hybridfree/eevblog-posts huggingface dataset:
LCD touchscreen w/ horizontal lines - Page 1
Forum section: electronics / repair

author: vindoline
author_rank: Unknown
timestamp: May 29, 2018, 03:05:56 am
content: I've got a piece of lab equipment with a problem touchscreen LCD. On power-up it appears to pass its self-tests, however the screen is not useable. Initially, I assumed it was a loose ribbon cable or a dirty zebra strip in need of cleaning. However, this does not appear to be the case. I've re-seated all the cables multiple times and I've checked the solder work on the ribbon cable under the microscope and it looks good. The LCD and touchscreen components are siliconed together and disassembly isn't feasible. Furthermore, it's possible to get the entire LCD to light-up white while inserting the 14-pin ribbon connector. I don't think there is damage to the LCD screen itself. I'm wondering it there's a known common failure mode that causes this. Any ideas are welcome.

author: ataradov
author_rank: Super Contributor
timestamp: May 29, 2018, 03:21:02 am
content: It is a bad connection inside the LCD. You need to undo the black bent clips, remove the board and clean or replace the zebra strips inside the LCD. It does not look like touch screen will be in a way.

author: vindoline
author_rank: Unknown
timestamp: May 29, 2018, 01:46:28 pm
content: Thanks Alex, I'll try and take a look at this tonight.

author: vindoline
author_rank: Unknown
timestamp: May 29, 2018, 04:45:41 pm
content: Alex, you're right that by straightening the aluminum clips the LCD can be disassembled. However, I still believe that the LCD itself is fine. With the frame off, gentle pressure or flexing has no effect on the horizontal lines in the display - however it does cause issues in the vertical directionAdditionally, the fact that I can get all pixels to light up briefly while inserting or removing the ribbon cable suggests to me that the LCD and its associated row and column driver chips (LC79401 & LC79430) are fine. I'm wondering if it could be the Epson controller (S1D13502) or its associated RAM? Any tips on how to troubleshoot this would be appreciated.

author: james_s
author_rank: Super Contributor
timestamp: May 29, 2018, 06:27:02 pm
content: If you get all the pixels activated while inserting or removing the cable that suggests that there may be a problem with whatever is producing the signal. Can you find a datasheet for the display that shows what the signal should be?

author: ataradov
author_rank: Super Contributor
timestamp: May 29, 2018, 06:31:58 pm
content: The cable is clearly just a parallel interface, so it looks like all pixels are activated on power cycle. This may be just some internal reaction of the LCD panel to transient voltages that happen on power up.

author: james_s
author_rank: Super Contributor
timestamp: May 30, 2018, 12:28:40 am
content: Sure but with a parallel interface it's still possible for a fault in the frame buffer to produce lines through the picture. The connection between the glass and drivers you suggested is the first thing I'd suspect though.
hp 837xx power calibration and firmware - Page 1
Forum section: electronics / repair

author: Staffan321
author_rank: Regular Contributor
timestamp: May 29, 2018, 08:30:35 am
content: Hello,This was posted originally in ’Test equipment”, but perhaps it fits better here.Does anyone know where I can find the power calibration routine (service disks) for the HP 83712/83732A RF signal generator? What would be second best (also good of course) would be a dump of the firmware - possibly being able to figure out the available GPIB commands.I have posted at the Yahoo group "HP/Agilent test equipment", but not too much attention unfortunately. Also checked ko4bb.Regards,Staffan

author: Bhannis
author_rank: Newbie
timestamp: May 29, 2018, 08:45:46 am
content: What about Artekmanuals.com?Not for free but..Orhttps://www.naic.edu/~phil/hardware/synth/hp83712/agilent83712CalibrationGuide.pdfSent fra min SM-G955F via Tapatalk

author: Staffan321
author_rank: Regular Contributor
timestamp: May 29, 2018, 09:05:39 am
content: Hello,Already bought the manual from Artek. I need the calibration software and - ideally - firmware for the unit.Regards,Staffan
Repair broken Logitech z5500 sub - Page 1
Forum section: electronics / repair

author: a.ekholm
author_rank: Contributor
timestamp: November 19, 2017, 03:16:51 pm
content: Hi!I'm trying to repair a Logitech z5500 subwoofer. When it was connected to power the subwoofer outputted a LOUD hum. It also smelled burnt.The smell located me to one of the tda7294 chips. I added some pictures of the board with closups on two burnt tda7294 chips, and also other parts.It feels like changing the two tda-chips will not fix the root problem. Where should I look for the case? Voltage regulators that are shorted?How should I proceed with trying to repair?As it behaves now I am not comfortable to measure with it powers on (when smoke came from the tda-chips.)1. Should I remove the chip and power it up?2. Could a variac help me, and how?3. Buy new chips (and spares) and replace and see if that helps? But when two chips are are burnt it seams like other issues exists? Likely they will also be burnt.4.?Thanks! /AndreasI'm trying to learn electronics so I hope to be in it for the long run. So any help is appreciated!Skickat från min SM-G920F via Tapatalk

author: a.ekholm
author_rank: Contributor
timestamp: November 21, 2017, 05:14:21 am
content: Does anyone have any idea how to proceed? And what may have caused the burnt components?Skickat från min SM-G920F via Tapatalk

