hybridfree/eevblog-posts huggingface dataset:
SurfTab Duo W1 - factory reset from SD, SIM or USB-Stick possible? - Page 1
Forum section: electronics / repair

author: markus_jlrb
author_rank: Regular Contributor
timestamp: November 29, 2021, 09:49:25 am
content: Dears need your help,my SurfTab running on Linux was set accidentally (stupid action from my side)from single to dual channel inside BIOS.Now I had trouble to boot the Tab.No PWR + '+' key combination helps.Do you have info's concerning a special keyboard key combination to reset the Tab.Or do you know if a fail save start from SD, SIM or USB stick with a proper FW imageis possible and how the structure if exist has to be prepared?Any useful hints are appreciatedMany thanks in advanceMarkusPS.: I have attached some images from inside of the Tab. perhaps useful for someone.The idea to upgrade the tab from 2GB RAM to 4GB would be nice but after openingof the tab I could see that it is not possible as no additional RAM slot exist.
SURT5000XLI CHARGER - Page 1
Forum section: electronics / repair

author: tomar1
author_rank: Newbie
timestamp: July 15, 2019, 09:04:46 pm
content: GOOD AFTERNOON, IF ANYONE NEEDS TO REPAIR THE CHARGER CIRCUIT, THE COMPONENTS ARE THE F703 / 704 AND THE 2 Q730 / 731I hope to be of help, (Google translator)greetings Bs As Argentina
Susumu dual analog delay line - Page 1
Forum section: electronics / repair

author: Aiy
author_rank: Regular Contributor
timestamp: December 06, 2021, 03:59:40 pm
content: Hello All,I have identified a failed part in my Agilent 54855A oscilloscope.It is an interesting component, a Susumu GL2L5MS450D-C which is a dual 4.5ns delay line in a SOIC-16 package.Does anybody know a modern equivalent?I found it on Digikey and other reputable distributors, but it is obsolete..Best regardsAIY
Switch mode power supply - feedback circuit-  schema explanation - Page 1
Forum section: electronics / repair

author: Libas
author_rank: Regular Contributor
timestamp: January 15, 2024, 07:34:19 pm
content: Hi, Im looking for some help with following schema of laptop charging adapter Dell PA-12?1) Does anybody recognize this schematic symbol of zener diode? What is the third pin marked as "R" ? Physically there is zener in SOT23 casing with marking Y7W ....which should be BZX84-C20. Pin 1 and 2 is connected together.2) Could somebody describe me please how this feedback circuit works in detail?

author: wasedadoc
author_rank: Super Contributor
timestamp: January 15, 2024, 07:40:46 pm
content: It is a TL431 or similar. Look at data sheet and application notes for that device.

author: dobsonr741
author_rank: Frequent Contributor
timestamp: January 15, 2024, 07:46:08 pm
content: Not a Zener, it’s the venerable TL431. Good read is athttps://www.ti.com/lit/an/sluaa66/sluaa66.pdf

author: MathWizard
author_rank: Super Contributor
timestamp: January 16, 2024, 06:46:51 am
content: Whatever the small signal model of this is doing, IDK yet, but very similar circuits I've worked on and simulated, pretty much just actted as a comparator for a large signal.So like for a computer PSU, if the 12V rail DC value went to 12.3V, the opto-coupler would turn on, and it would pull down it's output voltage from all the way off=logic high, to all the way on=logic low on the collector and some pull-up resistor. Then the controller IC see's that, and shut's off the switching, on the primary side, or slows it down, etc.But the 3-termainal adjustable regular, is basically a settable zener, to use as a nearly fixed voltage, or current sink, and then choose some of the resistors such that the LED part of the opto, is not on, they need about 1V to be running. And then when the Vin voltage gets a bit too high, the LED turns on, and opens the collector-emitter path, and the collector current pulls down some resistor voltage for a chip to see (that's it's not what it should be).For AC signals, there's the path through the cap's and other capacitiances that come into play, to get the system response needed, to cope with load changes. I've been too busy or lazy to learn the AC models for these yet tho, but they are just regular inverting amplifer and BJT circuits for the most parts I guess.

author: dobsonr741
author_rank: Frequent Contributor
timestamp: January 16, 2024, 07:13:31 pm
content: PH2 operates as a digital on/off, protecting against ivervomtage and overcurrent.PH1 operates as a linear feedback. Analog, not on-ff or comparator. Also covers from DC through AC up to a certain frequency.
Switch Mode Power Supply Repair....... Help! - Page 1
Forum section: electronics / repair

author: Robbie010
author_rank: Contributor
timestamp: April 12, 2022, 05:18:07 pm
content: Afternoon all, novice here, please be gentle........ I have been trying to bring an old amplifier back to life, it initially started up but there was obviously something not right, so after doing some initial inspections, minor tidying up inside and replacing a missing resistor, I powered her up and said missing resistor turned up...... shorting the output of the switch mode power supplyI have pulled 80% of the components off the power supply board for testing and have yet to find anything major, I have also done a full recap of all the electrolytics. Now, I have tried powering it back up with a variac but the output from the power supply cuts out at around 30v with a little squeak from one the components. From my initial testing, input to the SMPS is fine, 240v input (AC), gives 320v (DC) in to the SMPS as per the schematic.The only thing thus far that I have not attempted to remove and test is the transformer T603. Could anyone please take a look at the schematic and tell me whether it is likely that the transformer could have blown a winding?Any other pointers more than welcome....I have attached the schematic.

