hybridfree/eevblog-posts huggingface dataset:
Help Please Denon AVR receiver - Page 1
Forum section: electronics / repair

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 18, 2015, 07:57:24 pm
content: Hi,I have a Denon AVR-4520CI for repair. One Output transistor was shorted. I replaced both DHCT-C3 and DHCT-A3. Both pair of .22 ohm emiter resistors are okay. Before I returned the Amp Board to the receiver, I tested both the DHCT-C3 and the DHCT-A3 with a semiconductor analyzer against another pair in one of the good Amp Boards. The DHCT-C3 and the DHCT-A3 that I replaced shows a collector leakage Icbo of 4.7 ua versis 1.3 ua on the other boards. I have attached the schematic (FHL board). Could anyone tell me why I have 3.5x higher leakage? The other resistors and transistors check okay in circuit. Could D506 be the problem?Thank you,Chuck

author: singapol
author_rank: Frequent Contributor
timestamp: August 19, 2015, 06:14:55 am
content: If you have replaced with the same identical parts then maybe the new batches have different leakage current.Do remember you are measuring in-circuit when a more accurate measurementis out of circuit. I suspect the difference may not matter.BTW DHCT A3/C3 are darlington transistors.If you suspect D506 which is a zener then you should also check corresponding zener D508. Also check the 2 diodes connected to them.You can also check Z501 which symbol look like a thermistor.Also check D503 (zener symbol?) and diode D510.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: August 19, 2015, 02:10:11 pm
content: Thank you for your help.I tested both before I soldered them in circuit - out of circuit there was zero leakage. Since the components are SMD's and my vision is not what it used to be, I wanted to eliminate as much soldering as possible. The diodes test okay in circuit but to be sure, I will try to lift one leg of the diodes or thermister if possible to test out of circuit.Chuck
PM3285A repair - Page 1
Forum section: electronics / repair

author: david69
author_rank: Regular Contributor
timestamp: August 15, 2015, 07:50:06 pm
content: Hi, I could ask You, what I should measure on this VHF scope. I have trace down from screenon both chanels, what I should have on delay line driver? because of text on crt is fine, readoutworks well, focused OK. The final Y amplifier works? Voltage on position trace A and B, turnedfront button, changes 1 to -2V on delay line driver OM547Thank You David

author: david69
author_rank: Regular Contributor
timestamp: August 16, 2015, 08:44:27 am
content: I removed POT cable from socket X1102, and I have both trace A,B on right down corner of screen,when I conected calibrator, I saw partly signal on screen.There was broken elektrolyticum capacitor C1121 +5VD digital 1000uF/10V on Intermediate unit.I guess that something wrong on this unit. The capacitor was short circuited. The POT settings areline to microproccesor unit... The reference voltage +10V uA723 is in tolerance. What should I do?

author: david69
author_rank: Regular Contributor
timestamp: August 18, 2015, 03:25:18 pm
content: I desoldered MUX HEF4053 D1101 from Intermediate unit, this switch position voltage on delay linedriver OM547 N5031 on Signal unit, I suppose that +5VA will be centre trace on screen, but whenI connect force +5VA on circuit POSA, POSB of OM547, supply goes down, 0Vso MUX hasn`tsuch current. When I disconnect +13V on OM547, I have trace on half of screenDo You thinkthat delay line driver is broken?? Than You for any idea.

author: singapol
author_rank: Frequent Contributor
timestamp: August 18, 2015, 06:31:00 pm
content: Please put your country flag so we know where you are. I believe you are not native english speaker so it's hard for me to understand what you are trying to say. In general the delay line is seldom the problem. See the service manual for a clearer understanding of the scope's construction. Hope this can help you.http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Philips/pm3285a_pm3286a.pdf
Iiyama E481s LCD monitor - Page 1
Forum section: electronics / repair

author: bigsky
author_rank: Regular Contributor
timestamp: August 18, 2015, 02:42:35 pm
content: Dave's recent video on the Samsung LCD TV reminded me to ask about this.I have two iiyama E481s 19" LCD monitors with similar faults - the screen intermittently goes blank and then comes back a second later. I've replaced the elec caps on both - some were bulging - but the problem hasn't gone away.The SMPSU is based around an SG6841S IC and produces 12v DC which supplies the backlight inverters and two further regulators to give 5v and 3v3. All rails are normally good, but when the screen blanks the 12v rail drops to a few volts, so it's either cutting out or something is pulling it down. Lots of freezer spray hasn't revealed any possibilities, and I've looked at the boards with a magnifying glass and haven't spotted any dry joints. It's strange that both have the same problem. Perhaps someone has come across it before.They're not worth much but I'd hate to scrap them as otherwise they are fine.Any ideas?

author: ElektroQuark
author_rank: Unknown
timestamp: August 18, 2015, 03:15:59 pm
content: Try to see the image with a lantern when the it goes blank. If you show images on the LCD then the problem is with the backlight.

author: Rasz
author_rank: Super Contributor
timestamp: August 18, 2015, 04:51:43 pm
content: lamps might be going badis it repeatable? can you reproduce it quickly at will? if you can then experiment with different lamps connected
Analog Oscilloscope vertical cahanels linked - Page 1
Forum section: electronics / repair

author: darkness_electro
author_rank: Contributor
timestamp: August 17, 2015, 09:52:55 pm
content: I have a problem with a tesla bm 566 oscilloscope. It had some z amplifier problems, but i sorted it out (partially). Now i have another problem. Channel a and b seem to be linked together. The position controls from a changes the position of b and vice versa. Also, when i apply both cannels is seems to sum them up. Also, both seem inverted. Moreover, it doesn't go all the way, meaning it cannot be calibrated. I apply a 4 volt signal p-p and it only goes to max 3 divisions (1v/div) When i apply a positive voltage the beam goes down. Do you have any idea how to sort this out?

