hybridfree/eevblog-posts huggingface dataset:
Fluke 45 - Low ohms measurement error - Page 1
Forum section: electronics / repair

author: AndersJ
author_rank: Frequent Contributor
timestamp: March 18, 2017, 03:14:28 pm
content: On the lower Ohms range it shows about 12 Ohms too high.The error decreases slowly, up to about 4700 Ohms where the error is gone.Continuing up towards 10K it starts showing a too low resistance.The measurement current is 740 uA.On serveral other 45's the current is 800 uA, and the resistance measurements are spot on.Thinking current may be lost/shunted on the way from the current generator in the Fluke ASIC,I have measured the voltages across resistors on the way to the front panel.All mesurements are consistent, and it seems the ASIC outputs 740 uA.Perhaps the current is not the issue here.I did however find it peculiar that all others (I have another five instruments) use 800 uA.I have tried a front panel calibration,which slightly improved the situation, but the issue remains.In all other respects the instrument measures correctly, Volts, Amps, DC, AC etc.Any ideas, anyone?

author: AndersJ
author_rank: Frequent Contributor
timestamp: August 03, 2017, 07:49:45 am
content: I have nothing to add.Just trying again, hoping someone might have a comment this time.

author: The Soulman
author_rank: Super Contributor
timestamp: August 03, 2017, 08:51:02 am
content: Quote from: AndersJ on August 03, 2017, 07:49:45 amWhat low Ohms ranges? 300 and 3000? both the same fault?Did you measure the input resistance when set to dc-Volts?Attached is the service manual.Edit: Adding attachment doesn't work, link:http://media.fluke.com/documents/45______smeng0100.pdf

author: Armadillo
author_rank: Super Contributor
timestamp: August 03, 2017, 10:22:29 am
content: Yes, I can confirm that the current is 0.8mA @ 1.5V constant voltage source at output for ohms measurement.Check the input protection components A1RT1&A1R5, A1R6 & A1R7.Verify that U1 constant voltage source is OK [U1 is OK] by measuring the voltage at K2 Relay common [before the input protection]. If this voltage is OK, then the protection components are suspect.
Fluke 199C Scope dead chn A  - Page 1
Forum section: electronics / repair

author: Simon Spiers
author_rank: Regular Contributor
timestamp: August 01, 2017, 02:07:23 pm
content: I have a fluke 199C that was given to me a few years back as it had failed cal and was written off.When CHN A is enabled Channel B trace vanishes from screen and the scope is useless. I can use chan B on it's own as long as A is disabled.Enabling chn A only shows no trace at all.My question is does that sound like the A-D convertor has failed or something more serious?

author: Assafl
author_rank: Frequent Contributor
timestamp: August 02, 2017, 03:34:45 pm
content: Sounds to me like a logic issue.Both channels go to the S-ASIC for sampling, and then go to 2 ADCs. After that they go to the D-ASIC for display. Since they are parallel channels - If one channel would fail - why would it inhibit the other? That is why I am thinking some switching logic (or else turning on Channel A causes a problem elsewhere).There is a version of the service manual online with full schematics.
[Solved] Bench top power supply problems - Page 1
Forum section: electronics / repair

author: tabbas
author_rank: Newbie
timestamp: August 02, 2017, 09:37:45 am
content: Hello AllI have a circuit Specialist bench supply - Model CSI3005SM. Bought 2.5 years ago. I've used this thing practicallyeveryday without any problems.But a few days ago I noticed that there were huge fluctuations in the voltage readout. If I set it to 12 volts it would godown to about 5 or 6 volts for a few seconds then jump back up to 12v. It would stay at 12v for about 6 seconds thenrepeat the fluctuation - and so on.Does anyone know what the problem might be ? I consider myself to be at hobbyist level in electronics but I would beconfident enough to replace a mosfet/cap/diode etc if that was the problem.I do realise this is a cheapo unit (£60 from Amazon) but I would like to repair it if possible.Any help would be appreciated. Thanks for reading.

author: cowana
author_rank: Frequent Contributor
timestamp: August 02, 2017, 10:43:13 am
content: Does it seem to be worst when adjusting the voltage?Often the first thing to go in low-cost power supplies are the potentiometers, which become intermittent and allow the voltage to increase/decrease as the wiper skips across the track.

author: Nusa
author_rank: Super Contributor
timestamp: August 02, 2017, 12:02:03 pm
content: Circuit Specialists primarly sells rebranded Chinese stuff.As for that power supply in particular, you might find this useful:http://hackaday.com/2016/02/16/repairing-and-improving-cheap-bench-power-supplies/

author: tabbas
author_rank: Newbie
timestamp: August 02, 2017, 12:45:54 pm
content: @cowanaYes, most definately. Infact it's all over the place now.

author: tabbas
author_rank: Newbie
timestamp: August 02, 2017, 12:51:46 pm
content: @NusaThanks for your post and the link to that video - I'll try replacing the pots. I think I have 2 suitable 10k pots here andwill order 2 1K pots

author: tabbas
author_rank: Newbie
timestamp: August 02, 2017, 02:38:36 pm
content: Problem fixed.It was the pots that failed. I soldered in the 2 10k pots, put everthing back together and all is workoing normally now.When I receive the 2 1K pots I'll solder them in too.Many thanks for your help guys - It is appreciated. I will also leave a thanks to the guy who made that video.
[Solved] Cap leak cleaning? - Page 1
Forum section: electronics / repair

author: spilihps
author_rank: Regular Contributor
timestamp: July 09, 2017, 02:15:41 pm
content: Hello!Iam currently replacing caps on an old Super Nintendo board. One of them have leaked.It seems that it have gotten under the soldermask.Now, what is the best method to make it stop eating the trace? Should i "remove" the solder mask over the affected area and clean it.Please see the attached image..Thanks!

