hybridfree/eevblog-posts huggingface dataset:
Aixun T3A Soldering Station stopped Heating the cartridge/tip - Page 1
Forum section: electronics / repair

author: phunk
author_rank: Newbie
timestamp: July 25, 2022, 03:53:22 pm
content: UPDATE:Turns out I have a defective tip. Swapped it and the station is running fine again.Hello,my barely used Aixun T3A, bought in November 21, all of a sudden stopped heating the tip. Station is powering up normally but the temperature reading is more or less stuck at room temperature and the station is not heating no matter what temperature goal I set. This behaviour is the same either with or without the cradle (which triggers the dormancy mode).I can heat up the tip externally with a heat gun and get a working temp reading.I tried to reset the station but no success.What could I look for? You guys have any ideas? I contacted the seller but there is little hope to be honest. Sending it back to CN is most likely not an option.Thank you.
AKAI AM 2600 service  - Page 1
Forum section: electronics / repair

author: MartinM87
author_rank: Newbie
timestamp: June 22, 2025, 07:01:37 pm
content: Hello,I would appreciate any help with servicing this amp.There is a crackling sound on power up that lasts from 2 sec up to a minute.Also protection relaycuts out as soon as the volume is above 25% or there is lots of low frequencies.I posted the service manual.Amp is around 50 years old and I know it needs to be recapped,just not sure where to start.Is there anything obvious I could check first?

author: David_AVD
author_rank: Super Contributor
timestamp: June 22, 2025, 11:04:59 pm
content: C22 and C23 (gone low in value) will likely be the cause of the protection relay issue. Sort this out first so you can test the other issues properly.Your next step is to find the crackle. Does the crackle level change with the volume control position (and no crackle if volume left at minimum) ? Same question for the MUTE switch.If it does vary with the volume control, is it only with the phono input selected?Come back with answers and we'll go from there.

author: MartinM87
author_rank: Newbie
timestamp: June 30, 2025, 04:09:59 pm
content: Ok I have received the parts and swapped the capacitors.That solved the protection problemThat crackling noise doesn't always appear so I can't re create the issue to test the mute switch.I never used phono it was always on AUX input.But when it does happen,the VU meter bulb flickers and it seems like there isn't enough power coming to the amp.When it settles down eventually, the relay clicks in and sound comes through.

author: David_AVD
author_rank: Super Contributor
timestamp: June 30, 2025, 07:29:19 pm
content: It sounds like the contacts inside the power switch are oxidised/ corroded. With the power disconnected measure the resistance of it in the ON position. Another way is to measure the resistance across the mains plug (active to neutral) and see if you get a stable reading, Wriggle the power switch slightly during the test. You could also temporarily bypass the power switch if in doubt. Also make sure all fuses and their holders are tight and clean.
Akai AMX10 losing B+ Voltage - Page 1
Forum section: electronics / repair

author: average joe strummer
author_rank: Newbie
timestamp: October 09, 2019, 06:00:35 am
content: Hello all.New here. Glad I found this forum looking at the knowledge here. I usually work on guitar tube amps but took on the repair of a small Akai PA head. Symptoms were speakers cutting out. I looked at the speaker relay, suspecting it was the culprit but it tested fine. I tested a few points on the PCB where voltages were printed and notices the B+ wasn't stable. It was in-fact disappearing until so low that the relay opened and cut speaker power. The B+ then spiked back up, closed the relay and speaker functioned again.So, I measured across the main filter cap. Voltage was rock solid, but if I place the negative probe on chassis ground, and positive on the cap, the voltage started dropping towards zero again. I'm at a loss as to where the voltage could be going. Would a leaky cap send voltage to ground? Any help would be massively appreciated.AJS.

author: benj38
author_rank: Frequent Contributor
timestamp: October 09, 2019, 11:22:59 am
content: Can you upload a schematic we can all look at?Your description hints at the possibility of some loose ground connection. Some instruments transmit the negative side of the voltage from the filter capacitor (which is connected to ground) to other boards not through a wire (like the plus side), but through the chassis, and screws that clamp the ground PCB trace to the chassis.

author: andy3055
author_rank: Super Contributor
timestamp: October 09, 2019, 04:36:45 pm
content: Quote from: benj38 on October 09, 2019, 11:22:59 amLike benj38 has mentioned, there should be a bad connection. Re-solder the filter cap terminals-especially the negative.

author: average joe strummer
author_rank: Newbie
timestamp: October 09, 2019, 10:04:43 pm
content: Thanks for the replies benj38 & andy3055.I couldn't find a schematic anywhere. If you know a secret site where rare schematics are located....I'm all earsI'll have to strip the power board out to get to the solder lugs, but will do that today and get back to you.Thanks again gents.
AKAI CS-M3 Cassette deck - motor always running - Page 1
Forum section: electronics / repair

author: michalism
author_rank: Regular Contributor
timestamp: July 15, 2019, 07:28:51 pm
content: Hello all.I'm restoring an old AKAI CS-M3 cassette deck and from the time I got it, the motor is always running regardless if the PLAY button is pressed or not. It is not responsive to any button (FF or REV). As soon as the unit is on, the motor is spinning. I have checked the PLAY button and it is working as expected (I have continuity on the meter if it is in the OFF position, and no continuity if it is ON).I checked the service manual, and I suspected that something may be wrong with TR6 and/or TR10, and the associated components but all checks show no problems. I even swapped TR6 with a new transistor but nothing changed.I'm looking for some guidance on how to continue since I have no clue what to do next.Not sure if I am allowed to attach the service manual here, or the schematic. I have it available for anyone interested to take a look.Thank you!Michalis

author: bob91343
author_rank: Super Contributor
timestamp: July 15, 2019, 09:08:45 pm
content: Trace the current path from the motor to the power supply. There is probably a little contact pair that may not be opening in the off position.Without a diagram I can't make any other suggestions.