author: tautech
author_rank: Super Contributor
timestamp: August 18, 2015, 03:18:12 am
content: Quote from: darkness_electro on August 17, 2015, 09:52:55 pmInvert and/or Add functions enabled?

author: darkness_electro
author_rank: Contributor
timestamp: August 18, 2015, 02:46:42 pm
content: No, they aren't, but they use ganged switches and are on a quite inacessible board. Can they be internally shorted?

author: tyguy2
author_rank: Unknown
timestamp: August 18, 2015, 02:51:18 pm
content: That sounds like a likely cause. Try testing the continuity on the switches. You may also have an issue with the scanning on the CRT.

author: mikerj
author_rank: Super Contributor
timestamp: August 18, 2015, 02:59:04 pm
content: Try giving the switches a squirt of contact cleaner followed by a good workout to remove any contact oxidation.

author: darkness_electro
author_rank: Contributor
timestamp: August 18, 2015, 03:33:15 pm
content: i tried wiggling the switches, but it doesn't seem to be working. also, in alt or chop mode i still have only one trace.
Really old laptop problem (possibly the power supply) - Page 1
Forum section: electronics / repair

author: MrZwing
author_rank: Regular Contributor
timestamp: August 15, 2015, 05:03:59 pm
content: Helloi have a CAF PROlite 286/16 laptop one of those really old "portable" computers that still require you to plug in a cable to the mains since it has no battery but a power supply built into it.Now when i have pulled every plug from the motherboard and other items and the power-supply starts without any problem.and when i hook in a floppy drive it shows no problems.now the motherboard has 2 sockets for power and its the same kind of power-cable as the floppy disk has and as soon i hook up either of the power inputs the power-supply just doesn't start but instead just lets out a ticking sound almost like a relay or like a tiny discharge.so the question is is the motherboard broken or is it something wrong with the power-supply. since i cant see anything on the motherboard that indicates something broken.MrZ

author: Ketturi
author_rank: Regular Contributor
timestamp: August 16, 2015, 12:06:25 am
content: Ticking sound from a power supply can indicate short circuit, supply tries to start but as soon as voltages raises, a protection kicks in and shuts off it again in constant loop (well this is what happens with a Toshiba T5100 "laptop"). Start to check with multimeter if any of the power pins have shorts to each other or ground. If not, then it could be the supply not handling full load due old n' dry electrolytics.

author: MrZwing
author_rank: Regular Contributor
timestamp: August 16, 2015, 02:05:33 pm
content: Hmm i will do some testing and see if i can find some kind of error.could possibly be the caps as you mentioned.
philips magnavox tv no pic or sound just thumpin thru speakers - Page 1
Forum section: electronics / repair

author: PLASTERED1506
author_rank: Newbie
timestamp: August 15, 2015, 10:09:53 pm
content: hello members, I have a Philips Magnavox model no. 25TS56/C121. it has no power when plugged in with no pic or sound but just a thumping noise thru the speakers.I took the back panel off and looking for obvious signs but don't see any.I'm think it has something to do with a fuse but can't see any on the board. Any thoughts or suggestions please!!!!
Serial Port Repair (MAX232) - Page 1
Forum section: electronics / repair

author: SirWhy
author_rank: Contributor
timestamp: August 14, 2015, 03:46:33 pm
content: I think for something to be repaired it has to work in the first place right?Anyway, I have a Replica 1 from Briel Computers that I built a few years back but the serial port has never worked on it. Now that I have a shiny new Rigol DS1054z, I flt it was time to track down the issue. A look at the schematic and it seems to me that the MAX232 on the board isn't functioning correctly. I measured the voltages from pins 2 and 6 with respect to ground and they read 4.73V and 0.1V respectively. I don't know a lot about the 232, but looking at the datasheet, this is definitely not right.Now I'm just wondering if its a simple job of lifting out the old MAX232 and replacing it, or if the caps/other parts of the circuit are the problem? I've tried to post this on the Briel Computers forum, but you need approval to post and Vince seems to have gone AWOL.Hopefully you fine people can help! Thanks

author: bookaboo
author_rank: Frequent Contributor
timestamp: August 14, 2015, 03:52:49 pm
content: I'd change the caps too on the very off chance they are faulty, time and cost is negligible to change both chip and caps. I would check that there's nothing pulling on the RS232 or TTL lines pulling the supply rails up/down (bend the pins), also check you have a nice clean supply in to start with.

author: SirWhy
author_rank: Contributor
timestamp: August 15, 2015, 02:27:57 pm
content: Checked the supply and the voltage rails, all clean, nothing unusual. Will just replace all the caps and the MAX232. I'll put them in with my next component order. Thanks
Sansui AU-X410R - Page 1
Forum section: electronics / repair

author: rahandford
author_rank: Regular Contributor
timestamp: August 14, 2015, 08:36:03 am
content: Hi GuysTrying to do a repair/restoration on the above unit and was wondering if anyone can point me in the direction of either a schematic or service manual. Many thanks in advance for any help received.