author: madires
author_rank: Super Contributor
timestamp: July 09, 2017, 02:42:16 pm
content: I'd try a glass fiber brush/pen and IPA. Use the brush gingerly.

author: spilihps
author_rank: Regular Contributor
timestamp: July 09, 2017, 06:22:28 pm
content: Thanks for your reply!That is for removing the soldermask?

author: madires
author_rank: Super Contributor
timestamp: July 09, 2017, 09:26:34 pm
content: Yep, the brush for removing the soldermask and the IPA to remove the remaining mess.

author: WastelandTek
author_rank: Frequent Contributor
timestamp: July 09, 2017, 11:24:13 pm
content: I find the mask flakes off pretty easily when it gets like that. Post up pics once you have it clean so we can see how it came out.

author: Flappy
author_rank: Contributor
timestamp: July 10, 2017, 07:22:24 am
content: I like to immerse, soak and gently scrub boards to make sure all traces of electrolyte are gone. The solder mask in your photo looks like it will flake off easily. Use an antistatic brush.

author: spilihps
author_rank: Regular Contributor
timestamp: July 13, 2017, 10:26:57 pm
content: Thanks everyone!Ive ordered a brush and Circuit works pen overcoat pen.Will update the thread when work is done!

author: spilihps
author_rank: Regular Contributor
timestamp: July 16, 2017, 11:40:59 am
content: So the glassfiber brush is great!Ive cleaned as much as i dared. Some dark spots left under the microscope. But i dont want to eat on the trace.Will have a go at some scrap boards with the overcoat-pen now and then Close this up.So far:

author: WastelandTek
author_rank: Frequent Contributor
timestamp: July 16, 2017, 03:46:58 pm
content: looking good

author: spilihps
author_rank: Regular Contributor
timestamp: August 01, 2017, 05:56:29 pm
content: Thanks!Here is a final Picture of the repair.All caps replaced and the unit works!Thanks for all your help.
HP 54510A Oscilloscope firmware (without the FFT option) - Page 1
Forum section: electronics / repair

author: TimInCanada
author_rank: Regular Contributor
timestamp: July 31, 2017, 06:16:42 pm
content: Attached is the firmware files for the two EPROMs in the 54510A, in case anyone in the future is looking for these.There was a later revision with built-in FFT calculation. Google shows there have been a number of people asking for that version, but it doesn't look like anyone has come up with that version. Maybe if someone does, they can add it to this thread.Cheers,Tim

author: alm
author_rank: Super Contributor
timestamp: July 31, 2017, 07:14:49 pm
content: Thanks for posting those files. How about uploading them toKO4BBandxdevs.com(TiN's site)? I am happy to do it if you do not want the hassle.

author: TimInCanada
author_rank: Regular Contributor
timestamp: August 01, 2017, 05:46:30 pm
content: Done! Thanks for the links.
SSPA Low DC current alarm - Page 1
Forum section: electronics / repair

author: ksb
author_rank: Contributor
timestamp: July 31, 2017, 09:14:13 am
content: Hi everyone. I am new to this group. Currently im repairing aSSPA (Solid State Power Amplifier)Paradise Datacom model HPAC2200XXXXX which having faulty and the alarm stated "Low DC Current alarm". This alarm trigger only when the M&C cable is connected to J4 (means when the amplifier is in enable mode).Does anyone of you know which part/component cause this fault.thank you,Regards,Alan.
Troubleshooting a dartboard - Page 1
Forum section: electronics / repair

author: Tiller
author_rank: Newbie
timestamp: August 05, 2017, 11:17:46 am
content: Hello,My friend has a dartboard for which he lost the AC adapter. While trying some random AC adapter, he probably broke the board and now I'm trying to troubleshoot it with my limited knowledge.The main issue is - I think - that the board took a 19V input instead of the expected 5V (yes.. I know...). There is a chance (50% ?) that the polarity was also reversed (+ on - and - on +). From there, I swapped the 19V he put by a 5V but got no response from the board, before realizing the polarity was reversed and then I put everything in its proper place.So now the board is properly powered (5V DC) and some LED lights up when I plug it (https://stuff.stooit.com/d/1/598596612dbb8/20170804_194402.jpg), but it doesn't do much more. There was a capacitor near the input that had a bad look (it was bubbled on the bottom) so I replaced it (replaced a 19V 220uF cap by a 19V 330uF) but I still have the same result. I went ahead and replaced all capacitors of the board (there was ~6 104 ceramic capacitors, that I replaced by new 104 ceramic capacitors), but still the same result.With a multimeter, I checked all resistors on the board and they're OK (or looks like it). I also tried to test the transistors but I wasn't sure how to test it. I simply tried to see if current flowed from the base towards the 2 other pins.And there I am... I'm out of idea and I'm afraid that it might be the microcontroller that's dead... So before repurposing the board (I'll try to replace the microcontroller with an arduino) I just wanted your opinion on what might be the issue there...Here is the top of the board:https://stuff.stooit.com/d/1/598596469147e/20170805_115148.jpgAnd here's the bottom:https://stuff.stooit.com/d/1/5985962a54e51/20170805_115209.jpgThanks.
Tektronix Transformer color codes? - Page 1
Forum section: electronics / repair

