hybridfree/eevblog-posts huggingface dataset:
LED boost converter destroying FET - Page 1
Forum section: electronics / repair

author: MarkC
author_rank: Newbie
timestamp: February 19, 2022, 05:36:03 pm
content: I have an LED boost converter that keeps destroying the FET.If I fire it up without the FET I get the expected 55v on the Drain and a crazy 95% duty cycle drive on the Gate. I have changed the driver IC (OB3350CP) but this made no difference. Any ideas what else can cause the driver IC to do this. The inductor is going to saturate like this and the resulting failure of the FET is understandable.

author: fzabkar
author_rank: Super Contributor
timestamp: February 19, 2022, 06:13:52 pm
content: There is a current sense resistor which should protect the MOSFET. Perhaps the inductor has shorted turns?https://www.electronica-max.com/pdf/OB3350CP-226708.pdfPerhaps you could disconnect the LED string and then inject a small variable voltage into the FB pin of the OB3350CP. You could then see whether the duty cycle changes.

author: rob77
author_rank: Super Contributor
timestamp: February 19, 2022, 06:29:34 pm
content: you get max duty cycle when the controller thinks it's neededeither the current sense resistor is too small or the voltage feedback is calculated wrong. post your schematic with actual used component values.
LED driver boost converter blown - Page 1
Forum section: electronics / repair

author: MarkC1970
author_rank: Newbie
timestamp: February 11, 2022, 07:55:05 pm
content: I have an LED boost circuit that is faulty. The FET (AOD458) and the rectifier diode (SR320) were both short. I replaced them both as well as the input and output caps.Applying power to TV gets me the standby light and 55v but the instant I power the TV up the FET smokes and is dead again. I think the coil is short as well because it reads just 0.09 ohms.My understanding, limited, is that the FET in a boost converter grounds and releases the coil momentarily and the EMF this generates in the coil results in a voltage spike on release that is passed through the rectifier diode and stored in the output capacitor.The rectifier diode is dead again as well and so I am a little confused. If the coil is short the current through the FET would be massive when the Gate is triggered and I can see why it would die again but why would the rectifier diode die again, it isn't seeing massive current or voltage?When I started repairing TV's we literally had valves and so an old dog is trying to learn new tricks here. Any pointers would be much appreciated.The boost controller is an OB3350CP and the board is a TP.MS6486.PB711. I can't find a schematic but I would be grateful for a link.Thanks all...

author: TheMG
author_rank: Frequent Contributor
timestamp: February 12, 2022, 03:58:39 pm
content: If it indeed is just a simple boost converter, perhaps the output is being overloaded. Boost converters can't output a voltage any less than the input voltage to the boost converter, and thus can not offer overload or short circuit protection.Have you checked the LED array to make sure it's good? A large number of shorted LEDs could create such a situation. Although normally most TVs would have a more advanced LED driver which would have the ability to disable output to the backlight completely if out of spec.

author: thinkfat
author_rank: Unknown
timestamp: February 12, 2022, 05:23:56 pm
content: Have a look at the datasheet of the OB3350CP. You can assume that the circuit in the data sheet is identical to the one in your TV. If the rectifier is blown, too, it's a given that the LED strip has a short circuit.
LED driver fault - Page 1
Forum section: electronics / repair

author: rogerggbr
author_rank: Contributor
timestamp: April 05, 2025, 03:07:21 pm
content: We had some LED lights replaced at work, not very old, the sparkys left them behind but I was curious. They told me it is usually the driver so I brought them home.I have 5 x drivers and every one has the same fail - R4 is crispy and a dry joint next door. I thought I may find one with R4 intact but not so lucky! So what value for R4?This appears to be across the first inductor on the primary side of a typical switch mode power unit, in this case constant current for LED driving.I took a stab at a 12k resistor - soldered across very temporary on the basis that I had nothing to lose. Sure enough it worked and the strip lights up!What I would appreciate is comments on likely value I should use for R4 and why it failed.All the lights are installed in similar conditions, none in a particularly hot area i.e. appear to be random fails.