author: Rasz
author_rank: Super Contributor
timestamp: November 21, 2017, 07:27:12 am
content: usually its power supply that dies first in those speakersdisconnect it from main board and check voltages, afair one of the pins powers it up, otherwise you will only get standby 5VBUT, since pcb is charred you will have to dremel out substantial part of the pcb and bodge connections to replacement amplifier chip, and lets not forget logi 5500 is a shitshow of a speaker system (10% THD)

author: Chris56000
author_rank: Frequent Contributor
timestamp: May 29, 2018, 07:40:17 pm
content: Hi!I realise this thread hasn't been dealt with for over four months, but I felt I had to offer this suggestion!How about using one of these kits:-https://www.ebay.co.uk/i/282980639214?chn=ps&adgroupid=51701849453&rlsatarget=pla-413069991248&abcId=1133946&adtype=pla&merchantid=6995734&poi=&googleloc=9041126&device=c&campaignid=1058609649&crdt=0. . .to repair the subwoofer?A set of four would be less than £15 (free shipping!), and it shouldn't be too difficult to trace the Audio and Power Supply terminalsfrom the original damaged PCB and use four screened cables plus a twisted pair of 16/0.2 cables for each replacement module!Chris Williams
Alpine 3541 amp - Page 1
Forum section: electronics / repair

author: Devcam
author_rank: Newbie
timestamp: March 29, 2018, 05:55:04 am
content: Hi my amp seems to be getting hot very quickly so i put on a ammeter .its reading is jumping up and down from 800ma to sometimes over 4 amps .any help will be much appreciated thanksSent from my SM-J320F using Tapatalk

author: orbanp
author_rank: Regular Contributor
timestamp: March 30, 2018, 01:41:59 pm
content: Hi Devcam,Which part is getting hot inside?I could not find schematics for this amp, just for the Alpine-3550:https://elektrotanya.com/alpine_3550_schematic.pdf/download.htmlI am guessing that it is a similar amp with a different power rating.You need to verify that!Assuming it is similar, do check the power supply, from the PS filter cap voltage ratings it must be something like +/-25V - +/-28V.The PS uses a TL494 type IC, you could debug the PS circuit based on the IC's datasheet.The amps are "regular" linear audio amps, using ICs and discrete power transistors.Lots of info out there on how to debug those.Do verify if your amp matches this "generic scheme".Let us know if this is the case, and any other questions you might have.Regards, Peter

author: drussell
author_rank: Super Contributor
timestamp: March 30, 2018, 04:01:34 pm
content: Do you mean it gets unexpectedly hot quickly, just at idle, not producing any sound but otherwise still functions correctly, sounds clear and un-distorted, etc. on speakers of the correct impedance?or...Does it not work and just sit there getting hot and draw random current even with a muted input, etc?You need to be a bit more specific for us to be able to really help you.

author: Devcam
author_rank: Newbie
timestamp: May 28, 2018, 03:47:27 pm
content: Thanks guys for yols help ive changed all power supply caps and amp works perfect.Thanks for responding .Sent from my SM-J320F using Tapatalk
Hitachi V-650F - Page 1
Forum section: electronics / repair

author: rmcloud
author_rank: Newbie
timestamp: May 29, 2018, 10:16:11 am
content: Hi!I purchased a Hitachi V-650F oscilloscope on ebay. It functions, however I tooka look inside and noticed that the earth ground connection has been disconnected. myfirst thought is that I should reconnect it for safety reasons. I am learning as much as Ican about earth ground and why scopes are connected in this way. I would just like to ask for adviceand perhaps understand why it would have been disconnectedto begin with.Thanks in advance!Bob

author: PKTKS
author_rank: Super Contributor
timestamp: May 29, 2018, 11:06:23 am
content: This question is a matter of debate.The 3rd pin or earth is not required.It is assumed to be a "safe" fallback in case of discharge.In some grid areas there is not even a 3rd pin availableIn those cases even "connected" it connects nothing.The real "safe" thing in a bench is having isolation transformers.The advent of Switch Mode PS have done this a wild problem**IF** your (OLD) scope functions based on an isolated transformerjust forget that 3rd pinOtherwise IMHO the best safe option is still an isolation transformerOne for the instrumentationOther for the loadsMore safe than having an earth connection wide spread on your benchBut that is a matter for debatePaul

author: tautech
author_rank: Super Contributor
timestamp: May 29, 2018, 11:18:37 pm
content: It's safer to leave the scope grounded and have the DUT in isolation from mains ground.Consider where you might clip the reference (gnd) lead from a scope probe.If the scope is removed from mains ground the scope chassis takes on the same potential as the probe reference lead so that can place a significant risk to the user of electric shock or even death.This is known as 'floating the scope' and a practice generally frowned upon.The safest workaround is to get an use differential probes.
Repairing Heathkit nixie multimeter - Page 1
Forum section: electronics / repair

author: rea5245
author_rank: Frequent Contributor
timestamp: May 27, 2018, 07:47:31 pm
content: Hi,I scored a Heathkit IM-1202 nixie tube DMM at a flea market. I've cleaned it, replaced the power cord, re-soldered a broken connection, and I've been going through the calibration procedure. It read DC volts correctly, but resistances always show the meter's version of "infinite" (an overrange light is on and the display shows 86.3).I'm not too good with anything non-digital, but based on the manual and the schematic (attached), it looks like +15V is supposed to go into the emitter of an MPSA20 transistor that acts as a zener diode, so that 7V comes out the base. That goes into the base of 2N3638A transistor causing a constant current to flow through it. That current goes through the resistor under test and the multimeter measures the voltage drop.When I measure the voltage at the MPSA20's emitter, it's 14.3V instead of 15V. The voltages at the 2N3638A's base, collector, and emitter are also a lower than the schematic says they should be, by 0.7V or so. I can understand that would cause the resistance to be measured inaccurately, but I wouldn't expect it to be reported as infinite. Am I wrong? What could account for this?It also brings up the question of why the 15V source is low. Is this the sort of thing old capacitors could cause?And advice on troubleshooting and repairing this would be appreciated.Thank you,Bob

