hybridfree/eevblog-posts huggingface dataset:
MY-64 Digital Multimeter fault - Page 1
Forum section: electronics / repair

author: g8bnr
author_rank: Contributor
timestamp: May 05, 2015, 08:13:04 am
content: My MY-64 doesn't zero. It reads around 2.3 on all ranges. I suspect that the ICL7106 has been damaged, it is not a packaged chip but is a plastic blob on the board.Am I correct in my analysis, if so, is there anything that can be done? Or is it a bin job?Dick G8BNR

author: wraper
author_rank: Unknown
timestamp: May 05, 2015, 08:24:55 am
content: Are there pads for the IC in package? If yes, you could just remove that blob and solder packaged IC.

author: g8bnr
author_rank: Contributor
timestamp: May 05, 2015, 04:59:21 pm
content: The answer is, sadly, no, unless the IC package is about 0.5" square!! The only ICL 7106 chip that I have seen is a large DIL package!Dick G8BNR

author: wraper
author_rank: Unknown
timestamp: May 05, 2015, 05:01:51 pm
content: Quote from: g8bnr on May 05, 2015, 04:59:21 pm

author: retiredcaps
author_rank: Super Contributor
timestamp: May 06, 2015, 05:57:02 am
content: Quote from: g8bnr on May 05, 2015, 08:13:04 amDo other functions like measuring a 9V battery work?
Tektronix 475 No Trace - Page 1
Forum section: electronics / repair

author: michelk005@gmail.com
author_rank: Newbie
timestamp: April 29, 2015, 12:54:27 pm
content: I have a 30 year old Tektronix 475 that I have a problem with. It powers on, no trace. I have opened it up and per the service manual checked all the LV power supply values and they are all within specs. What I believe is the issue is no High Voltage. Does anyone have any experience with a similar problem that was related to the High Voltage section that can share any troubleshooting thoughts.Thanks,Keith

author: tautech
author_rank: Super Contributor
timestamp: April 29, 2015, 01:02:13 pm
content: Welcome to the forumStart with this:http://www.sphere.bc.ca/test/tek-parts/troubleshooting-scopes.pdf

author: Addicted2AnalogTek
author_rank: Frequent Contributor
timestamp: May 05, 2015, 03:41:47 pm
content: I've been starting my old Tek scope repairs by doing a very thorough cleaning of all the switch contacts and dripping some deoxit down the pot shafts and working them around, and also re-seating all of the socketed components. If it hasn't been used/running properly fairly recently, then this would be a great place to start. Then you can get a good idea of what is really wrong without having to worry about bad contacts.On both my 465 and 468, doing this solved a number of issues that the scopes had. Hope this helps!
Repairing Hakko 926 - Page 1
Forum section: electronics / repair

author: mac
author_rank: Newbie
timestamp: May 05, 2015, 06:56:27 am
content: Hello all,I am in the middle of repair frustration.Recently had some issues with my Hakko 926 with a (what I thought was genuine) replacement tip that I had from many years ago warping and thus corrupting the tip enclosure on the 900m handle.Replacement with a new tip, tip enclosure 900m-002 and nut 900m-006 resulted in the iron no longer switching on and off (simply heats and stays on until it glows red hot).Hakko manuals suggest testing of the connections in the handle to ensure no shorts, to ensure the heating element is good and to ensure the cable is good. Also ensured proper grounding of the grounding spring through the unit from the tip to the ground lugs on the transformer. Pins 1 & 2 measured 49ohms - pins 4 & 5 2.9ohm - pin 3 and tip under 1ohm which were all within spec.To be sure, (and in accordance with the Trouble Shooting manual for the 926), I ordered a new genuine replacement heating element A1321 and installed - same conditions of over heating remained.I then remeasured all of the connections at the pcb to eliminate the possibility of the multipin connector or internal unit wiring being the culprit - no joy.Manual then suggest testing of the triac resistances on the pcb - tested in circuit and then removed for testing but was found to be good. Reinstalled - same overheating condition remains.AAAHRGH - running out of ideas on this one. All suggestions apart from binning the iron would be welcomed. All the new parts are sourced from Element14 and thus I trust are genuine.Mac.
Thunderbird M-100 Electric fence controller - Page 1
Forum section: electronics / repair

author: tytower
author_rank: Contributor
timestamp: May 01, 2015, 08:47:46 am
content: I have a blown up one in which both of the large brown caps have blown and there is no identification written on them that I can see.I would like to replace them but being high voltage cannot guess what their values would be . Anybody know?Anyone have a circuit diagram or suggestion of what the circuit might look like?

author: SeanB
author_rank: Super Contributor
timestamp: May 01, 2015, 09:38:59 am
content: 2uF 630VDC, but they must be rated for pulse application. You probably will be best to get a 4uF 400VAC motor run capacitor with push on terminals, and use 2 short thick ( 1.5mm) wires to connect them to the board. That way when it next fails ( after a year or two) you just plug in a new 4uF capacitor.