author: TheMG
author_rank: Frequent Contributor
timestamp: April 12, 2022, 06:51:41 pm
content: Couple of things:1) SMPS generally don't like being ramped up slowly on a variac. In fact, some SMPS won't start up at all if you do that especially if they are a self-oscillating design, and many have under-voltage lockout and won't operate below a certain voltage either.2) SMPS transformers are rarely a point of failure. If you have continuity through the windings then it is very likely just fine. Nearly impossible to damage from a momentary overload or short. Primary switching transistors and mains fuse will pop long before any damage is done to transformer.

author: inse
author_rank: Super Contributor
timestamp: April 12, 2022, 07:01:12 pm
content: Oh heck - miraculous discrete Sony circuit.I wonder at which frequency this SMPS is running (or should be).Is the transformer chassis mounted or on the PCB?Nevertheless, transformer damage is rather unlikely.Did you check the secondary diodes?Is the power supply disconnected from the load?
Switch mode power supply - TOP258MG replacement (Denon AVR-1911 repair) - Page 1
Forum section: electronics / repair

author: bc
author_rank: Newbie
timestamp: July 22, 2025, 12:58:10 am
content: I picked up a Denon receiver for cheap knowing that it had a no power on issue. It seems that the IC in the power supply is faulty, based on some troubleshooting according to the service manual and research (not getting 5v to HDMI board).I am now facing the issue of replacing the TOP258MG as there aren't really any on eBay or at least in Australia that I can find.I found the TOP258PN, which seems like it will do the trick. But it seems like I will have some trouble with the new pin layout P (7 pin) vs the old layout M (9 pin).What would be a safe way to adapt this to the current circuit?Fly-leads? socket adapter? I don't want to go to the effort of making a pcb, but I can make a protoboard type of fix if needed. I'm just cautious due to the voltages involved.I'm also exploring the option of finding another device that has the TOP258MG and salvaging it from there.Keen to hear any experience or recommendations. Cheers!

author: wraper
author_rank: Unknown
timestamp: July 22, 2025, 01:11:27 am
content: Use TOP258MN, same thing, just different pin coating.

author: bc
author_rank: Newbie
timestamp: August 02, 2025, 04:15:06 am
content: Looks like I can get this one in Aus for reasonably cheap too ($10 posted). Cheers.
Switch mode PSU for testing battery device - Page 1
Forum section: electronics / repair

author: davelectronic
author_rank: Frequent Contributor
timestamp: October 04, 2020, 12:39:32 am
content: Recently I've come across an old garaged mobility scooter, it's near 30 years old. But it's very clean and serviceable. The batteries have been removed, as the scooter won't power up from these old 12 Volt 34 Ah batteries. I get a terminal voltage reading of just over 3.5 Volts on each battery. Having a battery charger with a cell repair function, I've connected the batteries to this charger. I'm fairly Shaw that the batteries have had it and are dead as a doornail. What I wanted to try was powering up the mobility scooter to see if it will actually start up. Before I throw good money after bad and buy new batteries, I was hoping to at least see it turned on. I have a pair of 12 Volt server power supply I can put in series to get 24 Volts DC. Is it possible to just power up the scooter with a switch mode power source ? Or do you think the motor speed control module could be damaged by non pure DC. It really is just to see if it will power up, but I'm uncertain as 24 Volts from two server power supply's might not be welcomed by the scooter circuit. Any thoughts would be appreciated, before going and buying a pair of new batteries.Thanks for reading.
Switching 36V@7A doesn't work after connection with Buck Step Down - Page 1
Forum section: electronics / repair

author: Crios816
author_rank: Newbie
timestamp: August 16, 2023, 09:49:26 pm
content: Good morning everyone.I bought a 36V@7A switching power supply (this is the seller's link:https://it.aliexpress.com/item/1005002641974879.html?spm=a2g0o.order_list.order_list_main.22.1875369674TJ9G&gatewayAdapt=glo2ita)As soon as it arrived I tried switching without a load and read correctly 36V out.After that I connected a Buck Step Down Converter (this is the seller link:https://it.aliexpress.com/item/1005005274933083.html?spm=a2g0o.order_list.order_list_main.79.1875369674TJ9G&gatewayAdapt=glo2ita) to withdraw 12V. (in the project I have to make, part of this voltage is used to power an arduino nano).After connecting the Buck Step Down Converter the switching stopped working. now supplies 5V instead of 36V.The power supply, by specification, has these protections:- overvoltage protection- overcurrent protection- short circuit protection.Do you have any suggestions to clarify why it stopped working?Do you have any suggestions to get it working again?Thank you.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 16, 2023, 10:37:19 pm
content: You hot-plugged it (connected regulator to SMPS while active), right?Put an electrolytic or TVS (say P6KE43CA) across the input, at the DC-DC input terminals. This reduces the peak voltage overshoot due to inrush.But because it's only rated 40V, this probably won't be enough. Choose a 60V regulator instead.Tim

author: Crios816
author_rank: Newbie
timestamp: August 17, 2023, 12:18:11 am
content: HI.yes, i hooked up the Buck Step Down after turning on the switching power supply.Why did the over current/over voltage protection or switching power supply short circuit protection fail?There is a possibility of reset the switching power supply ? or do I have to look for and replace the broken component?Thanks so much