author: rogerggbr
author_rank: Contributor
timestamp: April 05, 2025, 03:23:52 pm
content: Here is the sketchy fix to test it
LED Driver IC 51LP  - Page 1
Forum section: electronics / repair

author: maselectron
author_rank: Newbie
timestamp: March 14, 2020, 12:29:06 am
content: Hi All,This is my 1st post and I apologize if it is in a wrong section. Please feel free to delete or move to the right section.I have a 9W LED bulb and it has a transistor like TO92 IC marked as 51LP and beneath it marking F48, which is blown up.I want to repair this and coudln't find the part nor a datasheet to see if possible to find a substitue.Attached are few shots.Thanks

author: shakalnokturn
author_rank: Super Contributor
timestamp: March 14, 2020, 01:26:01 am
content: Hello,Check here:https://electronics.stackexchange.com/questions/414791/troubleshooting-defective-led-bulbshttps://datasheet.lcsc.com/szlcsc/1907311706_KIWI-KP1051FPA_C261502.pdf(You'll have to run it through a translator yourself)

author: JFJ
author_rank: Regular Contributor
timestamp: March 14, 2020, 02:08:51 am
content: There's a link to a one page datasheet, in English, on the manufacture's website:http://www.kiwiinst.com/product_detail.aspx?k1=2&k2=6&k3=24&id=132There appears to be a small number for sale here:https://www.olx.ro/oferta/kp1051-51lp-integrat-ic-tranzistor-mosfet-quasi-resonant-buck-IDcS5Ld.html#55cc21ad46

author: TheMG
author_rank: Frequent Contributor
timestamp: March 14, 2020, 02:33:19 am
content: Have you first checked that the LEDs are still ok? Quite often when the driver goes *bang* like that, the LEDs are smoked too. The current sense resistors (RS3, RS2) are burnt which likely means a lot more than the normal amount of current flowed, and that current path could have been through the LEDs.Assuming the LEDs are ok, you'll have to calculate from the datasheet info and reverse-engineering of the circuit, what the proper value for RS3 and RS2 are supposed to be, since they don't appear to be readable anymore.Obviously, electrolytic capacitor is shot too. Possibly other components as well. Test everything.

author: rvalente
author_rank: Frequent Contributor
timestamp: March 14, 2020, 12:39:32 pm
content: THe 51LP TO92 package is not a transistor but a LED controller in "transistor" package, I probably won't be able to buy it in small quantities or in the local market.So, the lamp is dead for good. For educational purposes its fun to investigate and try to repair, but usually, for the price point of these things, its nonsense to fix them
Led driver SMD SOT25 identification - Page 1
Forum section: electronics / repair

author: bermo96
author_rank: Newbie
timestamp: January 19, 2025, 11:07:51 pm
content: Hello,I'm trying to repair an industrial led lamp, it has 20 pcb with 9 leds and some of the leds have burnt out. I have the photo of the other board for reference but I can't find the right part for the sot25 housing, the marking isA63.VG.Can anyone tell me what this marking means?Here is the value measured on another working pcb :Pin 1 = PWM ?PIN 2 = GNDPIN 3 = 0.220vPIN 4 = 24VPIN 5 = 24VAttached the picture of the parts needed for replacement

author: fzabkar
author_rank: Super Contributor
timestamp: January 20, 2025, 06:54:49 am
content: AL8805W5-7, Diodes Inc, high efficiency 36V 1A buck LED driver, marking A6ywx, SOT25:https://cdn.sparkfun.com/datasheets/Components/LED/AL8805.pdfhttp://markingcodes.com/search/c/a6xxx

author: bermo96
author_rank: Newbie
timestamp: January 20, 2025, 01:45:11 pm
content: Thank you ! That's the oneI searched for A63 on the smd marking codes site, but couldn't find anything relevant.
LED edge-lit backlight - Page 1
Forum section: electronics / repair