author: Gip-Gip
author_rank: Contributor
timestamp: July 30, 2017, 07:34:32 pm
content: I have a PN120-0730-00 that is disconnected from the power supply board. It says on the transformer that the color codes are in the manual but alas, nothing was foundI have everything I need to find the ratios, I'd just like to check with everyone else to make sure that's the route I'll have to take.PS if anyone knows a good way to test transformers of this size I'd greatly appreciate it. Right now I'm just hooking up an AC-AC adapter to the primaries and reading the voltages
Lecroy 9314L scope goes nuts from time to time after pressing auto trigger - Page 1
Forum section: electronics / repair

author: slow_rider
author_rank: Regular Contributor
timestamp: August 08, 2017, 05:20:20 pm
content: I have bought this scope a few months ago at an electronic junkyard after making sure everything is working well. Overall the scope is in good condition, only had to replace a single encoder which was bad.I only started using it a few days ago (need 4 channels) and I have noticed that from time to time after selecting the auto triggering mode, the scope will display random vertical lines while and clock and time are still showing, these lines will move up and down for a few seconds after that that only static lines will show up on the screen. The only way to move along is to reset the device. This happens once in 10 to 20 times I push the auto trigger button. I have looked through the service manual but could not find anything immediate.Any thoughts on this?*** Sorry for the picture quality, the light was dim.

author: alm
author_rank: Super Contributor
timestamp: August 12, 2017, 10:24:41 am
content: Sorry, no advice except that this looks like a digital (acquisition memory/ADC?) problem to me. Maybe our resident Lecroy expertWuerstchenhundhas any ideas? Send him a PM if he does not respond within a couple of days. You might also search theLecroy owners group(public mirror) for similar problems.
DVM810 - Page 1
Forum section: electronics / repair

author: lionelkjh
author_rank: Frequent Contributor
timestamp: July 24, 2017, 06:53:58 pm
content: Good evening everyone! I am looking for the main integrated circuit mounted on a multimeter DVM 810 (chip on borad). Is this an ICL 7106 ?? Does anyone have the schema ?? Thank you for your help!

author: retiredcaps
author_rank: Super Contributor
timestamp: July 24, 2017, 08:53:53 pm
content: Quote from: lionelkjh on July 24, 2017, 06:53:58 pmThat would be my guess. What is wrong with the meter?

author: Armadillo
author_rank: Super Contributor
timestamp: July 24, 2017, 09:16:12 pm
content: $6.69, it would be cheaper to buy the kit.http://www.apogeekits.com/digital_multimeter_dmm810.htm

author: Armadillo
author_rank: Super Contributor
timestamp: July 31, 2017, 04:01:57 am
content: Pin 1 is the +ve of the battery supply voltage;Pin 26 is the -ve of the battery supply voltage;Set the meter to voltage mode or current mode and confirm 100mv is at Pin 36.Edit: Probe at Pin 38 with a digital logic probe, confirm there is clock oscillation.Use your fingers to touch the circuit traces near the Pin 27 to 31, you should see the LCD digits change and jump randomly.The attached circuit is the closest  for your reference.The chip normally does not fail alone.It would be cheaper to buy the whole kit/meter and wiser.
Help identifying a part - Page 1
Forum section: electronics / repair

author: perdrix
author_rank: Frequent Contributor
timestamp: July 30, 2017, 10:43:30 am
content: I'm fairly sure it is a capacitor, it has colour code bands and text saying "1P0" (I think).Lead torn off so can't measure it (don't ask!).Colours look like red, violet, green so it might be 27 * 1E5 = 270nF? If that is the value, then I'm puzzled by the text marking of 1P0Does anyone recognise this and know the value type and voltage rating?ThanksDave

author: Gyro
author_rank: Super Contributor
timestamp: July 30, 2017, 10:50:48 am
content: It's a ceramic plate capacitor - 1pF. The colours indicate dielectric type (I've only seen one colour before) at that value it will be NPO.It's a very low value, something RF?

author: perdrix
author_rank: Frequent Contributor
timestamp: July 30, 2017, 12:07:07 pm
content: It was in series with an 18M2 (Brown, Grey, Red, Green) resistor across a Vishay S102L precision resistor (20K000 0.05%). This resistor is part of a precision attenuator, and the R and C were mounted under the board. The other resistor in the attenuator (289.3 Ohms) also has series RC trim under the board in parallel with it (274K in series with a cap marked n22 AFAICT, so maybe 220pF).The two main resistors appear in the schematic, but these under board parts don't.If I had to guess, I would think they are there to trim the frequency response of the attenuator.RU sure that it's 1pF? Finding a leaded 1pF cap will be non-trivial.Dave

author: SeanB
author_rank: Super Contributor
timestamp: July 30, 2017, 01:19:46 pm
content: 1pF is common, though you can replace it with a twisted wire adjuster cut to the right length. Easy to get as a NPO leaded part as well.

author: perdrix
author_rank: Frequent Contributor
timestamp: July 30, 2017, 01:54:43 pm
content: I had some 1pF 0805 parts so used one of those.Thanks, Dave
DVM810 - Page 1
Forum section: electronics / repair

author: lionelkjh
author_rank: Frequent Contributor
timestamp: July 30, 2017, 02:20:47 pm
content: Hello; I have to replace the chip on board of this multimeter, can you tell me if it is well: ICL7106Thank you for your help (if someone has the schema?)

author: lionelkjh
author_rank: Frequent Contributor
timestamp: July 30, 2017, 02:25:28 pm
content: the following....

