hybridfree/eevblog-posts huggingface dataset:
A capacitor on a SMPS failed and I don't know the value. - Page 1
Forum section: electronics / repair

author: 460voltclub
author_rank: Contributor
timestamp: December 11, 2022, 07:07:50 pm
content: The SMPS ran a medical type fluorescent fixture with two tubes. I want to repair this board because I am too cheap to buy another one but I will if I have to.If I need to get a new ballast how would I choose one.

author: tunk
author_rank: Super Contributor
timestamp: December 11, 2022, 08:15:54 pm
content: A photo of the back may help.Do you know how the capacitor looked like? - e.g. likethe green ones on the left or the red-brownish ones?

author: 460voltclub
author_rank: Contributor
timestamp: December 12, 2022, 12:17:52 pm
content: Thank you for the reply. The capacitor is a brown film cap. I will get a photo today of the back side. It has a lot of surface mount components.

author: jonpaul
author_rank: Super Contributor
timestamp: December 13, 2022, 01:30:57 am
content: resonant cap, likely FETS and other parts blown as well.Replace ballast perhaps $10 or junk fixtures, use LEDSJ

author: 460voltclub
author_rank: Contributor
timestamp: December 13, 2022, 07:21:16 pm
content: Thank you for your reply. There are several components I need to check and replace.I have a lot of test equipment in my man cave. My OCD compels me to fix and use original parts and pieces.

author: 460voltclub
author_rank: Contributor
timestamp: December 13, 2022, 07:25:11 pm
content: Here are photos of the back.

author: MathWizard
author_rank: Super Contributor
timestamp: December 14, 2022, 05:27:23 am
content: It looks like a nice mix of easy to solder/desolder parts. IDK these types of SMPS but if the chips on the back have datasheets, you could find the general layout from that. I don't see the labels on those chips. But if you're like me, I just map out the whole circuit in a simulator, as a way to learn them and keep track of it.To check SMD caps, I have tweezer probes, but it's still very hard to use them without the part going flying. So I just flow the solder, and flip the cap or SMD part up onto 1 pad. Makes checking them 1000x easier, and plus I don't loose them.My LCR meter can read some little caps in circuit, but not all.

author: 460voltclub
author_rank: Contributor
timestamp: December 14, 2022, 04:17:47 pm
content: Thank you for your response.I purchased a "Smart Tweezer" from a company in Canada. It will read any components in circuit without desoldering.I don't know how it works but I'm glad I bought it.If you need to measure a tiny component use masking tape doubled over and stick it to your bench then stick the component to the tape and it will hold the component in place to measure it. The masking tape wont leave any residue.
A clear circuit schematic of fluorescent bulb's PS - Page 1
Forum section: electronics / repair

author: abdulbadii
author_rank: Frequent Contributor
timestamp: June 22, 2022, 11:11:23 am
content: Anyone have (and would upload directly) clear circuit schematic of fluorescent bulb's AC-DC power?Preferably with brief explanation yet complete of start to end

author: Uunoctium
author_rank: Frequent Contributor
timestamp: June 22, 2022, 01:19:43 pm
content: If the classic energy saving bulb is meant, this circuit (without intelligent components) may fithttp://www.seekic.com/circuit_diagram/Basic_Circuit/Fluorescent_lamp_driver_circuit_composed_of_FET.htmlhttps://patents.google.com/patent/US6472827B1/en

author: fzabkar
author_rank: Super Contributor
timestamp: June 22, 2022, 05:28:32 pm
content: Lots of examples of CCFLs here:http://www.pavouk.org/hw/lamp/en_index.html

author: james_s
author_rank: Super Contributor
timestamp: June 22, 2022, 06:20:30 pm
content: They're not AC to DC, they're AC to high frequency AC, with a DC intermediate step. Almost all CFL ballasts are based on a Royer oscillator.

author: strawberry
author_rank: Super Contributor
timestamp: June 23, 2022, 09:23:09 am
content: IR2153 is better more efficient than cheap BJT versions
a decent 9 volt battery connector? - Page 1
Forum section: electronics / repair

author: Stray Electron
author_rank: Super Contributor
timestamp: December 16, 2023, 05:22:18 pm
content: I'm looking for a recommendation. I'm repairing a piece of TE that has a broken 9 volt battery connector. Does anyone know of a decently constructed 9 volt battery connector (with wire leads) that is readily available? Preferably somewhere like Amazon or Ebay so I don't have to deal with an absurd shipping charge and/or minimum purchase. I can get 10 for about $8 on Amazon which is not unreasonable but I'm dubious of the durability. Can anyone recommend a particular seller or brand?

author: BlownUpCapacitor
author_rank: Frequent Contributor
timestamp: December 16, 2023, 06:12:48 pm
content: Do you need the lead to come from the middle or the side of the connector?

author: BILLPOD
author_rank: Frequent Contributor
timestamp: December 16, 2023, 08:53:15 pm
content: Disassemble an old 9V battery and make your own

author: TimFox
author_rank: Super Contributor
timestamp: December 16, 2023, 09:58:50 pm
content: You didn't specify a country, so I don't know how hard it is to get these.I have always used Keystone connectors for 9 V batteries:https://www.keyelco.com/category.cfm/Battery-Coin-Cell-Holders-Contacts-Clips/9-Volt-Connector-Straps/p/404/id/421

author: Stray Electron
author_rank: Super Contributor
timestamp: December 17, 2023, 02:57:00 am
content: Quote from: BlownUpCapacitor on December 16, 2023, 06:12:48 pmI don't think that it matters. The battery space is pretty large.

author: David Hess
author_rank: Super Contributor
timestamp: December 17, 2023, 06:04:18 am
content: Quote from: BILLPOD on December 16, 2023, 08:53:15 pmThat is what I do. I have a parts drawer full of 9 volt battery end caps, but I throw away the plastic ones because soldering melts the plastic.