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: October 27, 2020, 02:12:09 am
content: My Breville toaster oven finally struck out the third time yesterday. The LCD backlight went dim a long time ago, but now the door closing spring snapped apart quite loudly. So I took the thing apart. It's a monster with a lot of screws and stuff.I dug down to the control PCB with the LCD.I pulled the backlight out from under the LCD.I took that apart as well, it's a piece of transparent plastic with silvered edges and diffusers, lit by a tiny PCB with 4 blue LEDs. One is burnt out and the other 3 look dirty and charred a bit.Super awesome, but I am not sure what LEDs I should get, what viewing angle is best? I'm guessing as wide as possible to keep the light even.The LED driver on the PCB doesn't seem that complex, a transistor switching a 470 R to ground. I guess this means you can't have more than about 10mA total for the 4 LEDs.I just want to solder and build this up once, what LEDs should I use? Wadda ya think of this:https://www.digikey.ca/en/products/detail/kingbright/APT1608LVBC-D/5177434Has anyone ever seen a PCB like this, 52mm x 2mm wide? I feel it's even smaller than a LiPO protection PCB. I don't suppose it's a standard thing I can just buy?

author: Ordinaryman1971
author_rank: Frequent Contributor
timestamp: October 27, 2020, 04:50:03 pm
content: You can use the LEDs that are used to replace backlight on older monitors. I've got few of those from ebay. You can cut them every three LEDs and they are powered with about 8V-12V.on ebay search for: Universal LED Backlight Strips Kit 15~24 CCFL LCD Monitor To LED ReplacementOr you can pull the LEDs from broken screen... I see that the ones you have are on very thin flex. That could be better solution possibly.
LED headlamp - Page 1
Forum section: electronics / repair

author: bonesy1116
author_rank: Newbie
timestamp: May 08, 2025, 12:52:28 am
content: It's not worth the time, I know. I've already ordered another, but I it's a mini-hobby I guess.This headlamp has five settings. The first three settings are a combination of the white LED's. The fourth is the two lit red LEDS below the little PCB in the center (see photo). The fifth is off.When I turn on any of the white settings, the light can be bright like normal, but fades away in intensity. Eventually, I can't turn on any of the white LED's (after a few seconds). The red ones are always at full intensity (setting #4).I can see the resistors. I believe the 2 black things are diodes and say 1N1859 on the side. On the PCB just below them are D1 and D2. Would a bad diode cause this problem?Thanks for reading.

author: cruff
author_rank: Regular Contributor
timestamp: May 08, 2025, 01:21:01 am
content: Sounds like a possible battery problem. What type of batteries does it use? If rechargable, how old are they?

author: bonesy1116
author_rank: Newbie
timestamp: May 08, 2025, 02:20:37 pm
content: Hi Cruff,Triple A batteries. I replaced with new ones. Twirled them around as well.

author: tunk
author_rank: Super Contributor
timestamp: May 08, 2025, 02:48:35 pm
content: It looks like a simple circuit, maybe you could reverse engineer it?I assume it uses 3 AAAs? Measure the voltage across them when it's on.

author: bonesy1116
author_rank: Newbie
timestamp: May 08, 2025, 07:57:41 pm
content: Dummy me. It was the batteries after all. Thanks for your help.
LED identification - Page 1
Forum section: electronics / repair

author: barmaley
author_rank: Newbie
timestamp: July 30, 2023, 10:44:36 am
content: Hello everybody,I have a Leica LED MEB123 ring light and I need to replace one smd led component. Who can please help with the identification of the LED.Where can I find such LED? There is a "H9bd" label and its on 3VWBRP.S. it looks like Osram LUW G5AP...but what analog can be used?
LED Lamp PSU board, help to identify a component - Page 1
Forum section: electronics / repair

author: Aheld
author_rank: Regular Contributor
timestamp: December 25, 2024, 04:04:48 pm
content: Hi Forum,I have a PCB of a PSU for a LED lamp with approx 150cm lenght.I seems to be a series issue that some of the lamps start to switch on and off with a frequency of approx. 5Hz with reduced brightness of the Lamp.I started to redraw the schematic and found one component I can't identify (I would guess the PWM controller). Marking: ZTCIA (SOT23-6?)After touching one of the feedback components to the ZTCIA IC with the oscilloscope probe, flashing frequency slows down and brightness increases.Can anybody help me to find the datasheet of this device?Does someone knows this issue with this kind of PSU?ThanksAxel

