hybridfree/eevblog-posts huggingface dataset:
German Translation Help?? Extech 382275 = Manson HCS-3402 = Maas  HCS 3402 PSU  - Page 1
Forum section: electronics / repair

author: cinetron
author_rank: Contributor
timestamp: March 23, 2017, 07:09:32 am
content: I have a dead Extech 382275 bench top PSU and after removing the board discovered it has a couple of other names by other manufacturers. The board inside says HCS-3400 Power Board by Manson . Looking on-line I discovered it is also sold as a Maas HCS-3402. I found a video in German that discusses repairing one of these supplies but I can't follow it, and turning on English subtitles just makes it quite hilarious as the translation is so bad. Anyway at one point the person in the video I believe discusses the problem which I think are blown diodes. I was wondering if anyone who speaks German could take a quick look around the 15:30 mark and let me know if this is indeed the issue. When I measure the same diodes in circuit they appear shorted but not sure if they are or it is just surrounding circuitry that makes them appear that way. I have no schematics and it is difficult to trace the circuit? Anyway if there is anyone who could help I would sure appreciate it. I really don't want this supply to end up being unusable. Here is the link to the video.Thanks!!

author: carl_lab
author_rank: Frequent Contributor
timestamp: March 23, 2017, 07:18:04 am
content: He said, there's 2 diodes in one case, as schema shows.He tested by using a multimeter in diode test mode.What is self-explainig...Do you have more questions?

author: nugglix
author_rank: Regular Contributor
timestamp: March 23, 2017, 07:23:28 am
content: And he said that he removed the diodes prior to testing them.The left one was blown and got replaced.

author: bktemp
author_rank: Super Contributor
timestamp: March 23, 2017, 07:25:29 am
content: Around 20:00 both mosfets fail after he replaced the diode. He doesn't know if this was related to the shorted diodes, but could be.

author: Armadillo
author_rank: Super Contributor
timestamp: March 23, 2017, 09:28:28 am
content: This forum is amazingly international!

author: cinetron
author_rank: Contributor
timestamp: March 24, 2017, 12:15:13 am
content: Wow thanks so much for the help with this. I was at a loss to know what he was saying. Hopefully this will lead to a revived power supply

author: dundee
author_rank: Regular Contributor
timestamp: March 26, 2017, 10:05:49 pm
content: Hi Cinetron,i have the same (Manson branded) device here with a blown current shunt resistor.Is there a value printed on it?If not, are you able to measure the value for me?Manson is the original manufacturer. They do not provide schematics
MULTIMETER VOLTCRAFT VC650 - Page 1
Forum section: electronics / repair

author: lionelkjh
author_rank: Frequent Contributor
timestamp: March 19, 2017, 05:34:20 pm
content: Hello; I am currently restoring a multimetre voltcraft vc650, I have the schema, but I can not figure out which VDD and VSS should be, because they are not detailed (is it: -5V / + 5V ??). Can you help me? (I join the complete Shema with) Thank you for your answers

author: JFJ
author_rank: Regular Contributor
timestamp: March 19, 2017, 06:00:41 pm
content: From a data sheet for theKS57C2616CPU:VDD = 2.7V to 6.0VVSS = Ground

author: madires
author_rank: Super Contributor
timestamp: March 19, 2017, 06:02:31 pm
content: The charge pump for VSS is at the top left on page 2 (negative voltage), and at bottom right on the same page is the voltage regulator for VCC (U16, presumably 5V).

author: Armadillo
author_rank: Super Contributor
timestamp: March 19, 2017, 06:10:03 pm
content: See picture attachedVDD = +5VVCC = ~ +3VGND = 0VVSS = ~ -5V

author: lionelkjh
author_rank: Frequent Contributor
timestamp: March 20, 2017, 12:22:54 pm
content: Hello; Thank you for this information. I did the measurements. VDD is at 5v, but vss is only -3.3v. I have checked the diodes D9, D10, they are good. I checked c11, c12 (replaced), and the voltage is still -3.3v. What do you think?? Can the circuit 74hc04 (u15) be involved

author: madires
author_rank: Super Contributor
timestamp: March 20, 2017, 12:49:19 pm
content: -3.3V seems to be fine for Vss. The output voltage of such a charge pump can't go up to -Vcc. And the voltage drop by Q9 is maybe 0.2 or 0.3V, so Vcc is about 4.7V (in case Q9 is in saturation mode).

author: lionelkjh
author_rank: Frequent Contributor
timestamp: March 26, 2017, 02:56:09 pm
content: Hello, the voltage of -3.3v is not correct, it must be around -5v, it is missing -1.7v. Only the ohmmetre and diode tester parts are faulty. It is either too high or too low on a caliber of the ohmmetre. The entire circuit around the operational amplifier has been checked and checked, and there is nothing abnormal about it. An idea??

author: Armadillo
author_rank: Super Contributor
timestamp: March 27, 2017, 01:40:42 am
content: Use another meter to measure the voltage of the voltcraft at the probes, red to red, black to black.1.0 put voltcraft to diode mode - how many volt measured?2.0 put voltcraft to ohm mode - how many volt measured?I think -3.3v should be fine due to loading of the circuit.

author: Armadillo
author_rank: Super Contributor
timestamp: March 27, 2017, 02:54:03 am
content: What exactly is the meaning of this "Only the ohmmetre and diode tester parts are faulty. It is either too high or too low on a caliber of the ohmmetre."??Put a known ohm X ohm say 100 ohms or something, what is the reading?Put a know diode X say 1N4148 or something what is the reading?
DC-to-DC Transformer Testing - Page 1
Forum section: electronics / repair