author: SeanB
author_rank: Super Contributor
timestamp: July 30, 2017, 03:54:09 pm
content: Yes it is, but it is the COB version, and a replacement chip is likely to actually cost more than the meter itself. What makes you suspect the IC is faulty, they generally are reasonably robust and survive a lot unless you blow up the input along with it as well.

author: retiredcaps
author_rank: Super Contributor
timestamp: July 30, 2017, 05:50:52 pm
content: You already started a thread on this.https://www.eevblog.com/forum/repair/dvm810/And people, included myself responded. Keep all your posts in one thread.

author: Simon
author_rank: Unknown
timestamp: July 30, 2017, 06:00:18 pm
content: Seehttps://www.eevblog.com/forum/repair/dvm810/
Stripdown of faulty Toshiba laptop battery - Page 1
Forum section: electronics / repair

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: July 29, 2017, 04:01:22 am
content: I mentioned sometime ago (I can't locate the old post) that I bought a Toshiba laptop battery (Labeled Replace PA39050U-18RS) from China and it showed poor battery 'health' from day 1 and would simply shut down ungracefully (crashing my laptop) when it ran low on charge. Finally got a genuine Toshiba replacement at a high price and opened up the Chinese one to see if they used recycled batteries or had an obviously dodgy control board. The manual for it said not to allow it to discharge completely to avoid damage, while I expected a proper control system would prevent that. Anyway, turns out the innards do include a seemingly adequate control board and what appear to be new batteries (attached photo). The batteries are labelled "PH Great Power Li-Ion ICR18650 2000mAh 3.7V 20160926" - I've taken the latter to be the manufacture date, which is close to when I bought them. The control board has a 20 pin IC SA1414SE (Li-battery protection chip) and an ATMEL414 24C04N which appears to be a serial EEprom. All the cells measured 3.8V with no load, so no obviously dead cells. So it doesn't appear to be lacking obvious material parts. I assume the poor performance from new is down to bad construction or quality control. Unless they rewrapped old batteries with new plastic covers and invented dates - I guess that's not out of the question.Posted in case others are looking at trying cheap Chinese batteries - 1/3 the cost of Toshiba parts in Oz but not worth the hassle in this case.

author: amyk
author_rank: Super Contributor
timestamp: July 29, 2017, 04:43:48 pm
content: You can do a charge/discharge test on the cells to see if they're really 2Ah. The 5.2Ah rating on the case is obviously a lie, although it suggests there should be 2.6Ah cells inside if this is a 3S2P pack.

author: Armadillo
author_rank: Super Contributor
timestamp: July 29, 2017, 06:58:19 pm
content: FeedbackLoop has a lot of videos on battery capacity testing and plotting.Recommended to watch.

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: July 29, 2017, 11:34:57 pm
content: Would be good to test them but I don't have an electronic load at present and my other loads are pretty crude. Test video was useful - thanks. Also have five or six other repairs in progress and limited time for any of them at present. They'll go in the drawer for a rainy day. They did give a rather interesting demonstration of rapid flammability while being dismantled!Not hard to why they're high risk items on planes.
Help identifying ICs - Page 1
Forum section: electronics / repair

author: brendan-petrol
author_rank: Contributor
timestamp: July 29, 2017, 03:19:21 am
content: G'day all,I've got an old Panduit LS8EQ labeller here that someone at my work broke (apparently put the power adaptor in the wrong way around.... somehow...), and I'm tinkering around with it to see if I can get it to work. I figure it's probably beyond repair, but it might be possible and it's good practice regardless.I've managed to power up the screen's backlight, and I've also discovered a dead short between the 3.3 V power rail and the 0 V rail. My assumption is that the linear regulator is dead (I figured it was as good a place as any to start, but I have no reason to think that). Can anybody think of a better place to start? I was hoping someone could help me identify an IC which I believe is the voltage regulator - since an identical part on the main processing board it is connected to both the 1.8 and 3.3 volt rails.I've attached a picture below - ignore my terribly soldered wires, I found it easier to access the 3.3 volt rail that way. The IC which I think may be the voltage regulator is the one marked "TI15 AHV". I've searched for many combinations of that code and I can't find anything at all. I also can't find any information on that ST part "1T60 Y114", which is another candidate, but it doesn't seem to connect to the 9 V rail so I think that's less likely.

author: brendan-petrol
author_rank: Contributor
timestamp: July 29, 2017, 03:49:09 am
content: Wow thanks - that was fast!I'm glad to see that my hunch that the TI15 was the voltage regulator proved correct!It looks like there's a short between 3v3 and 0v on both boards, not just the power input board like I first suspected. Does anyone have any tips for finding short circuits?Edit: whoops, looks like I was too reliant on the results of my continuity testing and in my impatience, I mistook a GND pin for 3v3. Probably just made that worse. Wish I had a service manual!
Available replacement for SRAM HM62256BLFP (low standby power ~ 1uW)? - Page 1
Forum section: electronics / repair

author: carl_lab
author_rank: Frequent Contributor
timestamp: July 27, 2017, 11:01:07 am
content: I try to find an available replacement for SRAM Hitachi HM62256BLFP (low standby power ~ 1uW +/-).3V, 5V tolerant2.7V data retention voltageDatasheet of original:http://ee-classes.usc.edu/ee459/library/datasheets/hm62256.pdfCan anybody help?

author: YTSOC
author_rank: Contributor
timestamp: July 28, 2017, 06:39:10 am
content: why not just order it of ebay?

author: carl_lab
author_rank: Frequent Contributor
timestamp: July 28, 2017, 10:26:36 am
content: Can't buy from ebay by business account.