author: fzabkar
author_rank: Super Contributor
timestamp: December 25, 2024, 05:08:19 pm
content: SY5839https://uploadcdn.oneyac.com/attachments/userfile/b3/f8/1594696923597_3851.pdf

author: Aheld
author_rank: Regular Contributor
timestamp: December 25, 2024, 06:46:10 pm
content: Hi Fzabkar,thank you so much. Do you already know this device or where did you find this information?Br.Axel

author: fzabkar
author_rank: Super Contributor
timestamp: December 25, 2024, 07:56:57 pm
content: I guessed that it was a Silergy part.https://www.google.com/search?q=filetype%3Apdf+%22absolute+maximum%22+ztxyz+silergy

author: Aheld
author_rank: Regular Contributor
timestamp: January 03, 2025, 03:45:14 pm
content: Hi all,may be is helps another person.The lamp is working like new. It was a defect Zener Diode (18V, 500mW).I attached the schematic (without warranty) from this lamp.The lamp was a RIDI, PFYB 1500/60000-840 DV3Br.Axel

author: Swake
author_rank: Frequent Contributor
timestamp: January 04, 2025, 10:06:13 am
content: Thanks for the feed back and the schematic. It looks like it is a good design.Always interesting to see something is repaired. Better than recycling and much much better than landfill material.

author: Aheld
author_rank: Regular Contributor
timestamp: January 04, 2025, 01:26:41 pm
content: Yea, I fully aggree.And it was a nice starting point for SPSU investigations.Mean while, I recieved another lamp with same failure behaviour and same defect zener diode. Easy going
LED Monitor Repair - Can the screen do this? - Page 1
Forum section: electronics / repair

author: RockoS13
author_rank: Newbie
timestamp: July 19, 2020, 09:07:04 pm
content: Hi, I am a newbie here, hope you don't mind me jumping in right away with a question!I am trying to repair an HP 25BW IPS LED monitor. The symptoms are that every 20 minutes or so, the screen turns black and monitor "freezes up" to the point you need to disconnect power and reconnect to get it to reset.The monitor has one of those "capacitive" buttons where you only need to touch your finger to it for it to turn on and off. When the screen turns black, this button remains illuminated (suggesting the power is still fully on) but when you touch the button to turn the monitor off, it wont respond. (Which is why I say it freezes). The only way to turn the black-screen monitor off is to cut power.Another symptom, possibly related, possibly not, is when the screen is working, sometimes the upper-right quadrant of the LED backlight is a bit dark.Would you all mind coaching me through how to diagnose this? I figure if the LED backlight was failing, the monitor power controls wouldnt freeze when screens turn dark, would it?Thanks

author: Rasz
author_rank: Super Contributor
timestamp: July 20, 2020, 02:51:47 pm
content: depends, led strip might be going short after warm up, sagging the supply and freezing whole thing
Led step-up converter identification help - Page 1
Forum section: electronics / repair

author: jerryk
author_rank: Regular Contributor
timestamp: January 18, 2023, 03:35:24 am
content: I have a board that has two led outputs that are driven by the attached circuit layout below. U10 is marked RY6SA and appears to be a dc/dc step-up led driver of sorts. The voltage at each led is 34V and the input voltage is 12V. I would like a look at the datasheet for U10 but keep coming up dry on which IC it is. Any suggestions?Another question is - Can this step-up converter be driven without the load of the led? I'm worried I might have messed up by turning it on without a load.Jerry

author: fzabkar
author_rank: Super Contributor
timestamp: January 18, 2023, 04:52:04 am
content: SY7301, Silergy, High Current Boost LED Driver, 2.8V - 40Vin, 2A, marking RYxyz, TSOT23-6:https://uploadcdn.oneyac.com/attachments/userfile/20/c5/1596011741476_5635.pdf