author: Stray Electron
author_rank: Super Contributor
timestamp: December 17, 2023, 08:11:28 pm
content: Quote from: TimFox on December 16, 2023, 09:58:50 pmThanks for the suggestion of the Keystone parts, they look like what I was looking for. Digikey, Mouser, Allied and all of the other large parts houses carry them and they're available in Europe and in North and South America so I should be GTG. I placed an order this morning and I should have the parts soon.
A good hot melt glue gun? - Page 1
Forum section: electronics / repair

author: iXod
author_rank: Frequent Contributor
timestamp: February 04, 2021, 02:34:19 am
content: No sub-forum for tools (other than test equipment) so here I go.I use glue guns lightly (maybe 20 10” sticks per year). A year ago I got a full-size (not mini) “low temp” (AKA not advertised as a high temp mode) glue gun. After a year the nozzle stopped flowing glue. These nozzles have a check ball in them so no simply unclogging it. Replacement nozzles NLA.What’s the recommended high-temp glue gun? Bonus if replacement nozzles are available for it.Thanks.

author: bdunham7
author_rank: Super Contributor
timestamp: February 04, 2021, 03:24:02 am
content: https://arrowfastener.com/tool/gt300/?gclid=CjwKCAiAsOmABhAwEiwAEBR0ZoOyGbCGMX0VUbi1eRKSdT6yKAOgemXfUT14XfCSizavCIMoWvzk5RoCFtoQAvD_BwEInsulated nozzle, but not replaceable. I don't see why a glue gun nozzle would clog--with what?

author: HalFoster
author_rank: Frequent Contributor
timestamp: February 04, 2021, 11:01:01 am
content: I've been using this one frequently for a couple of years:https://www.amazon.com/gp/product/B07G71GMYX/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1I find the long nozzle really makes a difference in negotiating tight spaces - much more useful than you might think.Hal

author: coromonadalix
author_rank: Super Contributor
timestamp: February 04, 2021, 03:36:17 pm
content: we use the surebonder brand, they are on 8hrs a day, 40hrs a week, and we use all year long, never had a trouble with them

author: ttx450
author_rank: Regular Contributor
timestamp: February 05, 2021, 12:09:50 am
content: there are commercial models out there google.beware of hot melt guns cheaper ones.. they are known to start fire by themselves.. had a few myself do that. never leave unattended, unplug when not used
A hopefully not to sick HP 3585B. - Page 1
Forum section: electronics / repair

author: Zenwizard
author_rank: Regular Contributor
timestamp: September 03, 2019, 11:43:45 pm
content: I have a HP 3585B on the bench that is in immaculate condition. And from preliminary testing everything seems to be working except for one small hiccup. When I turn it on it is failing calibration 02 during warm up. And after leaving it on for a while for a weird reason the crystal oven is not powered on all the time in this one. it keeps saying error 2 if you power cycle it hot it goes in to a LO unlock state and will not lock the LO. I have hooked the oven up to a scope and I am getting a nice sign wave out. My frequency counter says the oven is off by 1 Hz in 10 Mhz. I have fixed a few scopes but a spectrum analyzer is in another league. Not sure where to start on this one.

author: wn1fju
author_rank: Frequent Contributor
timestamp: September 04, 2019, 01:01:31 pm
content: You do have the jumper cable on the back panel from the oven ref out to the external reference in?Download both the operation and service manual from Keysight's web page. It's a bit tedious, but you can march through the debug procedures.Sometimes, due to age, the internal oscillator drifts out of adjustment and can't lock to the external reference. Tweaking the adjustments often helps. You could try and see if this is the problem if you use a good signal generator (with 1 Hz resolution) at 10 MHz as the reference and adjust it a few Hz up or down.

author: Zenwizard
author_rank: Regular Contributor
timestamp: September 19, 2019, 03:02:09 am
content: Seems this was a noise issue on the input for the reference oven. The cable got pinched between the board and the top of the case. I got it moved and cleaned some slightly tarnished board pins and the LO unlocked is gone. Let the unit run for a few hours to get good and hot and it did not through a single error so it looks like all is good.
A line on left and right side of monitor is it dangerous  - Page 1
Forum section: electronics / repair

author: sairfan1
author_rank: Frequent Contributor
timestamp: November 30, 2020, 05:33:29 pm
content: I have an Lenovo monitor, when i turn it ON in the morning i noticed it has a small line on left and right side it disappears after 5 minutes.I want to know is it some growing problem or dangerous sign toward monitor's life or something i should not take care of.

author: bob91343
author_rank: Super Contributor
timestamp: November 30, 2020, 09:35:45 pm
content: If it works nicely, ignore it. If it gets much worse and interferes with operation, replace it.

author: TheMG
author_rank: Frequent Contributor
timestamp: December 01, 2020, 03:59:44 am
content: First question: is it under warranty? If yes, better take advantage of it now.There's absolutely no predicting if this will get worst, but at the same time, there's nothing you can really do about it to fix it or stop it.
A Possible Solution to USB Problems - Page 1
Forum section: electronics / repair

author: German_EE
author_rank: Super Contributor
timestamp: January 01, 2020, 04:04:26 pm
content: The USB interface is quite robust but it IS possible to kill it if you try hard enough, in this case an incorrectly wired plug sent 12V into one of the data lines and now the FTDI chip has a hole in it. This particular chip is also obsolete and there are no pin compatible replacements even if I had access to a hot air station to remove it. Instructions from the device owner were to repair the unit if at all possible.Step forward the Polulu CP2104https://www.pololu.com/product/1308This little module uses the Silicon Labs chipset with a Micro-USB in and 3.3v TTL out. You can use either hardware or software handshaking (or even none at all) and you even get 5v and 3.3v outputs to power the rest of the PCB. The module is so small that you can remove a type B USB socket and fit this little PCB into the board area that is left. Software drivers are easy to install and worked first time, all I needed to do was change the COM port number.Anyone using one of these modules has a little work to do tracing the data I/O lines from the FTDI chip then either cutting the two PCB traces or, in my case, removing two 1K resistors. The new module then supplies a connection using two jumper wires and the existing traces.Recommended.