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 17, 2023, 01:24:04 am
content: Most likely OC had nothing to respond to.This is somewhat unimportant as far as complexity level versus functionality, but what's happening is: the equivalent circuit is the SMPS output capacitors (a few 1000 uF?), starting with some initial voltage (36V), switched into wiring inductance (maybe 0.1-2uH? depends on length), into regulator input capacitance (a few uF?).Such a circuit has an RLC transient response of overshoot and ringdown, before eventually stabilizing at the supply voltage.This is exacerbated by the ceramic capacitor having less C as its voltage goes up, and having fairly low loss so that the ringing proceeds more or less in full.The loss of an electrolytic absorbs the ringing energy instead, or a TVS clamps the overshoot.This is easily enough simulated in a tool like LTspice, though if you just want stuff to stick together, it doesn't matter, get a new reg, appropriate ratings, protection.Tim
Switching power supply conversion 110 in 220 - Page 1
Forum section: electronics / repair

author: maher471
author_rank: Contributor
timestamp: January 28, 2022, 09:50:50 pm
content: I have a switching power supply designed to run the "Camping cooler" that use a peltier thermoelectric cooler, TEC1-12706 in the 110 V sector, and I want to convert it for the 220V sector. I attached the diagram. I will replace the capacitors C9 and C1 with 400V and add a resistor of 1M ohm in series with R2. I ask your help in confirming this change.2nd question can i use the set of triac and bridge diode like the image below, thanks in advance

author: ambrosia heart
author_rank: Regular Contributor
timestamp: January 29, 2022, 12:22:24 am
content: ". I will replace the capacitors C9 and C1 with 400V"If I were you, I could not do this. You can do it and it, SMPS,will work some time. It breaks finally. Believe it or not.You will seek help in here after it breaks. Can you repairit after it bresks? Negative, of course.

author: maher471
author_rank: Contributor
timestamp: January 29, 2022, 08:53:00 am
content: it's funny

author: TheMG
author_rank: Frequent Contributor
timestamp: January 29, 2022, 04:26:44 pm
content: Very good chance it will just release the magic smoke. Transformer turns ratio, the breakdown voltage of other components like diodes and especially the switching transistor, etc. Lots to consider, pretty much end up re-engineering the whole power supply by the time you're done.Replace the entire power supply with one suitable for 220V, or get a step-down transformer.
Switching Power Supply repair PSS-28G from Power Switch Corp. 25.4V @ 6A - Page 1
Forum section: electronics / repair

author: PCS Electronics
author_rank: Newbie
timestamp: January 22, 2021, 05:41:46 pm
content: Switching power supply failed. It is 25.4V 6A unit out of some telecom equipment. Two primary drive transistors to the HF transformer are shorted. They are 2SC2625. Everything else seems fine. I repair a lot of power equipment with FETs. I will often power up the units without the transistors installed to verify that the gate drives are good before replacing the transistors. But these are bipolar NPNs so I know I am dealing with a current not a voltage. When I put my isolated scope probes on the base to emitter I am getting alternating push-pull spikes from 0 to 6 volts at 24 khz. Voltage might be ok (transistors are not installed) but the frequency seems low. Buss voltage is 360 volts so I think it should run a lot faster. Is there a better way to check this? Should I just throw some transistors in and try it?

author: CJay
author_rank: Super Contributor
timestamp: January 22, 2021, 06:00:37 pm
content: What's the controller chip, does 24KHz make sense for it?

author: TheMG
author_rank: Frequent Contributor
timestamp: January 22, 2021, 07:01:22 pm
content: It could very well be the frequency the power supply is designed to operate at. Many older SMPS designs often ran in the range of 20-50kHz. It also may not operate at a fixed frequency depending on design topology.

author: PCS Electronics
author_rank: Newbie
timestamp: January 22, 2021, 07:21:42 pm
content: The PWM chip is a Fujitsu MB3759. Data sheet says 40khz. Is it because there are two outputs which alternate which would be double the frequency?

author: CJay
author_rank: Super Contributor
timestamp: January 22, 2021, 08:34:12 pm
content: Pretty sure that's functionally identical with TL494, 24KHz isn't unreasonable for one of those

author: PCS Electronics
author_rank: Newbie
timestamp: January 22, 2021, 09:30:07 pm
content: Ok I have ordered the transistors. When they come in I will put them in and stand back. Thank you for the help.

author: George Edmonds
author_rank: Frequent Contributor
timestamp: January 22, 2021, 10:43:02 pm
content: HiReplace all the diodes around the switching devices at the same timeInitially test it with a light load and a 100W incandescent light bulb in series with the supply hot/live.This will current limit the line current supply and prevent it immediately self destroying againGeorge
Switchmode power supply repair - Page 1
Forum section: electronics / repair

author: Wazza
author_rank: Contributor
timestamp: October 14, 2024, 12:54:09 am
content: Can anyone confirm or deny that Mount Hay Technology in NSW, Australia, (switchmode power supply repair) is still in business?Regards,Waz

author: BILLPOD
author_rank: Frequent Contributor
timestamp: October 14, 2024, 06:04:27 pm
content: Good Morning Wazza, their website has contact info, including phone numbers; give them a call.http://www.haytech.com.au/Contacts.htm
Sydney, Australia | May I borrow a SA? - Page 1
Forum section: electronics / repair

author: alexturner
author_rank: Contributor
timestamp: December 17, 2023, 10:56:00 am
content: Hi all,Hate to ask! I'm trying to repair a W&G SNA-23 which has gone deaf (and is my primary and really, only, SA in my lab). No idea what's killed it at this point, but it seems as if there's no measurable LO and I'm in need of an SA to verify and validate. Is there anyone out there who could lend me or come and let me use an SA that can do >7GHz. Happy to pay, water with beer, etc, etc.Thanks!
Sync issue on EV-9031 CRT - Page 1
Forum section: electronics / repair