author: jerryk
author_rank: Regular Contributor
timestamp: January 18, 2023, 06:55:02 pm
content: Thanks for the datasheet. I'm still amazed what you can find. I spent hours on that and came up empty. It does appear that I can enable the boost converter without a load but there is a problem. The capacitors hold their charge without the leds connected. My goal is to reverse engineer the input from the microcontroller to the enable pin. The enable pin is connected directly to the microcontroller pin so the only way to isolate it would be to remove the boost converter which I would like to avoid. If I connect the leds they draw too much current for this 3cell battery simulator I made and it causes the input voltage to oscillate.So the goal now is to put an alternate load across the led+/- pins to have the circuit still work but at a much lower current draw. I am trying to measure the flashing sequence timing with an oscilloscope so I can attempt code this into a replacement microcontroller. There is a real chance that I'm doing this the hard way.Any ideas appreciated.Jerry

author: fzabkar
author_rank: Super Contributor
timestamp: January 18, 2023, 08:23:45 pm
content: The current draw would be set by the current sense resistor on the FB pin. ISTM that you could use resistors in place of the LEDs.BTW, I've been staring at Silergy chips and datasheets over the past month, so I immediately recognised the ABxyz format.Then I searched for ...https://www.google.com/search?q=filetype%3Adoc+OR+filetype%3Apdf+"absolute%20maximum"+silergy+RYxyz
LED TV backlight LED voltage drops from 123 Volts to 52 Volts - Page 1
Forum section: electronics / repair

author: robsims
author_rank: Frequent Contributor
timestamp: December 29, 2023, 01:33:24 am
content: Hi,I have a Berklays 32" LED TV. When i power the Tv on there is sound and the LED screen in front works fine too. But there is no LED backlight. The backlight LED's don't turn on. When i power the TV on and i measure the output voltage on the main board for the LED backlights, i measure 123 Volts. Gradually the 123 volts drops to 52 Volts. I don't have a LED backlight tester. I only have multimeters. How can i fix this backlight problem. Many thanks in advance
LED TV Grundig Model: 40 VLE 5324 BG --blue layer shifted, where start to repair - Page 1
Forum section: electronics / repair

author: roffelkartoffel
author_rank: Newbie
timestamp: September 09, 2020, 08:15:22 pm
content: Hey fellas,I got the aforementioned TV for free due to image problems. The blue "layer" is flickering for a few seconds sometimes (not exactly sure when switching to the used HDMI-channel) but stabilises after all. The issue with the blue "layer" is that it's shifted by approx 20-30 px to the bottom, red and green are fine (resulting in yellow).I've already replaced the mainboard but had no luck so far. Have you any idea what possibly be wrong or where to look for further info?Greetings from Germany
led tv psu repair need help - Page 1
Forum section: electronics / repair

author: Shopy
author_rank: Contributor
timestamp: October 22, 2020, 10:49:25 am
content: helloi need help on repair a led tv psuthis is a 65 Hisense smart led tv that does not start .the stand by led is on .i checked the voltages on the psu and i found: 12v is stable .18 v is not stable.it flickers from 18 to 15 v so is the 24 v for the backlight.i checked all the electrolytic cap on the board with an esr meter and they are oki checked the MOSFETs and they are ok.i can't figure what is the problem.attached is a picture of the boardthanks
Left my Metcal PS-900 for days on, now it doesn`t work.  - Page 1
Forum section: electronics / repair

author: Neshco
author_rank: Contributor
timestamp: July 17, 2024, 10:04:10 am
content: Any advise where to start with troubleshooting with this soldering station?I left it accidentally work for few days and recently found that.Green indicator light work, there is some resistance inside the cable of the tip, but it doesnt heat.Any tips appreciated.

author: artag
author_rank: Super Contributor
timestamp: July 17, 2024, 03:43:00 pm
content: Have you tried another tip ? They do die, even in ways that leave the green light on.If you feel you'd rather not replace the expensive tips until you're sure it's dead, buy one that's a usefully different shape so it's not wasted. Also look at replacements from thermaltronics (though I think for a PS900 you have to change the handle too).

author: Smokey
author_rank: Super Contributor
timestamp: July 17, 2024, 07:11:50 pm
content: Ya, the tips have a run time. That's why you can find used tips on ebay pretty often. Companies replace them when their guaranteed run time has been used up even through they still work for a while after that.