author: mzacharias
author_rank: Frequent Contributor
timestamp: July 15, 2019, 09:54:36 pm
content: Quite normal on many models.Edit - checked the schematic - this is normal for this model.

author: coppice
author_rank: Super Contributor
timestamp: July 15, 2019, 09:56:15 pm
content: Quote from: mzacharias on July 15, 2019, 09:54:36 pmYeah, even expensive ones. My father had quite an expensive Akai cassette machine where the motor started as you pushed the on button.

author: coromonadalix
author_rank: Super Contributor
timestamp: July 15, 2019, 10:03:47 pm
content: yep seen the circuit, this one is normal behaviour, it will spin once powered on ...Service manualhttps://elektrotanya.com/akai_cs-m3_cs-m4.pdf/download.htmlFree registrationhttps://www.hifiengine.com/manual_library/akai/cs-m3.shtml

author: floobydust
author_rank: Super Contributor
timestamp: July 15, 2019, 11:27:29 pm
content: Cassette decks with power-assist transports have the motor running all the time.The motor moves the transport (head, capstan) and for no lag, it's always running.On older cassette decks, the play/ff/rew buttons directly moved the transport, it takes more force.More expensive machines have a second motor dedicated to just moving the transport.

author: michalism
author_rank: Regular Contributor
timestamp: July 16, 2019, 06:18:56 am
content: ok!!Thanks for the education! I was not aware of that...So ffw and rev buttons have no effect to the speed of the motor. correct?
AKG K550 Headphone repair - Page 1
Forum section: electronics / repair

author: cncjerry
author_rank: Unknown
timestamp: August 27, 2019, 04:39:24 pm
content: so I kept getting my feet wrapped in my AKG K550 headphone cord and finally I had a problem with a connection. I re-soldered the wires and just couldn't find the problem. Finally I found that the wire that looped to the other ear was broken at one connection to a thin copper ribbon cable. It couldn't be repaired as there was no room. The ribbon cable slips inside a flat channel that covers it so the sliding headphone adjustments wont wear on it. I tried using a piece of expensive flat speaker cable made for slipping under rugs. It just about fit. I guess I could have flattened it in a machine vise but didn't think of that until now.Anyway, here's the picture of the flat cable needed. It is about a foot long with two solder pads. I can double it back and make the pads if I can find the cable. It's really thin, probably .010" and I'll measure that thickness if needed.I called AKG and they only sell accessories. I can see why because reconditioned units are only around $100 now, about half what I paid for them on sale years ago. I probably have half that in the speaker wire I used. I looped the speaker wire outside the channels for now. They are decent phones and I recently replaced the ear pads. So yes, I know I should pitch them it's just that I've grown accustomed to their sound. I have other phones, bose, etc noise canceling types that hiss a lot and I have to have a wired connection to my keyboards.Anyway, I've looked around for the ribbon cable. Any ideas?Thanks,Jerry

author: GLouie
author_rank: Regular Contributor
timestamp: August 27, 2019, 05:27:12 pm
content: Try contacting a pro audio dealer like Full Compass or Sweetwater. They often carry parts not widely advertised or can get them.Sadly, AKG has been reorganized in recent years after Samsung bought Harman, and seems to be a shadow of its former self. I understand most of the engineers in Austria (not Australia) were laid off, so they formed a new company, Austrian Audio.
Akura Retro Phono n BT Player AITVS550 BTRB - Page 1
Forum section: electronics / repair

author: spike47
author_rank: Contributor
timestamp: August 04, 2021, 05:53:35 pm
content: Hi have been given a couple of Akura Retro Phono n BT Players and of course they don't work, where do I start to test voltages etc on it, getting 5vdc out of transformer and to the board, the battery is giving out 3.7vdc , don't realy know where to test for any voltages , tried to find a schematic etc for it, but no luck up to now.SpikeAttachme

author: spike47
author_rank: Contributor
timestamp: August 04, 2021, 08:11:01 pm
content: Exactly the same has thesehttps://vinylrestart.com/victrola-vs-crosley-turntable-comparison/

author: spike47
author_rank: Contributor
timestamp: August 05, 2021, 08:54:23 am
content: IC's as in order left to right as per pic uploaded:1st: top 28pin, BK3254SS28B2nd: top 8pin, HT135T1st: bottom 6pin, B6286T2nd: bottom 16pin, YD3412

author: spike47
author_rank: Contributor
timestamp: August 05, 2021, 08:57:27 am
content: On one of them the charging light comes on and a blue ( bluetooth ) led comes on then blinks and I can connect my phone to it, but then after a short time it goes off and only the charging light remains on, but no activity with the turntable motor activating !.on the other one no lights come on .cheersSpike

author: spike47
author_rank: Contributor
timestamp: August 06, 2021, 08:22:04 am
content: NewFound the same burnt out chip on both boards .4054, Standalone Linear Li-Ion Battery Charger with Thermal Regulation in ThinSOTspike
Alcatel power supply identification  - Page 1
Forum section: electronics / repair

author: more_stars
author_rank: Regular Contributor
timestamp: March 04, 2021, 05:37:02 pm
content: Hello guys,I have a pcb here given by one of my friends and hw did not know what it was but he knew I like electrical stuff.I took a look at the PCB and it seems it is a power supply made by alcatel but I was not able to find any information about it.On the label there is a 45V 5.3A DC sign but as I said, I do not know anything about it.If there is any info on how I can get this thing wired and maybe use it with an rd6006 power supplie interface, that would be grate.Thanks!