author: leham
author_rank: Regular Contributor
timestamp: May 03, 2015, 02:26:54 am
content: Hope you aren't using this for any serious application (non temporary fencing)..The one my parents use on their property will land you on your ass haha it's been running non-stop for over 7 years (wasn't cheap).Top Tip: Don't use them too close to wells or boars haha makes using the shower an "exciting" experience, found that out the hard way hahahaha
Philips 42PF3320/10 plasma TV flashing - Page 1
Forum section: electronics / repair

author: IM Back!
author_rank: Newbie
timestamp: May 04, 2015, 07:45:36 pm
content: Hi,Im tring to repair a old (2005) plasma tv. the tv turns on and flickers at aprox 1hz between allmost white then black (see video).1 rails are at their correct voltages but there is alot of ripple (see picture 1 and picture 2) during the blink "on" phase on all rails.2. There is a buzzing commig from the Y-sustain board.3. There is no stable y-sus wave when the logic board is attached4. If the logic board is detached there is a stable y-sus wave (picture 3)5. I have changed the IPMS's on the y-sustain6. Upon serching on the internet i found that missing/low 5v on the y-buffers or missing y-sch could cause this issue. but i dont know where these are found.Can anyone help?picture 4: y-sus boardpicture 5: y-buffer board

author: IM Back!
author_rank: Newbie
timestamp: May 04, 2015, 07:46:54 pm
content: More pictures (attachment limit)

author: IM Back!
author_rank: Newbie
timestamp: May 04, 2015, 07:50:24 pm
content: one more picture, the 2000kb limit is anoying.

author: IM Back!
author_rank: Newbie
timestamp: May 04, 2015, 07:52:00 pm
content: I tryed mesureing vsch between these pins (pins in the same rectangle are ganged) but there is no voltage no matter how i measurei dont know if im mesureing it wrong or if this is a fault.

author: SaabFAN
author_rank: Frequent Contributor
timestamp: May 04, 2015, 08:53:58 pm
content: Try replacing all the electrolytic caps. They are the components with the most wear and replacing them solves a great majority of issues in erratically functioning devices.
Schematic for BK Precision 2831D or similar? - Page 1
Forum section: electronics / repair

author: klr5205
author_rank: Regular Contributor
timestamp: May 01, 2015, 01:34:12 pm
content: I was wondering if anyone had access to a schematic or repair manual for a BK Precision 2831D? I emailed their technical support hoping they wouldn't mind giving out a schematic or service manual for an obsolete product, but I never even got a response.I bought one for $5 at auction and its in need of some repair. It's about 80% functional but there are a few resistance and current ranges that do not work.I've only just begun my research so all I can say so far is that I don't believe it to be a simple blown fuse because some ranges on both the 2000mA and 20A jacks do work.Some documentation would be best but I'd be happy to hear any words of wisdom before I tear into it one of these days!
Play Station 3 - Page 1
Forum section: electronics / repair

author: tazelikechickn
author_rank: Regular Contributor
timestamp: April 20, 2015, 09:34:38 am
content: Hey Guys,I have been given a PS3 that had the yellow light of death. I repaired it using a heat gun and the method shown on ifixit.comhttps://www.ifixit.com/Store/Game-Console/PlayStation-3-Yellow-Light-of-Death-YLOD-Fix-Kit/IF213-028-3Before anyone says - yes I know that this method is usually short lived.It operates well - apart from the game not loading. It initially had an issue with the tray not centralising, which apparently is common when the power has shut down, but I have fixed that now. But, the disc goes in, the light flashes, but the disc will not come up on the screen. You can see it thinking about it on the top right corner, with the disc rotating sign, but no game on the menu. I have also tried DVDs, - nothing.I have a second PS3 (both given to me by my son-in-law, who obviously figured it was cheaper to keep buying them than to try and repair them.....(this one also has YLOD)So I tried the blue-ray player out of the second one and the same thing happens. I have changed the cable going to the main board - nothing.Is it possible that I may have damaged the mainboard heating it? Everything else works fine. All photos, music, videos, etc., work off the drive, but not off the disc.I have also done a reset (not a factory reset as I can't seem to copy the files from the drive thru a SATA HDD Docking station for some reason - can anyone make suggestions with this as well?) otherwise that is my next idea.Anyone out there come across this problem before?Any help would be greatly appreciatedCheers

author: lukem9962
author_rank: Newbie
timestamp: April 29, 2015, 12:49:05 am
content: did you try the swap the pcb from the dead drive with the drive you tried to install ? on consoles sometimes there linked to the original motherboard

author: macboy
author_rank: Super Contributor
timestamp: April 29, 2015, 01:48:17 pm
content: This is definitely true of the PS3. You need to swap the old optical drive's PCB onto the new optical drive mechanism. The motherboard and optical drive are 'married' permanently. I wonder if your first PS3 had the optical drive replaced incorrectly, and the original optical drive PCB is now discarded?

author: savril
author_rank: Regular Contributor
timestamp: April 30, 2015, 03:56:41 pm
content: There are several methods to re-marry drives pcb and motherboard. It work only on the first models and you need to downgrade the firmware (like 3.55). It can be done with NAND flash or via a dongle.
Repair of HP8648 Signal Generator - Page 1
Forum section: electronics / repair

author: mitslo76
author_rank: Newbie
timestamp: March 11, 2015, 08:45:21 pm
content: Hi Everyone,My HP8648A just died. Magic smoke went out. Apparently it's power supply unit, that produce +15,-15,+5 and +38V... I want to try to repair it, but I have two problems. I couldn't find Schematic and also some resistors and one diode near to HV MOSFET IRF840 burned out so I couldn't read values. I was wondering if someone has schematic or at least if someone can take photo of similar unit so I can begin from replacing burned parts. Building totally new power supply is I guess an option too, but as last resort I guess. Any help is more that welcome. Thanks in advance.Best Regards,Slobodan

author: lowimpedance
author_rank: Super Contributor
timestamp: March 11, 2015, 10:40:12 pm
content: I t would seem that HP only suggested whole assembly repairs in the service manual.If you have not seen this thread it 'might' be of some use ! .https://www.eevblog.com/forum/repair/video-teardown-and-repair-of-an-hp-8648c-synthesized-signal-generator/msg152221/#msg152221good luck

author: mitslo76
author_rank: Newbie
timestamp: March 12, 2015, 12:52:38 am
content: Thanks for the link. Actually I saw this tread but as you noticed the HP Operation and Service Guide doesn't have a schematic, they recommend module change... I was thinking since is of the shelf part (its Computer Products Power Supply 510160) maybe someone has the schematic...