author: magic
author_rank: Super Contributor
timestamp: January 01, 2020, 05:34:51 pm
content: You don't need hot air to remove SOP and similar packagesBTW, which FTDI chip it is?

author: German_EE
author_rank: Super Contributor
timestamp: January 02, 2020, 04:56:00 pm
content: The FTDI chip that died was an FT232BM with 32 pins, removing that without either hot air or chipquick would not be fun!

author: magic
author_rank: Super Contributor
timestamp: January 02, 2020, 05:51:26 pm
content: Damn quadsA few years back as a total noob I have actually desoldered one, but destructively and the PCB needed some repair too

author: fzabkar
author_rank: Super Contributor
timestamp: January 02, 2020, 10:19:44 pm
content: The CP2104 chip can handle I/O voltages as low as 1.8V, if its Vio input is properly powered. This feature is becoming indispensible with the newer LVTTL interface voltages.https://www.silabs.com/documents/public/data-sheets/cp2104.pdfSince you are modifying your adapter, I would add 1.8V and 2.5V LDO regulators, plus a rotary selector switch or jumper block. Then you will be able to support 1.8V, 2.5V and 3.3V LVTTL I/O.
A Rotary Encoder replacement: how to identify and find a substitute. - Page 1
Forum section: electronics / repair

author: Kohei
author_rank: Newbie
timestamp: November 03, 2024, 03:02:07 pm
content: Good day! I am looking to replace a what seems to be a rotary encoder for my NOVA Neptune lathe. Not sure what has happened but I somehow knocked off a speed controller knob along with a shaft of the encoder. It should be a simple fix. But I am not sure what was the original part. This one has a push button. I am not familiar with digital encoders so much. What are the specs or other criteria when looking for a substitute? Thanks!

author: madires
author_rank: Super Contributor
timestamp: November 03, 2024, 04:16:38 pm
content: Detents/steps and Gray code steps per encoder detent/step (usually 2 or 4).

author: Peabody
author_rank: Super Contributor
timestamp: November 03, 2024, 05:05:28 pm
content: What are the characters on the top of the encoder? I can't tell from the picture.What is the physical size of the encoder?You need to know the number of detents per revolution, and whether the two encoder switches are open at each detent, or alternate between open and closed from one detent to the next.Edit: I think in Canada you can order a replacement from Digikey once we've identified which one you need.

author: squadchannel
author_rank: Frequent Contributor
timestamp: November 03, 2024, 05:23:48 pm
content: taowaves?https://www.taowaves.com/

author: fzabkar
author_rank: Super Contributor
timestamp: November 03, 2024, 05:49:32 pm
content: Product catalogues:https://pub-mediabox-storage.rxweb-prd.com/exhibitor/document/exh-1399b1d8-f4bf-4421-8d2f-7112489a4ce9/ca1157e6-409d-4aef-838c-fa33e34c94ed.pdfhttps://www.tw-gs.com.tw/tw-gs_new2022.pdf
A shiny new dime to the one that identifies this FET - Page 1
Forum section: electronics / repair

author: Tim88
author_rank: Regular Contributor
timestamp: July 08, 2024, 02:24:48 am
content: Picked up a non-working high end 32" Acer gaming monitor. Was hoping it was just a bad cap on the power board but not so lucky this time. Anyway, I think I found the problem. This SMD FET, and I know at least it is a FET cuz the pins are marked G, D, and S. This FET sends greater than 1.8V to turn on a pair of LED controller IC's, no voltage present. This FET is on the main board. Power board, I believe is good, puts out 19v which gets converted to 12v out to the main board and 28v for the leds. Looked all over the interweb for this daggum FET but can not find it. 15F46 is how its marked.

author: fzabkar
author_rank: Super Contributor
timestamp: July 08, 2024, 02:36:10 pm
content: This thread may provide a clue:https://www.reddit.com/r/AskElectronics/comments/o7f4dh/unable_to_identify_this_blown_transistor_on_an/There is a similarly marked MOSFET with a long underline. Its marking code is12YWW.http://www.cheertech.com.tw/Niko-sem/Data sheet/P5002CMG.pdfBased on that info, I found this:P3202CMG, NIKO-SEM, N-channel FET, 20V, 5A, 32mOhm, marking 15yww, SOT23:http://static6.arrow.com/aropdfconversion/6102f8517d342f42a66055ecc3de449c1247defd/13600317634731824.pdfhttps://pl.aliexpress.com/item/1005004532955022.html(photo)

author: Tim88
author_rank: Regular Contributor
timestamp: July 08, 2024, 04:15:26 pm
content: Wow, that was some brilliant detective work! I found an Infineon Technologies IRLML6244TRPBF that is rated a little higher amperage that I think will do the trick!
A slightly sick AA501 - Page 1
Forum section: electronics / repair

author: Zenwizard
author_rank: Regular Contributor
timestamp: September 19, 2019, 02:57:33 am
content: It seems I have some more sick gear on the bench. This time it is a AA501. It is reading a VERY VERY high distortion on clean sign waves. Like 100% distortion. This is when sine waves above 1Khz. As soon as the frequency drops below 969 Hz the function output collapses in to what appears to be a possible oscillation somewhere in the THD circuit. It does not seem to do this in the voltage detection mode only the THD mode. I am thinking I might run it through a Cal process and see if it is a pot that is WAY out of adjustment or if there is larger issues. Switches have been cleaned. Any input would be appreciated as to the next steps in the troubleshooting process.Thanks for the helpZen

author: jonpaul
author_rank: Super Contributor
timestamp: September 19, 2019, 04:20:46 pm
content: Did you recap the radial tamtalum capacators,they are notorious for shorting or loading power rails.Just a thought,Jon
A Strange Problem with Xiaomi Redmi (MI) AirDots Bluetooth Earphones! - Page 1
Forum section: electronics / repair

author: hesam.moshiri
author_rank: Regular Contributor
timestamp: March 27, 2021, 02:12:07 pm
content: What's the problem with this earphone? so weird!