author: singapol
author_rank: Frequent Contributor
timestamp: August 15, 2015, 02:31:57 am
content: The closest I could find is AU 441 which could be similar in some parts.Good luck.http://www.eserviceinfo.com/index.php?what=search2&searchstring=sansui+au-x410r
Fluke 8050a repair - Page 1
Forum section: electronics / repair

author: Arkham
author_rank: Newbie
timestamp: August 11, 2015, 07:18:02 pm
content: Hi folks, recently I damaged my trusty old 8050a by accidentally reading high VAC (around 700VAC) on the 20VAC scale. I replaced an open internal 1/16A fuse, but now all of the meter functions are wacky.For example, VDC and VAC read low by ~10% and resistance measurements in all ranges just dance around.I do have the service manual (attached), but before I try the individual troubleshooting tips, might there be something more obvious which would be affecting all of these features?I'm comfortable with electronics but have not serviced a DMM before.Thanks so much for reading.http://assets.fluke.com/manuals/8050a___imeng0200.pdf

author: vindoline
author_rank: Unknown
timestamp: August 11, 2015, 08:18:05 pm
content: Hi, my guess would be that you fried the 3 430 volt varistors used as input protection. I've done that before on my Fluke 8060A when measuring HV. They are normally high impedance, but when they go, they go low impedance. This leads to all kinds of squirrelly behavior. They are marked as RV1, RV2, RV3 on the schematic you supplied. $0.86 each. The Mouser part # is: 576-V430MA7B

author: Arkham
author_rank: Newbie
timestamp: August 11, 2015, 08:36:45 pm
content: Indeed, the first two measure ~20ohms, and the third 10MohmsThanks so much for the tip and part #I will update this thread when I get them installed

author: Arkham
author_rank: Newbie
timestamp: August 17, 2015, 09:10:29 pm
content: Following up for posterity --Replaced the three varistors, and R2 which had gone open.Working great once again!Thanks for the help!

author: vindoline
author_rank: Unknown
timestamp: August 18, 2015, 12:35:13 pm
content: Great news
HP 6235A Repair - Page 1
Forum section: electronics / repair

author: liquibyte
author_rank: Frequent Contributor
timestamp: August 14, 2015, 03:32:05 pm
content: Does anyone have the service manual for this and could upload decent images of the component locations and schematic? I'm trying to repair one and really can't see the numbers on the schematic from the downloaded version. The component locations diagram is legible for the most part but the schematic is a mess.I've also got an extra 2K resistor across CR25 that doesn't show in my version which I'm curious about. I'm getting -16V at TP1 and -28.7V at TP7. R6 is TP1 so I've found that, R2 I can't identify on the component locations, R1 is the pot for the voltage on the panel if I'm not mistaken. I think this might be a bad or dirty pot because the voltage will max out at both ends of the range but jumps around oddly while being set somewhere in the middle.Edit: I just pulled the 18V pot out and it's bad so I'm going to put in a 10 turn 10K I have sitting here. If anyone does have a service manual, I still wouldn't mind a nice clear picture of the schematic and component location pages if you wouldn't mind.
BK Precision 1627A DC Power Supply - Relays not firing - Page 1
Forum section: electronics / repair

author: epakai
author_rank: Newbie
timestamp: August 12, 2015, 03:10:04 am
content: I bought this 1627A as a "powers on untested" unit. It is a single output 30V 3A DC supply with constant current/voltage controls.I started out checking the bridge rectifier, but this was cut off from the transformer by some relays. Pulling this main board (pictured below) I checked the voltages on the main taps seeing 8V and 18V.Connectors counter-clockwise from bottom left:4 main taps / Main bridge Rectifier / 20V tap going to diode bridge on board / Slave/Master switch / Front Panel connector / Large capacitor / Main transistor sense linesSince the transformer was working and I saw no other apparent damage I tested the relays with the board disconnected and they clacked normally. I reconnected the board and powered the supply. Fired one relay manually using a second supply and the power supply was working.I didn't do any testing under load, but the full voltage range was available.Since then the relay firing has been intermittent. It seems to work for a while even if the supply has been unplugged, but once it fails I haven't been able to get it working without using a second supply to manually close a relay.I understood enough about the linear supply to follow that path, but I feel mostly at a loss when it comes to troubleshooting any logic controlling these relays. I have no schematic.

author: singapol
author_rank: Frequent Contributor
timestamp: August 13, 2015, 03:36:57 am
content: If the power supply is intermitant, it could be pcb track/contact problem.Check the solder side for leadwire cold solder joints or cracks ( use of magnifying glass is helpful and bright lighting) . Trace the relay solenoid wiring trace, that will give you some idea what it is using to trigger them.Could be logic signal and amplification to energise solenoid.Good luck.
Schematics for HP 33321RK step attenuator - Page 1
Forum section: electronics / repair

author: wedge
author_rank: Contributor
timestamp: August 10, 2015, 12:16:32 pm
content: Hello guys,I'm looking for the schematics of this rf attenuator.It's non working, and I'd like to check at the it before removing all screws and solder around the solenoids.I search the net, but I only got the light manual..Thank you!Regards!

author: tomlut
author_rank: Regular Contributor
timestamp: August 11, 2015, 12:36:37 am
content: Did you see this repair, no schematic but a lot of detail:http://ve2azx.net/technical/HP_StepAttenuatorRepair.pdf

author: wedge
author_rank: Contributor
timestamp: August 11, 2015, 01:49:10 pm
content: Hello,Yes, i had a look at it, but my model is different.I have no problem with attenuation, my problem is I think is on the pcb (no switching and some ICs are very hot...).Anyway, I managed to remove the pcb from the solenoid without breaking any pin (at first glance, it looked very weak..)I can see now the traces and vias, i'll make my own schematic.Thanks!
Repair HP 53131A - Page 1
Forum section: electronics / repair