author: madires
author_rank: Super Contributor
timestamp: March 04, 2021, 05:54:43 pm
content: 48V DC is most likely the input voltage (typical for telco devices).

author: tunk
author_rank: Super Contributor
timestamp: March 04, 2021, 06:06:19 pm
content: Maybe you could check the voltage rating of thecapacitors, if some are 400-450V, then maybe?

author: more_stars
author_rank: Regular Contributor
timestamp: March 04, 2021, 06:31:35 pm
content: Ohh, yep, I forgot about the input caps and so, there is no 400v caps and also there is no ac to dc rectifier.

author: picburner
author_rank: Frequent Contributor
timestamp: March 05, 2021, 06:48:38 am
content: In fact, the symbol Unicode (U+2393) indicates that the power supply must be DC.

author: TheMG
author_rank: Frequent Contributor
timestamp: March 05, 2021, 02:31:40 pm
content: I agree that 48V DC must be the input rating. Components and layout dont at all make sense for an AC power supply.As for the output voltages, it looks like there might be several. Probably 12V, 5V, etc.
ALDI AUTO XS CPL 2054 6/12V charger repair - part burnt IC identification - Page 1
Forum section: electronics / repair

author: synoptica
author_rank: Contributor
timestamp: January 09, 2023, 12:15:49 am
content: Hey all,I'm trying to resurrect an old Aldi battery charger so I can keep one of my cars on a maintenance charge.This charger died a while ago, and I finally got around to opening it up, and much of the magic smoke has escaped, mostly in the form of a UC384x PWM controller.Fortunately, the chip blew its cap off somewhat cleanly and I was able to read UC384 - but not the last number. I've found an image online of the guts of the unit which have enabled me to ID the blackened resistor, which is one step closer:https://cdn.milwaukee-vtwin.de/attachments/178/178260.jpg(sadly I can't ID the chip here, shown as U3 in the lower left of the image.)The datasheet for the IC can be found here:https://www.ti.com/lit/gpn/uc2845On page 3, we can see that the UC3842 and UC3843 offer 100% max duty cycle, so one of these would appear to be my logical choice, however both feature different UVLOs.UC3842 features "TURNON AT 16 V, TURNOFF AT 10 V, SUITABLE FOR OFF-LINE APPLICATIONS"UC3843 features "TURNON AT 8.4 V, TURNOFF AT 7.6 V, SUITABLE FOR DC-DC APPLICATIONS"Does anyone have any suggestions about how I might go about determining which of these is the unit I need?Many thanks in advance!

author: fzabkar
author_rank: Super Contributor
timestamp: January 09, 2023, 02:04:35 am
content: What is the rating of the capacitor on the supply pin of the IC?

author: synoptica
author_rank: Contributor
timestamp: January 09, 2023, 02:30:04 am
content: Quote from: fzabkar on January 09, 2023, 02:04:35 amI just pulled the board out of the unit to check the traces, and I've discovered that it's a bit further gone than I realised - there's not many components on the rear of the board, but looks like a couple of SMD components have been cooked off the board too.I think this one is officially beyond repair at this point

author: ingalopez
author_rank: Contributor
timestamp: January 09, 2023, 11:24:33 pm
content: Hi.If the topology is that of a Flyback converter, you should use the 50% Duty cycle versions, the 43 or 45. Flybacks are simpler and are almost always used under 150W. There is not a bulky inductor on the rectifier output filter (maybe a small one , for EMI)About the UVLO, it depends on the type of power supply it uses to start. Typically, if the power is derived from the rectified line (via a hi value resistor), then the wide UVLO version is the choice. The more restricted supply voltage histeresis is used when the chip is fed from a separte (standby) power supply, that may not be the case on a small charger.Good luck
alesis BRC repair - Page 1
Forum section: electronics / repair

author: cncjerry
author_rank: Unknown
timestamp: July 25, 2024, 08:35:05 pm
content: Hello people,I have an Alesis BRC, short for " Big Remote Control". Issue is it doesn't want to lock to the 48Khz word clock coming from digital devices. I checked the word clock output of the BRC by itself and the 48.000Khz is sitting at 48.026Khz. This is because the FPGA crystal that should be 20.000Mhz is at 20.010830Mhz. The FPGA generates a 250hz signal to control the VCO and the 250hz is actually 250.125hz. The 250hz PCM signal biases an FET that controls the VCO. I guess I could search for the cap that it uses but no schematics. I know it uses an MC108 in the VCO.My options are to replace the crystal, I guess, or try to pull it down to 20.000Mhz. I tried adding 10pf to the crystal loading, it uses two 10pf today, and it brought it down to 48.020Khz, so I guess I would have to add quite a bit of capacitance to bring it down to 48.000khz. Then the risk is it won't start. I have more accurate ways to generate 20Mhz and was thinking of using a DDS but that seems like overkill. There are other options.It's a FOX crystal installed, marked 20.000Mhz but it drifted over the years, I guess. The reason I'm not jumping at just replacing it is because I would have to purchase a few and make a test setup.Thoughts?Thanks,Jerry

author: fzabkar
author_rank: Super Contributor
timestamp: July 25, 2024, 11:21:45 pm
content: I guess one reason for the increase in frequency could be that a "dag" may have broken off the quartz over time, thereby decreasing its mass.