author: Unrockstar
author_rank: Newbie
timestamp: May 01, 2015, 07:50:01 pm
content: Hello,I repair my Powersupply at this time too,I shot a photo and Upload it tomorrow.Can you make a Photo from your Supply?My Powersupply doesn´t power up correctly after repair.I think i have make a Mistake by a wrong restistor
Repair Minato 1863  Eprom programmer schematics - Page 1
Forum section: electronics / repair

author: xantia_99
author_rank: Contributor
timestamp: April 30, 2015, 08:28:50 am
content: HiI got a Minato 1863 eprom programmer that have serios problem with the keyboard.http://www.timonradiosivut.fi/Minato_1863.htmlDoes anyone have service manual and schematics for this euipment. As I want to program some old TMS2532 with 25 Volt needs. I have not so many choices. Minato company does not have it.Best Regards

author: PA0PBZ
author_rank: Super Contributor
timestamp: April 30, 2015, 08:49:00 am
content: Quote from: xantia_99 on April 30, 2015, 08:28:50 amThe foil keyboard has probably worn out or got corroded inside. No need for schematics to check that and if it's gone and you really still want to use the device replace it with a switch matrix.
Help ID'ing resistor type - Page 1
Forum section: electronics / repair

author: cozza
author_rank: Regular Contributor
timestamp: April 29, 2015, 11:25:08 pm
content: Hi all. I am repairing a lighting ballast, and I need to replace a couple of snubber resistors which are out of spec..Does anyone recognise this type of resistor? The value is 10 ohm, 2W, and the service manual has no further information than this.I need to know whether it is a non inductive carbon type resistor, or just an encapsulated mini wirewound type. If all else fails I'll cut one open and find out. Thought I'd ask first

author: tautech
author_rank: Super Contributor
timestamp: April 30, 2015, 01:38:49 am
content: So you've lifted a leg and measured it?Looks like a standard old carbon resistor, for a snubber I don't think the type will matter much.I you think it's loading might have caused it to drift, up it to a 5W.

author: ludzinc
author_rank: Unknown
timestamp: April 30, 2015, 02:10:12 am
content: In my experience, metal film resistors don't work well in snubber circuits.The film develops a weak spot and the parts fail from there. Use a carbon composite.

author: cozza
author_rank: Regular Contributor
timestamp: April 30, 2015, 03:25:37 am
content: There are two in parallel, out of circuit they measure 12.4 and 13.4 ohms on my digital LCR meter.I cracked one open and it appears to be a carbon type, with a very thick outer encapsulation. A search of the usual parts places (RS and element14) turns up nothing physically similar.
Idenitfy this diode - Page 1
Forum section: electronics / repair

author: 71cudalover
author_rank: Newbie
timestamp: April 29, 2015, 09:36:14 pm
content: I'm trying to do some repairs on a circuitboard with a number of IRF450 mosfets which have become shorted to gate and taken out some neighboring components. I have some diodes on the board that I am trying to identify. They have number 59 on them and a logo with a solid triangle and an open ellipse passing through them. It shares some similarity with Vishay in the proportion of the triangle. The cathode is marked with a double band with one of the bands being slightly thicker than the other. Someone else has done some repairs to this board previously, successfully, and used some that are marked with a number 76 and 3K400 it almost appears that these have the letters ISC printed in the cathode band. The body is about 5 mm in diameter. This is of Japanese manufacture circa 1989.Does anyone recognize these.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 29, 2015, 10:37:13 pm
content: Old Vishay logo I think??"3K400" *might* be something like a 3kW peak, 400V TVS diode. But it could also be a UF5404 sort of thing (3A 400V, high speed -- just guessing from the general nature of the circuit?)."59" could be anything. BYVxx comes to mind, but I have almost no familiarity with those. "Insert prefix here", anyone's guess...Can you trace the circuit and see how it connects? It's usually more obvious what the components are for when you see them connected.Tim
Glass tube temperature or current cut out - Page 1
Forum section: electronics / repair

author: tytower
author_rank: Contributor
timestamp: April 26, 2015, 09:43:49 pm
content: I have a switch pulled from a battery charger because it was broken . It is marked DL-01LL with something like a Mitsubishi badge after it . I think it is a current cut off at a certain temperature or flow .I want to replace it but have not been able to identify it properly .Can anyone suggest what I should be looking for ?

author: tautech
author_rank: Super Contributor
timestamp: April 26, 2015, 10:36:26 pm
content: Quote from: tytower on April 26, 2015, 09:43:49 pmPhoto would be good.Rated current for the charger?Guess would be a self resetting thermal fuse.

author: tytower
author_rank: Contributor
timestamp: April 27, 2015, 09:25:39 pm
content: Thanks -Poor photo but charger is 10 amps

author: SeanB
author_rank: Super Contributor
timestamp: April 28, 2015, 07:20:22 pm
content: Thermal fuse, non resettable.http://za.rs-online.com/web/p/non-resettable-thermal-fuses/1769435/This will likely fit, and will be around the right temperature to protect the transformer.