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 26, 2017, 03:58:58 am
content: I have a switching power supply from a desktop computer. PSU keeps shorting one particular MOSFET and the fuse, so I pulled the DC-to-DC step-down transformer for testing. The MOSFET that keeps shorting is the one that made the burn mark on the transformer. I have continuity across all row A terminals and continuity across all B terminals and no continuity from A to B. Does this indicate a properly functioning transformer? I have reviewed the fundamentals of transformers, but I would rather ask before I conclude.

author: Armadillo
author_rank: Super Contributor
timestamp: March 26, 2017, 05:08:26 am
content: Your test is inconclusive and incorrect.Firstly identify the primary coils and the secondary coils, you can either trace from the circuit boards or if you have the service manual then refer to the schematic or refer to the manufacturer datasheet for the transformer which is the best. Identify the primary coil, auxiliary coil and secondary coils.Take thecoiltransformer out from the circuit - Measure the dielectric breakdownbetweenthe coils. This measurement should indicate infinity ohms.then you either RING the coil or measure the inductance of the coils to detect internal coil shorting that alters the inductance beyond acceptable tolerant. Primary Coil failure rate is always the highest.The answer above is limited to reply to the subject question only, specifically DC to DC transformer testing.
AWA Carphone and Tela Verta receiver - Page 1
Forum section: electronics / repair

author: Bendba
author_rank: Regular Contributor
timestamp: March 26, 2017, 04:24:58 am
content: Hi,I found a couple of interesting items at a antique shop today (I probably spent more money then I should have to buy them, $120 for the two)One is a AWA Carphone radio, very little informations on it, I don't know what voltage supply it needs or what frequency it works on.The other is a little AM receiver, in relatively good condition, the bakelite case doesn't have a crack and the knobs turn freely.Any informations about them would be useful. I'm definitely going to restore the AM receiver first. I don't know much about the radio, I will probably have to learn about dummy loads and so forth as I don't expect to be told I can put it on air.
Repairing my brand new µCurrent GOLD - Page 1
Forum section: electronics / repair

author: krautguy
author_rank: Newbie
timestamp: March 25, 2017, 08:50:14 pm
content: A few days ago I got my brand new µCurrentGOLD, yay.It works perfectly, except for that it doesn't.The on/off-switch is jerky as hell:https://bues.ch/misc/ucurrent_onoff.aviSurely this can't be by design. So there must be something strange going on with that switch.The switch is fairly easy to open, so let's do that.One of the contact sliders doesn't show much wear at all (compared to the other one). That's a bit strange. I don't know which side this slider was on, though.But let's look at the contacts. Looks pretty good....But ...... what's that strange dot there on contact 3?Let's clean it with some rubber and isopropanol.After greasing it with some silicone grease (that's what I had at hand) it works like a charm.Thanks Dave for this great tool.

author: krautguy
author_rank: Newbie
timestamp: March 26, 2017, 10:25:10 am
content: I did not take pictures while opening the on/off switch.So here are some pictures of the range switch.The required tools are:- Three needles- Tweezer
Repair HAMEG oscilloscope - Page 1
Forum section: electronics / repair

author: mpavlica
author_rank: Newbie
timestamp: March 23, 2017, 12:30:12 pm
content: HelloI have HAMEG HM604 which is in mint condition. Only couple of working hours. My dad barely used it...Anyway, I started using it, and suddenly, beam intensity is lost.When I switch it ON, i get beam with high intensity and it is wide on X axis. After second, or two, intensity is lost and I can barely see beam. Also, beam is narrow/short on X axis, covering only center of screen, about 1cm shorter from each side.Ive opened it up and first i checked PSU, all good, voltages are fine.I measure on Z board volts, and there I found a problem.When Component Tester is OFF, point where VR601/R620 and T604 are, and schematic says that it should go from 0...1.4V for DARK, i get 1.3...2.8V... And R639 voltage, that should go from +8..55V goes only up to 33VWhen component tester is ON, i get 0V at emitter of T604 and +55V at R639, but beam intensity is still low.VR601 at wiper side is OK, i get from -11,5....+11,5V so thats fine.BIAS INTENS i can adjust to have +82V, thats okay.When i switch lights off so i can see beam, i can regulate focus, i can see changes on a beam.Any ideas where to move on? I am a bit lost now...THANKS!!73 de YU7XW

author: WaveyDipole
author_rank: Frequent Contributor
timestamp: March 23, 2017, 02:03:55 pm
content: You say that VR601 seems to have the correct voltages around it (+11.5/-11.5). Do you see any variation in intensity when you operate the INTENS control? If so, then this section is probably OK, but it might be worth checking the biasing resistors in case any have drifted value - R620, R621, R622, R623, and whether R624 is open.If BIAS INTENS is at 82v as indicated then your HV output is probably OK.Have you checked voltages around VR604 as well as VR605, also the heater voltage (F1/F2)?

author: mpavlica
author_rank: Newbie
timestamp: March 23, 2017, 02:18:52 pm
content: Yes, I do see, a very small, from complete loss of beam, up to just to see it when it is at MAXVR604 and VR605 voltages are same as in manual. Heater voltage is 6,3 so thats fine.Also, resistors 620 up to 624 are okay and within specs.