author: cncjerry
author_rank: Unknown
timestamp: July 27, 2024, 04:37:56 am
content: I ordered a batch of crystals and will find the closest. I also found a way to run the word clock to the sending recorder and that then syncs track 1, the one with the noise. I don't get it, as usually the sending unit would send the word clock. But I guess the clock being so far off it won't sync to any clock so I have to use the BRC clock until the crystals get here.It's fun setting up this old gear. Can't believe all the great music that was recorded this way and with the analog equipment before it.Jerry
Alesis USB MiDi controlller Photon x25 - Page 1
Forum section: electronics / repair

author: adeser
author_rank: Newbie
timestamp: February 25, 2022, 09:43:59 am
content: I got this 25 keys midi controller as not working for realty cheap as a puzzle to solve during cold days.

author: Vicus
author_rank: Regular Contributor
timestamp: February 27, 2022, 09:38:31 am
content: U2 and U15 are P channel mosfet so in order to turn on the Vgs has to be negative. If full_pwr_en is low U2B turn on that turn on Q5 that turn on U2A and U15. That means that U1 that generate the full_pwr_on signal is not happy. You have to find why. I think it's doing more that usb interface.

author: adeser
author_rank: Newbie
timestamp: February 27, 2022, 11:18:49 am
content: Yeap. The U1 is not happy and shoots 3V on the mosfets gate. If I disconect the Full_Pwr_On, every Drain shoots 5V and 3.3 as normal. So all mosfets work. Next week I’ll get hold of an oscilloscope and try to find out if there is any communication between U1 and memmory. Can the 24C memory be erased by some short circuit or any static?
Alhambra II or? - Page 1
Forum section: electronics / repair

author: Adrian_Arg.
author_rank: Frequent Contributor
timestamp: October 21, 2020, 06:36:15 pm
content: An Alhambra II plaque is worth buying for $ 66, or there is something better for that price. What I liked is the software that ICEstudio can use.in spanishVale la pena comprar una placa Alhambra II por u$s 66, o hay algo mejor por ese precio. Lo que me gusto es el software que se puede usar ICEstudio.

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 21, 2020, 07:34:58 pm
content: subscribed until proven guilty (as indicated by deleted post)
Alienware gtx1070 r4 gpu failure - Page 1
Forum section: electronics / repair

author: Deadr4user
author_rank: Newbie
timestamp: December 11, 2019, 11:58:11 pm
content: Anyone know of repair places that arent just reballing gpu. Im not a gamer but use my rig for graphics modeling and rendering. I can get to login screen on linux and then it turns off when i log in. So its shutting down when leaving basic graphics mode. Dell replaced my gtx1070 motherboard under warranty and its out again. Id love to send it to rossman, but he seems to only be doing macbook stuff. Alot of people are having alienware failures on these laptops. Should I buy a gpu and find a place to replace the component?

author: aqibi2000
author_rank: Regular Contributor
timestamp: December 12, 2019, 12:20:11 am
content: I offer reballing, and can therefore fit a new GPU if you supply. UK only

author: Deadr4user
author_rank: Newbie
timestamp: December 12, 2019, 06:41:50 pm
content: Sorry not in the uk man but thanks. I might just buy the gpu and drop it off at a place nearby.

author: wraper
author_rank: Unknown
timestamp: December 12, 2019, 06:56:58 pm
content: Quote from: Deadr4user on December 11, 2019, 11:58:11 pmHell no. First of all you will be buying one salvaged from e-waste and in unknown condition. Any half-decent repair shop will send you to f.ck off with chip you brought to them, and they will be right to do so. Secondly very likely it has nothing to do with GPU. 1070-1080 series had quite a lot of RAM problems. Thirdly in this particular GPU series reball (real reball, not frying with a heat gun) might be a viable repair. These series do not have widespread defect of older series when GPU died like cockroaches and heating revived them temporarily. And before soldering anything, any decent repair shop should run Nvidia MODS/MATS test utility to check if there is a problem on any particular RAM channel.

author: aqibi2000
author_rank: Regular Contributor
timestamp: December 12, 2019, 10:49:40 pm
content: By the way I specifically mentioned for the OP to supply the new GPU because it’s not physically possible to purchase them.Your comment shows you have endured these pains at some point too

author: Deadr4user
author_rank: Newbie
timestamp: December 13, 2019, 09:40:42 am
content: Yeah i searched for the chips already and nothing but used stuff available. I appreciate the response though. Not buying laptops with embedded gpu will be my priority from now on. 2 years and 2 failures. Im good. Thanks.

author: Rasz
author_rank: Super Contributor
timestamp: December 15, 2019, 11:38:47 am
content: Those guys are competent and charge moderatelyhttps://www.youtube.com/user/1servicecore/about
Align laser diode - Page 1
Forum section: electronics / repair

author: nccer
author_rank: Newbie
timestamp: May 25, 2024, 02:53:51 am
content: Hello everyone.I am trying to repair a laser depleted OLS4100.I have successfully replaced the diode. What can I do now to realign the light path?Thank you all.Here is a video of pinhole test.https://youtube.com/shorts/GamDuwWfotM?feature=share

author: daisizhou
author_rank: Super Contributor
timestamp: May 25, 2024, 11:18:41 am
content: If you want others to help you, then you need to introduce as many problems as possible and pictures of the device from various angles.Don’t shoot short videos, long videos are more detailed

author: Runco990
author_rank: Frequent Contributor
timestamp: May 25, 2024, 03:54:50 pm
content: I can't really help you on that unit, but I used to repair laser disk players. This required a set of jigs to coarse adjust the beam, and then a jig to break out the optical sensor to a scope to fine adjust for max signal on the photo cells. Doing it on the fly is difficult, but possible IF you know the unit and did a lot of them. It's obviously a very, very fine adjustment.....Can you find a manual at all?