author: ardiesse
author_rank: Newbie
timestamp: July 18, 2024, 05:15:26 am
content: Check the internal power supplies. I had a Metcal MX-PS5000 stop working, with the same symptoms. The oscillator power supply failed. The cause was a shorted diode at the output of a switching regulator.

author: Neshco
author_rank: Contributor
timestamp: December 09, 2024, 05:26:40 pm
content: Just for the record, forgot to conclude this one, needed to replace the coil. Now is up and running again.Thank you all for answers.

author: MathWizard
author_rank: Super Contributor
timestamp: December 14, 2024, 06:22:58 pm
content: A few years back, for a couple of days I was using my cheap iron to light smokes. With it cranked up on max, it would take on the order of 1 minute, of holding the twisted over paper tip, against the iron, for it to smoulder. I didn't kill the iron, but the tip needed sanding.This reminds me, I don't have a spare heater element for my Hakko, it would be nice to have a replacement on the shelf.

author: Arts
author_rank: Regular Contributor
timestamp: December 14, 2024, 08:48:10 pm
content: Quote from: Neshco on December 09, 2024, 05:26:40 pmDon't forget, with the PS-900 you need to turn the unit off before changing the tip. You may be lucky and get away with it, but usually you'll burn the coil.I have two PS-900's, and they have been indestructible. And the tips are very long lasting too, despite their low price.
Leica LED3000 MEB115 schematic needed - Page 1
Forum section: electronics / repair

author: xchg.ca
author_rank: Contributor
timestamp: July 19, 2023, 06:33:13 pm
content: Hey guys looking for schematic for Leica LED3000 / MEB115 LED light moduleLooks like tiny zenner is gone and the module if not operationalWill be nice to have schematic or service manual to fix itIt is very hard to use microscope without appropriate lightThank you !

author: xchg.ca
author_rank: Contributor
timestamp: July 20, 2023, 03:11:28 pm
content: Here is how the board looks likeAfter tracing the board, it looks like blown diode is a protection diodeWhat would you guys suggest to replace it with?

author: coromonadalix
author_rank: Super Contributor
timestamp: July 20, 2023, 05:00:52 pm
content: check u7 markings and try to see if the diode is used around it, try to find application notes for u7, you could find some infos

author: Jon_S
author_rank: Contributor
timestamp: July 21, 2023, 11:44:11 am
content: U7 is the venerableLM2675.If you have traced the board and are sure it isn't a series diode for reverse protection, then D2 was possibly a TVS. I can't really make out the tracking from the photo.The absolute maximum input voltage for the 2675 is 45V, so you need a TVS with a clamping voltage at or below this to be of any use. It looks like the package is SOD-323, so something like this one possibly:D22V0S1U2WS-7Found a picture of the device and it says the operating voltage is 24V. Need a TVS with a higher standoff for that, and that makes the gap between standoff and clamping narrow for a TVS, not much choice. I only found one suitable diode after a quick search:https://www.vishay.com/en/product/85915/

author: xchg.ca
author_rank: Contributor
timestamp: July 25, 2023, 02:40:17 pm
content: Thank you guys for helping outI forgot to mention very important info - that power supply is 33V DC for this LED moduleAnd using my cellphone as light source and the microscopeI had barely made out E3 on charred body of the diode. This seems to be falling under switching diodes judging by Google research results.Can it be reverse polarity protection diode - regular switching diode? Not sure why would it die though.... as this module using has own proprietary power-supply, no way you can put it reverseOnly possibility higher current that diode can handle.

author: xchg.ca
author_rank: Contributor
timestamp: September 27, 2023, 03:35:09 pm
content: I have fixed it.Turned out it is one of ceramic caps that sits on +30V rail got shorted !Here is how it looksNew diode is 1n914 ( smallest I had on my hands )
LEM Baby Echo Mixer Amp Issue - Page 1
Forum section: electronics / repair

author: uslrs
author_rank: Contributor
timestamp: April 23, 2024, 10:33:58 am
content: Hi All, I'm restoring this LEM Baby (built in the 1970's) and there has been a major issue with the power amp and repairs carried out at some point in the past. I've been unable to find a schematic, only one for a later version which has an IC in the first stage and has a complementary output pair, which mine hasn't. I've produced a schematic (attached) from the pcb but most of the transistors are unmarked and I'm not sure whether they are original or replacements. I'm struggling to make any sense of this design so would much appreciate any help or information which might enable me to get this power amp working. I've attached a notated photo of the pcb components to identify the transistors in the schematic. Hoping someone recognizes this and can provide some information. Many thanks.