author: hwatkins
author_rank: Newbie
timestamp: June 04, 2023, 09:22:13 pm
content: I recently got a 9" Green Monochrome CRT off of ebay to go with a Apple II Plus computer, the model is EV-9031 it was manufactured in 1984 for Electronics Associates (Tiawan) LTD by Tiwan Kolin Co. The number on the back panel is 2101353007, it seems very similar to the Sanyo monitors produced around the same time, but I can't find a circuit diagram.The monitor has a video sync issue as shown in this video, the video shifts horizontal in a snake like fashion then scrolls vertically but will lock for a half second before repeating.https://youtube.com/shorts/lceWEf17JRo?feature=shareI replaced some of the electrolytic capacitors although they measured ok with a multimeter capacitor function and a ESR meter, there were some signs of leaking on the PCB, this did not make a difference. I list some of the capacitors and values below along with which ones I replaced, all replacements were high quality Panasonic or Nichicon. I also used deoxit on the pins coming off the crt to the connector on the small pcb.The plug is Europlug type two round pin configuration, so I thought it might be PAL. I tried a inexpensive NTSC to PAL converter, but could not get any signal with that adapter. I'm using a Composite to VGA adapter from the Apple II successfully so the output of the Apple II appears OK or at least in spec enough for that adapter to sync.Capacitor List EV-9031C605 100uf 35v (replaced)C310 2200uf 16v (replaced)C604 3300uf 25v (replaced)C417 1000uf 16v (replaced)C314 1000uf 16v (replaced)C607 220uf 16vC202 470uf 10vC503 1uf 160vC406 4.7uf 16vC202 470uf 10vC607 220uf 16vC305 4.7uf 16vAny help on finding a circuit diagram or troubleshooting steps would be helpful.

author: inse
author_rank: Super Contributor
timestamp: June 05, 2023, 08:09:31 am
content: Are there any pots for h-sync and v-sync?

author: hwatkins
author_rank: Newbie
timestamp: June 05, 2023, 01:09:17 pm
content: Yes, It has H-Hold and V-Hold pots on the front, the youtube video was after adjusting those. On the back there are H-Width, V-Line, V-Size and Focus, I did not change any of those.
Synology Capacitor Identification - Page 1
Forum section: electronics / repair

author: milkandbourbons
author_rank: Newbie
timestamp: May 26, 2021, 03:52:01 pm
content: I've searched Google and this forum for a clear answer on identifying capacitors from the values printed on top of them but I'm drawing a blank.This is the main board from a Synology NAS that's circling 8 years old but I love it and use it daily. The fan bearing started to get noisy so i popped her open and replaced the fan in the back with a nicer Noctua one, as well as dust bunny removal and thermal paste replacement.In doing this i noticed that all the caps are starting to get cap juice all over the board so I was hoping to replace them with equivalent ones and clean off the juice w/ isoalcohol. Here's where I'm stuck. The markings on the tops of the caps are alien to me (little to no electronics experience) and can't find a reliable source to tell me what the numbers mean.Can a kind user point me in the direction of how to identify the caps from the numbers (and maybe a good supplier for the same in the UK)?

author: mariush
author_rank: Super Contributor
timestamp: May 26, 2021, 04:56:11 pm
content: The Nichicon FP capacitors (red) are 100uF 16v polymer capacitors. 101 = 10 x 101= 100 . You can probably replace with 100 , 120 or 150 uF and something rated for 16v or 25v , but 100uF should be easy to source.The blue one is 560 uF 6.3v ... united chemi-con ... the diameter is big enough that they don't have to use the short notation. You can probably use 680uF if you can't find 560uF and you can use 10v or 16v rated capacitors if you can't find 6.3vSame about the second picture ,,, 560uF 2.5v .. could use 4v rated or 6.3v rated polymer capacitors.The capacitors are solid / polymer, they don't have electrolyte so they should not leak any liquids.If you insist on buying capacitors, you have Farnell (or their uk retail site :https://cpc.farnell.com/) or tme.eu or rs componentsHere's a rs components with polymer capacitors with filters pre-applied to show only your values and voltage ratings) :https://uk.rs-online.com/web/c/passive-components/capacitors/aluminium-capacitors/?applied-dimensions=4293395787,4292049503,4292049087,4292049502,4292049401,4292049504,4294466453,4294465515,4294465526,4294466461,4294466607,4294817747,4294466465

author: gamalot
author_rank: Super Contributor
timestamp: May 26, 2021, 05:33:41 pm
content: I think you don't need to replace those capacitors. The stain on the PCB in your picture looks more like residual flux.
Synthesizer main board. XP-80 CPU? - Page 1
Forum section: electronics / repair

author: sampler1
author_rank: Regular Contributor
timestamp: August 18, 2022, 11:54:25 pm
content: Hi All something a bit different.Im working on a synthesizer Roland XP-80 that won't boot. I replaced all the SMD Caps as many were leaking But it's still not booting. I am wondering if someone can shed some light for me . I checked the clock on the CPU ( IC12) HD6437034 and that seems ok. I then checked the Reset and its high. From what I read if its high the CPU should reset.I have never checked RESET. Can someone clarify ? I think if the Reset was low the cpu would function.https://www.synthxl.com/roland-xp-80/Any help would be great!Regards

author: wasedadoc
author_rank: Super Contributor
timestamp: August 19, 2022, 12:46:48 am
content: No, the reset pin is active low. See the HD6437034 datasheet. Low resets the CPU. High lets it run.Page 11 ofhttps://docs.rs-online.com/4ca5/0900766b80c2b5e5.pdf

author: sampler1
author_rank: Regular Contributor
timestamp: August 19, 2022, 03:09:47 am
content: Thank you !So if I get this my clock is working and the CPU is running. Time to move on to something else.Now the question is .All the rails are ok, all the caps are changed, CPU is ok. HummmmBig thanks !
SYSTRON DONNER 410 Sweep/Function Generator - Manual/s  - Page 1
Forum section: electronics / repair

author: rkabz
author_rank: Contributor
timestamp: June 10, 2022, 12:45:11 pm
content: Hi Group, does anyone have an operating or service manual for a Systron Donner 410 Sweep/Function Generator? It's basically working but could use a tune up and I'm in the process of cleaning it up and restoring it to original health. Ex Uni of SA. Last Cal date July 2004! Searched the web for info with no with no luck so far. Thanks in advance, Richard.