author: perieanuo
author_rank: Frequent Contributor
timestamp: March 27, 2021, 04:15:15 pm
content: don't had the strenght to watch your video, but i just mastered (repaired to be clear) the pogo pins on some similar thing, his pins were real 'obsolescence programee', planned obsolescence

author: hesam.moshiri
author_rank: Regular Contributor
timestamp: March 28, 2021, 07:32:30 am
content: Quote from: perieanuo on March 27, 2021, 04:15:15 pmYou mean the pins are not clear to make good contact? well no, I just bought this a week ago and I have charged it once or twice before. contacts are clean

author: cozza
author_rank: Regular Contributor
timestamp: March 28, 2021, 08:43:39 pm
content: Under warranty + small to ship. Send them back
A stuck at home electronic to-do list - Page 1
Forum section: electronics / repair

author: cvanc
author_rank: Frequent Contributor
timestamp: April 06, 2020, 12:45:15 am
content: I'll start...Check the motor start/run capacitors on your HVAC blower motors! Mine were both ~30% low and replacing them made a significant difference. They run stronger and smoother now.So, what else should we do with all this time and test equipment? Speak up!

author: ArthurDent
author_rank: Super Contributor
timestamp: April 06, 2020, 01:08:47 am
content: After staying home all this time I just realized that the person sitting on the other side of my breakfast table was my wife! I also realized that the reason I hadn't finished all my electronics projects had nothing to do with with having enough time.

author: m3vuv
author_rank: Super Contributor
timestamp: April 06, 2020, 02:08:54 am
content: Ive got a shitload of electronic stuff to be getting on with but most of my test gear is on a job 60 miles away that i cant get to them due to the lock down,had to order replacement meters etc!!

author: Electro Detective
author_rank: Super Contributor
timestamp: April 06, 2020, 04:19:34 am
content: Quote from: m3vuv on April 06, 2020, 02:08:54 amThe undisputed winner of the-Bad Luck Award-at this thread

author: Haenk
author_rank: Super Contributor
timestamp: April 06, 2020, 11:51:14 am
content: Quote from: cvanc on April 06, 2020, 12:45:15 amSort your box of mixed caps. Then continue with the box of mixed resistors. Next the "misc" box. And don't forget all those various screws, nuts and boltLuckily, we are still allowed to work at our office, not much to do though, so getting home early and doing some gardening'n'stuff.
A very interesting observation fixing a Kenmore Vacuum  - Page 1
Forum section: electronics / repair

author: Carl E
author_rank: Regular Contributor
timestamp: September 26, 2020, 09:16:31 pm
content: While troubleshooting a Kenmore vacuum that lost power to the power head, I discovered that I lost continuity on one leg of the AC wiring along the wand. After tearing the wand apart (P/N KC99PCPMZV06) I discovered the manufacturer embedded a 10A pico fuse in the wand which was totally covered in plastic. If the fuse blew you now faced replacing a 20 cent part with a new $80 wand.Thanks for letting me vent. I hope this helps someone, someday. Now I can go back to troubleshooting the dirt sensor which was the original problem.

author: bob91343
author_rank: Super Contributor
timestamp: September 26, 2020, 09:46:24 pm
content: This crap happens all the time. I have had to throw away transformers where an embedded fuse has opened and it's glued together so well that it wasn't worth driving myself nuts fixing it.
A3YV sot23 p-type mosfet - Page 1
Forum section: electronics / repair

author: najrao
author_rank: Regular Contributor
timestamp: April 27, 2022, 11:26:30 am
content: I apologize to ask, but can anyone lead me to a datasheet, or at least basic ratings for this miserable device holding me up in repairing this charging circuit? I have spent hours already.Thanks.

author: mariush
author_rank: Super Contributor
timestamp: April 27, 2022, 11:41:27 am
content: Maybe Si2303DS from Vishay ?Seehttps://www.vishay.com/ppg?70770

author: gamalot
author_rank: Super Contributor
timestamp: April 27, 2022, 12:28:38 pm
content: It's more like AO3403 considering it has a 4 letter top marking.http://www.aosmd.com/pdfs/datasheet/AO3403.pdf

author: fzabkar
author_rank: Super Contributor
timestamp: April 27, 2022, 08:24:40 pm
content: http://www.smdmark.com/en-US/search/code?id=a3xx
a8t6d  SMD code sot-23 - Page 1
Forum section: electronics / repair

author: salviador
author_rank: Regular Contributor
timestamp: November 13, 2023, 02:27:35 pm
content: a8t6dSMD code sot-23what is that?