author: fmashockie
author_rank: Frequent Contributor
timestamp: May 28, 2024, 01:30:22 pm
content: I have some experience aligning lamps and lasers for lab equipment. But not the OLS4100 laser scanning microscope you have here. Have you tried reaching out to Olympus for support? Even if they refuse to give you the alignment procedure (Which is common in my field) they might be able to give you some clues.
All Mode Talkback (AMT) not working - Page 1
Forum section: electronics / repair

author: UltimateX
author_rank: Contributor
timestamp: September 18, 2023, 12:08:10 am
content: Hi,I am trying to trace a fault in a multimode 10/11 meter transceiver (schematic and block diagram attached) that has fault preventing the talkback feature from working. The talkback feature is basically the ability to listen to yourself during transmit no matter which mode (AM, FM, USB, LSB) you choose to use. The volume of this talkback, monitored through an external speaker connected to the radio, is controlled via an AMT volume control on the front of the radio (VR112). The fault on this radio is that in AM, USB and LSB you can hear the mic audio coming through the speaker no matter where the AMT control is set, but the AMT, as feature, does nothing on FM. I have already checked the AMT pot with my DMM and it responds normally as the knob is rotated back and forth through its range. Any suggestions on the test points to check that might reveal where in the circuit it's failing to use the AMT pot and likewise, presumably, why FM is failing to engage the feature at all?Thanks
Allen and Heath XONE S2 service manual - Page 1
Forum section: electronics / repair

author: JTaylor
author_rank: Newbie
timestamp: April 24, 2025, 08:02:12 am
content: Hi all,I’m looking for a service manual for an Allen and Heath XONE S2. The only ones I can find on the internet are only 6 pages and not complete.Does anyone have one?
Allen Smart Engine Analyzer - Page 1
Forum section: electronics / repair

author: CoffsHackerSpace
author_rank: Contributor
timestamp: April 29, 2020, 12:37:40 pm
content: Hey All,Today i had a Allen smart engine analyzer 62-000 come in for repair.i have a service manual sorta was faxed from states so bits and pieces are missing.wondering as this is almost as old as i am. if there was anyone around that may of repaired them who could point me in the right direction.powers on, scope comes up ok but analyzer is stuck on loading program. diagnosic is first led floppy drive status light on (no disk)would love to get my hand on media for this too as a backup for if i have to look after this in future.also idea's on replacing the disk to something more modern and reliable.any advice greatly appreciated

author: ivi_yak
author_rank: Regular Contributor
timestamp: April 30, 2020, 12:03:08 am
content: Hi seems no luck with this black box, try to found launch x431

author: CoffsHackerSpace
author_rank: Contributor
timestamp: April 30, 2020, 10:26:42 am
content: launch x431 are only good for cars made in the last 20 plus yearsThe Allen SEA doesnt require the car to have any computer.so i understand why a mechanic who specialise in older vintage cars want this up and running.

author: ivi_yak
author_rank: Regular Contributor
timestamp: April 30, 2020, 10:40:46 am
content: https://www.bobcourtemanche.com/allen/sea.html

author: ivi_yak
author_rank: Regular Contributor
timestamp: April 30, 2020, 10:42:18 am
content: seems Bob can help
Solved:Alpha Elettronica AL 626 S bench PSU: no current - looking for schematics - Page 1
Forum section: electronics / repair

author: agent_power
author_rank: Regular Contributor
timestamp: April 08, 2024, 08:53:23 pm
content: Hi allI've got an Alpha Elettronica AL 626 S bench PSU, 5 + 15V 20A.Upon turning it on, the amp needle slams to the max. When measuring the voltage with no load it looks correct but when I attach a car light bulb to it the voltage needle drops and the overcurrent and shutdown lamps light up randomly. The bulb never lights up.It also does this for a while after I turn it off (it doesn't appear to discharge itself).Does anyone know where I can get schematics for this? Any idea what could cause this behaviour? There are no smells, smoke or sparks otherwise. I have no idea about lab PSUsThanks!

author: coromonadalix
author_rank: Super Contributor
timestamp: April 08, 2024, 09:21:45 pm
content: they seems alive on the web, pop them an emaila schematic who could ressemble to your unit ...normally theses have a simple design like many on the web IE: pyramid power supplies psk-21 etc ...

author: agent_power
author_rank: Regular Contributor
timestamp: April 15, 2024, 06:06:26 pm
content: Ok, their customer support was nice and sent me the attached documents. Not sure if the "S" variants has major differences but I'll find out soon enough.Where do I start measuring? What is a "simple design"? Are these all based on the same principle?I got it apart so I can work on the PCB.Thanks for any hints

author: agent_power
author_rank: Regular Contributor
timestamp: April 17, 2024, 08:09:47 pm
content: If someone compared the PCB with the schematic you might have noticed that they have little in common, only the chunky PSU parts match it but I don't have any ICs on mine.Anyway, I poked and prodded at some point it worked, so I thought it's a cold solder joint. After reflowing the solder joints on the PCB it went back to its previous behaviour.So I poked and prodded outside of the PCB area and found out that there is some intermittent in the Amp meter movement.I don't know what exactly it is, but when I push the plastic window it goes back to 0 and I can use the PSU. The light bulb now lights up.Any ideas what could cause this? I'll probably take the Amp meter apart... is there anything I could substitute it with in case it breaks entirely?

