum.I need help.I recently bought an used Agilent 6627A PSU.It has four independent outputs.OUT1, OUT2, OUT3 work fine.OUT4 is always in "UNR" state, even whitout load.I note that the OUT1, 2, 3, when the PSU starts, show about 0 V; OUT4 instead shows -0,3 V.Yesterday I opened the cabinet and I cleaned the inside from dust.Any suggestion?Thank you in advance