author: el.designer2012
author_rank: Newbie
timestamp: January 07, 2025, 08:48:52 pm
content: Hi, Richard! I have the same Systron Donner 410 Sweep/Function Generator produced in 1975 - 1976 and can`t find any documentation too. I was already fix some problems with PSU (change old 1N4005 in diode bridge to SR2200 200V 2A schottky and mount Nichicon GU series caps).But I have some missed parts on the board. Did you find any documentation? Or maybe you can please make hi-res photos of the both sides of PCB with components?Thank you and best regards!
Systron Donner 7110 Information - Page 1
Forum section: electronics / repair

author: Arts
author_rank: Regular Contributor
timestamp: January 30, 2022, 10:48:34 pm
content: Hello all,I am looking for information (manual, if possible) for my Systron Donner 7110 digital multimeter. It's a six digit nixie tube dinosaur that has gone senile. Any help appreciated. Thanks!

author: lowimpedance
author_rank: Super Contributor
timestamp: January 31, 2022, 12:43:42 am
content: Systron donner manuals are rare beasts, and this one seems to be no exception !.Perhaps you can get some useful information from other dmm models manuals linked in the thread below.https://www.eevblog.com/forum/testgear/ancient-5-12-digit-dmm-voltage-with-floating-inputs/
T-862 Infrared rework station - lamp replacement - Page 1
Forum section: electronics / repair

author: sicco
author_rank: Regular Contributor
timestamp: December 17, 2021, 12:33:17 pm
content: This was going to happen, and Murphy made it happen just when i needed it… The 100W 12V halogen lamp in my T-862 stopped shining. Looked inside, searched the web, saw various offerings for replacement units, ended up ordering via Alibaba, ~50 EUR ish, but now have to wait till new year i fear. So looked again and noticed that the lamp bulb inside the gold-ish collimating reflector is a fairly standard 12V 100W halogen bulb that resembles the ~1 EUR GY6.35 Schiefer or Philips 100W/12V projector (or car headlight?) bulbs.I pulled out my blown bulb, and that came out of some foam chalk ish potting compound - quite easily.My question: anyone else managed to successfully replace just the inner bulb?And: what’s the right mounting position for the fan - is it with the text label facing up, or down?

author: sicco
author_rank: Regular Contributor
timestamp: December 20, 2021, 02:51:20 pm
content: It worked for me.Philips Capsuleline 100W 1850 Lumen 4000h clear halogen bulb.Slightly shorter pins, but fitted nicely in the original reflector despite losing / pulverizing some of the potting compound.6 EUR instead of 50-100 EUR for the thing with the collimator reflector...
t.mix PM400 Mixer Amplifier schematics - Page 1
Forum section: electronics / repair

author: ascomm
author_rank: Contributor
timestamp: April 10, 2022, 10:54:51 am
content: I'm troubleshooting my friend's t.mix PM400 mixer amplifier (old Thomann device) which have strange distortion issue when applying delay/echo. It uses very common PT2399 digital delay IC.I've been unable to find schematics for the mix-amplifier. Does anyone have any tip where I could get those?<edit> Ok. Just after I posted this I noticed two cracked solder joints on the delay/echo area on the pcb.Resoldered those and voilà, it freaking works!!So, no need for schematics anymore.
T1 Marking on PCB - Three terminal dipped device - what is it? - Page 1
Forum section: electronics / repair

author: DaJMasta
author_rank: Super Contributor
timestamp: December 09, 2020, 06:08:13 am
content: What is this thing? I would have expected a T marked part on the silkscreen (this is T1) would be a transformer, but it's this little three pin dipped part that looks more like an oscillator than any transformer I know.Looks like pins 1 and 3 are basically shorted, but pin 2 is floating. Under the coating on the outer legs it almost looks like ferrite beads - is this a pair of beads with a single turn in the middle or something... but then it's marked like a cap/inductor...

author: AndersJ
author_rank: Frequent Contributor
timestamp: December 09, 2020, 06:15:40 am
content: It’s a LCL EMI filter.Ferrite - Capacitor to ground - Ferrite

author: floobydust
author_rank: Super Contributor
timestamp: December 09, 2020, 06:30:34 am
content: It's a Murata EMI filter"EMIFIL",which is two ferrite beads and a cap to ground in the middle. So pins 1, 3 are a short, and pin 2 open circuit to any other besides 1,000pF capacitance.

author: DaJMasta
author_rank: Super Contributor
timestamp: December 09, 2020, 06:36:26 am
content: Thanks for the quick replies, no idea why the layout designer decided to use a T, but that certainly looks like a match and what's being described.

author: bdunham7
author_rank: Super Contributor
timestamp: December 09, 2020, 06:52:57 am
content: You can get them naked.https://www.allelectronics.com/item/223d50-fb/emi-suppression-capacitor-w/ferrites/1.html
Tablet repair: Looking for datasheet of USB-C PD Controller EtronTech EJ898H - Page 1
Forum section: electronics / repair

author: 0xPIT
author_rank: Regular Contributor
timestamp: May 11, 2020, 08:42:16 pm
content: Hello all,I'm aiming to repair a tablet. Someone already used what must have been some sort of welding device at the USB-C connector.... pads are missing. Might be hard to fix.So, I'm looking for datasheet (Pinout) of the USB-C PD Controller: EtronTech EJ898H so that I can maybe bypass and use the Tablet using an alternative power source.tl;dr: Looking for the datasheet or pinout of EtronTech EJ898H USB-C Power Delivery controler.Thanks!