author: floobydust
author_rank: Super Contributor
timestamp: May 28, 2018, 04:32:43 am
content: Given the age, I would replace all electrolytic capacitors, sight unseen. It's just less time and effort than troubleshooting them down to the component level, and there are only 7 totaling a few dollars.The +15V rail is low at +14.3V, possibly due to open C117 or excessive load on the +15V rail, or bad 15V zener D14 1N4166A (1N4744A). I'd start with replacing the caps.But the voltage low by 0.7V should not make the ohms function not work at all, unless there is too much AC ripple which again points to the cap.With input leads shorted or a low value resistor in place, the A/D should not see "over" voltage on ohms function.The function switch might have a bad connection. With the meter powered off check continuity from the input jack back to the A/D input (C101). Polarity switch must be (+) for ohms function.
looking for an audio source on this board - Page 1
Forum section: electronics / repair

author: connor.bisby
author_rank: Contributor
timestamp: May 25, 2018, 09:21:24 pm
content: Hello im looking for help into finding a left and right audio source on this board. it come from the cd player in my head unit and as i dont use cd's i was trying to pluck an audio source from the board. any info on these chips would be great i have tried the usual google search but turned up with nothing. cheers in advance

author: Zucca
author_rank: Unknown
timestamp: May 28, 2018, 07:45:48 am
content: A look on the other amplifier board could help.
Repairing a USB port on a bike light let the magic smoke out. - Page 1
Forum section: electronics / repair

author: jld
author_rank: Newbie
timestamp: May 30, 2018, 09:44:16 pm
content: I was dumb and plugged by USB rechargeable bike headlight to charge in while it was mounted to my handlebars. My bike fell over and the strain between the USB cable and the light ripped the USB port out of the PCB. The light was off (but charging) at the time, but continued to work with the busted USB port.I ordered some replacement through hole mini-USB female plugs. I desoldered the bits of the old port that remained, and soldered the replacement port in place with no issues. I confirmed that there was no continuity between any of the pins before going any further.I plugged the light it into the usb charger, and component U3 burnt up instantly, and the light stopped working.I'm surprised as the fault was seeming a straight forward physical one, and I turned it into an electrical one.Can anyone offer advice on what I might have done wrong, and perhaps on what component U3 might be so I can see if I can replace it?Thanks!

author: donkey77
author_rank: Regular Contributor
timestamp: May 30, 2018, 09:56:18 pm
content: I can't help with M3:s but seem to remember when repairing a BlackBerry playbook a few years back that it wasn't a standard micro USB connector. Can't remember exactly but I think it was either flipped or something?! Are you sure the one you fitted was correct?

author: jld
author_rank: Newbie
timestamp: May 30, 2018, 10:32:15 pm
content: I can't be positive, since the port body got torn off and then pins remained in the pcb, but the replacement dropped right in.Looking at all the options for mini USB B jacks on digikey, they all have their pins mapped through the same way. It's possible there is a different format where the pins get routed differently from board to port, but I doubt it.http://www.tensility.com/pdffiles/54-00027.pdf

author: tsman
author_rank: Frequent Contributor
timestamp: May 30, 2018, 11:38:48 pm
content: You can try tracing out the 5V and ground pins on the USB connector to see if they connect to the appropriate pins on that chip. It is hard to see from your photos as it has black soldermask and some kind of conformal coating.

author: jld
author_rank: Newbie
timestamp: May 31, 2018, 12:14:18 am
content: I’ll give that a shot. I’m new at this, which pins are typically 5v and ground?
PWM Controller Fuse?  And Where to get a new one - Page 1
Forum section: electronics / repair

author: Veramacor
author_rank: Regular Contributor
timestamp: May 23, 2018, 01:21:47 pm
content: Hello all,I bought a couple 100 AMP PWM controllers that I want to use for my two trolling motors.They worked fine of course on land, but when on the boat I did the most basic stupid thing in electronics - I reversed the polarity of the battery mains!So lesson learned, attached are pictures of what I believe is a burned brass fuse.The trouble is, I don't know what formal name of this type of fuse is called. Is it a shunt serving as a fuse? A few google searches turned up nothing because I know I'm not using the right terminology.Can anyone point me in the right direction to possibly find replacements? I don't just want to bridge the gap with just anything, I would like to replace what was there.Thanks for any help!Jeff

author: oventech
author_rank: Contributor
timestamp: May 23, 2018, 10:43:40 pm
content: One question is what PWM controller did you get? Pics of the whole controller would be useful. Might be able to identify the part that needs replaced.
tek 317 scope repair - Page 1
Forum section: electronics / repair

author: KV8E
author_rank: Newbie
timestamp: May 19, 2018, 03:45:47 pm
content: I am restoring a Tektronix 317 single trace scope from the early 60s. got it working good but need to replace some of the neon ne-2 bulbs used for current limiting. need to know the voltage and current rating of the bulbs used in these scopes. there r many different types and the manual only says ne-2 type but there r several types of ne-2 bulbs with different ratings. thanks kv8e doug

author: Cyberdragon
author_rank: Super Contributor
timestamp: May 21, 2018, 04:36:37 am
content: The manual specifies NE-23 bulbs.