author: mpavlica
author_rank: Newbie
timestamp: March 23, 2017, 02:58:13 pm
content: OK, I just took my TDS3014 to measure some signals, i used multimeter before...So, ZUP SQW from TB board is okayFirst photo shows square wave signal at D613 ANODE. Looks okaySecond photo shows signal at cathode D613 / anode D612Third photo is signal at cathode of D612.Any ideas?
WANTED: Systron Donner RS Series Manual/Service Manual  - Page 1
Forum section: electronics / repair

author: Shock
author_rank: Super Contributor
timestamp: March 23, 2017, 12:56:46 pm
content: Require the Manual or Service Manual covering the RS Series of power supplies or specifically theSystron Donner RS 160 3C, which is a 160V 3A DC supply. Lower spec model shown here.
SOAR MS-6022 Oscilloscope Repair - Can't find Service Manual (nothing, really) - Page 1
Forum section: electronics / repair

author: foton
author_rank: Newbie
timestamp: March 22, 2017, 09:02:46 pm
content: Hi!First post here.Bought a Tek 2225 (inspired by Dave's video) and it seems to need repair, because the signals are all convoluted and I can't seem to find the problem.Today I thought it would be nice to have another oscilloscope to use as a reference.Then I talked to some people here where I study and soon enough I got a very old and dirty oscilloscope from some very dark room baaaaack there. I also got a tour from the power supply facility, what was awesome!Well, thing is, this oscilloscope is really bad, the signal is all weird and stuff.Then I took it apart.Then I remembered: well I could die, better discharge the dischargeable stuff.But googling the oscilloscope model, I could not find the service manual, even the manual, really, only this ad:http://www.ebay.com/itm/Soar-Corporation-MS-6022-Oscilloscope-MS6022-20-MHZ-117V-240V-/130533750688Does anybody know a place I could search for the service manual for the oscilloscope?Thanks!Attached some pictures of itP.S.: After some minutes on, some white smoke appearde, so I turned it off

author: foton
author_rank: Newbie
timestamp: March 22, 2017, 10:27:46 pm
content: update: googling for some part number on the power supply board I found a pdf and... tadaaa: it seems to be the same (with different model name)edit: the link, if someone need it:http://www.magearu.ro/Ftp/Datasheet_3/Multimetre/Hung+Chang+OS-620.pdftomorrow I am going to investigate it furtherfeeling of the moment: will I be able to re assembly it?
Malfunctioning Behringer x1222usb mixer - Page 1
Forum section: electronics / repair

author: Saud Salaam
author_rank: Newbie
timestamp: March 23, 2017, 12:50:31 pm
content: My behringer x1222usb has stopped working. Once plugged in the main mix led lights begin to oscillates/pulsate and every other led light blinks. In addition, once I hook the speakers up it makes this beat sound that sort of sounds like a kick thats in sync with the blinking led lights. I already replaced the power supply board. What else could be my issue? What would be the best guess according to all the symptoms I've given?
PSU diagram wanted for HP 8904A XL51-5601 - Page 1
Forum section: electronics / repair

author: TheDefpom
author_rank: Frequent Contributor
timestamp: March 20, 2017, 09:35:09 am
content: I am in the process of repairing a HP 8904A, which I am doing a video for on my channel here:The smoke is from the infamous IEC line filter blowing up whilst I was testing the PSU voltages!I MAY have identified the cause of the dead power supply, Q4 which is shorted out, however I would like to try and find a circuit diagram for it just in case (I am waiting for a replacement part to arrive).All other testing I have done of components in the power supply seem to be OK (as seen in video).The various numbers on the assembly are:XL51-560108904-610017000005-01510005I have searched around and downloaded the various manuals for the unit, but the PSU is not part of the service manual, and its diagram doesn't seem to be findable online, so I am hoping that someone else has a copy, or have reverse engineered it, switchmode supplies are not exactly my strong point.
12V DC motor repair help. Car heater blower fan. - Page 1
Forum section: electronics / repair

author: wilfred
author_rank: Super Contributor
timestamp: March 19, 2017, 03:48:40 am
content: /.

author: tpowell1830
author_rank: Frequent Contributor
timestamp: March 19, 2017, 04:32:19 am
content: Do you watch Ave? This is not exactly the same but the treatment of brushed motors is Universal (hehe).

author: SeanB
author_rank: Super Contributor
timestamp: March 19, 2017, 08:08:55 am
content: Likely brushes, and check the armature for shorts or open sections. While you have it apart clean out the bushes with solvent, and relubricate with engine oil, leaving it to soak into the pores. If you can get them out put in a small bath of oil and heat till the oil is just smoking a little, and leave to cool, to draw it into the pores. Oil the felting reservoirs as well, and polish the shaft with a cloth to get it shiny where the bushes are. Do not misplace any of the washers on the shaft, and put them back in the same position and the same way round.Commutator clean with 1200 grit paper and then polish with the back of the paper to burnish, and leave like that after a degrease. Assembly put a drop of molyslip grease on the shaft as lube, wipe to a film on both sides. Brushes make sure they are free to move in the holders, and slide freely. Then put back together, apply 12V, with it held down firmly, and check it runs well and spins down without much cogging or noise.

author: drussell
author_rank: Super Contributor
timestamp: March 19, 2017, 02:25:51 pm
content: SeanB is right on the money above....Your problem is almost certainly caused by worn-out brushes. Check the windings while you have it apart anyway, clean and re-oil-impregnate the Oilite bushings (they are usually just those bushings rather than full roller bearings) and it should run fine for another decade or two.
HP 8594E ntsc setting - Page 1
Forum section: electronics / repair

author: Daxxin
author_rank: Regular Contributor
timestamp: March 26, 2017, 03:05:00 pm
content: Swapped the crt from an 8593 that supports only ntsc my configuration is set to NRM PAL i view only garbled thingssomeone has this scope can pls post picture about CONFIG steps to push correct buttons until i can restore NTSC.thanks

author: MarkL
author_rank: Unknown
timestamp: March 26, 2017, 03:50:42 pm
content: This is from an 8495E, but it should be the same:First, press the CONFIG button.Then, press side button #6 twice to get to the SYNC menu.Then:Press side button #2 to toggle between NRM and NTSC-or-Press side button #3 for DEFAULT SYNC-or-Press side button #4 to toggle between NRM and PALYou could also try plugging a monitor into the back to see what you're doing.