author: fzabkar
author_rank: Super Contributor
timestamp: May 11, 2020, 11:02:02 pm
content: See page 51:https://bugs.freedesktop.org/attachment.cgi?id=144392

author: 0xPIT
author_rank: Regular Contributor
timestamp: May 12, 2020, 07:59:09 am
content: This is great, thanks a ton!Does not seem too trivial to bypass, though, maybe need to bodge some new USB-C connector on this one.
Tabor Electronics 8553 Arb signal gen repair - Page 1
Forum section: electronics / repair

author: Romain
author_rank: Regular Contributor
timestamp: October 18, 2021, 08:07:39 am
content: Hi, I have this arb signal generator that had a rough ride.When powering it on, it made cracking noises and released the magic smoke. I suspect the mains caps and should have checked them first, but didn't have the time...My question is: is it worth fixing, or just dump it...(same question for the scope in another thread)Tks

author: Kleinstein
author_rank: Super Contributor
timestamp: October 18, 2021, 09:01:14 am
content: If there was litterally smoke, after not using it for an extended time there is a chance this would be input filtering caps. Such a failure is usually relatively easy to repair though the unit may stays smelly for quite some time and really to remore the last residue can be hard. It is at least worth a try and look.

author: inse
author_rank: Super Contributor
timestamp: December 24, 2022, 07:14:41 am
content: Hello Romain,do you still have the generator and did you succeed with the repair?I recently bought one as well.With 50MHz bandwidth, it's a rather capable unit.Unfortunately I have not been able to find any kind of documentation for the unit.Even Tabor Electronics itself is not able to provide anything.
Tactile switch keycaps:  Where can I buy some? - Page 1
Forum section: electronics / repair

author: cvanc
author_rank: Frequent Contributor
timestamp: April 14, 2020, 04:00:55 pm
content: Please see photos, I want to replace these triangular caps with identical ones that are a different color. Are these still made? Any idea where I can buy a small quantity? Thanks...

author: senso
author_rank: Frequent Contributor
timestamp: April 14, 2020, 04:41:29 pm
content: What remote is it from?Your best bet might be modelling them and printing them in a resin 3D printer.

author: coromonadalix
author_rank: Super Contributor
timestamp: April 15, 2020, 03:14:08 am
content: you could even use thick plastic shets or anything who could be shaped in the knob you need ?? with a dremel, a steel filer ...What is the remote brand and model if any ?And yes a 3d print could work very well for you.
Tailgater satellite Dish repair ? - Page 1
Forum section: electronics / repair

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: October 09, 2024, 08:09:00 pm
content: Found a broken unit on craigslist , had a fall , took it apart and found one of the mounts inside for holding to gear base was broken .That was an easy fix .Now I am wondering if there maybe a timing / gear set issue , or procedure ?Have not plugged yet , till I get some confirmation / to avoid more issuesDid come with carrying bag , receiver-card inside , remote .

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: October 09, 2024, 08:12:58 pm
content: Forgot another question , as I had apart saw some type of splitter , but on connection was open , I am under the impression that having a [ guessing ] 75 Ohm terminator should be inplace for interference / noise .I think it came without a terminator , no sign of anyone else opening .

author: richnormand
author_rank: Unknown
timestamp: October 10, 2024, 01:09:03 am
content: Have a look at this guy's channel:Also do a search on Hackaday.Lots of info there.Best of luck with it and do not forget to have fun

author: richnormand
author_rank: Unknown
timestamp: October 10, 2024, 01:16:13 am
content: Here is one that goes in more details:

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: October 12, 2024, 07:40:43 pm
content: Seems like his stuff all about control / programing .Did not see anything about electrical , mechanical info .I had seen his channel a long time ago .Thanks
Takeda Riken / Advantest reset codes - Page 1
Forum section: electronics / repair

author: DavidKo
author_rank: Frequent Contributor
timestamp: February 25, 2022, 09:39:16 am
content: Based on the information fromkipp. I have copy pasted his information to google and the first hit can be usefull. Since it is general document I have posted it here.Advantest_Reset_Instructions.pdfUploaded to xDevs, back up at home
Taking it apart. - Page 1
Forum section: electronics / repair

author: davelectronic
author_rank: Frequent Contributor
timestamp: July 10, 2021, 02:00:34 pm
content: Needing to get access to a mobility scooter control panel and cowling. I've trawled through every thing I can find to remove the outer cowling of a Shoprider sovereign mobility scooter. The reason is the key switch is loose, not terrible at the moment, but will loosen more with time and use. Even more so, because if the mobility scooter is on and stood still for more than 5 minutes, it puts the scooter to sleep, and the key switch has to be cycled to remove it from sleep state. I have looked all over this cowling, I can't find any fixings that would allow access to the control circuit, and key switch. I'm hoping someone out here has knowledge of how to remove this cowling and get access to the key switch to tighten it, and add a drop of blue semipermanent thread lock. I would really appreciate some help if you know how this comes apart. I not wanting to force anything, and risk doing damage to this enclosure. Thanks for reading, I've added some images hopefully someone knows. There is an exploded diagram, that appears to show two hole fixings, but in the actual part there is no hole fixings. Help if you can. Thank you.

author: jdragoset
author_rank: Frequent Contributor
timestamp: July 12, 2021, 09:03:27 pm
content: It appears the piece with the two square holes must be pried down until they are free of the square pegs they are locked on to.wooden or plastic wedges should work.

author: amyk
author_rank: Super Contributor
timestamp: July 13, 2021, 01:21:57 am
content: This time, theservice manualprovides a useful hint:Quote
Taking stupid white glue off pc boards - Page 1
Forum section: electronics / repair

author: tkamiya
author_rank: Super Contributor
timestamp: April 03, 2021, 05:07:45 am
content: I'm restoring a power supply board for HP53181A. There are those annoying white glue or something everywhere, mostly near electrolytic caps. Is there a good way to remove these? I've been using needle nose and tweezers, but there's always a chance of destroying nearby components. It didn't react at all for IPA.