author: edpalmer42
author_rank: Super Contributor
timestamp: April 28, 2015, 08:34:27 pm
content: Is this battery charger old? I've seen old self-resetting circuit breakers that look like that.Ed

author: SeanB
author_rank: Super Contributor
timestamp: April 28, 2015, 08:52:59 pm
content: True, but those have a visible metal strip inside that is the thermal sensor, and a small magnet that provides the spring force to reclose the contacts when it is cool enough, so they snap together and pop apart very fast so there is no arcing. They are very visible, and in this one you just have what looks like a a single shot with a thin element that has melted and pulled the 2 wire ends apart.

author: tytower
author_rank: Contributor
timestamp: April 28, 2015, 09:37:18 pm
content: Quote from: edpalmer42 on April 28, 2015, 08:34:27 pmYes its pretty old - maybe 10-20 years thanks it used to reset . The metal strip disconnected and is loose in the tube now . Definately needs resetable on a battery charger.
HP 1741A oscilloscope - volts/div problem on channel A - Page 1
Forum section: electronics / repair

author: archimedespi
author_rank: Newbie
timestamp: April 27, 2015, 12:11:40 am
content: I picked up a HP 1741A (and a Tek 475) for free. The HP performs great except for one problem - on channel A, the trace *disappears completely* on certain volts/div options. I mean *completely*, I can't find it *anywhere*, and if I hold "BEAM FIND" and rotate the A "POSN" knob, the beam-find trace doesn't move. I've done some testing - it seems to happen in the vertical preamp board (A3).Does anyone have any idea what this could be, or how to fix it?

author: lowimpedance
author_rank: Super Contributor
timestamp: April 27, 2015, 12:59:05 am
content: Channel B still working okay?. If yes you have a reference for DC measurements to compare, which seems likely to be root cause of the trace stuck off screen.Also check for mechanical issues with these vintage CROs (both TEK and HP have noisy switches and pots that occur with with age ).Perhaps there is issues with the push selector switches, need a squirt of contact cleaner.

author: archimedespi
author_rank: Newbie
timestamp: April 27, 2015, 01:17:26 am
content: When the trace disappears, it'sgone. It doesn't show up anywhere in the amp circuits.Interesting thing though - I have the vertical preamp boardcompletelyapart, and in one of the gain-control stages connected to the v/div switch for channel A, I found this: (see attached)It doesn't seem normal, apart from the scorch marks it looks like one of those resistors was replaced (badly) in the past.I think that those symptoms could be caused by dumping too much voltage/current through on a certain v/div gain, which could have blown some of those passives.

author: lowimpedance
author_rank: Super Contributor
timestamp: April 27, 2015, 07:07:25 am
content: Okay so it does not matter which channel is selected, the disappearing trace is specific to the volts/div at certain settings whether using A or B??.What about using Alternate or chop settings.It is important to know if BOTH are affected the same or is it just channel A, (the description so far does not yet convey enough info.)

author: archimedespi
author_rank: Newbie
timestamp: April 27, 2015, 10:15:14 pm
content: Itonlyhappens on channel A - channel B is perfectly good on all settings.Turns out that burnt area of the board had a resistor in the signal path that *should* have been 50 ohms, but had failed open in the signal path.I'm going to replace that and a toasted cap from that area later this week - hopefully that'll solve the problem.

author: lowimpedance
author_rank: Super Contributor
timestamp: April 28, 2015, 12:55:27 am
content: Okay sounds good, please leave an update as to the problem when fixed for reference of others.Thanks
Leader 522 Oscilloscope repair advice - Page 1
Forum section: electronics / repair

author: Neuromodulator
author_rank: Regular Contributor
timestamp: April 29, 2015, 06:20:24 pm
content: I bought this oscilloscope for $2, but after checking it out I noticed its got some issues. I'm fairly new to electronics, so I figured I could ask here for some help to figure out whats wrong. I noticed that there seems to be some compression/expansion issues across horizontal axis. It happens just in when the beam crosses the middle of the screen as you can see in the pictures. I also noticed that it happens on XY mode as much as in the sweeping mode, which makes me think the problem may be somewhere between the horizontal amplification and the crt. Its also interesting that when on XY mode plotting the same sine wave, depending on the frequency of the signal (in the pictures 1,000hz and 10,000hz) the artifact "behaves" different.The scope is this one:http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Leader/LBO522%20&%20LBO523.pdfAny help or hint on how to fix it would be appreciated.Thanks in advance

author: poot36
author_rank: Frequent Contributor
timestamp: April 30, 2015, 04:07:54 am
content: I would start by verifying the scope settings and after that check the voltages on the J5 and J6 connectors on the power supply board are within spec. Don't forget to check for ripple on the power rails with a multimeter set to AC mode. You should have less then 100mV of ripple if possable.

author: tautech
author_rank: Super Contributor
timestamp: April 30, 2015, 07:46:38 am
content: Service manual:http://www.eserviceinfo.com/downloadsm/28249/leader_lbo510-511.htmlEnsure the PSU is correct FIRST.PSU ripple specs in the schematic.Then work through the troubleshooting charts.
GPS Locator device antenna broke off... (device takes GSM Sim card) - Page 1
Forum section: electronics / repair

author: salil
author_rank: Regular Contributor
timestamp: April 25, 2015, 05:28:56 am
content: This is one of those GPS things you can stick in a car and it will send you text messages back with the GPS coordinates using a prepaid GSM sim card, similar to this but it can also do audio:http://www.ebay.com/itm/Mini-Global-RGPS-Tracker-GSM-GPRS-GPS-Tracking-Tool-For-Children-Pet-Car-hg-/281513973063?pt=LH_DefaultDomain_0&hash=item418b8a5547Unfortunately, I lost the hard-to-find charging cable for a while, (since found) so when I decided to open up the unit, the antenna broke off the board at it's single weak connection point. (see upper left corner of picture below)Is there any way of reattaching this? My first thought was that the pad for the antenna had lifted. Upon scraping off some of the board in the area where the antenna was attached, I found copper and a continuity check told me it was tied to ground.One of my EE friends suggested that they may have used a very small amount of insulation between the antenna solder point and the ground layer of the board to act as a tiny, tiny capacitor? Any idea if this is repairable? What are your thoughts? Thanks for reading.