author: Daxxin
author_rank: Regular Contributor
timestamp: March 26, 2017, 07:41:53 pm
content: Thanks it works , i tried to make VI in labview to do that but unsuccesfil
Anritsu MG3671A: No RF output - Page 1
Forum section: electronics / repair

author: kc7gr-15
author_rank: Contributor
timestamp: March 12, 2017, 06:22:00 am
content: Anyone have any experience troubleshooting Anritsu instruments, specifically their MG3671A? I've not been able to, as yet, find a maintenance manual for it and its innards are not what I would call overly intuitive.The unit comes to life, all the controls work, all internal self-tests pass... but it has no RF out at all. Reference oscillator is fine. My first thought is the protection network is tripped, but the unit doesn't give any indication of this condition.Thoughts?Thanks much.

author: jkf1000
author_rank: Regular Contributor
timestamp: March 18, 2017, 11:38:39 pm
content: Unfortunately service material for a lot of the Anritsu product range is none existant. I have a spectrum analyser that fails self test which I am having to try and reverse engineer from just a block diagram. Try contacting Anritsu direct, you never know untill you ask. Karl

author: TheSteve
author_rank: Unknown
timestamp: March 19, 2017, 05:51:47 am
content: No RF out and no fault is pretty odd. I assume the "RF out" button works fine and the LED toggles when it is pressed?

author: PA0PBZ
author_rank: Super Contributor
timestamp: March 19, 2017, 10:06:50 am
content: If it is like others they will sample the output at the input of the attenuator, so if someone smoked that it will not know. Can you find out if there is a signal at the input of the attenuator?
Reviving dead laptop battery - Page 1
Forum section: electronics / repair

author: tooki
author_rank: Super Contributor
timestamp: March 18, 2017, 01:09:21 pm
content: My old MacBook was sitting on the shelf, and I didn't notice that its MagSafe cord had come unplugged, allowing the battery to deep discharge. The computer recognizes the battery (so it can read out the total capacity, charge cycles, serial number, etc), but will not charge it. Measuring the external battery terminals showed 0V (so presumably it must be triggered by a signal), opening the battery itself and measuring across the only two large solder joints on the board (labeled VG and VP) shows 3.8V. The whole battery is nominal 10.8V, and the six cells inside are labeled 3.7V. It's hard to be sure about the topology without destructive disassembly, but as best I can tell, it's three pairs of paralleled cells, in series, with two thermistors in between the stacks.This picture indicates two solder joints for the cell junctions:https://forums.macrumors.com/attachments/a1181-battery-board-jpg.433649/Measuring from VG to the 2/3 junction shows 3.8V (actually a few mV higher than between VG and VP), and VG to the 1/2 junction measures 2.35V. This makes me think that cell pair 1 is at 2.35V, cell pair 2 at 1.45V, and cell pair 3 at zero (it measures -43mV actually).Here's someone else's pix of the insides of this battery model:https://www.ifixit.com/Teardown/MacBook+Core+2+Duo+Rechargeable+Battery+Teardown/5173Can I wake this battery up by applying a charge voltage (10.8V?) directly to the cells for a few mins with a bench PSU, just long enough to get them above whatever the controller's threshold is? Or is that just asking to set my house on fire?

author: Jeroen3
author_rank: Super Contributor
timestamp: March 18, 2017, 01:30:14 pm
content: QuoteCell 2 and 3 are certainly not in good shape if this is true. There is a reason the battery controller disabled itself, and is not enabling when you apply voltage. You might need to change cells and reset the controller.I wouldn't mess with these pyrotechnics you put on your lap when in use.

author: tooki
author_rank: Super Contributor
timestamp: March 18, 2017, 02:39:27 pm
content: Quote from: Jeroen3 on March 18, 2017, 01:30:14 pmIn which case it's not worth it to DIY; it looks like the cells cost $12-17 each on eBay for no-name ones, so six of them is really close to the cost of a new good-brand replacement battery ($55-90). Quality cells from Conrad are $45 each.
Power switch for HP 3468B Failure - Page 1
Forum section: electronics / repair

author: xrunner
author_rank: Super Contributor
timestamp: March 16, 2017, 11:56:09 am
content: Does anyone know where to obtain one, other than another parts unit? It's fubar inside, I'm going to try to fix it but if I can't ...

author: wn1fju
author_rank: Frequent Contributor
timestamp: March 16, 2017, 12:36:18 pm
content: I've had pretty good luck with C&K switches as replacements in many HP pieces. Go to Mouser and search for "F4UEE".

author: xrunner
author_rank: Super Contributor
timestamp: March 16, 2017, 02:07:43 pm
content: Quote from: wn1fju on March 16, 2017, 12:36:18 pmThanks!I'm checking the dimensions and so far so good. I removed the original switch and took it apart. The problem with it is it's really "sticky" and won't go in and out without you pulling on it. I polished the contacts and checked it out and re-assembled it, but it still acts "sticky". I don't see why, but a new one might just be the ticket in this case.

author: cvanc
author_rank: Frequent Contributor
timestamp: March 16, 2017, 02:30:10 pm
content: Maybe you could remove all traces of old lubricant and replace with fresh?

author: xrunner
author_rank: Super Contributor
timestamp: March 16, 2017, 02:32:13 pm
content: Quote from: cvanc on March 16, 2017, 02:30:10 pmOh I did. I've cleaned and polished and re-assembled several times. It just won't work well anymore. I think we've reached the "it's plum wore out" diagnosis.