author: bob91343
author_rank: Super Contributor
timestamp: April 03, 2021, 05:42:38 am
content: That is likely silicon rubber, a pliable insulating compound. I use your method. It is there for protection from shock, such as dropping a unit. Only heavy components, usually. I don't know of anything that dissolves it without destroying everything around it.

author: Bud
author_rank: Super Contributor
timestamp: April 03, 2021, 06:02:45 am
content: I first make a few cuts through that stuff, close to components, using a sharp knife, then remove piece by piece.

author: tkamiya
author_rank: Super Contributor
timestamp: April 03, 2021, 06:07:47 am
content: I was afraid of that.... I'm almost tempted to custom make this power supply... It's always on and it's so fragile especially when fan fails. I see clear sign of gross overheating on PCB material. In fact all 4 I have have some type of heat related degradation.
Tantalum SMD Capacitor Polarity Markings - Page 1
Forum section: electronics / repair

author: SoundTech-LG
author_rank: Frequent Contributor
timestamp: April 12, 2020, 10:38:41 pm
content: They are REVERSED the Band is Positive.

author: jpanhalt
author_rank: Super Contributor
timestamp: April 12, 2020, 10:56:11 pm
content: Quote from: SoundTech-LG on April 12, 2020, 10:38:41 pmAll solid electrolytics, even aluminum, are "reversed." Wikipedia explains why.

author: SoundTech-LG
author_rank: Frequent Contributor
timestamp: April 12, 2020, 11:41:01 pm
content: Sad news about solids.

author: james_s
author_rank: Super Contributor
timestamp: April 13, 2020, 03:16:54 am
content: Why is this sad? It's always been this way, I don't see what the problem is. Before you use a part, read the datasheet, always.

author: digsys
author_rank: Unknown
timestamp: April 13, 2020, 06:05:44 am
content: SMD can be a minefield .. markings, part numbering, packages sizes between manufacturers .. caps and leds definitely ... I always keep manufacturers charts handy, and if I come across a new part, I always download and print a description sheet FIRST !! ... and 1 in 100 times, even that can go wrong .. welcome to SMD :-)

author: Zero999
author_rank: Super Contributor
timestamp: April 15, 2020, 11:04:10 am
content: Quote from: jpanhalt on April 12, 2020, 10:56:11 pmWhere? It just states the polarity marking is opposite for solid, to wet electrolytic capacitors. No mention is made of the reason.https://en.wikipedia.org/wiki/Electrolytic_capacitor#Polarity_marking

author: SeanB
author_rank: Super Contributor
timestamp: April 15, 2020, 12:06:54 pm
content: You want some fun, I have some old solid tantalum capacitors where the polarity is marked by the lead plating. gold and silver leads at each end, and I still have not got a definite datasheet for them either.

author: Psi
author_rank: Super Contributor
timestamp: April 15, 2020, 01:07:53 pm
content: Think you've got problems.Sometimes the same manufacture will use dot=cathode for one color of led and dot=anode for another color led within the same product range.
Tantalums in Fluke Handheld 80xx Meters - Page 1
Forum section: electronics / repair

author: Excavatoree
author_rank: Frequent Contributor
timestamp: February 28, 2024, 01:08:21 am
content: I got the aluminum electrolytic capacitors changed in the meters I have that "slipped through the cracks," and just to be sure I re-checked the others.I noticed that some of the oldest meters, the "A" variants have tantalum capacitors. In this application, is it necessary to change those? If so, can I replace them with aluminum electrolytic capacitors, or should I buy new tantalum capacitors?

author: bdunham7
author_rank: Super Contributor
timestamp: February 28, 2024, 01:44:05 am
content: That's an interesting question and my thought is that you don't have to change them at all. There have been many previous discussions on solid tantalums and I think the need for replacement or upgrading to higher voltages is not there in battery powered devices. Supposedly tantalums were studied determined to be the most reliable type of capacitor with their primary weakness being intolerance of reverse voltages exceeding 2% of their rating. That sort of thing happens during power up (or down) in some mains PSUs but not in a battery operated device.

author: rsjsouza
author_rank: Super Contributor
timestamp: February 28, 2024, 02:11:14 am
content: I follow the same logic based on my experience with tantalums - battery operated equipment usually does not suffer power supply transients and spikes, thus I haven't seen tantalums blow up. Naturally, if the DMM suffered a heavy fall that cracked parts inside, then all bets are off.

author: aeg
author_rank: Regular Contributor
timestamp: February 29, 2024, 12:58:19 am
content: I had a tantalum go shorted in the switching power supply section of a Berry trunk test set, powered by a bunch of D cells. The on-off switch is after that board, so I had to frantically remove all the screws and disassemble the unit while smoke was pouring out.I would imagine that capacitor experienced a lot more Dv/Dt than one in a DMM.

author: Jeff eelcr
author_rank: Frequent Contributor
timestamp: March 01, 2024, 02:58:11 am
content: I always check them for shorts first, if other problems still show then troubleshoot for source.Very few times have I needed to replace all tant's in any units. (not Fluke)Jeff
Tektronix TAS 455 Faulty high Voltage module? - Page 1
Forum section: electronics / repair

author: sebbonit
author_rank: Newbie
timestamp: June 28, 2023, 02:41:25 pm
content: Hello guys.Maybe you have some ideas where can i find a schematic for Tek TAS 455 with that module? So fary every one i've seen doesn't have that module there or I'm reading it wrong.I received it in working order but while I was testing it around (It was working for around 14minutes) a Mosfet IRF640 on a high voltage module broke.New fets are also getting very hot and die.Does anyone have any idea what might be the problem?Thank you for all your help!