author: ap
author_rank: Frequent Contributor
timestamp: July 28, 2017, 11:25:02 am
content: Digikey e.g. has them, even lower typ. standby current.

author: carl_lab
author_rank: Frequent Contributor
timestamp: July 28, 2017, 11:45:35 am
content: Quote from: ap on July 28, 2017, 11:25:02 amCan you provide the link, please?

author: JFJ
author_rank: Regular Contributor
timestamp: July 28, 2017, 11:51:50 am
content: The search results forSRAM 32Kon theFarnellweb site provides several equivalents to the Hitachi SRAM, e.g:http://de.farnell.com/lyontek/ly62256sl-55lli/sram-256k-32kx8-2-7-5-5v-28soic/dp/2253655

author: carl_lab
author_rank: Frequent Contributor
timestamp: July 28, 2017, 01:27:13 pm
content: Great, thank you!Can I use faster than original (55ns instead of 70ns)?

author: Tomorokoshi
author_rank: Super Contributor
timestamp: July 28, 2017, 02:19:33 pm
content: Quote from: carl_lab on July 28, 2017, 01:27:13 pmIt should be fine when it comes to data access.Note that there are other parameters that have timing changes. For instance, tCHGand tWHZ. However, these shouldn't be a problem unless it is being accessed by something outside of a typical processor given the (for these days) relatively slow access.Also compare the output load rating to the original part. This one is listed as "CL= 50pF + 1TTL". For instance, if the slower original is rated to 100pF for it's timing, etc. then it may all balance out anyway.

author: JFJ
author_rank: Regular Contributor
timestamp: July 28, 2017, 02:34:16 pm
content: Quote from: carl_lab on July 28, 2017, 01:27:13 pmThe address access time quoted is the maximum access time (no minimum time is specified). The price for the 70ns version is exactly the same:http://de.farnell.com/lyontek/ly62256sl-70ll/sram-256k-32kx8-2-7-5-5v-28sop/dp/2253657That might suggest that the 55ns and 70ns versions are identical, with just the markings changed.

author: carl_lab
author_rank: Frequent Contributor
timestamp: July 28, 2017, 07:00:02 pm
content: Quote from: Tomorokoshi on July 28, 2017, 02:19:33 pmExactly!Dataheet HM62256B:Quote
Walkman azimuth adjustment - Mechanical problem - Page 1
Forum section: electronics / repair

author: steve30
author_rank: Frequent Contributor
timestamp: July 30, 2017, 03:53:10 pm
content: As mentioned in another topic, I've been doing some work on a very pesky Sony Walkman WM-10 for someone. It all works fine now expect for the azimuth adjustment which is giving me trouble.A few times, the adjustment was causing the head to not retract when one pressed the stop button. A bit of adjustment with the adjust screw fixed that, then the screw would turn, but not actually adjust anything. After a bit of poking around, the screw turned, but eventually got stuck, and now doesn't turn at all. Its so stuck that some of the screw-head got stripped.Can anyone figure out how this works/why it might have gone bad/how to fix it? I've attached an annotated photo and a demonstration video. It is a bit of an unusual adjusting mechanism compared to your usual Walkman/tape deck.Thankssteve30
nodevice.com - legit or not? - Page 1
Forum section: electronics / repair

author: usagi
author_rank: Frequent Contributor
timestamp: July 27, 2017, 11:53:06 pm
content: I need a service manual to repair a Sharp Air Conditioner. I've looked everywhere and the only site claiming to have a service manual is here:http://www.nodevice.com/manual/newmans/upsharp/CVP12LXPDF/get52438.htmllooks scammy to me? yet eevblog lists it:http://www.eevblog.com/wiki/index.php?title=Service_manuals_and_repair_information
Problem identifying burned Texas Instruments IC in TSSOP-8 package - Page 1
Forum section: electronics / repair

author: Straho
author_rank: Newbie
timestamp: July 26, 2017, 05:18:47 pm
content: Hello, amazing people!The magic smoke has escaped from an element on an integrated circuit board I have ....and I have difficulties identifying it. It is a Texas Instruments IC in TSSOP-8 package and from what is left of it I can see that it ends with 22 on the first row and with 5240 on the second. Does any of you has any idea what this is ... Thanks in advance

author: Straho
author_rank: Newbie
timestamp: July 26, 2017, 05:39:03 pm
content: Ahhh I think it is a TI SN75240 quadruple, unidirectional usb transient voltage suppressor. The board communicates with the other part of the system via usb ...so it makes sense. I am going to leave the thread for indexing purposes if someone else on the Internet has a similar issue. Your opinion is welcomed of course ..cause i might be wrong

author: rsjsouza
author_rank: Super Contributor
timestamp: July 27, 2017, 06:20:09 pm
content: I agree with you, especially seeing the two matched traces coming out of the pins "C" and "D".Glad this part still has decent part markings... These have become so minimalist these days...

author: Samogon
author_rank: Frequent Contributor
timestamp: July 28, 2017, 02:17:36 am
content: Quote from: ivi_yak on July 28, 2017, 01:05:44 amReally?