author: oventech
author_rank: Contributor
timestamp: May 23, 2018, 02:46:27 am
content: Hello KV8E Here is the link to the 317 Wiki page. For Manuals.http://w140.com/tekwiki/wiki/317
HP 3312A Repair (Bad Switch Contacts) - Page 1
Forum section: electronics / repair

author: Jackson
author_rank: Contributor
timestamp: May 22, 2018, 11:21:01 pm
content: Hello all,I'm currently working through a back log of teardowns/repairs I'm working on (and have finished). This one is a successful repair from a couple months ago, an instrument I obtained over the winter (along with several others) from a Craigslist deal. The function generator worked well except for the range switches (see video below). It seemed to be stuck on a certain range. Looking at the schematic (attached) and seeing the way the range switches were all laddered together, I went about testing them all when pressed/unpressed for continuity. Sure enough, the 1 MHz and 100 kHz range switches both showed spotty continuity. A bit of Deoxit and some actuation later and the thing was as good as new!https://youtu.be/JVX2LxFuFkQ

author: Jackson
author_rank: Contributor
timestamp: May 22, 2018, 11:24:48 pm
content: And for followup, here are some general images of the insides that I took when I had it apart. Nice and tidy inside. Unseen in the top of the last picture is the bottom row of BNC connectors and dials, which are obscured by the metal frame.
Convert stereo slide potentiometer to mono? - Page 1
Forum section: electronics / repair

author: belzrebuth
author_rank: Frequent Contributor
timestamp: May 21, 2018, 08:17:53 am
content: Hi all,I've got to replace a failed 10KB mono potentiometer and I've found one with the same dimensions but it's stereoI thought about using just one track of the stereo pot and cut the other set of the legs off but I'm wondering if there could be another way.(ideally using both carbon tracks)The stereo slider is the same value else I could just wire it in parallel I guess but I couldn't find a 20k one..

author: Electro Detective
author_rank: Super Contributor
timestamp: May 21, 2018, 09:51:54 am
content: Adjacent carbon tracks can differ no matter how good the qualityOtherwise no big deal to use one side of a twin pot, been done many times and no one the wiser

author: belzrebuth
author_rank: Frequent Contributor
timestamp: May 21, 2018, 07:59:23 pm
content: Thanks I'll do that..!
Philips Lumea SC1992 Teardown / Repair help needed - Page 1
Forum section: electronics / repair

author: Felicitus
author_rank: Regular Contributor
timestamp: May 21, 2018, 01:24:16 pm
content: Curiosity killed my device. I was keen on confirming my theory of operation of my Philips Lumea SC1992, but in the process of tearing it down (ugly one way clip mechanism) I killed R202, unable to find it again.It seems they're using the L6562A to charge the capacitor, the resistor in question was connected between the CS pin and the 100 Ohms current shunt resistor. Unfortunately I didn't figure out how to calculate R202, maybe someone can give me a pointer? The datasheet for the L6562A unfortunately doesn't give many formulas, and the reference schematics also don't fit the use case.Maybe someone has a (defective) device and can measure R202 for me?

author: fourtytwo42
author_rank: Super Contributor
timestamp: May 21, 2018, 05:57:08 pm
content: Having a stab, it's very unlikely the current shunt is 100R as this would give an output power of only a few hundered mW if that. There is probably a capacitor from CS to ground so the resistor is there to form an RC filter to get rid of the mosfet turn-on spike and prevent false triggering of the current sense input. If R is to large the delay will be to long, but as you almost certainly dont know C (SMT brown blob with no markings) some experimentation would be nececery, its better to err on the low side and work up so I would go for 100R and no more than 1K if that helps

author: Felicitus
author_rank: Regular Contributor
timestamp: May 21, 2018, 07:53:52 pm
content: Quote from: fourtytwo42 on May 21, 2018, 05:57:08 pmWhoops yes, you're right, I've most likely read it upside down. It's more likely to be 0.001 Ohms, odd thing is that the dot is on the right side. I think I'll desolder the cap and see which value it reads, but yes, something between 100R and 1K is certainly a good idea. Realized later that the resistor is in series and not in parallel, forming a filter instead of a voltage divider.Thank you
Fender Princeton 3 prong grounded power plug conversion - Page 1
Forum section: electronics / repair

author: jcrubin
author_rank: Frequent Contributor
timestamp: May 21, 2018, 12:21:41 pm
content: In this video, I update a Fender Princeton Reverb tube amplifier with a request for a 3 prong ground power plug upgrade to stop the owner from getting shocked when on the road with this unit. A brief inspection is conducted with regard to the amp as well as the simple process along with some stop motion fun.
Progressive Dynamics PD9280 Converter repair & mosfet ID - Page 1
Forum section: electronics / repair