author: agent_power
author_rank: Regular Contributor
timestamp: April 18, 2024, 07:52:45 pm
content: I cleaned and deoxited the contacts / screw posts of the amp meter and now it doesn't seem to be intermittent anymore.problem solved!
Altec-Lansing ATP3, some foil missing from circuit board at DIN cconnector - Page 1
Forum section: electronics / repair

author: MechanicalGenius
author_rank: Newbie
timestamp: January 01, 2021, 09:49:38 am
content: I want to HACK this unit into a stand-alone operation and control. As luck would have it, three short pieces of "foil" circuitry have been torn from the board at the DIN connector. The missing pieces only go to one or two solder points distant. I want to "replace" these missing "foils" with solder, foils, electrical paint, wire, etc. Can some body set me up with a schematic or, preferably a photo of the circuitry leading to the DIN. There is enough there to "guess" the circuitry, but why take a chance with all the help available.I would be grateful for your help and it would be fantastic to me! (My handle is "Mechanical Genius", not Electronic Genius -- I know my limits.) Anyhow email me your solutions. And ya'll stay safe and keep up doing all the good you do.
ALTERA-EP4SGX180FF35C4N for help - Page 1
Forum section: electronics / repair

author: daisizhou
author_rank: Super Contributor
timestamp: December 27, 2021, 01:04:28 pm
content: I am repairing an image processing motherboard,The main chip is ALTERA-EP4SGX180FF35C4NI want to know, is there a program in this chip? Can I buy a new chip to replace it?
Alternate probe for Peak Atlas ESR70 - Page 1
Forum section: electronics / repair

author: rfengg
author_rank: Regular Contributor
timestamp: April 27, 2023, 01:49:38 pm
content: Hello All,Though the Peak Atlas ESR70 is a wonderful instrument for repair work, both the alligator clips and the banana jacks that come with it are a pain to use in in-circuit tests.Does anyone know what size banana jack would fit the original plus that come with the ESR70?My plan is to get some good quality DMM probes and interface them to the plugs on the meter with some jacks that I can solder the DMM leads to.

author: Swake
author_rank: Frequent Contributor
timestamp: April 27, 2023, 03:48:58 pm
content: I don't own that thing but found some pics on the net. They look like 'standard' 2mm banana jacks.You should be able to find adapters ready made from 2mm to 4mm banana plugs

author: Gertjan
author_rank: Frequent Contributor
timestamp: April 27, 2023, 04:58:23 pm
content: Just use the originalPeak RSR70 accessoires.TheirENP90 - ESR/LCR Needle Probesare excellent.Also theirESRLHP2 - ESR Hook Probes(mini grabbers) are very handy.With these two I use my ESR70 99% of the time. The needle probes for in circuit, the very good mini grabbers for the rest.regards, Gertjan.
Alternative for RP500x dc/dc converter IC - Page 1
Forum section: electronics / repair

author: Vicus
author_rank: Regular Contributor
timestamp: June 22, 2024, 04:15:57 pm
content: I have to replace a dc/dc converter in a Korg triton tactile. It's impossible to find the model by the marking on it but I find in another product the same dsp and I think the same dcdc converter. It's a RP500N333 but this part is impossible to obtain in small quantity. Does anyone know an alternative that is more available?https://www.nisshinbo-microdevices.co.jp/en/pdf/datasheet/rp500-ea.pdfThanks.

author: Vicus
author_rank: Regular Contributor
timestamp: June 24, 2024, 09:36:13 pm
content: My threads always generate a lot of interest.

author: Vicus
author_rank: Regular Contributor
timestamp: June 24, 2024, 09:40:16 pm
content: By the way the max1921 seem to be what I'm looking for but need to be rotated 180°.

author: fzabkar
author_rank: Super Contributor
timestamp: June 25, 2024, 01:14:42 am
content: Quote from: Vicus on June 24, 2024, 09:40:16 pmClever hack!

author: Vicus
author_rank: Regular Contributor
timestamp: July 06, 2024, 07:26:31 am
content: An update jus for fun (my fun). I choose the wrong voltage. The 1V5 is shorted not the 3V3. I found also that Ti LM3670 and Microchip MCP1603 should works, 180° rotate.
Alternative for Sharp PQ012FZ01ZP - Page 1
Forum section: electronics / repair

author: peteru
author_rank: Regular Contributor
timestamp: August 03, 2019, 07:18:05 pm
content: My Denon AVR has a dead DSP board. It looks like the voltage regulator module is faulty. According to the service manual it uses a Sharp PQ012FZ01ZP "Low Voltage Operation Low Power-Loss Voltage Regulator" in a SC-63 surface mount package (equivalent to EIAJ SC-63). I'm getting 0.3V where I expect 1.2V.I can't find a source for the part or anything that looks like a suitable alternative. Any suggestions as to where to look?Thanks!

author: amyk
author_rank: Super Contributor
timestamp: August 03, 2019, 08:57:46 pm
content: It's a 1.2V 1A LDO with enable input and external bias supply. The last characteristic is not really necessary but the first three should be relatively easy to find. SC-63 is also known as SOT428, DPAK, and TO-252.

author: peteru
author_rank: Regular Contributor
timestamp: August 04, 2019, 04:02:05 am
content: Thanks for the tips. I looked at the commonly available LDOs and so far have not been able to locate anything with a compatible pinout.The existing part most likely failed due to thermal issues (judging by the discolouration of the PCB), so whatever solution I end up using, needs to take thermal dissipation into account.

author: amyk
author_rank: Super Contributor
timestamp: August 04, 2019, 07:06:00 pm
content: Check that the output is not shorted. A burnt regulator is a common symptom of a short circuit downstream of it.