author: ivi_yak
author_rank: Regular Contributor
timestamp: July 28, 2017, 08:54:09 am
content: SN65240PW

author: ivi_yak
author_rank: Regular Contributor
timestamp: July 28, 2017, 08:58:08 am
content: http://www.jameco.com/Jameco/Products/ProdDS/909564.pdfits absolutely SN65240PW because 5 pin on the GND
RIGOL how to flash firmware JTAG - Page 1
Forum section: electronics / repair

author: ivi_yak
author_rank: Regular Contributor
timestamp: July 27, 2017, 01:16:48 pm
content: I want to make a clear algorithm of restore steps for bricked RIGOL oscills, if you have some info about it please share with us. It was a first step for open source firmware like this threadhttp://hackaday.com/2017/04/27/help-wanted-open-source-oscilloscope-on-rigol-hardware/https://www.eevblog.com/forum/projects/rigol-ds10xxz-firmware-re-write/.Fear to brick oscill is the main wall to made and test open source firmware. Let's break this wall!
Palit Jetstream 780 doesn´t receive power from PCI-Express and not initialize - Page 1
Forum section: electronics / repair

author: Netcrusher
author_rank: Newbie
timestamp: July 26, 2017, 03:13:13 pm
content: I have checked with a multimeter my Gtx 780 Palit Jetstream , the card doesn´t initialize anymore and the fans are not spinning , I have checked that the Pci Express power line (Pin 1-2-3) don´t give any value with multimeter setted on diode/beep mode, what should I check to recognize the culprit for this problem???Thanks

author: agehall
author_rank: Frequent Contributor
timestamp: July 27, 2017, 05:26:49 am
content: What exactly did you measure?I would start by inspecting the board closely to see if there are any visual clues as to why it isn't working.
CRT hameg 203 - Page 1
Forum section: electronics / repair

author: Aspro
author_rank: Newbie
timestamp: July 26, 2017, 09:51:38 am
content: Bonjour a tous !Je possède un oscilloscope hameg 203 , seulement j'aimerait l'équiper d'une sortie Z, comme de pouvoir connaître la valeur du condensateur entre la cathode et D1 . Tout se indiquer sur la page 7https://ia800208.us.archive.org/16/items/hameg_HM203/HM203.pdfCordialement

author: carl_lab
author_rank: Frequent Contributor
timestamp: July 26, 2017, 10:17:26 pm
content: "wired cap"? parasitic cap or piece of koax or twisted pair cable?what function does that cap has? it couples z-amplifier to horizontal deflection...flyback blanking? isn't that the function of the optocoupler?can you post photos of that capacitor?why do you want to know the value?

author: tronde
author_rank: Frequent Contributor
timestamp: July 27, 2017, 02:02:37 am
content: I understand him so that he want to install the optional Z-input.The schematics indicates that 1N4149, 100k, 33pF, 10nF/3kV and 1M is part of this input in addition to the "wired capacitor".I attach part of the schematics for HM203-5 showing the same circuit. The "wired capacitor" is not present there so I guess it is not important for the function, but they show an extra TTL Z-input in addition that might be useful.

author: Aspro
author_rank: Newbie
timestamp: July 27, 2017, 06:31:37 am
content: Bonjourje ne possède pas de photo de se condensateur, par contre" tronde" a raison !!Sur le faite que je cherche a rajouter une entrée Z en option....De plus wired cap en Français signifie ( Chapeau câblé??)Cdl

author: carl_lab
author_rank: Frequent Contributor
timestamp: July 27, 2017, 12:19:39 pm
content: I sent your postings to google translator:QuoteQuoteQuote from: tronde on July 27, 2017, 02:02:37 amFirst I would try without the "wired cap".I'm quite sure it will work without.
Denon/Marantz AVR HDMI board regulator IC's - Page 1
Forum section: electronics / repair

author: SoundTech-LG
author_rank: Frequent Contributor
timestamp: July 26, 2017, 05:16:57 pm
content: Hi,This might be a cost effective time saver for someone trying to replace thes 38 pin QFN regulators on the HDMI boards.I searched high and low looking online for the parts marked as EX3AV. Nothing listed anywhere with any useful information. The Denon/Marantz service manuals do not list the actual Denon/Marantz part#, just "nsp" Not Supplied Part.Eventually searched on 38 pin QFN, and found a trail to Altera, and EN6337QI. That is the correct 3 amp regulator IC. Quite expensive at Digikey over $9 each.Have fun!Turns out there IS an unrevealed (in Service Manuals) part #, which is 231810089509S. Turns out to actually be much cheaper than Digikey or Ebay! at $3.86 each.
Strange LCD behavior on Acer E1-570 Laptop - Page 1
Forum section: electronics / repair

author: TheGenesis
author_rank: Contributor
timestamp: July 24, 2017, 08:49:41 pm
content: I have a E1-570 Laptop from Acer (Compal LA-9535P Mainboard) wich has a strange failure.On Startup the LCD is blinking a few times (without Backlight) then goes black while still booting.This is the Version with an onboard GTX 750M. Everything is perfectly fine on external VGA + HDMI outputs.If I connect a external Monitor and push the Fn+LCD Button, the Monitor goes black and the same blinking is happening (as on startup) then the machine switches back to external.Could this be the backlight circuit or the hole LCD-Panel?On older laptops backlight and panel will still come on even if one is damaged.There are no liquid damage or burned components on the pcb.Anyone any idea?

author: amyk
author_rank: Super Contributor
timestamp: July 25, 2017, 03:03:31 am
content: Shine a torch on it. If you can see an image, the backlight is damaged.

author: YTSOC
author_rank: Contributor
timestamp: July 25, 2017, 05:15:59 pm
content: it could be as bad as a dead graphics chip(even it other outputs work), it could be a broken lvds cablefirst i'd try and rule out the gpu by desoldering the coil(s) of the psu for the GPU(only the discrete one) This will deactivate itand in some casesthe board automatically switches to the intel one.