author: albert001
author_rank: Regular Contributor
timestamp: May 19, 2018, 09:03:37 pm
content: Hello,I have a Progressive Dymanics Converter / Charger (PD9280) that was installed in a RV and all of sudden stopped putting out any DC as one it's 20 amp fast acting ceramic fuse keeps blowing.One end of the 20 amp ceramic fuse has continuity to the AC black hot and one of the white wired of the rectifier. Possibly the rectifier is bad, however what's causing the fuse to blow can be somewhere after the rectifier and after the other end of the fuse , as anything connected to the circuit potentially can cause the fuse to blow.I've been looking at the rectifier as these have been known to fail. The rectifier I'm able to find a part number and replacement.https://www.digikey.com/product-detail/en/comchip-technology/KBPC2504-G/641-1851-ND/3300067However there are two mosfets that potentially can go bad. Qa1 and Qa2. (neither have any continuity to the fuse) I have the schematics and other documentation from it's patent however I'm not able to find a part number for the two mosfets as it appears the part numbers have been distorted by a marking pen of some sort. (see pic)https://patents.google.com/patent/US7782002Link to schematic with mosfets Q1a and Q2bhttps://patentimages.storage.googleapis.com/US7782002B2/US07782002-20100824-D00004.pngI've only cleaned up two mosfets as it appears both will need to be cut out and I'm still trying to determine a part number before removing.After cleaning up the mosfets which appeared to have some corrosion, the 20 amp ceramic fused blew again.here's a pic of the mosfets which have some corrosion. Both have plastic tubing installed near the bottom where the pins connect to the pcb. The mosfets I'm looking to replace are the two on the left.

author: Chris56000
author_rank: Frequent Contributor
timestamp: May 20, 2018, 09:02:34 pm
content: Hi!I've been reading that Patent Document, and, in my honest opinion, 2 X IRFP460 (Farnell, Digi–Key or Mouser!) should be found satisfactory to replace the original scratched–off devices – these are in an identical TO-247 package and have approximately the same Rds–on as the types suggested in the Patent!I would NOT attempt to over–rate the devices as higher–power or higher current devices may have a substantially greater Qgs (gate–charge rating), which may require much more gate–drive current than the drive circuits can provide, leading to possible overheating and early failure of the replacement devices!The Patent Document is very comprehensively written with excellent circuit descriptions and well worth a careful study!Chris Williams
CTEK MXS 5.0 - Page 1
Forum section: electronics / repair

author: razirafi
author_rank: Newbie
timestamp: September 17, 2017, 07:54:20 am
content: A good day to all. I have a CTEK MXS 5.0 that is already out of warranty (I think) and it has stopped working. When I plug it in I can hear a buzzing sound and no lights whatsoever. So I opened it up and started checking. The primary side seems to be OK as I have about 15.8 Volts at the secondary side across each output filter capacitor. I also found out that one of the two 8-pin SMD MosFETs have shorted. Another of the components which I think is also shorted looks like a DPAK transistor so I tried removing it from the board. I lifted the two outer legs off the board and as I was about to lift the center leg which is internally connected to the metal tab, the epoxy package broke off. Does anyone know the part number of this part. The marking on it looks like a D113iG or D1131G.Note: If I were to use the conventional marking of semiconductors this would come to be a 2SD1131 device. I just need someone to confirm if this is so. If it uses SMD style marking, then it is a different story.

author: hendorog
author_rank: Super Contributor
timestamp: September 17, 2017, 07:58:57 am
content: Hope you get it fixed - those things have a 5 year warranty and based on the experience of myself and another forum member they are very good about replacing them.

author: razirafi
author_rank: Newbie
timestamp: September 25, 2017, 11:32:51 pm
content: Update. I have already found out what part it is and have ordered them. I'll see how it goes when I solder them in.

author: Vetor
author_rank: Newbie
timestamp: May 17, 2018, 10:42:53 pm
content: razirafi, it worked after replacing that component?My also broken and has this buzzing sound...

author: razirafi
author_rank: Newbie
timestamp: May 20, 2018, 12:08:37 am
content: Yes, my charger has been working again after the replacement of the regulator. The problem with yours could be entirely different with mine, so there are no guarantees that it will work for you.
~60kHz oscillation on bench power supply output - Page 1
Forum section: electronics / repair

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: May 19, 2018, 12:13:14 am
content: I have a triple output bench power supply (HYelec HY3003-D) that has developed a problem on all outputs (inc. fixed 5V) in CV mode. There is an approx. 60kHz oscillation at least 0.2V in amplitude (0.6V at 15V output). The problem is not present in CC mode. It is present in independent, parallel and serial configurations. As the photos show, even with zero output the oscillation is still there. The file names indicate the voltage and mode.Has anyone seen this fault before and, if so, were you able to make your own repair?Thanks.

author: Jwillis
author_rank: Super Contributor
timestamp: May 19, 2018, 04:49:34 am
content: I swiped this from another post. The LM741's are the mode indicators I believe.Maybe one has gone funny .Does that 60khz appear on both master and slave .Does it appear on the 5 volt output as well?

author: David Hess
author_rank: Super Contributor
timestamp: May 19, 2018, 11:28:16 am
content: Make sure output capacitor C20 which is required for frequency compensation is not shot.