author: mzacharias
author_rank: Frequent Contributor
timestamp: August 04, 2019, 07:55:27 pm
content: Quote from: peteru on August 03, 2019, 07:18:05 pmUTSource carries it.https://www.utsource.net/sch/PQ012FZ01ZP
Alternative to SMAJ170 Transient voltage Suppressor - Page 1
Forum section: electronics / repair

author: noobiedoobie
author_rank: Regular Contributor
timestamp: March 10, 2024, 06:57:04 pm
content: Hi,I am not able to find TVS diode SMAJ170 for a washing machine board that I am trying to fix, full post here: (https://www.eevblog.com/forum/repair/what-is-this-component-alternatives-washing-machine/msg5340179/#msg5340179The only component I am able to get in the market is SMAJ120 which is the same the same thing but voltage limited to 120V.What are my options? Is there a more commonly used part that I can substitute for this? Also there is space on the board to fit a bigger component, say a through hole version

author: bateau020
author_rank: Frequent Contributor
timestamp: March 11, 2024, 08:38:28 am
content: The SMAJ170 is indeed obsolete, and replaced by the SMAJ170A (seehttps://www.littelfuse.com/products/tvs-diodes/surface-mount/smaj/smaj170.aspx). That part is available in india (digikey amongst others). Don't go for the SMAJ120(A), the voltage is much lower, and risks blowing up on you.

author: noobiedoobie
author_rank: Regular Contributor
timestamp: March 11, 2024, 09:49:10 am
content: Even the SMAJ170A is not available in the local market.The problem with Digikey and mouser is that their pricing is many times expensive than the local component market and upon that their shipping charges are 40 times the cost of the component you in case you buy few pieces of SMAJ170... so in total buying it from Digikey will cost more than getting an entire refurbished power board itself.I would like to add that there is enough space on the board are there any through hole components that can do the job?

author: bateau020
author_rank: Frequent Contributor
timestamp: March 11, 2024, 10:06:56 am
content: The problem is that the SMAJ series is very common.You could try the SMBJ, SMCJ, SMDJ series or the 1.5KE or the P6KE series. They are rather common.There is also the TGL41 series, but I don't think they are easy to find.Make sure to get the unidirectional versions, not the bidirectional versions (mostly ending with CA).
Amazon Echo Show and Spot screen flickering plague - Page 1
Forum section: electronics / repair

author: SteveSi
author_rank: Contributor
timestamp: October 07, 2019, 12:43:56 pm
content: Has anyone got any clues on the screen flicker problem which seems to be affecting hundreds (thousands) of people?Seems to be worse when the brightness is turned up or the unit is warm.I have a 2yr old Echo Show that does it and am looking for hints before I rip it apart (its glued together).https://www.amazonforum.com/forums/devices/echo-alexa/499751-echo-spot-screen-flickeringhttps://www.bbc.co.uk/news/technology-49728471https://www.amazonforum.com/forums/devices/echo-alexa/492249-echo-show-screen-is-flickeringSomeone needs to solve this mystery...Steve (UK)
Amazon Fire HD10 - Inductor? - Page 1
Forum section: electronics / repair

author: andrew_c
author_rank: Regular Contributor
timestamp: November 16, 2024, 08:53:40 pm
content: I have an Amazon Fire HD10 (2019) that won't charge. Outlet shows the tablet is pulling 2.5A, with or without the battery connected to the motherboard.I have identified an inductor that is getting uncomfortably hot and has scorched the board. I feel like the inductor is just a symptom and not the cause. I've no FLIR camera, just alcohol. Tried to identify if a cap was shorted and getting hot - couldn't see anything outside of the shielding.Great tablet, which I would hate to go to e-waste.

author: MathWizard
author_rank: Super Contributor
timestamp: November 18, 2024, 10:13:41 am
content: So it's a tablet, with say a 12V or 5V wall-jack PSU ? What voltage is the battery ? IDK if anything on these would need a DC-DC step-up/boost converter, but there's probably a few DC-DC step-down/buck converters. Sometimes they have them in series on the input voltage too. They should be very low DC resistance, and not heat up much, even with a lot of current.Do you know what circuit the inductor is part of ? Is it the black thing in the pic above the REV1 ? Or is that just another part with a bit of dirt of blackening around it ?If it's part of a converter circuit, there should be a controller IC and diode or 2 and some mosfet, very very close to the inductor.In general these PCB's, are a nightmare, because they have so many layers, traces disappear under all kinds of chips too, and then soldering on them and even just probing on them can be hard. And then a lot of the chips probably won't have public datasheets, and they might not have a label, or anything a search engine can find.If you are a lucky, it is just a power type issue, and has nothing or little to do with any chips, or operating systems, besides some power controller IC, or MCU.
Amber 3501A: Service / Operators manual needed - Page 1
Forum section: electronics / repair

author: Paceguy
author_rank: Regular Contributor
timestamp: December 31, 2021, 11:12:57 pm
content: I will be working on my Amber 3501A soon and I need the service / Operators manual. I already have the manual for the 3501 but it's not exactly the same as the 3501A. Any help would be appreciated !