author: smgvbest
author_rank: Unknown
timestamp: August 11, 2015, 01:44:36 am
content: I picked up a HP 53131A off ebay really cheap. It had major case damage and seller only listed as powers on.I took a chance on it hoping I could repair the damage as seen in the photo'sI received the unit and did a fast power on test and got ALL: PASSEDSo I started testing it out and every test I thru at it it passed. including some very low amplitude signals and up to 2.1Ghz. Much to my surprise it had the 100Mhz - 1 GHz option installed but only the basic Timebase.I hooked it up to a GPSDO 10MHz signed for it's external reference and hooked a Rb source to Channel 1 and it read out very good. So after testing it thoroughly I went to repair the case which while dented pretty good I was able to re-work the case to square, replaced the rear bezzle, added the bumpers and handle and it's now working quite good and even look quite good. It is lacking a ovenized time base so I will be adding one of those soon.Here's pics of the repaired unit measuring a Rb sourceCan't fully see how the case is repaired but it is.I'm very happy and for $125 with shipping I've got a nice counter.Also, I do have 2 HP 5316B's I've listed on eBay.They are both working, one has Options 03 & 04 the other has no OptionsI'm sure the could use a better cal than I did to them but they are functional if anyone is interested.This is the one with Options 03/04 installedhttp://www.ebay.com/itm/231649468563?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1586.l2649And this is the one with no optionshttp://www.ebay.com/itm/231649450133?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1586.l2649
help identify smd component - Page 1
Forum section: electronics / repair

author: Daxxin
author_rank: Regular Contributor
timestamp: August 15, 2015, 09:54:32 am
content: what rf transistor this , separating the output from circuit i get 3,1 ohm between this pin and gnd ..thats regular?

author: andybarrett1
author_rank: Regular Contributor
timestamp: August 15, 2015, 11:02:21 am
content: Looks like a MAR6 or MAR8 type device...Can you tell us a bit more about the CCT.BRAndy

author: Daxxin
author_rank: Regular Contributor
timestamp: August 15, 2015, 11:50:58 am
content: thanks for reply , this is IF AMP / LPF stage of anritsu spectrum analyzer , have no output from this stage

author: MagicSmoker
author_rank: Super Contributor
timestamp: August 15, 2015, 12:24:13 pm
content: It's not a MiniCircuits MMIC because the input and output traces are reversed (MiniCircuits marks the input with a dot). The most likely candidate I can come up with is a GaAs RF MOSFET, part # ATF-10736. In any event, the resistance between that pin and ground should not be so low.That said, cutting through the input trace to make that resistance measurement was a bad move, as the trace is designed to act as an impedance matching network at high frequencies (>1GHz). Thus you can expect degraded performance (higher noise floor, more spurs, etc.) even if replacing this part solves the problem.

author: Daxxin
author_rank: Regular Contributor
timestamp: August 15, 2015, 01:18:59 pm
content: thank you for answer i think is that the component ..alredy ordered.
Can anyone identify this type of connector? - Page 1
Forum section: electronics / repair

author: cozza
author_rank: Regular Contributor
timestamp: August 06, 2015, 11:29:27 pm
content: Hi all. I have been requested to make up a couple of cables for a repair job.I do not have the cable in my hands yet but hopefully someone will be able identify these connectors, possibly a Molex type, but I am not sure. I have been told the equipment is between 10 and 14 years old.Any help is appreciated! I'll post some better pics when the cable arrives.Thanks!

author: dr.diesel
author_rank: Super Contributor
timestamp: August 06, 2015, 11:32:06 pm
content: Sorry, but I don't see any picts attached?

author: cozza
author_rank: Regular Contributor
timestamp: August 06, 2015, 11:34:50 pm
content: oops, sorry the attachment didn't stick. Here's another view.

author: dacman
author_rank: Frequent Contributor
timestamp: August 07, 2015, 03:15:19 am
content: Possibly a SMS24P1 with SC16M1TK6 and SM16M1TK6 contacts. A SMS24PDH1 comes with a strain relief.

author: cozza
author_rank: Regular Contributor
timestamp: August 07, 2015, 09:53:50 pm
content: Thank you! That looks like the one.. And the best part, readily available...
Samsung SyncMaster T19B300 Repair - Page 1
Forum section: electronics / repair

author: walterharriman
author_rank: Newbie
timestamp: August 03, 2015, 05:05:50 pm
content: I recently acquired a Samsung SyncMaster T19B300 18.5" TV monitor, completely dead - not even any life from the LEDs under the capacitive front panel buttons. Opened it up (yes, I understand about SMPSU voltages and dangers, though I have done little work on them - I have been discharging capacitors safely and using a Fluke meter) and followed the First Rule of Troubleshooting - tada, apparently no output, except for one rail which was under voltage!Removed the PSU and looked in more detail. First of all, recapped it - being a Samsung TV, I'd probably have to do it eventually anyway - and tested again. Still same as before! Next, tested more components in detail. Found a Schottky diode which was open both ways at position DM861 on the board and replaced that with an equivalent part (checked datasheets) - still the same! I can't find any other obvious potential points of failure (obviously fuses etc are good), and can't find anything on these symptoms - the person who gave the TV to me said it just randomly wouldn't turn on one day.The bridge rectifier is giving out a steady 335V, whilst Vamp, B5V and B13V are all completely dead. A5V holds at around 3.68V, whilst Vled is at 0.95V. I have noticed the P_ON and B_ON pins in the power connector - this could be a PEBKAC on my part, but might it be necessary to short one of those pins to ground or A5V, ATX style, to bring the PSU up?Thanks guys!Images:P.S. I haven't bothered cleaning the flux residue off the board because I'm still working on it. Also, my iron sucks.

author: tautech
author_rank: Super Contributor
timestamp: August 05, 2015, 03:13:31 am
content: How's this going?