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: May 19, 2018, 06:59:38 pm
content: Quote from: Jwillis on May 19, 2018, 04:49:34 amThanks. I've taken apart my unit. There are two identical PCBs labelled 2SD2163. The only difference I can see is that the slave has a yellow and a brown wire in the bundle connecting to the left side as shown in the attached image whereas the master board has jumper wires. The schematic you provide is a bit different. Does the dashed outline for the slave identicate that it is the same except for the specific components shown?Contrary to what I said earlier, the oscillation is not on the 5V. It is always on the master in CV mode (irrespective of Independent/Serial/Parallel) even at zero output. It doesn't show on the slave in independent mode. In serial mode, it does show but at a difference frequency (80kHz vs 60kHz approx.) In parallel mode, the output of the slave is identical to the master. Note, the frequency for the master is always the same. I've also operated the unit without the slave board and see the same behaving with the master. So, it seems the fault lies with the master board.I suppose an obvious next step is to operate in independent mode and probe around starting at the input from the main regulator board until I see a difference.

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: May 19, 2018, 07:12:13 pm
content: Quote from: David Hess on May 19, 2018, 11:28:16 amThanks. I tested it for the master channel. The cap itself is on a small board for the front terminals. It appears okay out-of-circuit.
HP34970A Memory Replace Help - Page 1
Forum section: electronics / repair

author: pete99
author_rank: Contributor
timestamp: May 23, 2018, 10:06:17 pm
content: Hello,Hope this message is suitable for the forum.I have an old HP34970 now with errors 742, 743, 744, 745, 746, and 749.I believe these indicate a memory problem.I purchased 4 pieces of 1818-6821 4K FRAM ICs from Keysight.I would like to pay someone to replace the memory ICs and restore the EPROM data stuff.I live in California.Thanks,Steve

author: HighVoltage
author_rank: Super Contributor
timestamp: May 24, 2018, 09:18:41 am
content: Search for other threads here on the forum, related to the 34970A.There have been a few people from CA, that repaired their instrument.May be you will be more effective, sending them a PM.

author: pete99
author_rank: Contributor
timestamp: May 25, 2018, 09:54:31 pm
content: Thank you for the reply and suggestion.Cheers,Steve
Repair SainSmart DDS140 - Page 1
Forum section: electronics / repair

author: afarre
author_rank: Newbie
timestamp: March 25, 2018, 09:23:27 am
content: I just burned out my DDS140 doing an unsafe ground probe connection. It still partially woks letting me to see test signal at some scales. Signal generator and Logic Analizer are still working.I just made some cheks on PCB circuit but I am at some point where I cannot continue troubleshooting without the SCHEMATIC.I am positive that it could be easily fixed having the schematic. Any input about it?Thanks

author: coromonadalix
author_rank: Super Contributor
timestamp: March 25, 2018, 11:40:02 am
content: Ask them, not sure they will provide schematics, or ask them under an non disclosure agreement ? or maybe just the input sectionOr provide us with pictures of the board, we can help identify some chips, normally you have some coupling chips or maybe some who do somekind of isolation ??

author: afarre
author_rank: Newbie
timestamp: March 25, 2018, 12:33:52 pm
content: Quote from: coromonadalix on March 25, 2018, 11:40:02 amThank you for your reply.I asked them right after my post here, but saying the truth, not sure if it was a good idea. I got an auto-reply that says they are going to answer in 24h. If I get some sort of negative answer, it is a good idea to ask just for input section, thanks fot that.About the pics there are plenty of them at this forum thread:https://www.eevblog.com/forum/testgear/sainsmart-dds120-usb-oscilloscope-(buudai-bm102)/and here with detalis of some IC's:https://sigrok.org/wiki/SainSmart_DDS140but don't worry about it, I have already checked the IC fuse, the IC LDO 3.3V, all diodes and some transistors. Next I need to unsolder some transistor for proper test but first I prefer so see if I get the schematic.On wednesday I am to receive my new oscope Siglent SDS1202X-E (https://www.siglent.eu/sds1202x-e.html)once having it I could make some more advanced checks like some OA's that could be acting as isolation, as you said.Thank you again.

author: coromonadalix
author_rank: Super Contributor
timestamp: March 25, 2018, 01:23:07 pm
content: well you have input signal diodes, cd4052 switches an the ad converter, it may have blown up to that chip, or the worst, up to the cypress chip, or maybe you have an fused pcb traceFor thoses puppies i would have automatically installed an usb isolator ... for any usb plugged measurement tool, and or an isolated / floating supply if needed, had to much problems at my work, had to order ftdi isolated usb rs232 cables. Bad signals / distortion, and mostly ground potentials problemsgood luck

author: K6TWO
author_rank: Newbie
timestamp: May 19, 2018, 12:51:51 am
content: I have a DDS140 with the signal gen encroachment. but I do not have the software any more. Do you have the complete software and could you nor anyone burn me a CD with the auto install and all the required drivers and software. Ill reimburse you for your time. Right now it is just a brick to me.619 518 2547 text me
Help with BM235 startup issue - Page 1
Forum section: electronics / repair