author: bdunham7
author_rank: Super Contributor
timestamp: December 31, 2021, 11:17:24 pm
content: https://bama.edebris.com/download/amber/3501a/Amber_3501a-Navy.pdf

author: Paceguy
author_rank: Regular Contributor
timestamp: January 01, 2022, 01:07:23 pm
content: Thanks bdunham7, I downloaded it this morning, Happy New Year !
AMD Elan SC400 processor does not read ROM - Page 1
Forum section: electronics / repair

author: Mykeil
author_rank: Contributor
timestamp: May 10, 2019, 08:54:18 am
content: Hello Dear Engineers,I am facing with Elan SC400 microcontroller for some time.Short brief: The processor does not read the program's memory (not switches /ROMCS0 low).The processor communicates with ROM Flash by parallel bus. The same bus is used for ISA. Immediately after the power-up procedure, the processor releases the ISA reset and ISA starts to operate and occupies the bus, which should be actually free to read program memory from ROM.Datasheethttp://pdf.datasheetcatalog.com/datasheet/AdvancedMicroDevices/mXwtyr.pdfUser Manualftp://ftp.phytec.de/pub/Products/MM-486/Doku/21030.pdfRegister Setftp://ftp.phytec.de/pub/Products/MM-486/Doku/21032.pdfThe bus is configured by pinsCFG1-0: 00 - 8-bit data bus width,CFG2: 0 - ROMCS0 decode on the /ROMCS0 pin (not on PC Card Socket A),CFG3: 1 - Enables the SD bus buffer control signals /DBUFOE, /DBUFRDL, and /DBUFRDH on the I/O pins.There is buffer on the board between cpu and Flash.The buffer is controlled by /DBUFOE, /DBUFRDL, and /DBUFRDH.The power-up sequenceDatasheet, page 92Measured:Cpu switches RSTDRV low, which is ISA reset and ISA started to working.Passes power-up sequence.Unfortunately when ISA is running the System Address Bus is busy and cannot be taken by cpu for ROM reading.ROM read sequenceDatasheet, page 97Measured:SA25–SA4, SA3–SA0: x - Wrong- should be silent for ROM reading/ROMCSx: 1 -Wrong- should be 0 for switching the Flash chip ON/ROMRD: 1 -Wrong- should be 0 for switching the Flash chip outputs ON/ROMWR: 1 - OKSD15–SD0: 0 - OK/DBUFOE: 0 - OK, buffer is turned ON/DBUFRDL 1 -Wrong, buffer direction: transmit, should be read/DBUFRDH 1 -Wrong, buffer direction: transmit, should be readThe cpu does not switches /ROMCS0, /ROMRD, /DBUFRDL low./DBUFOE switched low, but /DBUFRDL not. The buffer is enabled but the direction is wrong.I cannot understand why /ROMCS0 is not switched low.If someone has the idea, it would be great.Thank you.Best Regards,Mykeil
amflifier/receiver input button need to be re-selected each startup - Page 1
Forum section: electronics / repair

author: kalli
author_rank: Newbie
timestamp: September 23, 2023, 11:02:28 pm
content: Hey all new here, first post and new to audio repair. its my own ampall works well, but when I switch it on,then the selected input does not work (whatever was selected before power off).buit when I change it to a different input it works. and re-selecting the last input it also works.not a big issue but I'm really curious what coud cause this.Any other ideas other than just looking for bad caps on input board? is that a typical proplem?Harman Kardon AVR 500thanks for any ideas

author: shakalnokturn
author_rank: Super Contributor
timestamp: September 24, 2023, 07:26:19 pm
content: This would be caused by a bad backup capacitor (it looks more like a small battery) it's usually to be found on the front PCB where the display is.

author: kalli
author_rank: Newbie
timestamp: September 24, 2023, 07:41:17 pm
content: thanks so much. glad I asked! I'll have a look to see also if I can find a repair manual for it to make sense of the problem :-)

author: David_AVD
author_rank: Super Contributor
timestamp: September 24, 2023, 09:10:51 pm
content: The backup capacitor / battery is often located on the digital / DSP board.Does it also lose the AM/ FM tuner preset stations?Has it ever remembered the last input while you've owned it?
Amico CUT-60HF won't arc - Page 1
Forum section: electronics / repair

author: plasmacutterchump
author_rank: Newbie
timestamp: January 27, 2021, 11:59:17 pm
content: Hi, got this issue suddenly and it's been rather annoying.Any help would be greatly appreciated!https://imgur.com/a/NVrdCxu

author: BreakingOhmsLaw
author_rank: Frequent Contributor
timestamp: January 28, 2021, 10:06:21 am
content: Looks like the high voltage is arcing in the device instead of the business end.Unplug the unit, wait for 10 minutes to allow the capacitors to discharge.There is slot cut into the pcb where the arcing occurs, that's for insulation. It looks like that has failed. Clean that slot, remove any carbonization. You might additionally try to apply silicone for more insulation.But...all that said. You are dealing with high voltage, and if you have no experience in electrical engineering I really suggest you take it to a local sparky and ask them for help. HV is not for beginners, hell, even seasoned EEs get their asses zapped. I've been dealing with high voltage for over 25 years, and it *can* and *will* bite you in the ass given half a chance.Good luck!
Amiga 1081 CRT monitor repair complete - Page 1
Forum section: electronics / repair

author: sausage
author_rank: Regular Contributor
timestamp: July 09, 2021, 02:40:15 pm
content: Wanted to share that I managed to repair an old Commodore Amiga 1081 CRT monitor this week. Link is at:http://blog.waynejohnson.net/doku.php/amiga_1081_monitor_repairShort version: came down to dry joints, a loose capacitor, a short on the composite-in RCA socket, and a badly tarnished socket input.

author: peteru
author_rank: Regular Contributor
timestamp: July 09, 2021, 05:36:14 pm
content: The 1081 and 1084S monitors almost always failed due to mechanical / soldering issues near the big capacitors.Congrats on the resurrection of a classic piece of vintage computing.