author: TheGenesis
author_rank: Contributor
timestamp: July 25, 2017, 10:18:49 pm
content: @amykThats what i have tried first ... no image and no backlight.I have desoldered the coil(s) ... nVidia is now gone ... the Intel HD 4000 is doing the same things as before ... the approach to switch to the LCD and back to D-SUB is now fasterAre these LVDS connections are communicating with the graphic adapter? Then proabably simply the screen or, as you mentioned, the cable is gone.I wonder, because older LCD's are flickering or doing some weird things instead of switching to an alternate display port.

author: YTSOC
author_rank: Contributor
timestamp: July 26, 2017, 11:16:03 am
content: weird, i think it's a basic panel, don't you have one to replace it?i'd measure on the panel logic board the voltages that are beying supplied from the motherboartd: 19v and 3.3v(there are 2 fuses on the panel logicboard, check the voltages before and after them)the 3.3 v is most likely ok as the screen blackens
HP E4418A - Page 1
Forum section: electronics / repair

author: wijogr
author_rank: Newbie
timestamp: July 25, 2017, 02:05:17 pm
content: I recently purchased an HP E4418A. It was sent out for calibration and has been used a few times. I went to turn it on yesterday and the power LED went from Red to Green and then back to Red. Hit the button again and then it turned on. I tried it this morning and it will not turn on at all now. I don't see anything in the manuals I have for troubleshooting this. Has anyone seen this or have any suggestions? I have the users manual and a service manual from the Keysight website.

author: alm
author_rank: Super Contributor
timestamp: July 25, 2017, 02:24:14 pm
content: If you are lucky, it could be something with the power supply. Start by measuring the voltage rails (DC voltage and ripple). There may be instructions for the manual for this, otherwise you will just have to reverse-engineer it. For example, if you see an 7805, the output should be very likely about 5V DC. If you find that the output is much lower, there is likely something wrong. Many large value electrolytic (aluminum and tantalum) capacitors will often be across a voltage rail, so could be a good place to measure voltage. There will be most likely be some 3.3 or 5 V rails for the digital logic, and some analog rails (possibly symmetric, e.g. +6 V and -6 V). Since it is not powering on at all, if it is a power supply issue, there are probably rails that are way off.Try to find the most recent power meter that still had schematics published. The HP 437A/438A is much older, but still had full schematics in the user manual. Not sure about more modern models. The principle of operation and possibly even the circuit of the probe interface and reference output may very well be very similar (since they could use the same sensors). The digital circuit is probably all different.
PJ2449LR - what it is - Page 1
Forum section: electronics / repair

author: IAmBack
author_rank: Regular Contributor
timestamp: July 24, 2017, 07:53:09 pm
content: Need help with identification of this element. It has size of "1812" resistor, except it is 2.5 mm or so high. Most probably it is suppression diode - most probably it is protecting output of the driver circuit, before power transistors. Now it is "short" and one of the transistors is dead (W15NK90Z), together with several elements (3x100 ohm resistors connected in parallel and 300 ohm resistor connected to the gate). Whole stuff is in BK9185 high voltage PSU.And finally, maybe someone knows where it can be purchased (with shipping to EU/Poland).--edit--The housing is most probably the DO214AA type.--edit--Best.

author: IAmBack
author_rank: Regular Contributor
timestamp: July 24, 2017, 10:24:49 pm
content: Ok, it looks like SMBJ17A diode. Can anyone confirm that?

author: IAmBack
author_rank: Regular Contributor
timestamp: July 24, 2017, 11:39:35 pm
content: Next info - manufacturer is most probably PanJit - never heard of them before...
Peavey Classic 30 intermittent fault - Page 1
Forum section: electronics / repair

author: Ziggy Roque
author_rank: Newbie
timestamp: July 21, 2017, 11:58:15 am
content: Hello Folks,I'm also new to this group and joined.. based on a problem I have with my Peavey Classic 30. My knowledge about electronics is limited. The problem I have is this: a few months back my amp started to drop out occasionally, usually after 20-30 minutes of playing, in a way similar to a weakening battery in an FX pedal (I use 4 pedals max, all battery-run), losing volume over roughly 30 secs to 1 minute, until no sound could be heard. This happened more often lately. Today I noticed that the power supply to the valves was dropping and slowly going off. The filaments would slowly stop lighting up.. while the pilot light remained on. - Using the simple 1st test method of kicking the amp slightly the power did come back on, but only briefly. The output valves are fairly new, the pre-amp valves not. The reverb hasn't worked in ages but that seems to be a circuit separate from the valve circuit (this I learned from this forum ..so, thank you very much. I have already learned something new..). - I should add that the amp made a rumbling, rushing kind of white noise before this new problem occured, sounding like the output valves were on the way out, but they are as I said fairly new. Does anyone have an idea what the problem could be? I have a MM but I don't know enough about what to measure where and how. I will study this matter further but perhaps someone can give me advice on what to look for. Should I replace the 3 x 12AX7s (the filaments in those remain 'on'...so that doesn't seem to be the problem, but...) ? Thank you.

author: 0xPIT
author_rank: Regular Contributor
timestamp: July 21, 2017, 01:46:17 pm
content: Lethal Voltages inside!Get the device to an experienced tech.