author: ls4300t
author_rank: Newbie
timestamp: May 20, 2018, 10:04:15 am
content: HelloMy BM235 unfortunately doesn't work anymore and I would like some help.I did do a search but didn't find anything similar to the issue I'm facing. I also viewed Dave's video repairing a BM235 and it's not that issue. To confirm, I have opened up my unit and confirmed the L3 thing is not broken and the solder connections are still intact.For starters, I bought mine about 1.5 years ago now. I mainly use it for resistance and voltage checking on small things. I have also used the temperature and electric field features on occasion. The rest of the time it is mainly carefully packed in a storage case. Recently I needed to check battery voltages and was surprised it has a strange startup issue and in the end it is unusable.I have a video demo'ing the strange startup issue.https://youtu.be/HKVtMOPewXIWhen I turn it on to voltage checking, almost all the LCD graphics components start flashing. I remember when it used to work, the display would almost immediately turn to zero and once I check a battery, the appropriate voltage numbers would show up. Instead this just doesn't work anymore.When I switch to resistance, it also doesn't work. In my video, I switch there from voltage and the display shows "300". When I check a resistance, the display doesn't change. It stays stuck at "300". If I switch to resistance from the off position, I see a zero voltage and testing any resistance doesn't show a change in the display.I'm wondering if my unit just somehow needs to be reset. I haven't found anything yet to do that. I have tried removing the batteries and waiting some time before putting it back in but the same thing happens. I have also tried fresh batteries but this strange behavior still happens.So I'm at a loss at what's going on. Other than using it as it was intended and opening it up to replace batteries and also opening the case to confirm the L3 thing is ok, I haven't done anything else to it like say drop it or do any kind of modifications.Any help is appreciated, Thanks!
4-20 ma 1-10 volte source repair  - Page 1
Forum section: electronics / repair

author: jamieblatant
author_rank: Newbie
timestamp: May 17, 2018, 08:57:48 pm
content: hi allneed a hand with this one as its past my knowledgethis device is a current voltage loop source as shown herehttps://www.timeelectronics.com/portable-voltage-current-instruments/7006-loop-simulator-source/it was accidentally injected with 24 volts and now wont work as you can see its got no ovious sings of damages so i suspect on od the 2 chips at the top or one of the transistorsany advice , i am not in a rush i have just started to work through all the parts checking as i gothanks

author: coromonadalix
author_rank: Super Contributor
timestamp: May 18, 2018, 01:15:24 am
content: Check the 8 pins ic, is it somekind of powersupply / controller / buck boost smps .... ka34xx number it has an coil and rectifier diode near it, maybe bustedSearch fo any 3 pins regulator transistor look a like ...Under the v3.0 you have an pic xxx controller, hope it is not bustedAsk the company for an schematic under non disclosure agreement ??

author: jamieblatant
author_rank: Newbie
timestamp: May 18, 2018, 05:08:53 pm
content: i think the item with v3.0 is a micro controller that controls the actions of the device and it works as it totall functionsi think the top 2 ic are the outputs and they dontthey are about £10 to buy so i might wasp them with sockets , i am at least going to test them some more and de soilder them as my next effort
DELL AS501 Soundbar - Make scratching noise - Page 1
Forum section: electronics / repair

author: 2X
author_rank: Frequent Contributor
timestamp: May 23, 2018, 06:23:42 pm
content: Hello,I have three DELL AS501 Soundbars but the one when it is connected to the PC makes a scratching noise (especially when the volume of the soundbar is at the maximum), without the present of any song. The other two soundbars don't do this. Does anyone guide me about how to repair this problem? Thanks in advance.Picture 1:Picture 2:Picture 3:Picture 4:Picture 5:Picture 6:Picture 7:Picture 8:Picture 9:

author: SeanB
author_rank: Super Contributor
timestamp: May 23, 2018, 07:33:46 pm
content: A suggestion is to remove the glue from the board, without damaging any components under it, and clean the board with alcohol to remove the residue. Very likely the glue is becoming conductive, like the recent repair of Dave with the conductive corrosive glue in a similar type of powered speakers.
GW Instek sfg-1003 unsteady output - Page 1
Forum section: electronics / repair

author: Pyra
author_rank: Newbie
timestamp: May 17, 2018, 10:31:20 pm
content: So I'm relatively new to the whole electronics game (about a year in) and I have slowly been gathering goodies to add to my toy box. I recently came upon a function generator for the low low price of free but soon found out that there was an issue with it. The signal it outputs is a tad.... jumpy? you can see what I mean in the attached image I hooked it up to a scope, set the desired output to 1 Khz and soon found out that there was a problem.With some button pressing and knob turning I have found that:-The problem persists across sine, square and triangle waves-Adjusting the amplitude would cause the signal to "steady" out at certain voltages. (I cannot remember the values) however I was never able to obtain a "clean" signal.-Changing the Frequency does not clean up the signal.-Nothing smells outright cooked.-No visual faults on the boardSo far I have tried:-To find some form of schematic or service manual for this thing but came up dry.-Started to draw out the schematic for a generally easier view of it before realizing that it was a lot of work and that I should just ask for help from more knowledgeable people.-Searched forums for someone with a similar problem.-Checked output Frequency of the crystal(all good)So I turn to you good people to see if anyone has any ideas as to what's wrong with it.
tektroinx 453 repair - Page 1
Forum section: electronics / repair

author: KV8E
author_rank: Newbie
timestamp: May 14, 2018, 07:40:02 pm
content: I have a 453 scope that works fine except for the rotary time base sweep knob. it will not go above 50ms position. acts like it has hit the end stop. have looked at the switch best I can through the boards and other things in the way and cant see why it will not turn further. acts like it is hitting something at the 50ms spot. any ideas?? switch does go down to the bottom with no problem.

author: huelter
author_rank: Contributor
timestamp: May 14, 2018, 07:43:01 pm
content: Try to spray some contact cleaner inside the knob. Other than that, I think you will need to remove it to fix/replace.