author: fzabkar
author_rank: Super Contributor
timestamp: November 13, 2023, 04:44:07 pm
content: Could it be a HUN2240 digital transistor? The "MOS1" circuit reference doesn't seem to fit an NPN transistor, though.http://markingcodes.com/search/c/a8thttps://www.alldatasheet.net/view_marking.jsp?Searchword=A8Thttps://www.datasheetarchive.com/datasheet?id=d761469fafe10b738d34c052097c5b2c80e637&type=M&term=hun2240
About AFJ EMI reciever R3010 - Page 1
Forum section: electronics / repair

author: lwtlwt
author_rank: Newbie
timestamp: February 09, 2024, 04:27:12 am
content: Hello, everyone.I have an AFJ R3010 EMI receiver, unfortunately it is broken, the fault is that the screen does not show the signal strength, as shown in the attached photo. After my inspection, I confirm that the IF signal is correct, and the problem arises in IF Diversity Receiver IC: AD6655, I checked its analog signals, reference source, and other signals are normal, the problem appears in the B channel no digital output,D0B~D13B are all low lever, but I observed that AD6655 has an output for a short period of time after powering on, after the FPGA initialization it, there is no. I also tried to replace the AD6655 but the problem still persists, I think there is probably a problem with the FPGA configuration program. I intend to update its firmware, but I can't find the firmware file. Do you have any suggestions or help? thank you very much.

author: lwtlwt
author_rank: Newbie
timestamp: February 09, 2024, 05:11:54 am
content: I float the pins of the B-channel digital output, and then touched these pins with tweezers, and I could observe that the screen output was some noise, which proved my hypothesis above: the B-channel was misconfigured by the FPGA through the SPI bus, causing it to have no output.

author: lwtlwt
author_rank: Newbie
timestamp: February 15, 2024, 09:53:29 am
content: I finally found that there was a problem with the AD6655 chip I purchased, and the problem has been resolved
About Shunt Resistor Replacement - Page 1
Forum section: electronics / repair

author: ercan4434
author_rank: Contributor
timestamp: January 10, 2025, 04:56:31 pm
content: Hi,I have a broken Autonics MD5-HF14 5-ph stepper driver and one of the shunts are blown up and others have brown spots on them (photos down below). They are 200mOhm shunts from KOA SPEER SLN3 or SLN5 series (I don't have a precision ruler). I don't have much experince with shunts but can I change them with similar resistance shunts because I can't get the same one in my country(Also I can't get products from Vishay Dale).Also I couldn't find any phase voltage data for the driver.Thanks.

author: Swake
author_rank: Frequent Contributor
timestamp: January 11, 2025, 03:16:59 pm
content: Yes, unless the circuit is of particular high voltage, (100V+ )You can replace them with any other brand. Even through hole resistors might do if that is all you can get and you manage to solder them on the board.You need to have the same resistance value of course, but also the same or biggerpower rating. That means that you have to find out how many watts these are. You could do this by measuring their size and compare with the datasheet.These will probable get hot in certain conditions, make sure that whatever resistor you replace them with has enough room around it to dissipate the heat.

author: Swake
author_rank: Frequent Contributor
timestamp: January 11, 2025, 03:18:43 pm
content: btw, I would replace them all to play it safe as most have 'it was hot here' marks on them.

author: ercan4434
author_rank: Contributor
timestamp: January 11, 2025, 05:51:01 pm
content: I checked the voltage on the shunt resistor pad after removed them. Its around 15V and the mosfets have 200V rating but I dont think its a high voltage driver.I found some 5W 0R2 THT resistors. I will try them and the clearance around them very good.

author: bte
author_rank: Regular Contributor
timestamp: January 13, 2025, 11:57:04 pm
content: Quote from: ercan4434 on January 10, 2025, 04:56:31 pmRSdelivers is not the cheapest vendor but you can find many brand-name components easily. For example, here are 200 mOhm SMD resistors:https://tr.rsdelivers.com/browse/elektronik-komponentler-guc-modulleri-ve-baglant%C4%B1/pasif-devre-elemanlar%C4%B1/sabit-direncler/smd-direncler-yuzeye-montaj-direnc#ps=60;af=3340_203408,3340_49557;In your case other brands would work fine as well. I just wanted to point out RSDelivers as an option in case you may need a certain item that would be hard/impossible to buy otherwise.
Absolute newbie: not working GPU  - Page 1
Forum section: electronics / repair

author: Tatsuya94
author_rank: Newbie
timestamp: March 04, 2022, 06:31:07 pm
content: Hi guys, Im kinda broke so I have to figure out how to fix my RTX 2070s by myself. Ive got a friend who has a working one so I compared the two with a Multimeter and the only difference I found was in the component down in the attachments.

author: tooki
author_rank: Super Contributor
timestamp: March 05, 2022, 01:41:58 pm
content: For starters, you haven’t described what the malfunction is.Second, your pictures show the red probe, but not the black one. So we don’t know what you’re measuring.Third, you’re measuring the working board in a different multimeter mode than the first board. So I don’t think you know what you’re even trying to measure, never mind how to interpret the result.Try reading this, so you can ask your question effectively:http://www.catb.org/~esr/faqs/smart-questions.html
AC Coupling Not Working in a Tektronix TDS420 (Quick Reference Guide Too!) - Page 1
Forum section: electronics / repair

author: Smoky
author_rank: Frequent Contributor
timestamp: February 02, 2020, 02:51:16 am
content: During my last oscilloscope project, I learned how to test for AC ripple in the power supply circuit using three Tektronix oscilloscopes that I own. A 465B, a 222A, and a TDS420.The TDS420 had problems.So today I set the test back up as before to check the +300 VDC rail in a 310 oscilloscope project I'm working on.I hooked the probe to the test point and I brought up the screen of the TDS420 where I choose between AC or DC Coupling.No matter if I chose AC or DC, the +300 volt waveform remained the same on the screen. I did not hear any clicking noises within the TDS420 associated to any relay switching either. But I don't know if a relay is supposed to be heard or not anyway.I tried this in all four channels of the TDS420 and the results were the same. No change in the waveform.Two years ago, I replaced all of the electrolytic capacitors in the TDS420 and it always passes its self-tests and signal path compensation every time I use it. Maybe, AC/DC coupling isn't tested? And to let you know, every time I use this scope, I go to the menu where you can revert back to "factory settings" so that it clears any previous changes I have made in the past.Being that this oscilloscope is without any available schematics, I can only hope that someone has experienced this before within their TDS series scope and found a way of repairing it.Anyway, thanks for any help you can give me!