author: xrunner
author_rank: Super Contributor
timestamp: March 16, 2017, 03:43:16 pm
content: Allright then, I ordered a couple from Mouser, since they weren't expensive. I'll follow up with the repair since I started a thread. Technically, the new switch is a tiny bit higher, in terms of the center of the push rod to the top of the circuit board, by 1.5 mm, but I've checked and that won't make enough difference to matter; i.e. the pushrod will still function OK. All the other dimensions seem to check out OK.

author: xrunner
author_rank: Super Contributor
timestamp: March 18, 2017, 01:19:37 pm
content: Got the new part and installed it - works perfectly!Many thanks to wn1fju for the part reference.Yay!
Fluke 8840A doesn't go to zero - Page 1
Forum section: electronics / repair

author: ashwinsawant
author_rank: Newbie
timestamp: March 17, 2017, 04:50:34 pm
content: Hello everyone, I got a used Fluke 8840A from Ebay. It seems to be able to measure voltage, however once I disconnect the probes, it continues to show a slightly lower voltage reading and it takes a long time to 'discharge'. For example, see the attached images: Image01 shows 1.6V across a battery, Image02 taken 30 seconds after disconnecting the probes from the battery shows 1.4V and Image03 taken 30 minutes thereafter shows 1.3V! If I touch the probes to one another, the reading goes to zero as expected, but then spontaneously rises to around 200 mV.Has anyone else experienced this kind of a problem before? I am wondering where the fault might lie.

author: cncjerry
author_rank: Unknown
timestamp: March 17, 2017, 05:20:28 pm
content: short the probes and it goes to zero. Completely normal. It has to do with the high impedance input of the meter. Nothing to drain down the integrating capacitor in the ADC.

author: ashwinsawant
author_rank: Newbie
timestamp: March 17, 2017, 06:48:15 pm
content: Thank you. I learned something new today, and saved myself unnecessary hassle and expenditure. I love this forum.

author: tooki
author_rank: Super Contributor
timestamp: March 18, 2017, 08:44:55 am
content: Hahaha the asset tag that says "HP 8840A"!!!

author: mzacharias
author_rank: Frequent Contributor
timestamp: March 18, 2017, 10:21:49 am
content: To expound on this just a bit further - The 8840A input impedance is about 10 gig-ohms on DC function up to 20 volts. Voltage ranges above that are standard 10 meg impedance. For lower DC voltages you can almost consider this a "Touch-Hold" feature. If you ever find this annoying or want to defeat it, manually switch to the 200 volt range.Come to think of it - I'm not sure if the AC 20 volt range works the same - I'm guessing not...
858D v8 temp scale completely wrong - Page 1
Forum section: electronics / repair

author: pmars
author_rank: Newbie
timestamp: March 17, 2017, 05:46:46 pm
content: Just received a generic 858D (board says YH858D v8) rework station and first thing I noticed is the actual temp scale is always around 638 to 700. Temp set buttons seem to work, but the heater is all over the place. sometimes hot sometimes cold. I have tried the calibration pot on front panel but little to no change. Sometimes display shows "5-E" I have read many posts here about this model and realize this could be a hopeless battle as this one I have received is even crazier than most.I have compared wiring diagrams and all seems fine except I cannot confirm the polarity of the thermocouple and I'm not sure if this would make any difference. I am thinking about reversing the red and blue thermo wires on the handle circuit board and see what happens. Any suggestions other than "trash it" ? Only cost $29 US and ebay seller has already refunded my purchase price. He doesn't want it back!!! Thanks

author: pmars
author_rank: Newbie
timestamp: March 17, 2017, 08:04:28 pm
content: OMG... UPDATE: I just kept fiddling with this and found the problem!! Dumb luck. After much inspection with a magnifier and after rewiring the black lead to be fused and switched (instead of the white wire as manufactured) I plugged it back in to check it one more time and since the board was still exposed I wiggled the calibration pot and the up/down temp set buttons and noticed the display jumping between really low numbers like 026 and 680 or higher. Hmmmmm... I settled on the Down Arrow button as the culprit. broke it open, cleaned with an eraser, melted it back together with small soldering tip and added some fresh solder to the 4 leads.. IT WORKS!!!!!!!!!! Maybe the "pop-disc" was in crooked or a bad solder joint?Now I will get out the k-sensor for my multimeter and recalibrate this thing. YES!!!!!!

author: bitseeker
author_rank: Super Contributor
timestamp: March 17, 2017, 08:38:17 pm
content: Good sleuthing. Probably bad solder job.

author: pmars
author_rank: Newbie
timestamp: March 17, 2017, 09:30:34 pm
content: Calibration is complete, but only in the sense that it's basically a loose averag. I set the temp for 250 and get a swing from 225 to 275 as the heater kicks in and out roughly every 10 seconds. Not sure if this is normal. Seems like the circuitry could be a lot more sensitive. Wonder if there is a sampling rate that can be adjusted. The K sensor of my meter responds instantly and continuously.

author: bitseeker
author_rank: Super Contributor
timestamp: March 18, 2017, 12:49:08 am
content: The default firmware of earlier versions doesn't regulate the temperature all that well and is notorious for overshoot. I don't know if it's improved since. There's another thread about replacing the firmware/microcontroller.
Sony home cinema DAV-SA30 0uH inductor - Page 1
Forum section: electronics / repair

author: spiller
author_rank: Newbie
timestamp: March 18, 2017, 05:07:26 pm
content: Hello folks,in my old home cinema system has 2 inductors, which have leaked. The service manual (http://archivos.diagramas.mx/audio/HCD-SA30.pdf, page 103) says that they are 0uH inductors, but I can't find 0uH inductors anywhere.0uH seems bizarre to me.Anyone has any ideas, which will help me further?EDIT: Apparently the liquid is wax, which is usually dripped on power inductors to stop from vibrating. But the 0uH?EDIT: Measured the resistance of the inductor coils, 0.8 ohms - so the inductors themselves are good.Cheers,Tim

author: Rasz
author_rank: Super Contributor
timestamp: March 19, 2017, 10:07:07 am
content: what exactly is your goal? are you poking inside it because you are curious?