author: picburner
author_rank: Frequent Contributor
timestamp: April 23, 2024, 02:39:03 pm
content: From what I can see LEM took the amp schematic from this old RCA databook (RCA Transistor Manual SC12 1966)..... with some small variations, but it's very similar.

author: uslrs
author_rank: Contributor
timestamp: April 23, 2024, 02:53:26 pm
content: Many thanks Picburner - that seems to be very much like the LEM circuit. It will certainly be a help with the repair process.

author: MathWizard
author_rank: Super Contributor
timestamp: April 23, 2024, 05:53:45 pm
content: So it looks like an amplifier, but C5=100uF, is that there to delay the signal to the top output transistors and make the echo effect ?I play guitar, but I haven't tried any effects circuits yet.

author: donlisms
author_rank: Frequent Contributor
timestamp: April 23, 2024, 06:14:27 pm
content: That capacitor seems to be for filtering.Effects of all kinds would be done at earlier stages and lower signal levels, and the power amp just makes it bigger.
Lenavo Yoga 720: Is 7 Ohms a Vcore short to ground? - Page 1
Forum section: electronics / repair

author: keerthi123
author_rank: Contributor
timestamp: September 07, 2020, 01:59:49 am
content: I am trying to fix a Lenavo Yoga 720. The buck converter near CPU shows 7Ohms short to ground. No schematic and I guess that is CPU VCore. Is is something normal?

author: wraper
author_rank: Unknown
timestamp: September 07, 2020, 02:03:51 am
content: Don't know about what's normal for particular laptop motherboard but 7 ohms is not a low resistance on Vcore. Often it's much lower. Most likely it's fine.

author: keerthi123
author_rank: Contributor
timestamp: September 07, 2020, 02:06:32 am
content: Thank you. Is there any place to find the schematic? Just googling didn't work.

author: wraper
author_rank: Unknown
timestamp: September 07, 2020, 02:09:29 am
content: As far as I know there is no publicly available schematic.

author: keerthi123
author_rank: Contributor
timestamp: September 07, 2020, 02:26:03 am
content: In diode mode its shows 7 Ohms instead of mV.

author: aqibi2000
author_rank: Regular Contributor
timestamp: September 07, 2020, 10:12:20 am
content: 7 ohms is generally a very healthy for a VCore to gnd impedance

author: Refrigerator
author_rank: Super Contributor
timestamp: September 07, 2020, 03:13:46 pm
content: Quote from: keerthi123 on September 07, 2020, 02:06:32 amYou might have better luck finding a schematic at the BadCaps forum.Quote from: keerthi123 on September 07, 2020, 02:26:03 amOh no

author: modoran
author_rank: Regular Contributor
timestamp: September 10, 2020, 03:01:34 am
content: 7 ohms is good for cpu and gpu's, some are well under 1 ohm and still working fine.
Lenavo Yoga 720: No power from USB-C port - Page 1
Forum section: electronics / repair

author: keerthi123
author_rank: Contributor
timestamp: September 07, 2020, 05:25:12 am
content: I am trying to fix Lenavo Yoga 720 and no power is coming from USB-C. Seems TPS6598 (see attached image) is communicating with USB-C port.according to the attached image:What is 1175J?Also two other 4 pin ICs nearby 1175J?Also for testing can I cheat by providing external signal to TPS6598 get the power rails activated?

author: keerthi123
author_rank: Contributor
timestamp: September 07, 2020, 06:09:36 am
content: So no power at nearby fuse (visible in the image) . Is battery charge controller IC (BQ25700) also communicating with the USB-C charger?