author: richard.cs
author_rank: Super Contributor
timestamp: April 26, 2015, 09:35:37 pm
content: Looks to me like it's designed so that the same board can be used with an external antenna by snapping that bit off and using that connector nearby. You may find there's a link you need to fit to use the connector or it may connect when you fit the mating half.

author: Rasz
author_rank: Super Contributor
timestamp: April 27, 2015, 07:40:49 am
content: Quote from: salil on April 25, 2015, 05:28:56 amno its not, it uses GSM tower location, no gps there
atx psu is ticking won't provide constant power [Solved] - Page 1
Forum section: electronics / repair

author: DeadSk8er
author_rank: Newbie
timestamp: April 22, 2015, 12:50:52 pm
content: right so I've build a power supply from an old atx psu, but now it started making this ticking noise like a clock.It had some bad caps I replaced, but the ticking is still there can't really find anything else that looks bad.oh yeah also when I connect a led to it, it blinks at the same interval as the ticking noiseany advice on what it could be?it's a super flower psu Model NO: SF-400P14P

author: Grapsus
author_rank: Regular Contributor
timestamp: April 22, 2015, 12:59:28 pm
content: Please explain us the what you modified in the PSU. Was it working before the mod ?Ticking may be an overcurrent condition or bad mains filtering caps or another more subtle problem.

author: DeadSk8er
author_rank: Newbie
timestamp: April 22, 2015, 01:08:58 pm
content: I'm not 100% sure if it was, was running fine on old pc and I never noticed the ticking left it standing for about 4 months without powering it upall I did was seperate all the different voltage rails so basicly I took all the 12v, 5v and 3.3v so I got all the different voltages on different outputs and the ground of courseadded a 5w 22ohm dummy load between a 5v and gnd. and replaced all the bad caps. as far as I was able to seealso placed a switch between the gnd and the power on cable

author: marinedalek
author_rank: Contributor
timestamp: April 22, 2015, 09:30:54 pm
content: Sounds like typical PC PSU behaviour when running on too small a load. Try a car bulb on the 12V rail to see if it becomes steady. If it does, you need to experiment and find the minimum current draw.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 22, 2015, 10:09:35 pm
content: You didn't put the load resistor on the standby 5V supply, did you?Tim

author: DeadSk8er
author_rank: Newbie
timestamp: April 25, 2015, 09:26:21 pm
content: thx for the advice I'll try the bigger load some other time..I worked on it for hours couldn't figure it outthink my fluke multimeter is fucked or something aswell..anyways ended up grabbing one of my other old psu's I had laying around,had it working in 20 mins so now I got a lab power supply that works,again thx for the help.

author: retiredcaps
author_rank: Super Contributor
timestamp: April 25, 2015, 09:46:44 pm
content: A number of suggestions.1) If you only replaced the obviously bloated capacitors, there may be more capacitors that are bad, but require out of circuit testing with an ESR meter.2) Ticking suggests the SMPS is trying to start, but can't becausea) the startup capacitor (generally 22uF to 47uF/25 to 50V) is bad due to high ESRb) the SMPS IC is badc) there is something shorted on the secondary side like a diode3) If you think your Fluke meter is not working properly, start a new thread and I will try to provide suggestions on what to check.
Memorex md6459-mp3 repair - Page 1
Forum section: electronics / repair

author: Anora
author_rank: Newbie
timestamp: April 25, 2015, 01:16:41 am
content: I have this cd player that can play mp3's from cd (Memorex md6459-mp3) that dose not want to turn on, power dose seam to go true it and all but that's about it i can figure out, id relly love having it work again has it is one my favorite things i have
Yamaha RX-V420RDS won't turn on at all - Page 1
Forum section: electronics / repair

author: Blocki
author_rank: Newbie
timestamp: April 22, 2015, 09:12:13 pm
content: Hey folks,I have an Yamaha RX-V420RDS on my bench which won't turn on at all. Not even a relay click. The voltage regulator transistors are already switched and there is no 22µF cap.Once I was able to get 1 relay click while pressing the on-button but nothing more happened. Another time I had a constant relay clicking like a minigun but display stayed off.I cannot even bring it into DIAG mode as it won't turn on at all.I have the schematics if required.My main problem is that I have no real idea where to actually start the real debug. I only have a DMM to work with.

author: mzacharias
author_rank: Frequent Contributor
timestamp: April 24, 2015, 05:19:17 pm
content: T start with, I would be checking to see if perhaps the standby 12V is low - also check the microprocessor B+ (perhaps 3.3 volts) and it's oscillator crystal and reset lines. The crystal typically is about 1/2 Vcc DC volts on either side, and the reset line should toggle LOW when the unit is plugged in, and rise to B+ pretty quickly and smoothly.Also, you can just look at the relay turn-on line coming to the standby power board and see if there is any action there when you press the Standby / On button.Come to think of it, that should be your FIRST step.If, for example you see that line budge but not go much more - you could have a leaky relay drive transistor.
Powercube Usb Original Usb Supply Repair - Page 1
Forum section: electronics / repair