author: Armadillo
author_rank: Super Contributor
timestamp: March 19, 2017, 11:52:06 am
content: The inductors are for the buck converter DC to DC step down. Accordingly it should be around 100uH for 125khz switching filtering. Since you measured 0.8 ohms, so it confirmed it is not just a jumper wire but a coil/inductor as it should be. [take it as printing error then].You should be measuring the inductance or simply measure the voltage at pin 4 of each of the 3 ICs to read, 12v, 5v and 3.3v to confirm that this part of the circuit including the inductors are functioning.
Acer Laptop no display (No CPU enable signal to LCD) - Page 1
Forum section: electronics / repair

author: Bskitter
author_rank: Regular Contributor
timestamp: March 16, 2017, 02:55:21 pm
content: I am trying to fix a friends laptop.The problem is that the screen never turns on. Nothing on the HDMI either.He took it to the Repair store and they quoted him 2500 crowns (100 Dollars)They played with the BIOS chip and the screen is now iterating over White black and RGB flashes on the screen. (Seems like the Altered BIOS puts the GPU in some test mode)I bought a new bios of Ebay and received it today.I have installed it and the screen is now dark again.I have messaured the voltage for the screen and 3D3v_LCDVDD_PWR is not 3.3 volts.From what I have tested all the rails to the CPU and GPU are good.3D3v_LCDVDD_PWRNo boot beep happens either, but this could be default tho.Above is the schematic of the power on circuit. eDP_VDDEN_CPU is not going high.Can anybody recommend me something to try/test ?Laptop Model is Acer vn7-571gSchematic Available herehttps://www.google.cz/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=Acer+vn7-571g+schematic&*Byron

author: orbanp
author_rank: Regular Contributor
timestamp: March 16, 2017, 10:16:52 pm
content: Hi Byron,More info and measurements would be needed!I take you tested 3D3V_S0, that must be the 3.3V source, or rail voltage, that U5201 switches to the screen, and it is 3.3V ?Do look at it with a scope, not just with a DMM.When you had that eBay BIOS and the screen was flashing, did you look at the enable signal, eDP_VDDN_CPU, with a scope?If not, do check it with a scope!It is active high, it should have pulsed as the screen was flashing.If it was pulsing that means that the 3.3V source and the switch is working, and the CPU is not giving that enable signal for whatever reason with the other BIOS.Also, did the signals look with the scope as "proper" logic signals, going down to the ground, going up close to the 3.3V level, or they looked as something "loading down" the signal?Good luck, Peter

author: Rasz
author_rank: Super Contributor
timestamp: March 17, 2017, 04:00:59 am
content: Quote from: Bskitter on March 16, 2017, 02:55:21 pmno hdmi output = its not lcd circuit problem, its broken laptop problemQuote from: Bskitter on March 16, 2017, 02:55:21 pmand? did he pay? was it a diagnostic/scam fee?Quote from: Bskitter on March 16, 2017, 02:55:21 pmtypical cooked nvidia gpu error mode. Im guessing repair store baked your gpu to make it display somethingQuote from: Bskitter on March 16, 2017, 02:55:21 pmwas it programmed? sounds like you installed blank/wrong chipQuote from: Bskitter on March 16, 2017, 02:55:21 pmits NOT the lcd enable.what was the original problem? how it happened(spill, mechanical trauma, during operation)?are the leds working when turning it on? whats the power drain from the supply?its a shit Acer, they are cheap for a reason, your friend needs a new motherboard, or preferably new laptop
Any hope of finding service info for a Brother all-in-one printer/fax/scanner? - Page 1
Forum section: electronics / repair

author: cvanc
author_rank: Frequent Contributor
timestamp: March 16, 2017, 09:15:50 pm
content: Model MFC-J6720DW to be exact.Any help finding tech info (hell, even how to take the darn thing apart) is most welcome. It's too young to be dead... thanks.

author: PA0PBZ
author_rank: Super Contributor
timestamp: March 16, 2017, 09:48:05 pm
content: Here you go:https://www.dropbox.com/s/5f7nnwamdlu9wyz/2-%20SM-MFCJ6520-6720-6920-6925.pdf?dl=0

author: cvanc
author_rank: Frequent Contributor
timestamp: March 16, 2017, 10:07:07 pm
content: Oh wow, thanks so much. Less than an hour from request to manual. Love this forum!!
Tube question - Heathkit IO-12 'scope - Page 1
Forum section: electronics / repair

author: Paul Moir
author_rank: Frequent Contributor
timestamp: March 13, 2017, 05:37:37 am
content: Lately I've been playing around with my old Heathkit IO-12 oscilloscope; replacing capacitors and drifted resistors, adding a probe calibrator. Not doing a restoration but rather having some fun and hoping to learn something.While everything is working pretty well, I've run into a problem with the vertical amplifier. While the bandwidth of these oscilloscopes is pretty horrific, +-1dB to 2.5MHz then 5dB down at 5MHz according to the O-12 manual, mine seems even worse. I'm starting to roll off before 1MHz and down below 10dB at 5MHz. The problem seems to be in the 2nd and 3rd stage amplifier, which use a 6AN8A tube as it's active component. I'm loosing about 50% of my signal from 1-5MHz in the 2nd stage and the rest in the 3rd. The losses are moderate in the first stage and seemingly very small in the plate driver.So my question is: can an old tube loose bandwidth, or is there something else I'm overlooking? The plate voltages are a little high (+10V) as is the supply (112V). The 40uF cap is new and the resistors are in tolerance. Neither .1uF cap seems to leak at all, though the pin 2 grid voltage is a little high (0.73V). The only other seemingly relevant observation I made is this stage has some distortion at the top and when driven hard clips at the top far before it distorts at the bottom.