author: m k
author_rank: Super Contributor
timestamp: July 05, 2023, 02:46:17 pm
content: Tek Wiki has something.Preregulator seems to be the usual, so bypassing it and feeding a current limited 43V directly in can give some ideas.

author: sebbonit
author_rank: Newbie
timestamp: July 07, 2023, 04:14:39 pm
content: It seems like B020 serial number units if I look at the schematic have completely different power supply unit. I cant even locate where the 43volt should be in mineAlso the voltages should be correct because everything is working as it should when i change the mosfet for a new one, i have the display working and so on but it is just getting hot and dies after some time.Mosfet gets around 15V between drain and source and the gate 11.1 at around 52.6kHz

author: m k
author_rank: Super Contributor
timestamp: July 07, 2023, 05:38:47 pm
content: Dang, and I thought this TL594 style is ancient.Seems that older schematics are hiding.Maybe some other model has it also.

author: sebbonit
author_rank: Newbie
timestamp: July 07, 2023, 05:40:52 pm
content: Will search the whole wiki soon.Anyway thanks for trying to help!

author: m k
author_rank: Super Contributor
timestamp: July 07, 2023, 06:27:59 pm
content: Maybe some 2000 series models are its forefathers but keep in mind that their numbering has nothing to do with their age.
Tektronix TAS 465 power supply AA18020 adjustment - Page 1
Forum section: electronics / repair

author: jmpmex
author_rank: Newbie
timestamp: August 16, 2023, 02:52:37 am
content: Hi, The power supplyof my TAS 465 is getting -8.7v on the -8.6v output, the manua indicate that the maximun have to be -8.64v, but in the service manual the model of the power supply is diferent, in that appears an R43 potentiometer to adjust it, but in my power supply all the circuitry is diferent, and the R43 potentiometer not exist, any one knows how to do the adjustment or the schematic of the power supply ASTEC AA18020?Thanks
TAS 485 schematic - Page 1
Forum section: electronics / repair

author: ratio
author_rank: Regular Contributor
timestamp: February 26, 2020, 12:39:30 am
content: Looking for one, &| a service manual. Note that this isnotthe Tektronix 485, but the TektronixTAS485. I already made that mistake.I did find a service manual for a TAS 465 on the TekWiki, perhaps it is close enough to be useful? (100 MHz 2 channel vs my 200 MHz 4 channel, otherwise the grainy monochrome scan seems like a visual match)On a side note, I have instrumentation for only a rudimentary calibration, so I greatly fear losing the current cal data, if it's even there still. Are there any gotchas that I might be able to avoid? Symptoms are failure to boot, no activity on the screen or in response to stimulus—including tube brightness, etc. All LEDs are lit solid. When I switch it off, there is a flash of the beam on the centerish of the tube, similar to the turn-off of an old TV, so I'm hopeful the HV is intact.

author: ratio
author_rank: Regular Contributor
timestamp: March 01, 2020, 06:25:18 pm
content: TheTekWikihas a few resources, aninstruction manual (PDF)andservice manual (PDF)that I guess are close enough to be useful. I found a reference to a TAS 485 service manualherethat covers serial numbers prior to B020099, after that they are repaired by module replacement. Sadly, the only reference Google has found for that part number is an old auction on eBay.es.
Tascam 32-2B capstan motor diagram - Page 1
Forum section: electronics / repair

author: Bargainhunter
author_rank: Regular Contributor
timestamp: March 23, 2021, 04:06:36 pm
content: I need a wiring diagram for the TEAC EM1449 capstan motor. It is a 24V 12W motor. I could not find a replacement so I am forced to rewind the armature. I tried to take notes when removing the old windings but many layers were fused together and I lost track. I am pretty sure there were 90 turns per coil. The motor has seven slots. I need to know if the coils advance clockwise or counterclockwise and the connections to the commutator.The Teac EM1446 is similar but lower wattage. It may be wired the same.If anyone can help me, I would greatly appreciate it.Thank you very much,Chuck

author: cheater
author_rank: Regular Contributor
timestamp: March 23, 2021, 04:17:39 pm
content: Try asking on the ProAud mailing list.

author: hd1200xlh
author_rank: Newbie
timestamp: March 19, 2024, 03:53:40 pm
content: Hi,Did you manage to get a diagram and info for the motor rewind?

author: amyk
author_rank: Super Contributor
timestamp: March 20, 2024, 12:22:43 am
content: Quote from: Bargainhunter on March 23, 2021, 04:06:36 pmYou can easily flip the connections if it turns in reverse. Just make sure all the coils are wound the same direction. As for the relative positions of the coils and commutator, this old book may help:https://archive.org/download/armaturewindingm00brayrich/armaturewindingm00brayrich.pdf
Tascam 34 - Page 1
Forum section: electronics / repair

author: commandgce
author_rank: Newbie
timestamp: July 04, 2020, 02:04:08 am
content: Wanted: A pinch roller or just the tyre for myTascam 34reel to reel machine.

author: Edwin G. Pettis
author_rank: Frequent Contributor
timestamp: July 06, 2020, 02:23:50 am
content: I know of at least one seller of tape deck belts and pinch rollers on eBay here in the states, a search for Tascam 34 pinch roller will turn them up. I've bought from them before.
Tascam DR-40 headphone jack part number - Page 1
Forum section: electronics / repair

author: R-1125F
author_rank: Regular Contributor
timestamp: April 25, 2023, 12:46:20 pm
content: I got a Tascam DR-40 that was missing the headphone jack. Since the part is missing, I do not have a good idea what to look for. I looked at hundreds pictures of jacks that are currently available and none of them look like an exact match. Could someone tell me the manufacturer and part number for the jack?