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: April 21, 2015, 05:57:14 pm
content: Hello a friend got me a Powercube as a Christmas gift and suddenly the USB supply did not work anymore...At first i tried disassembling it and i found a cold solder joint in one of the diodes. Then i got it working till today when it fell from the table... i cranked it open once again and i can not find any problem.I measured all the diodes with my multimeter but i could not find a damaged one....The IC is a OB2536AP (datasheet attached)Please help to track the cause of the problem.When i connect a device to the usb port i usually heard a noise coming from the transformer i suppose.Now the sound is gone.The thing written on the transformer is RM6H-112-4 or its a "B"like BM6H-112-4anyway i could not find a datasheet of anything....Photoshttp://postimg.org/gallery/3ivyiw4b6/Schematic : I could not find one if you want to reverse engineer it and post the schematic tell me.Thank you in advance

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: April 22, 2015, 12:26:10 pm
content: Any ideas ? What should i measure now ?
Req. Help ID'ing SMD Regulator - Page 1
Forum section: electronics / repair

author: Scotophor
author_rank: Contributor
timestamp: April 19, 2015, 07:27:46 am
content: Hello, I'm trying to identify and get the datasheet for this linear voltage regulator. I don't recognize the logo, and haven't been able to match it in the usual places online. Google and other sites have not helped me with the component marking "A2NK". It appears to be an SOT-23-5/SOT-25 or similar package, output and input at top left and bottom left respectively in the attached (enhanced) photo. This is the only part on the board with any logo, and an other-than-generic part number.

author: Psi
author_rank: Super Contributor
timestamp: April 19, 2015, 09:38:20 am
content: My guess would be IKSemicon for the brand.Their logo matcheshttp://www.iksemi.com/But I can't see any of their regs that use SOT-23-5.

author: Scotophor
author_rank: Contributor
timestamp: April 24, 2015, 07:55:22 am
content: Thanks for the tip. I tried to contact IK Semicon but they haven't responded.Following a lead to Google's cache, I found a page which lists a regulator byAnwell Semiconductor Corp.of Taiwan, in a different package, as using the marking "2NK", but there the "N" is said to represent Vout=3.1 volts, while my part would seem to be 3.3 volts. Also, I haven't found any indication of Anwell using a logo like this.The quest continues...

author: wraper
author_rank: Unknown
timestamp: April 24, 2015, 09:21:42 pm
content: If you know the voltage, why to bother to identify actual part at all? There are bunch of pin compatible regulators available if you need replacement.

author: Scotophor
author_rank: Contributor
timestamp: April 24, 2015, 11:03:36 pm
content: There's a lot more to a regulator's specs than just output voltage...

author: wraper
author_rank: Unknown
timestamp: April 24, 2015, 11:19:08 pm
content: Quote from: Scotophor on April 24, 2015, 11:03:36 pmWhat so much more? At this place almost anything will work. You can check the datasheet if it meets the minimum voltage drop requirement if input voltage is only a bit higher than output but I guess it is 5V. Check maximum input voltage, but usually it is about 6-7V anyway for 95% of such regulators. Current rating should be sufficient for almost all ICs, but you can measure actual consumption if in doubt, in most cases limitation would be PCB heat sinking capability rather than part maximum rating. Also you could check if it is compatible with ceramic output capacitor if such used. <5 minutes to read the datasheet and be 99% sure that part is compatible.
Triplett 630 NA Type 3 Reads low on x10ohms - Page 1
Forum section: electronics / repair

author: Burrjennings
author_rank: Newbie
timestamp: April 21, 2015, 11:12:22 pm
content: A 630 NA Type 3. Reads way low on x10ohms. New batteries, new fuse, cleaned ohms adjust and range switch. I'm somewhat of a beginner with circuit diagrams, but it looks like the end of each resistor is wired onto the range switch and is therefore out of the circuit until engaged by the switch. So I reasoned that the resistors could therefore be checked with my DMM without de-soldering. All resistors on the rosette read good. I've had others on another blog suggest a loose solder connection. I thought I'd try this blog to see if there is any advice on troubleshooting/repairing this meter. Thank you.
repairing led backlight in 2x20 type LCD display. - Page 1
Forum section: electronics / repair

author: station240
author_rank: Unknown
timestamp: April 21, 2015, 02:26:59 pm
content: I've got a device that has a LCD display in the control unit, it looks like a 2x20 type display, but I'm unsure if it's a standard device or not.Anyway, the ends have 3 SMD leds sitting below a glass (or plastic) plate to defuse the light, and the LEDs are half dead. Replacement cost for the entire device is in the $500 mark.Seems the only way to get to the LEDs is to take the metal shroud off. So anyone know what the chances are of getting the LCD working again after I reassemble it ?Anyone taken one of these apart that has the same backlight arrangement ?