author: walterharriman
author_rank: Newbie
timestamp: August 06, 2015, 11:00:42 am
content: I'm beginning to wonder if there might be an ID10T error here. I don't pretend to be an SMPSU expert, but there is no logic on the board that could communicate with the digital board to receive a power-on signal (the single IC on the bottom is a MAP3204 4-channel LED driver for the backlight). Maybe P_ON is "power on" and B_ON is "backlight on"? Do you think shorting one or the other to ground might bring the supply up - I see around 2.2-2.3V on P_ON with the meter.

author: fluxcapacitor
author_rank: Frequent Contributor
timestamp: August 07, 2015, 02:00:38 am
content: can you recheck your solderind to the left of capacitor c966 underneath .
Neo Geo with blown CPU, would a 68SEC000 have any compatibility problems? - Page 1
Forum section: electronics / repair

author: Mechanical Menace
author_rank: Super Contributor
timestamp: August 04, 2015, 05:40:57 pm
content: Title says it all really. I'm fixing this for a friend whose attempt at fixing it went wrong. He'd rather not cannibalise another console for the part and TBH I don't want to give up my Mega CD so he can have his AES... Yeah enough rambling, does anyone know if there's any compatibility problems between the static core 68000s I can still buy from Mouser and the original dynamic core ones?Thanks.

author: Gribo
author_rank: Frequent Contributor
timestamp: August 05, 2015, 11:08:32 am
content: The first page of the datasheet says it is a direct replacement, with code compiled for the 68EC000 running without a change on the 68SEC000.That being said, console games tend to do tricky things with their CPUs which might cause problems with this variant.

author: Mechanical Menace
author_rank: Super Contributor
timestamp: August 05, 2015, 01:47:00 pm
content: Quote from: Gribo on August 05, 2015, 11:08:32 amThat's what I was thinking, and I'm pretty certain even if their was a revision of the 68K that had "undocumented" features that were later fixed it would have been long before the Neo Geo came out. But tbh it could be fun finding out if and how anything is broken.Thanks.

author: Grapsus
author_rank: Regular Contributor
timestamp: August 05, 2015, 02:34:27 pm
content: I have a broken MVS, it was totally beyond repair and I already took a few chips out of it to repair other units. I'll post the exact part number of the CPU if you're interested.

author: Unknown
author_rank: Unknown
timestamp: August 05, 2015, 02:36:28 pm
content: I have a partial working ( no audio but video is perfect) MV1B if you are interested.

author: Mechanical Menace
author_rank: Super Contributor
timestamp: August 06, 2015, 03:03:46 am
content: Quote from: Grapsus on August 05, 2015, 02:34:27 pmThe one I've got here was a HD68HC000PS12 so will have to bodge an adapter if I go through Mouser. Have found a Motorola 12 mhz part on ebay I'm going to risk first though.Quote from: exapod on August 05, 2015, 02:36:28 pmI might PM you about that.

author: marshallh
author_rank: Unknown
timestamp: August 06, 2015, 03:32:17 am
content: The "no audio" problems are usually caused by leaking batteries eating through the Z80 bus (sound cpu). Some work with an ohmmeter can usually find the problem(s).If you need a 68k you can just buy one off ebay for $10.

author: Unknown
author_rank: Unknown
timestamp: August 06, 2015, 08:56:36 am
content: Quote from: marshallh on August 06, 2015, 03:32:17 amThe no audio is caused by a blown amplifier, the board was in an old cabinet with a shorted speaker.
Farnell fg3 with output problem - Page 1
Forum section: electronics / repair

author: Deathwish
author_rank: Unknown
timestamp: July 29, 2015, 01:53:24 pm
content: Attached is what i think is the relevant part of the diagram.After turning it off for a day or so and then turning it back on there is no waveform output. However if I lightly touch VT4 it will output as normal, I don't think it is the board , a break on a trace or such as I can hold the board from the back and it will still do it, I can't see a dry joint or the likes and the traces dont move when it is touched. I did consider, or wonder if it was a capacitance problem with C8 as well but not anymore, it still does it when i use a plastic trimming tool and touch VT4. I would rather not have to remove the transistor but thought I would ask what you think anyway.

author: Deathwish
author_rank: Unknown
timestamp: July 29, 2015, 03:47:52 pm
content: It was VT4, they sit on top of little plastic formers, it seems that the leg to base was corroded and snapped at the body of the transistor.

author: Deathwish
author_rank: Unknown
timestamp: July 31, 2015, 09:56:07 am
content: Just so you can see what it looks like.

author: Deathwish
author_rank: Unknown
timestamp: August 05, 2015, 11:48:58 am
content: So, my rebuild of this is nearly finished, i had to sort out the output, rebuild a case it came in as it had screws inside to hold the board in that were loose as they were too long, and the pot is off centre and the knob on the pot turns ellipticaly and obscures the numbers on the front panel.I have a new knob and pot to go in but am waiting for solder to come. Once it does I will then post some pics of it back together. I then need to get some of that black sticky covering stuff to go over the case top.

author: Deathwish
author_rank: Unknown
timestamp: August 05, 2015, 01:03:39 pm
content: Excuse the state and clarity, only have a phone. Nice new Pot and Red knob and I can see the digits now, the inside was a bit of a spaghetti junction on the mains input wiring so i sorted that out and will cable tie them up inside . It is now fixed and works first time
Tektronix fg502 Repair - Page 1
Forum section: electronics / repair

author: Johnny10
author_rank: Frequent Contributor
timestamp: August 04, 2015, 03:40:10 pm
content: Anyone have a location for FG502 Service Manual?