author: Ziggy Roque
author_rank: Newbie
timestamp: July 22, 2017, 02:54:04 am
content: Thanks for the reply. I know how to discharge high voltage capacitors, I have some experience in amp repairs so I will first try to find the fault myself . I'm hoping to get some tips as to what steps would be logical to follow, or to find someone who has similar issues with this particular amp. Most valve amps are very sturdy in comparison. I've played a Vox AC30, a Musicman , various Fender amps etc and never had as many issues as with this Peavey. The current problem, the 'delayed' power outage seems to only affect the output stage so I may be close to isolating the fault. .. Thanks for the advice though.Cheers

author: SeanB
author_rank: Super Contributor
timestamp: July 22, 2017, 08:29:32 am
content: I will guess as the filaments go out you have dry joints on either the heater wiring, or corroded pins and sockets. First simply remove all tubes, clean the pins and sockets with a cloth moistened in IPA, and then place the tubes back into the same sockets. Then look underneath for cracked solder on the heater wiring, you could have a single poor connection on the power transformer winding or wires that has high resistance and causes this.
How to troubleshoot an FM radio. - Page 1
Forum section: electronics / repair

author: neo
author_rank: Super Contributor
timestamp: July 17, 2017, 10:05:15 pm
content: I have a Sony 7f-74DL 11 transistor radio, my favorite fm radio. It worked last year but it was misplaced and lost over the winter, i find it again and try to turn it on and nothing. No sound at all, though the light does work.Where should i start? I checked the battery voltage and it is exactly what it should be.4.52 on, 4.60 off, 4.40 with lamp all within tolerance of 4.5 volts.

author: RoGeorge
author_rank: Super Contributor
timestamp: July 17, 2017, 10:36:44 pm
content: No sound at all, not even when turning the radio on or off?Maybe the speaker went open circuit, or some contact for the external speaker connector get oxidized (if it has such a connector), maybe just a broken wire.

author: neo
author_rank: Super Contributor
timestamp: July 17, 2017, 10:40:06 pm
content: I clipped my oscilloscope to the speaker and did get some noise on it when turning the lamp on and off, though that is all i get on it.

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: July 18, 2017, 12:15:42 pm
content: Radio faultfinding: Check the obvious like PSU lines and the like, but then proceed to a logical half-split faultfinding technique.The speaker switch on the headphone socket is a favourite for going o/c especially after storage. Try headphones. If they work, that's your problem. Clean the contacts with WD-40 and working the plug in/out. (avoiding getting it elsewhere, of course)What you then really need is a signal generator. Try injecting 400Hz into the audio stages. The volume control, if analog, is a suitable injection point. If that works, try injecting IF, and then RF. That way, you can identify which stages the problem is in. Much faster than random poking with a voltmeter.Note that when injecting signals you need a small capacitor (say 10nF) in series with the sig gen hot lead. Otherwise the sig gen creates a path to ground, altering bias.If you don't have a sig gen you can 'scope for audio at the detector and possibly for the presence of 10.7MHz IF, but to check the RF stages that way you'd need a fairly high performance 'scope. Injecting and listening generally works better than measuring, especially as measuring signals depends on the radio being tuned to a station, which is kinda hard to confirm if it's silent!

author: Cyberdragon
author_rank: Super Contributor
timestamp: July 22, 2017, 01:20:02 am
content: Here's a manual for a similar model:https://elektrotanya.com/sony_7f-74w_sm.pdf/download.htmlCan't get the exact one due to needing accounts or having to pay for it (which is total).EDIT: apparently that is just the schematic, but that's all you really need. There is also a voltage check chart.
WavePro 950 - Page 1
Forum section: electronics / repair

author: grumpydoc
author_rank: Super Contributor
timestamp: July 21, 2017, 09:34:31 pm
content: Anyone know how to get one of these &^%^!!! scopes apart.There is a security attachment on the case of the one I just bought. Ideally I'd remove it but it looks as though it is bolted to the side top cover in which case removing it will leave a hole so it might as well stay but I can't figure out how to get the covers off to check.I have removed the side screws but they look to hold the bottom cover in place. I have removed the screws hiding in the feet which clearly fix the cover onto the chassis but the cover shows no signs of being even slightly loose after that and I don't want to get over violent with it.

author: tautech
author_rank: Super Contributor
timestamp: July 21, 2017, 09:56:36 pm
content: Check for any screws under a label.

author: grumpydoc
author_rank: Super Contributor
timestamp: July 21, 2017, 10:42:51 pm
content: Quote from: tautech on July 21, 2017, 09:56:36 pmNo labels really, but I have it figured.You have to remove the upper back feet then the front bezel (three screws underneath, then wriggle off which is tricky without damaging the plastic clips which hold it at the top), which reveals a further 7 screws around the front of the top cover - two on each side and three across the top. You can then slide the top cover off.The bottom cover just requires removing the visible screws and gently but firmly tugging.The security thing is not bolted through the cover so it is probably stuck on with epoxy or cyanoacrylate. I think I'll leave it as the bond is very probably stronger than the fairly thin sheet steel of the case. I've removed the hemisperical plastic cover which makes it look less obtrusive.It is similar to these "compulock" ones.Acetone might remove the glue but it might also remove the paint.
BK Precision 9185 diagram wanted. - Page 1
Forum section: electronics / repair

author: IAmBack
author_rank: Regular Contributor
timestamp: July 21, 2017, 05:54:09 pm
content: PSU does not switch off output (on off mode there's about 230V, about the same as supply), when ON it produces about 200V higher voltage than expected and shows "System error" message.Anyone has diagram of this PSU (at mainly it's high-voltage/output part)?
transistors replacement - Page 1
Forum section: electronics / repair

author: spdf
author_rank: Contributor
timestamp: July 21, 2017, 08:30:20 am
content: Hello!Yet another basic question is it ok to replace transistors:2sc2229 to 2sc22302sb1186A to 2sc32982sd1763A to 2sa1306and one more question does enyone know good replacment for tlr-112 diode. I added datasheet for it.Thanks in advance!