author: SeanB
author_rank: Super Contributor
timestamp: April 21, 2015, 06:39:24 pm
content: Pretty good, just use care when undoing the staking that holds the shield on. Then make a VERY CAREFUL NOTE of orientation of everything, including the LCD panel, the zebra strips ( beware some will have 2 strips, one being conducting and one just as a filler) and all other hardware. Taken a few apart and most worked after putting back together. You will have to get the same LED style ( probably a side emitting one) and after putting them in drop the current through them to get a better life out of them, they probably are being run at 30mA or more, when they should have 10-15ma through them.
BS3703 LCR Meter Problem in Inductance ranges. - Page 1
Forum section: electronics / repair

author: aorcan
author_rank: Newbie
timestamp: April 21, 2015, 07:39:40 am
content: Hi all,I have a BS3703 LCR meter by Caltek Industrial/BST showing 65/7/1... in 4/40/400mH ranges when the probes are shorted. It is probably an offset calibration problem as everything else works fine. The trimming pots, 7 of them are tucked in between two PCB's and I don't want to try them one by one. I would appreciate any assistance, schematic, service manual, tips.Thanks in advance.
Zener regulation - Page 1
Forum section: electronics / repair

author: Elesquare
author_rank: Newbie
timestamp: April 17, 2015, 09:57:17 pm
content: Hi,I've got a cheap led light that didn't work. Supply voltage is made by zener regulation and there was a shorted diode (can't be another zener, can it? No markings, however) in parallel with zeners. After removing this, the light is working again.What's the purpose of that diode?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 18, 2015, 06:19:29 am
content: It's literally on a resistor and cap, and nothing else??What markings on it?

author: Elesquare
author_rank: Newbie
timestamp: April 18, 2015, 07:23:42 am
content: Good morning,after a good night's sleep it looks that I shouldn't have forgotten the second half of the circuit: there's a light sensor, too.The mysterious diode must be making proper voltage for darlington! So with diode removed the switching point may be affected. But if I can live with it, there's nothing dangerous about that fix. Am I right?

author: Seekonk
author_rank: Super Contributor
timestamp: April 18, 2015, 07:59:44 am
content: It may not work for long if current can get high enough. D form a reference voltage for the constant current amplifier. Figure what current the LED should be at. Multiply that by the 75 ohm resistor for the voltage and add 1.2V for the darlington. That will be the rough voltage for the zener.

author: Elesquare
author_rank: Newbie
timestamp: April 18, 2015, 08:44:54 am
content: I have no idea of led (panel) current or even number of leds. Absolute maximum current with 240V mains and 100 ohm resistor after bridge is about 1.2A. Transistors are propably BC817, so max collector current is 500mA. Thus max voltage for D is 36V?

author: Fank1
author_rank: Regular Contributor
timestamp: April 18, 2015, 11:10:54 am
content: It's a classic zener voltage regulator circuit, designed to keep the voltage on the 75 ohm resistor constant and as a result the current thru the led's is regulated.

author: Seekonk
author_rank: Super Contributor
timestamp: April 18, 2015, 01:53:45 pm
content: Lets throw out some numbers. Suppose that 75 ohm is a 1W.100ma X 75 ohms = 7.5V100ma X 7.5V = .75W7.5V + 1.2V = 8.7V .......8.2V zenerUsing ohms law you can solve this for any size resistor. Your actual current is probably 15-20ma.

author: Elesquare
author_rank: Newbie
timestamp: April 19, 2015, 07:07:02 pm
content: Just installed 5V1 zener and lamp seems not too bright at all in full darkness. Going to give it a chance now!Thank you for help, all of you!
Panasonic WV-CP240 camera no image - Page 1
Forum section: electronics / repair

author: Puffie40
author_rank: Regular Contributor
timestamp: April 23, 2015, 04:40:06 pm
content: I have been cleaning and testing some CCTV cameras and I have one camera (see title for model) that did work, but after a few power bumps due to a bad AC plug connection led to the camera failing to produce a image.Upon a initial check of the power supply, I noticed a high-pitched hum coming from the board. This leads me to suspect some capacitors are bad.Is there any way for me to confirm this without pulling all the electrolytic caps?
Xicon resistors - Page 1
Forum section: electronics / repair

author: IvoS
author_rank: Frequent Contributor
timestamp: April 16, 2015, 09:16:22 pm
content: Well, I don't know where to ask but I am looking for these specific size Xicon resistors, 270-2.7K-RC. 270-1K-RC. 270-475K-RC.http://www.mouser.com/Search/ProductDetail.aspx?R=270-2.7K-RCvirtualkey21980000virtualkey270-2.7K-RCThe power rating is not that important but size matters. The case length should be 3.5mm.Mouser doesn't have them, neither DigiKey. I tried Arrow, Avnet, Newark but no luck there either. Is there any other distributor in US who can have it?

author: wraper
author_rank: Unknown
timestamp: April 17, 2015, 07:30:58 pm
content: A bit strange request. If you need particular part numbers to meet the BOM then why to write that power rating is not important? It just cannot be different than 1/8W. If particular part numbers are not required, then I just don't understand why try to get particularly Xicon.
Roland w-30 5.2 volt rail to ground  - Page 1
Forum section: electronics / repair

author: PINKBOY1006
author_rank: Newbie
timestamp: April 15, 2015, 02:10:46 pm
content: Hello, I am trying to repair my dads old Roland w-30 and one of the things we had to do is take the floppy connector off the board to try to get it working again. wellwe ended up pulling traces right off the board, and we soldered the wires to the things we could, then we had to microsurgery and solder directly to traces. Now comes the problem, I have 28.6 Ohms across 5.2 volts and ground, and I thought I would ask you guys before I let the all to well knownMAGIC SMOKEout. And me and my dad have looked the soldering and the traces for 1 week, and we see nothing so here is the schematic:http://www.deepsonic.ch/deep/manuals/roland_w-30_service_manual.pdflook for the main board, and some pics :http://www.mediafire.com/convkey/7748/x33od6v11g0i3ulzg.jpghttp://www.mediafire.com/convkey/c325/q9ca2fyefy9hkb2zg.jpgIs this bad or not?