author: papou_79
author_rank: Newbie
timestamp: August 04, 2015, 04:10:18 pm
content: Hello Johnny10,You can download the service manual for this address:http://w140.com/smb/FG502_SM.pdfRegards,papou_79

author: tautech
author_rank: Super Contributor
timestamp: August 05, 2015, 02:54:12 am
content: Quote from: papou_79 on August 04, 2015, 04:10:18 pm@ papou_79Welcome to the forum.Great way to start, helping others.
Yamaha O2R repair - Page 1
Forum section: electronics / repair

author: Rachie5272
author_rank: Regular Contributor
timestamp: July 20, 2015, 06:05:32 pm
content: I'm trying to fix a Yamaha O2R mixing board. One day, it simply decided not to turn on. Probing around revealed the obvious problem: one of the +5 V rails is dead. Visual inspection revealed a scorched transformer connector.The device uses a linear power supply. The two blue wires in the image go to one of the secondary windings of the transformer. The respective PCB header leads to a bridge rectifier, then a big 4 A linear regulator. The transformer reads around 9 VAC, with or without the plug connected. The DC output of the rectifier reads less than a volt. Nothing heats up as far as I can tell.I tried injecting 5 V with a bench power supply, but it still doesn't work. A relay starts clicking, but nothing else. The logic chips only get about 2 V, leading me to think there might be a short somewhere.Any ideas? I have the service manual with schematics, but it neglects things like test points, voltage readings, or troubleshooting.

author: poot36
author_rank: Frequent Contributor
timestamp: July 22, 2015, 04:01:49 am
content: I would start by checking the resistance between ground and the 5V line on all of the caps as well as the chips that use this line. It should help you find the area of lowest resistance and then you can start removing components to check them individually for shorts. How much current does it draw when you have it connected to your 5V bench supply? If it is more then what the regulator can put out then that is a problem. If you can remove the board and check the back side of it for damage that would help as well. Also if possible disconnect any other boards from the main board to rule them out as a problem.

author: Rachie5272
author_rank: Regular Contributor
timestamp: July 22, 2015, 05:40:52 am
content: I found the problem. The transformer winding is bad. It confused me, because it shows 9 VAC even when connected to a load. Injecting power at the transformer connector works. The original transformer is a custom multi winding toroidal, so I'll have to add a second one. It's a good thing there's so much empty space inside.

author: Anks
author_rank: Frequent Contributor
timestamp: July 22, 2015, 03:53:48 pm
content: I repaired one of these awhile ago. Much different type of repair and just be glad you didn't have to take the entire thing apart. Here is a link just in case you fancy a look.https://krisanks.wordpress.com/2013/06/03/repairing-a-o2r-digital-mixer/

author: Rachie5272
author_rank: Regular Contributor
timestamp: August 04, 2015, 06:07:25 am
content: I fixed it. As it turns out, the transformer was fine all along. The only problem was a bad connector. I measure the voltage from the top of the connector, which explains the anomalous reading. I guess I needed to be a bit more thorough.
Sony smps standby circuit - Page 1
Forum section: electronics / repair

author: mikesradios
author_rank: Newbie
timestamp: July 30, 2015, 11:55:55 am
content: I'm taking a look at the power supply in this Sony HCD-FC9 DVD player for a friend... it sits in standby mode, but won't power on. Been testing voltages, found low Vcc across the board. There's a 20v regulator (Q905) off the primary that continually powers the switching IC (IC901)... only measuring 14vdc at pin 4 instead of 18.1. On Q905 the voltages are 0.7-1.0-1.0 vdc. (Note: schematics are linked below. I am measuring to the correct ground when on primary vs secondary)On the secondary side (I know I should wait to get the primary working correctly) the Vcc rail that should be 15.8vdc is only 6.6vdc. So some part of the switching supply is working, however certainly not up to spec.Although I'm familiar with the switch mode part, I'm a bit lost on is the purpose of D919 and D920 from line/neutral to the Vcc pin of IC901. Voltages at PC902 (opto at primary) are correct at 2.9 and 1.9 vdc.I'm thinking IC901 is probably okay if it will do some level of switching, but I don't see what else would load down Vcc from the 20v regulator. C914, C901 are fine. Doesn't seem that the NPN Q905 itself is shorted.The main filter caps are all Rubycon, no leakage, and B+ off the bridge is healthy at 163vdc.Any thoughts or suggestions are greatly appreciated!-MichaelSchematic:http://s1179.photobucket.com/user/mjh850830/media/Sony%20HCD/ps%20schematic.png.htmlP/S block diagram:http://s1179.photobucket.com/user/mjh850830/media/Sony%20HCD/ps%20block%20diagram.png.htmlIC 901 block:http://s1179.photobucket.com/user/mjh850830/media/Sony%20HCD/IC901%20block.png.html

author: mikesradios
author_rank: Newbie
timestamp: July 31, 2015, 11:07:43 am
content: Solved this one last nite... the problem turned out to be C914, filter on the standby supply rail. 47uF measured at half its capacitance value.
Overtemperature (or something) in Epson Powerlite Home Cinema 3020 projector - Page 1
Forum section: electronics / repair

author: CHexclaim
author_rank: Regular Contributor
timestamp: July 30, 2015, 11:19:18 pm
content: Hello all,I need to solve a problem with an Epson Powerlite Home Cinema 3020 projector.The symptom is that sometimes, after running for a couple of hours, it shuts down. The behavior is not always exactly the same but it seems to be something related to overtemperature. Sometimes, after shutting down the fan runs for a while and stops, sometimes it stays running indefinitely. Also, the Temperature light and the Light lamp blink together or sometimes only one of them.It is difficult to explain because it happens sporadically and most of the times it is a third person that tells me what happened and what he/she observed. The lamp of the unit has relatively little use.The troubleshooting section of the user manual does not help. I do not have a service manual which will be of great help, as any comment of similar experience anyone could contribute.Thank you a lot,Charlie.