author: madao
author_rank: Frequent Contributor
timestamp: February 02, 2020, 06:22:11 am
content: Press channel 1 and then press vertical menu. You would found correct menu for ac coupling for channel.What did you wrong?You have enabled ac-coupling into trigger-menu. You got it AC-coupling trigger.Greetingsmatt

author: Smoky
author_rank: Frequent Contributor
timestamp: February 02, 2020, 07:22:54 am
content: Thank you so much Matt!I even have the Tektronix TDS420/460 Quick Reference Guide and it does not show this menuAnyway, you made my nightThis is the AC ripple of a Tektronix 310 oscilloscope found on its +300 VDC rail.This result falls in line with the other two Tek scopes that read the ripple.James_s, if you catch this, what I'm using here with the TDS420 is a new Tektronix 1x P6101 passive probe. I also used it with the 465B and posted updated pictures of the results on the 310 Project thread. Boy, does it work well.Have a great night!

author: Smoky
author_rank: Frequent Contributor
timestamp: February 04, 2020, 11:53:21 pm
content: To all of the owners of the TDS420 and TDS460 oscilloscopes, I just had the 8-page Quick Reference Guide scanned at 600dpi and in color.I uploaded the 30Mb file to Ebaman.com and it should be able to be downloaded within the next couple of days.Thank you for all of the the help with my projects
AC dimmer module causing transformer buzz - Page 1
Forum section: electronics / repair

author: John_MS
author_rank: Contributor
timestamp: August 27, 2019, 10:03:33 am
content: I have a microscope for repair with a 6V 30W transformer (powering a halogen lamp).The dimming is done by a module on the primary (mains) side consisting of a plastic 250K potentiometer, a few resistors, capacitors and a BTA08 600C Triac (photo to be attached if i can).. Triac is on the underside of the board.At low power the transformer buzzes loudly. I initially thought this was a transformer problem but switched it with a known good and the problem persists.I have briefly inspected the dimming module and can't see any obvious problems (cracked joints, burnt components, etc).Could anyone point me in the direction what the problem could be? Triac?Alternatively, does anyone know of an off-the-shelf replacement module which would do the same job?Thanks in advance.Kind regards,John

author: PKTKS
author_rank: Super Contributor
timestamp: August 27, 2019, 10:39:57 am
content: DIMMERS are pretty simple to the letter.BUZ kinda spark somewhere...POTENTIOMETER? CAPS? or else...pretty much you de-solder check replace themas is..just in case some "TRIACS" also incorporates the DIACsome even ditch them to be cheap... incorporated DIACsare hard to find. Nevertheless you can replace them witha pair DIAC+ TRIAC just finePaul

author: John_MS
author_rank: Contributor
timestamp: August 27, 2019, 10:57:52 am
content: Thank you Paul.Yes, I will desolder the components and test individually.It looks like that model of TRIAC is still available should I need one.Kind regards,John

author: themadhippy
author_rank: Super Contributor
timestamp: August 27, 2019, 11:19:21 am
content: Nothing unusual in a tranny buzzing with a dimmer.For silent operation move the dimmer onto the secondary side

author: John_MS
author_rank: Contributor
timestamp: August 27, 2019, 11:40:37 am
content: Thanks. The buzzing is very loud and not present on the other microscopes.However, yes I think this is a poor design with the dimmer on the mains side.Actually, I'm tempted to remove the entire workings and replace it with an LED as I've done in the past.It will be an interesting exercise to see if I an find the fault on this anyway.Kind regards,John
AC Fan Wiring w/ Pics - Page 1
Forum section: electronics / repair

author: vidarr
author_rank: Frequent Contributor
timestamp: December 18, 2019, 01:00:26 pm
content: This AC I got free came disconnected and I need to reconnect this fan motor to the control board and separate capacitor. It seems no matter which way I would reconnect wires, there is always an extra wire that I don't know where to connect it. The schematic on the side of the motor seems simple enough, but it doesn't match what is actually there. It looks like someone made some type of modification to the wiring too. This should be simple for you guys to help me. I don't want to attempt anything without knowing for sure it is correct, because this 240V.Thank You!

author: Andy Watson
author_rank: Super Contributor
timestamp: December 18, 2019, 01:22:35 pm
content: Yellow wire on motor goes to yellow wire on the capacitor.Orange wire on motorjoinswith brown wire from capacitor and then goes to the power connector.

author: vidarr
author_rank: Frequent Contributor
timestamp: December 18, 2019, 01:58:04 pm
content: Thank you, of course. As soon as mains power is involved, it is like self-preservation kicks in, shuts off my brain, and says ask someone smarter just in case. LOLThanks!
AC motor question - Page 1
Forum section: electronics / repair

author: jerryk
author_rank: Regular Contributor
timestamp: September 26, 2023, 07:29:29 pm
content: I have a motor out of a fairly recent Dewalt shop vac that has failed. Symptoms are that it starts up at max rpm but then slowly winds down. Brushes make a lot of spark that eventually wraps the commutator as it winds down. My attempt to repair it includes regrinding the brushes square and returning the commutator on a lathe. Testing the winding resistances, I could not detect any anomalies that I know of. I don't have any idea how to test the commutator itself. I always thought the windings on these motors were bullet proof.Before toss the whole shop vac is there any thing that I'm missing or doing wrong or is it a hopeless case? FYI - New motors cost near the price of the shop vac.JerryLink to motor in action.https://youtu.be/zMhZJSxdHrM