author: singapol
author_rank: Frequent Contributor
timestamp: March 13, 2017, 06:59:20 am
content: Tube specs. detoriate with age, if that happens it's time for a new tube.PS Normal consumer tubes are good for 2000 hrs. You may need to substitute 12BY7 with 12BH7 but compare pinouts and specs. first.

author: Ian.M
author_rank: Super Contributor
timestamp: March 13, 2017, 07:40:31 am
content: The voltages being off would all point to the tube having low emission. It looks like 6AN8A is still obtainable N.O.S. However the other tubes are probably headed in the same direction, so (assuming it has other loads) the +DD rail is likely to stay a bit high. It may be worth arranging a HV Zener string to clamp the rail at slightly over 100V to see if that makes any difference.

author: Paul Moir
author_rank: Frequent Contributor
timestamp: March 16, 2017, 09:24:07 am
content: Thank you for your advice. Ian.M yes, the DD rail only supplies this circuit; the others are pretty good. While everything is showing some wear, this 'scope is definitely moving into it's golden years. It won't be used more than a couple hours a year.I have a new... well another 6AN8A coming. We'll see how it does when it gets here.One thing I always wanted when this was my only scope was a vertical amplifier that did DC. Might be more fun than a tube swap?
IBM ThinkPad Hinge Repair - Page 1
Forum section: electronics / repair

author: steve30
author_rank: Frequent Contributor
timestamp: March 12, 2017, 10:45:00 pm
content: I just got a ThinkPad 570 off ebay. Its from around 1999 and has a Pentium II.Unfortunately the hinges are very stiff. I was dismantling the machine for cleaning, and to repair the LCD backlight, and while I was putting it back together, the hinges snapped as a result of the amount of force required to fold the screen down.I tried epoxying the hinges back together, but due to the stiffness, the epoxy wouldn't hold it. If the hinges were looser, the epoxy would have probably been fine.Is it possible to loosen up the hinges?Would it be possible to weld the hinges back together? I don't do welding myself, but I have a relative who does welding.I've attached some photos.Thankssteve30.

author: wasyoungonce
author_rank: Frequent Contributor
timestamp: March 12, 2017, 11:28:16 pm
content: The broken part looks to be a pot metal....it will not weld. I've done a few Lappy hinges before....Ebay is you best bet ora place like this

author: Bud
author_rank: Super Contributor
timestamp: March 13, 2017, 12:38:31 pm
content: Can you post a pic of the good hinge alone? I have a pair of hinges but cant remember if they were for Thinkpad or Dell that i had.

author: steve30
author_rank: Frequent Contributor
timestamp: March 13, 2017, 09:31:41 pm
content: This is a complete set of hinges:https://www.thinkpcparts.com/ibm-thinkpad-570-570e-570x-type-2644-hinge-set-05k6079-fru-12p4195.htmlI've seen one or two for sale in America, but there doesn't seem to be many here in Europe.Does anyone know of any way of loosening the hinges at all (to make them less stiff)?

author: cnqhdszq
author_rank: Regular Contributor
timestamp: March 14, 2017, 10:39:41 am
content: the best way is to buy one pair .

author: CommWiz
author_rank: Newbie
timestamp: March 16, 2017, 07:14:09 am
content: If there is enough matierial in the hing part to drill small holes and you could pin it with a steel pin. I have done this before and seemed to work well. Make sure to lubricate the hinge well so you don't pull the pin through the little metal left after drilling the holes.
APC UPS Backup Repair Question - Page 1
Forum section: electronics / repair

author: delfin2003
author_rank: Newbie
timestamp: March 16, 2017, 10:45:00 pm
content: Hey guys, I've got a APC UPS backup a while ago but have not used it too often. A couple of days ago I turned it on and it was making electrical buzzing noises every few seconds, then pause for a second and then the buzzing noise would repeat. It is loud enough to bother me so I took it apart. I believe it is a transformer that is making this noise but I also hear some very soft chirping sound from a nearby capacitor and both, the chirping and the buzzing, would start and stop at the same time. The capacitor is a 4700uf 35v and appears to be in good shape, at least visually. That being said I am not sure if it is the faulty transformer or the capacitor or maybe something else. I did not have a multimeter that could verify a capacitance so I went ahead and ordered a BM867 from tme.eu and it should be here Monday. It appears that I have to remove a capacitor before I can actually test it according to this video:. What is the best way to discharge a capacitor while it is still soldered? Would me measuring the voltage across the capacitor leads be enough to drain it while it is still soldered?

author: james_s
author_rank: Super Contributor
timestamp: March 17, 2017, 12:45:56 am
content: Usually a capacitor and connected circuit will discharge itself within a few seconds of the device being turned off. This does not necessarily apply to HV circuits but in this case the cap is only 35V so just check the voltage across it.Are you sure the capacitor is making the chirping sound? That would be rather unusual.