author: ElektronikLabor
author_rank: Regular Contributor
timestamp: April 15, 2015, 04:33:06 pm
content: Hello pinkboy,I would try it out; 29ohm would theoretically cause about 200mA of current.Did you measured the resistance in both directions?

author: PINKBOY1006
author_rank: Newbie
timestamp: April 15, 2015, 04:46:18 pm
content: If you mean that I checked in diode and ohms mode both ways, then yes and it was the same, but before I bite the bullet ill get some more opinions.

author: bookaboo
author_rank: Frequent Contributor
timestamp: April 15, 2015, 05:19:24 pm
content: I'd agree with medvedev, visually double check everything then go for it. 200mA on the 5V rail wouldn't be all that high for such an item. Besides it's a semiconductor circuit so won't behave in a linear V=IxR fashion.If you have a meter with mA range you could put it in series to monitor the current on that line.

author: PINKBOY1006
author_rank: Newbie
timestamp: April 16, 2015, 03:13:20 am
content: So what you are saying is that it is normal to have continuity between the positive and ground in this type of circuit?

author: bookaboo
author_rank: Frequent Contributor
timestamp: April 16, 2015, 11:24:33 am
content: You can't say for sure unless you had another unit side by side to compare with. 29Ohm doesn't stand out as a fault flag to me.On the flip side a high resistance reading on a power line doesn't necessarily indicate everything is OK either.

author: PINKBOY1006
author_rank: Newbie
timestamp: April 18, 2015, 03:27:13 pm
content: Well after much debate and inspection we plugged it and it worked. Booted up without having to make any changes. This was an ugly hack but at least it worked. Thank for the help.
Help identifying faulty SOT23 component - Page 1
Forum section: electronics / repair

author: mackrc1
author_rank: Contributor
timestamp: April 15, 2015, 10:09:11 pm
content: Hi all,My Satellite receiver box randomly stopped working so I checked it out with the power supply and found there was a dead short somewhere. I eventually (using my tongue) traced the fault to a surface mount SOT-23 package which I am failing to identify. The closest thing I could find is this (http://www.s-manuals.com/pdf/datasheet/2/n/2n5460%2C_2n5461%2C_2n5462%2C_sst5460%2C_sst5461%2C_sst5462_vishay.pdf).Unfortunately it doesn't seem this is the device as the specs don't seem to match up with fact that the package is right at the beginning of the power supply circuit. I could be wrong though, after all I've got no qualifications in this stuff!I was just wondering if anybody could help me identify it.The only markings on it are 'DMB' and then vertically 'B2'I managed to get a pretty good image of it though still nothing by Daves standards

author: 128er
author_rank: Regular Contributor
timestamp: April 15, 2015, 10:51:46 pm
content: Maybe this P-channel FET? Manufactured in FEB/2014?http://www.datasheetarchive.com/dl/Datasheet-069/DSA00304010.pdf

author: mackrc1
author_rank: Contributor
timestamp: April 16, 2015, 09:02:41 pm
content: Had a look, that looks like it, found some on ebay (quite expensive but better than farnells minimum £20 order).Will update when I get them.Thanks very much for your help.
Repairing a laptop Asus UX32V - Page 1
Forum section: electronics / repair

author: riccardo.pittini
author_rank: Regular Contributor
timestamp: April 15, 2015, 10:39:17 pm
content: Hi,I am trying to fix a dead laptop (power jack) and while trying that I noticed that someone has already tried to open the laptop and they broke a connector.The connector is a 7pin connector, the touchpad flatcable goes into it. it seems that one part is also missing (the one keeping the flat pressed).Any hints where to grab one? connector name?See in picture.

author: senso
author_rank: Frequent Contributor
timestamp: April 15, 2015, 10:49:05 pm
content: Its an FPC connector, Mouser, Digikey and other carry them, measure the pin pitch, count the number of contacts and of you go searching.That is one that as a little black "lever" on the top.

author: ElektroQuark
author_rank: Unknown
timestamp: April 16, 2015, 07:36:43 am
content: It's an 8 pin connector.

author: Grapsus
author_rank: Regular Contributor
timestamp: April 16, 2015, 12:25:21 pm
content: Would it still possible to assemble/disassemble the PC if the FPC cable was not removable ? If so you might get away with sliding the FPC cable under the pins and definitively solder them onto it.

author: riccardo.pittini
author_rank: Regular Contributor
timestamp: April 16, 2015, 06:33:44 pm
content: Damn me and my eyes.. ja 8pinThanks a lot!!! I will just buy.PS: I don't mind investing some bucks on this laptop, as it is supposed to be good (i7 + Nvidia), and it was to trash as the power jack on the motherboard was broken and someone not really skilled also broke the connector making a mess of everythingThanks again to everyone!!!
LCD problem on old cell phone - Page 1
Forum section: electronics / repair

author: fusionimage
author_rank: Contributor
timestamp: April 16, 2015, 04:43:21 pm
content: hi!i found an old motorola startac in a drawer, but sadly the lcd seems to be broken.i've checked the contacts to the lcd pcb and all seems fine. i guess that either the flat ribbon-cable to the lcd itself has some contact failure or the lcd is simply broken. it also looks like some liquid leakedusually it should initialize with every element black on the lcd. after this, motorola startac should be written on it, but only fragments appear.did anybody experience a similiar problem?

author: wraper
author_rank: Unknown
timestamp: April 16, 2015, 04:56:45 pm
content: Dead LCD itself.

author: fusionimage
author_rank: Contributor
timestamp: April 16, 2015, 05:18:31 pm
content: ok, thank you!this is, what i suspected