author: johansen
author_rank: Super Contributor
timestamp: September 27, 2023, 04:18:04 am
content: I have never been able to fix a motor with arcing that bad.But have also never found a motor that slowed down slowly. Usually what happens is the commutator heats up to the point thr bars loosen up and its all downhill from there

author: Swake
author_rank: Frequent Contributor
timestamp: September 28, 2023, 06:52:40 pm
content: That is some serious sparking, hahaIf you know for sure the carbon brushes are good and the commutator is clean then:Measure resistance from one block to an adjacent block on the commutator. You're measuring 2 windings. They should all measure the same resistance, if not it is for the bin. It is not the absolute value that is of interest, but more the same value. If you find adjacent blocks that are open, then it is for the bin.You could do the same test for the individual windings. Winding are connected on opposite blocks about 180° apart. All windings have to measure the same resistance.Third test is to measure resistance from winding (blocks on the commutator) to the body of the rotor and the shaft. If there is a short somewhere it is for the bin.
AC14 WWII era RX Made in Italy - restoration case, looking for schematic - Page 1
Forum section: electronics / repair

author: 9aplus
author_rank: Regular Contributor
timestamp: November 06, 2024, 07:36:15 pm
content: Possible restoration case - looking for schematic and all other useful info.All tubes are missing, 6 x ECH3 and stabilizer, power supply missing too.One MF transformer damaged.Here one working example from youtube

author: lokin4areason
author_rank: Contributor
timestamp: November 06, 2024, 08:20:49 pm
content: https://archive.org/details/Allocchio_Bacchini_AC14
acceptable voltage drop across a MOSFET? looking for clues - Page 1
Forum section: electronics / repair

author: jaunty
author_rank: Regular Contributor
timestamp: August 30, 2019, 08:08:18 am
content: I am trying to troubleshoot (and repair) a device that I'm finding bad power on - namely it's a hard wired 'remote control' for a piece of studio gear - but i won't trouble you with that. It seems to me that a lot of the symptoms are being created by the fact that the logic chips (some 4000 and some TTL SN7 stuff) aren't getting the required 5V they need ... only 3.2 something volts - even the five volt test point reads 3.2 volts - so i started poking around with the DMM and as near as i can figure the culprit APPEARS to be an IRDF 9120 MOSFET (this one:https://www.mouser.com/datasheet/2/427/sihfd912-104368.pdf) - it's the ONLY place in the circuit where the feed voltage drops from 5 (5.5 actually) to 3.2 volts ... though I KNOW a mosfet probably consumes some power for itself i'm wondering if i should be seeing a voltage drop like this here (obviously depends on implementation etc) - or is there a decent way to test this with normal lab gear (DMM, power supply etc)? Or would i do better to be suspecting ancillary components (caps etc) if this is what i'm seeing? Any hints? I hope i was clear enough to explain this decently ...

author: Jeroen3
author_rank: Super Contributor
timestamp: August 30, 2019, 08:16:50 am
content: The mosfet is probably part of the power supply circuit, and this supply is either defective or limiting.

author: jaunty
author_rank: Regular Contributor
timestamp: August 30, 2019, 08:44:30 am
content: Quote from: Jeroen3 on August 30, 2019, 08:16:50 amha! well yes it's certainly part of the power supply - i'm just trying to verify what part is defective so I can get everything working again

author: Jeroen3
author_rank: Super Contributor
timestamp: August 30, 2019, 11:38:36 am
content: Most likely not the mostfet, since it isn't a short or an open. But the thing operating the mosfet.

author: jaunty
author_rank: Regular Contributor
timestamp: August 30, 2019, 02:14:24 pm
content: yeah i was playing around with the mosfet a bit and it APPEARS as though maybe it's alright so i guess i'll be looking at the MC34060 driver next

author: jaunty
author_rank: Regular Contributor
timestamp: September 12, 2019, 05:04:12 am
content: i dunno man - i replaced that (the 34060 chip) and got no result - seems to me that little mosfet shouldn't be reaching 250F (120C) ??
Access Time of PROM, SRAM, and DRAM on an HP 3588A Memory Board - Page 1
Forum section: electronics / repair

author: Smoky
author_rank: Frequent Contributor
timestamp: July 25, 2023, 12:19:49 am
content: I have a question about the memory board in an HP 3588A Spectrum Analyzer.There are 16 unpopulated locations where I plan to experiment and add identical DRAM.What's on the board are ten PROM chips that have a max access time of 200ns.There are two SRAM chips that have a max access time of 120ns.And the 16 pcs of DRAM have a max access time of 100ns.Is there any benefit to replacing the two SRAM chips with ones having a max access time of 70ns? or would this cause instability?Thanks

author: Smoky
author_rank: Frequent Contributor
timestamp: July 25, 2023, 01:48:00 am
content: I'm going to go out on a limb here and take a stab at the answer.I went to the CPU board of the 3588A and I found a chip, a TMS320C25FNL, a digital signal processor.I read through the datasheet and it's described as having a 100ns cycle time.I'm guessing that a SRAM with a an access time any faster than 100ns would be no benefit.Am I even warm

author: srb1954
author_rank: Super Contributor
timestamp: July 25, 2023, 02:23:18 am
content: Quote from: Smoky on July 25, 2023, 01:48:00 amNo. The TMS320C25 DSP chip probably has its own separate memory immediately adjacent to it for fastest speed. This memory has to be much faster than 100ns, typically 30ns, if the DSP is running at a 10MHz clock.The memory on the PCB pictured is likely to be only for the main application processor, which will run at a slower memory cycle time than the DSP. The cycle time will be determined by the main processor clock so just putting faster SRAM chips in is not going to speed things up. You can generally substitute faster SRAM without any issue but these SRAM chips appear to be battery backed so it is important that the replacement chips have sufficiently low standby power to avoid the battery going flat prematurely.HP designs of this era often stored critical configuration and calibration data in the battery backed RAM and if this data was lost the instrument becomes uncalibrated or even unusable or severely curtailed in functionality. It would pay to check the battery voltage while you have PCB out.