author: amyk
author_rank: Super Contributor
timestamp: July 30, 2015, 11:42:30 pm
content: Clean the dust out of it.

author: CHexclaim
author_rank: Regular Contributor
timestamp: July 31, 2015, 12:11:33 am
content: Thank you for your comment.I forgot to mention that I have already replaced the air filter with no results. Also, looking from the outside the projector looks pretty clean inside.I will open it tomorrow and let you know if cleaning it solves the problem; I wish it will.Thanks, CH
Kenwood A-34 Amplifier - Page 1
Forum section: electronics / repair

author: rahandford
author_rank: Regular Contributor
timestamp: July 30, 2015, 09:37:41 am
content: I am trying to repair the amp (from landfill) and have some strange problems. I was wondering if someone could just check my logic.Observations so far:The R channel is working but L dead.A signal (say on Aux) is audible on all inputs.So far I have discovered:The non working channel has a signal as far as the input on IC3 but no output.When power is applied IC3 has the signal on all outputs.Conclusion - remove and replace IC3.What I don't understand is the unit has two jumpers to take the selected signal out of the unit and return it (EQ outputs) but if I remove the jumper the signal is still present on the input phono connector - how can this be? Could anything else on the input be shorted.All comments greatly received - I feel as if I am missing something obvious.Any help would be much appreciated.Roop

author: rahandford
author_rank: Regular Contributor
timestamp: July 30, 2015, 09:55:11 am
content: Just reading through this I think that I may have found the problem on pin 8 of IC3.Will keep you posted.
SDS1102CML LCD 26 pin - Page 1
Forum section: electronics / repair

author: gafbich
author_rank: Contributor
timestamp: July 20, 2015, 05:21:39 pm
content: Tell me what model screen SDS1102CML ordered the screen on the appropriate pinouts (connect - works) but a short trail (very short) does not reach the connector!

author: tautech
author_rank: Super Contributor
timestamp: July 21, 2015, 05:57:18 am
content: Quote from: gafbich on July 20, 2015, 05:21:39 pmDo you mean the 2 conductor LCD backlight power cable?OEM installation has an extender lead from the PSU to a position on the chassis that the LCD backlight cable can reach.Have you lost it?

author: gafbich
author_rank: Contributor
timestamp: July 21, 2015, 06:35:57 am
content: lighting connector that's all right, but the trail to connect to the main board is short, I can throw a video, it will be seen my trail!https://docs.google.com/file/d/0B_dQmKARz4hfSlhtU01yY1dlTXM/edit?usp=drive_web

author: tautech
author_rank: Super Contributor
timestamp: July 21, 2015, 08:04:22 am
content: It seems the ribbon cable for your LCD is too short.I suspect the LCD is the wrong one for your scope.Your are correct, it should be longer than the one you have.Return it to your supplier and get the correct LCD.You have removed the front panel labels so I expect your scope is a rebrand of Siglent SDS1102CML.What is the brand of your scope?

author: gafbich
author_rank: Contributor
timestamp: July 21, 2015, 08:41:05 am
content: Siglent SDS1102CMLI have a body and iron frame Siglent SDS1102CMLhttps://drive.google.com/open?id=0B_dQmKARz4hfM2ptbWM1aDF2WHc

author: tautech
author_rank: Super Contributor
timestamp: July 21, 2015, 09:05:55 am
content: The LCD is the wrong unit, it must be replaced with the correct LCD with a longer ribbon cable.Who is your local Siglent supplier?

author: gafbich
author_rank: Contributor
timestamp: July 21, 2015, 10:51:11 am
content: If you got some markings LCD, enter!

author: tautech
author_rank: Super Contributor
timestamp: July 30, 2015, 07:32:50 am
content: Here's a link to another thread with a display problem:https://www.eevblog.com/forum/repair/repair-siglent-sds1102dl/msg720259/#msg720259Read carefully, it seems there is a small PCB that interfaces between the ribbon cable from the motherboard and the cable from the LCD.Sorry I was not aware of this PCB as I had not had the LCD removed from any SDS1000 series units I have worked on.This fixes your problem with the LCD cable being too short.Have you got the interface PCB?
No Sound from Low Side Speaker on Panasonic Shelf Unit - Page 1
Forum section: electronics / repair

author: Nick B
author_rank: Newbie
timestamp: July 30, 2015, 03:04:57 am
content: Hi all. I am a noobie with electronics. It's kind of a hobby for me and I'm good with fixing things electrical/mechanical, but just starting to get into the word of real electronics. Anyway I have a 1999 or 2000-vintage Panasonic SA-AK25 stereo shelf receiver. It's worked fine until recently it's started acting weird. A year ago I could tell when I opened the CD-changer the servo motors didn't seem to have the spunk they did (seemed weaker), same with the servo releases for the tape decks. It worked fine until just a few weeks ago after replacing the return spring for the CD-changer door. The left and right low-side channels (for the 6" speakers-there are 3" and a 6" speaker on each box) stopped working. The high side works fine for both channels (L & R), but not the low side. I can plug the low side leads (2 leads come out of each speaker box) into the high side and the 6" speakers work fine, there is sound coming out, but not on the low side. I opened the case and inspected everything as good as I could without taking anything apart. Looking at the service manual, I am mostly interested in the power amp PCB (has the transformer(s) diodes, big caps, transistors, resistors) as the speaker outputs run off it. The unit itself works fine- it powers on, the relay clicks, FL display comes up, CD changer works fine, radio works, and there's sound from the low side speaker outputs. Any ideas? Suggestions on where to start digging in and checking components, voltages? What should I test and how? I have a multimeter, soldering iron, and basic electrical tools. I attached a picture of the suspect boards.Thanks a million guys.
Used car, internal dome light 12866 philips 12v 10w not working - Page 1
Forum section: electronics / repair