author: delfin2003
author_rank: Newbie
timestamp: March 17, 2017, 01:18:39 am
content: James, I am pretty sure it's the capacitor that makes a very soft chirping sound but I am not 100% sure. I guess I will de-solder the cap sometime next week and check it. I don't think there is a better way to tell where the sound is coming from...I'll post an update as soon as I check the cap
Sony professional camera repairers: Video camera PMW-F3 - Page 1
Forum section: electronics / repair

author: peteb2
author_rank: Regular Contributor
timestamp: March 15, 2017, 09:46:17 pm
content: Anyone out there who also works on such gear please? This is a charity case i admit so i am on the scrounge! I am after the loan/donation of the PCB that mounts in the handle of this camera that acts as intermediate drive for the little eyepiece viewfinder.I have taken on this particular unit as a total charity case because the video camera belongs to a TV production training school so as per usual funds are very short. Camera has had a rough life but would be a boon for the school if i can have it working again so they can wring a few more hours of use out of it. I have already rebuilt the broken side-LCD so it works and in maintenance mode the camera passes all self diagnosis tests so we are almost "THERE" but the viewfinder still refuses to come to life. I'm therefore unable to 100% say a replacement PCB will have the V/F working again so it becomes a huge ask for the school to stump up the hundreds of dollars to buy the part from Sony based on a maybe. My tests battling with a microscope so i can 'scope the flat ribbon connections feeding out to the viewfinder reveal the parallel bus video data is present and mutes when the side-LCD is opened which is what is expected. The last issue is what voltages should be present and there is no info in the Sony Service manual, no schematics etc....That's why a loan substitute PCB would be a real solution...Details:The PCB: DR-661,Sony Partcode: A-1799-078-ASo i am wonder if anyone out there who works on this stuff should happen to have a spare DR-661 they be prepared to loan me or donate to a good cause please?
BM audiolabs XR-888 missing component. - Page 1
Forum section: electronics / repair

author: Adiga
author_rank: Newbie
timestamp: March 15, 2017, 10:54:12 pm
content: Hi guys, im modding my car amp (xr-888) to use it as a home amp, somewhat good when it comes to speakers and stuff, still need lots of work with electronics.... While working on desoldering the volume potentiometers i managed to cut a part out and then step on it, yeah im an idiot with some issues regarding what my arms do, the part has 2 wires, and was covered with a blob and stuck to the chassi of the amp, ill be including images too, searched for the diagram of the amp but could not find it, the part is labled as TH01 on the board, any help with knowing what the part is an if the amp could still work without it would be great, thanks in advance.

author: Adiga
author_rank: Newbie
timestamp: March 15, 2017, 11:09:41 pm
content: I have managed to lose the part it self, the thing inside the blob looked like a small disc with a wire on each surface, the images of what i have remaining are attached, not so clear as im using a mobile cam and im posting through mobile too

author: Adiga
author_rank: Newbie
timestamp: March 15, 2017, 11:40:59 pm
content: I now know its a thermal sensor, the amp should still work, just 1 more thing, should i bridge the connection or not? Which option will cause the protection to shut down the amp?
Tektronix DPO 2024B doing weirdness - Page 1
Forum section: electronics / repair

author: andrew_c
author_rank: Regular Contributor
timestamp: March 13, 2017, 07:43:31 pm
content: First things first... this isn't my scope. An engineer came in today to examine a product of ours and as soon as he hooked his probes up to the 12Vdc rail his scope lit up, reading some 300V in a sine.It's certainly not a scope I'm familiar with. When I hook up my own scope everything reads perfectly fine!I'm sure someone on here will know exactly what's up! Please tell?

author: tautech
author_rank: Super Contributor
timestamp: March 15, 2017, 07:00:00 am
content: It looks like it has the Tekprobe interface so with a plain BNC connect probe it will have defaulted to probably whatever the Ch1 attenuation was set to, this you need check. Press the Ch1 yellow menu button and check the input attenuation matches the probe.

author: carl_lab
author_rank: Frequent Contributor
timestamp: March 15, 2017, 07:30:49 am
content: Does the screen show the correct waveform of your 12V rail? (3/4 sine)It doesn't look as a usual DC rail...
how does this circuit work? - Page 1
Forum section: electronics / repair

author: crazyhog
author_rank: Regular Contributor
timestamp: March 14, 2017, 11:40:01 pm
content: Hi guys,I came across the attached circuit diagram in the battery charging / power supply circuit of a Tek 212 oscilloscope. I don't understand this circuit.1) Normally, the primary and secondary of a transformer are separated. However, for the Tek 212, one prong of the AC inlet is connect to primary of T207 and the other prong is connected to the secondary (see green oval in pic)! The parts list doesn't have any detail on the spec of the T207 transformer. What is the purpose of T207 and how does it work in the circuit? What should I google to read more about this transformer circuit layout?2) What does R210 and C210 do in the circuit? How does it work? The manual suggest this is used for adopting to different line voltages. I don't understand how that is achieved.The attached circuit snappet is taken from the tek 212 manual. The original is herehttp://w140.com/tekwiki/wiki/2123) There is no filter cap to smooth out the voltage output of the rectifier before charging the nicad batteries BT216 and BT217 (6v each). Isn't that a problem?Please note that the s215 switch turns on the oscilloscope. Even when s215 is off, the battery charging circuit continues to charge the nicad battery (each 6v).

author: Andy Watson
author_rank: Super Contributor
timestamp: March 15, 2017, 12:44:54 am
content: T207 is a common-mode choke. Note the polarity of its windings.C210 acts as a potential dropper - limiting the current due to its impedance at mains frequency. R210 is there to discharge C210 such that there is no remaining potential when the unit is unplugged.I assume that the soothing is performed by the battery.Also note that if you are dabbling inside the unit, or with the battery, it is not isolated from the mains supply! Always unplug it before dabbling.