author: Smoky
author_rank: Frequent Contributor
timestamp: July 25, 2023, 02:58:44 am
content: Thank you SRB1954The battery was replaced due to the original having lost its power and it probably means that all calibration data was lost before I took ownership.Even though the analyzer passes its internal calibration routine, it's probably off.The relays can also generate a calibration fail message and someone recently was able to adapt newer relays to resolve the issue. I have those adapter boards and relays ready and waiting to be installed.I do not plan to replace the SRAM but I intend to add the additional DRAM.The service manual has a step-by-step procedure to calibrate the analyzer so the future still looks bright for this machine
Access tv service mode without a remote control when stuck on startup logo - Page 1
Forum section: electronics / repair

author: robsims
author_rank: Frequent Contributor
timestamp: October 10, 2024, 02:23:19 pm
content: Hi,I have a Panaview tv. When turning it on it gets stuck on the "Wisdom-Share smart Cloud TV" logo. Does anyone know how i can access the service mode of this tv without remote control to do a factory reset. The remote control is damaged. There are 6 buttons on the tv "CH-, CH+, Vol-, Vol+, Menu and Source". Anyone know which buttons or combination of buttons to press and when to press them? I tried a few. Or is there another way to access the service mode. Many thanks in advance

author: tom66
author_rank: Super Contributor
timestamp: October 10, 2024, 05:37:27 pm
content: Usually when a smart TV locks up on the boot menu this is because of a fault with the software due to corrupted NAND flash memory, this means there is no service menu available (usually).The fixes are one of:- Replace the main board - most expensive but usually works.- Flash the memory IC with a new image. Works, but you need a copy of a good image which isn't always available.- 'Root' the TV and repair the damage. This worked for me on one Sharp smart TV, as I was able to access the Linux console and see why the main application did not start, replaced the file it needed and it worked fine. But you need to understand Linux/embedded systems, hope that your TV has an exposed UART port that isn't locked down and that it is getting past the bootloader.

author: robsims
author_rank: Frequent Contributor
timestamp: October 10, 2024, 06:05:14 pm
content: Many thanks tom66. I'll ask the owner of the tv to sell it to me as scrap and then i will use the parts to repair another tv. Thanks again

author: darkspr1te
author_rank: Frequent Contributor
timestamp: October 11, 2024, 06:03:21 am
content: there are some firmware files and recovery mentioned herehttps://xdaforums.com/t/wisdom-share-cloud-tv-software-problem-i-dont-have-a-solution-anymore.4585585/darkspr1te
Accessing the brightness potentiometer of a TDS684C to fix a dim CRT - Page 1
Forum section: electronics / repair

author: tverbeure
author_rank: Regular Contributor
timestamp: May 08, 2025, 06:45:56 pm
content: My TDS684C has a dim CRT. I know there's the option to ditch the CRT altogether and use an LCD, but before I do that I first want to make sure that it can't be fixed with the turn of a potentiometer, as described in the service manual. Has anyone had success with that?In the service manual of the TDS500/600/700, in the "Display Assembly Adjustment" section, they have the following instructions:Access the inside of the oscilloscope: See Removal and InstallationProcedures in Section 6 to remove the cabinet.Adjust the display rotation: ...Adjust the display brightness: Locate R403 (BRIGHTNESS).It is one of the adjustments on theleft side of the instrument located just ahead of the fan.It is thefourth adjustment from the fan.The way it is described, it seems like it's just a matter of removing the case and accessing the potentiometer right next to the fan. Of course, when you actually try that, there are no potentiometers to be seen. Some further digging revealed that these potentiometers are located on a display board that doesn't seem to be immediately accessible.In practice, does this mean that I have to take apart the whole scope just to access those potentiometers or is there a location where I can squeeze in a screwdriver and still access it without taking the scope apart? (Not that inserting a screwdriver inside a dark place with CRT voltages is very appealing either.)I've been looking for YouTube videos that show me how it's done but so far I've come up empty handed.

author: tverbeure
author_rank: Regular Contributor
timestamp: May 09, 2025, 03:05:56 am
content: Well, that was easy...Before:After:Intensity totally fine again! No LCD upgrade required!(Blog post for posterity:https://tomverbeure.github.io/2025/05/08/Adjusting-the-Intensity-of-TDS-500-600-700-oscilloscopes.html)
ACD 30" Part Identification - Page 1
Forum section: electronics / repair

author: EEV_TechForum_drb
author_rank: Newbie
timestamp: October 17, 2022, 02:10:38 am
content: Ref: Apple Cinema Display 30” A1083Model: M9179LL/AMLB: LAQ55C Rev 3 Eax35328203Greetings:I discovered a missing diode, D204, while bench testing the MLB in the above reference, please see attached.The smd code for the diode would be very helpful.Thank you

author: fzabkar
author_rank: Super Contributor
timestamp: October 17, 2022, 07:33:57 pm
content: Can you identify U201?Are your sure D204 isn't normally unpopulated?

author: EEV_TechForum_drb
author_rank: Newbie
timestamp: October 17, 2022, 11:04:03 pm
content: 1/ U201 is a voltage detector whose set point is Vs = +2.9v. It throws a logic low to the uC reset pin during power up and sudden power interruptions.smd code 6F, device P/N KIA7029AF/AT2/ Upon closer examination with a 20x eye loop, it appears that the solder connections for D204 are smooth and of factory quality therefore intentionally unstuffed.Thank you so much for asking the question.I think I'm good for now