author: matrixofdynamism
author_rank: Regular Contributor
timestamp: August 02, 2015, 05:47:43 pm
content: So this is about the internal light of my new used car. It does not work.I used my fluke meter to measure the voltage on the terminals of the bulb socket in the car interior. With the bulb inside the socket, I get 0V. With the bulb removed I get 4.3V. The bulb itself is a "12866 philips 12v 10w". I have connected the bulb to my bench power supply and powered it from it. The bulb is not defective. I noticed that perhaps because it draws a lot of current, the voltage on the power supply output drops.I had expected that perhaps there is a problem with the fuse as I have come across on the internet. But if the problem was with the fuse, then I would not expect any voltage on the car internal bulb socket with the bulb removed where I get 4.3V. What could be the problem?

author: SeanB
author_rank: Super Contributor
timestamp: August 02, 2015, 06:35:38 pm
content: Most interior lights have an ability to be turned on with the doors closed. If it does then the door switches are faulty or disconnected. Have you tried opening all doors to see if it is not just the one door? Have you looked in the owner's manual and checked the interior light fuse, which often is shared with the internal accessory socket/ cigarette lighter circuit, and a blown fuse will lead to this, especially if it has just left a conductive metal vapour that will still allow voltage into the high impedance of the meter but not the low resistance of the bulb.

author: SL4P
author_rank: Super Contributor
timestamp: August 02, 2015, 11:06:28 pm
content: Consider also that many cars in the last 15 years have had delayed/dimming interior lights.Look at the bulb voltage with a scope rather than a DMM to see if there is a waveform rather than a simple voltage.Look for the PWM controller under the dash, or in newer cars, it may be part of the body computer.
Firmware for Solartron 7060 multimeter - Page 1
Forum section: electronics / repair

author: giosif
author_rank: Frequent Contributor
timestamp: July 28, 2015, 03:54:29 pm
content: Hi,It's a long shot, but I thought I'd at least try: anyone happening to have the firmware file from a Solartron 7060 multimeter?After many attempts to troubleshoot and fix this meter, I was finally able to confirm what I began to suspect after a while: the EPROM chip has failed (get different results with subsequent reads with my programmer/reader).Thank you!Regards,George
TV power Board 'vd' diode reference designator - Page 1
Forum section: electronics / repair

author: electronicskidney
author_rank: Newbie
timestamp: July 28, 2015, 04:43:31 pm
content: Hello, I am testing a TV power board and I was going through the Diodes but some of them have a 'vd' reference designator. Im not familiar with this designator and was wondering if anyone could help me out. Also they seem to behave oddly when I test them with my multimeter I am able to get a voltage reading in the wrong direction. The reading will creep up from .1 to .9 volts then overload. Is this part bad or is there just something I dont understand here?

author: sbeube02
author_rank: Contributor
timestamp: July 29, 2015, 06:46:28 pm
content: Maybe a zener diode? Could you post a picture?

author: electronicskidney
author_rank: Newbie
timestamp: July 29, 2015, 07:27:34 pm
content: http://imgur.com/a/3fcrG#0here is an album of pictures of the diodes being tested. The first is with correct current flow. Then there are sequential images as the voltage increased to about .8 volts(and stopped) with current flowing in the wrong direction. The last few are another diode i tested where the voltage kept increasing to .9 volts then hit OL. Thanks for taking a look!

author: N8AUM
author_rank: Regular Contributor
timestamp: July 29, 2015, 08:18:34 pm
content: Lift one end and test out of circuit
Fault Finding A Dead PSU - Page 1
Forum section: electronics / repair

author: HalfManHalfSaab
author_rank: Newbie
timestamp: July 15, 2015, 08:10:47 am
content: Hello All,I have a dead power supply from a Netgear 24port switch. I can see a few people suggesting they have replacement units however I would like to try and repair this unit if possible.It's blowing fuses immediately, even if there is no load (so I can't measure the outputs).My question is, what do I look for? There is no sign of anything burned out, no bulging caps or charred up resistors. Am I just going to be metering everything? Are there any tricks to isolate certain components to rule them out, or any common failures I can look for?All help welcomed!

author: tec5c
author_rank: Frequent Contributor
timestamp: July 15, 2015, 09:26:25 am
content: Blowing fuses immediately is a very strong indication that there is a short on the AC side. A good place to start is by checking the bridge rectifier. If this checks fine, perhaps posting up some photos of the inside of the unit can help us aid you in what to check.

author: German_EE
author_rank: Super Contributor
timestamp: July 15, 2015, 09:36:14 am
content: 1) Check the bridge rectifier2) Check the smoothing capacitor(s)3) There's going to be one or more large power devices (FET or transistor) on the primary side, check them.4) Protective devices such as MOVs can sometimes fail short circuit.

author: HalfManHalfSaab
author_rank: Newbie
timestamp: July 15, 2015, 10:02:01 am
content: Quote from: tec5c on July 15, 2015, 09:26:25 amThanks, I shall give that a go and post up a link to some photos.

author: HalfManHalfSaab
author_rank: Newbie
timestamp: July 15, 2015, 10:02:53 am
content: Quote from: German_EE on July 15, 2015, 09:36:14 amI'll give these a go too - many thanks for the suggestions.

author: coromonadalix
author_rank: Super Contributor
timestamp: July 28, 2015, 03:33:17 am
content: If you check the mosfets, remove them from the board, you can get falses readings depending how the circuit is designed.