author: PaulAm
author_rank: Frequent Contributor
timestamp: May 14, 2018, 10:09:05 pm
content: Is the B sweep locked? Can you advance the B sweep past the lock point? It should be able to go to the highest sweep speed.There may be something in the A/B sweep mechanical interlock that's preventing the knob from going further. You'll need to open it up to take a look. With any luck something fell into the switch and you can fish it out. I haven't looked inside a 453 for a while, but I imagine that it would be major surgery to get that switch out.I would not spray contact cleaner all over the switch, just sayin.

author: joseph nicholas
author_rank: Frequent Contributor
timestamp: May 14, 2018, 11:54:13 pm
content: I know this is not the place for this but here goes. If anyone is interested I have all of the boards for this plus a crt, transformer all in working condition. Just saying.

author: particleman
author_rank: Regular Contributor
timestamp: May 15, 2018, 02:49:41 pm
content: Does the variable timebase (red knob in center of time base) turn?

author: bob91343
author_rank: Super Contributor
timestamp: May 16, 2018, 05:13:08 pm
content: Some of the knobs require pulling out to get past the stop.
Help me repair a ASUS ROG G501J laptop - Page 1
Forum section: electronics / repair

author: a.ekholm
author_rank: Contributor
timestamp: May 14, 2018, 08:53:34 pm
content: Hi!I'm trying to repair a ASUS ROG G501J laptop that is copleatly dead.My finding so far is that the bios i lacking 3.3v.I have tryed to jump the two startup mosfets with 19v and get a current draw of about 0.1amp.I have used my Flir One to get some photos and got only one point that stands out from the rest.It seams to be a Dual Synchronous Step-Down Controller with 5V and 3.3V LDOs that is hot. Is i lkely that i have found the problem?Is this the same chiphttps://www.ebay.co.uk/itm/2x-TI-TPS51285A-TPS-51285A-Ultra-Low-Quiescent-Dual-Synchronous-Controller-Chip/112321234369?hash=item1a26de05c1:g:GbIAAOSwuxFYuBKGIt doesn´t have exactly the same writing on it...

author: wraper
author_rank: Unknown
timestamp: May 14, 2018, 09:01:29 pm
content: Quote from: a.ekholm on May 14, 2018, 08:53:34 pmIt's the same. Other symbols are date code, lot, etc...

author: Whales
author_rank: Super Contributor
timestamp: May 14, 2018, 09:19:41 pm
content: Be wary that a hot regulator could mean that there's a shorted component elsewhere trying to suck too much power.

author: a.ekholm
author_rank: Contributor
timestamp: May 17, 2018, 08:07:37 pm
content: Hi again! Do you think that i could inject 3.3 and 5v on the outputs and see if something is shorting the output and see if something gets hot?Skickat från min iPhone med Tapatalk

author: Rasz
author_rank: Super Contributor
timestamp: May 17, 2018, 10:22:16 pm
content: or you could just measure

author: a.ekholm
author_rank: Contributor
timestamp: May 18, 2018, 04:28:17 am
content: Yes I have measured and can see that the voltage regulator is not outputting 3.3v but as it could be that it's get hot when trying to deliver. Thats why I thought about putting the power supply not the outputs? How do you think I should proceed?Skickat från min iPhone med Tapatalk

author: Rasz
author_rank: Super Contributor
timestamp: May 18, 2018, 02:36:47 pm
content: you can measure more than output voltagecheck resistance to ground on its outputs
Tektronix 2235 - Volts/Div Malfunction - Page 1
Forum section: electronics / repair

author: CarsonReidDavis
author_rank: Regular Contributor
timestamp: May 15, 2018, 04:33:55 am
content: I recently bought a Tektronix 2235, and most of the functions seem to be in working order.However, something seems to be wrong with the high resolution portion of the Volts/Div adjustment on both channels.The adjustment works as expected from 50 V to 50mV, however things get weird from 20mV to 2mV. As the scope is put into 20mV and beyond, it becomes impossible to keep the signal centered on the screen. First it moves to the top, and then it disappears completely.Any ideas as to what might be happening and how it could be fixed?Photos of the ongoing repair are athttps://imgur.com/a/q7FfYSe.

author: tautech
author_rank: Super Contributor
timestamp: May 15, 2018, 05:14:14 am
content: Welcome to the forum.Work your way through the Service manual adjustments section and there should be an offset/zero adjustment just dedicated to the higher sensitivity ranges. Failing that being of any use there'll be a problem in the high sensitivity input attenuator like maybe someone has over-volted the input while at high sensitivity settings.Some study of the circuit description section should make what's going on pretty clear.If you haven't got this it can help too:http://www.sphere.bc.ca/test/tek-parts/troubleshooting-scopes.pdf

author: floobydust
author_rank: Super Contributor
timestamp: May 15, 2018, 05:22:24 am
content: The scope's balance needs to be adjusted, the symptom is the trace shifts up or down depending on the range. Most analog scopes will do this a little bit, depending on temperature.There is Attenuator Step Balance adjustment R10 and R60 which are probably first to try.The 2mV/5mV range have their own DC balance adjustment R33, R83.Two other balance adjustments R25 for 10mV variable (uncal) use, and R75 for Ch.2 invert balance.The2235 service manualalignment procedure gives info. Just make sure the scope is warmed up.If you can 't get it to behave and stay centered, then the front end might be damaged and have to troubleshoot that.

author: CarsonReidDavis
author_rank: Regular Contributor
timestamp: May 15, 2018, 05:57:12 am
content: Awesome, thanks for the suggestions.I'll read through that manual and post an update after making some adjustments.