author: winniethepooh_icu
author_rank: Contributor
timestamp: September 07, 2020, 06:36:26 am
content: You have one of two possibilities with the TPS65982:1) The internal power switch is controlling the 5V power.2) It is driving external NMOS via HV_GATE1 and HV_GATE2 pins.I can not see in your picture whether there are traces leaving HV_GATE2 on the top layer (it is on the edge of the IC so this is possible). If so, you can follow this trace to the power switch. If a trace leaves SENSN you can follow it to the sense resistor which will allow you to find the power path. If there is an external power switch, you should watch the gate when you connect a device, the gate should be driven somewhere between 4.5V and 7.5V only when a device is attached. The power switch (whether internal or external) will not activate until attach is detected on the CC pins.The ESD protection level of the TPS65982 is rather poor and it would be assumed that there is external protection for the CC pins; It would be worth checking to see if the CC pins are behaving normally - See USB Type C specification from USBIF.org for an explanation of how these pins work.

author: keerthi123
author_rank: Contributor
timestamp: September 08, 2020, 05:38:45 am
content: I found that there is crack on BQ25700 and going to replace it frist.
Lenovo Display ThinkVision LT3053p Repair - Page 1
Forum section: electronics / repair

author: Nebukad
author_rank: Contributor
timestamp: October 01, 2019, 01:45:40 pm
content: Hi all,I'm trying to repair a Lenovo 30" monitor from 2014.The initial issue was, that it would not detect any signal from the DP input anymore, but would instead go to "power saving" and switch off.While diagnosing this issue, at some point the LED started flashing (instead of staying solid orange to signalize standby).I checked the PSU, which is completely fine. On the Digital board I found a voltage rail, that was doing a lot of funny stuff. It stayed between 1.65 and 1.80 Volts most of the time, but it started dropping to 0 from time to time.This rails is created by an LDO (Sot23-5 package) from a 3V3 rail, see picture attached. That IC gets crazy hot (>100 °C) after some seconds.I got the set to work by supplying 1.85 V from an external supply to that rails. It works with every input except DP. When I plug in DP source, something draws up to 1 A from that ~1.8 V rail and still, it is not detecting the input.My theory now is, that something in the DP-input circuit (which is part of the main ASIC) is broken and draws excess when activated. This has lead to a malfunction of the LDO.My plan is now to replace that LDO and never plug anything into the DP input ever again.Does anyone know that LDO IC (U707)? It's in an SOT23-5 package, Pins 1 and 3 are 3V3 (one will be Vin, the other some kind of enable signal), Pin 5 is the output (~1.8V) and Pin 4 is connected to a feedback network (30 k from Out to FB, 20 k from FB to GND). The Marking on the chip says 91410.Of course I could just retrofit any other LDO and change the resistor network, but I would like to get an exact replacement, and I would like to know the exact voltage, that the rail should be at.Any help would be greatly apprectiated!
Lenovo Laptop Battery Stuck at 43% – BMS Active but Blocking Charge/Discharge –  - Page 1
Forum section: electronics / repair

author: dhanushranga
author_rank: Newbie
timestamp: May 16, 2025, 05:58:51 pm
content: Hi all,I'm reaching out for help regarding a smart lithium-polymer battery in my Lenovo Slim 7 ProX variant) that seems to have entered a BMS lock state. I'd appreciate advice from anyone familiar with battery controller resets or has experience with TI-based fuel gauge ICs.🔋 Battery Info:Model: L21M4PC7Chemistry: Li-PolymerDesign Capacity: 70 WhCurrent Full Capacity: 60.6 Wh (86.6%)Cycle Count: 460Voltage (Fedora + HWInfo): ~15.4VReported Charge %: 43% (stuck)Status: Charging (but current = 0W)Controller Manufacturer (likely): TI or similar (BQ series suspected)Smart Battery Controller: Unknown exact chip (haven’t opened pack yet)🧠 What Happened:System ran hot while on Fedora Linux, discharged the battery from ~80% → 3% in 3 hoursPlugged into AC: charged extremely slowly from 3% → 44% over 6 hoursAfter 44%, battery froze: no further charging, percentage stuckSystem immediately powers off if unplugged from AC, despite showing 43% chargeThe issue has persisted for ~3 days across both Fedora and Windows📋 Diagnostic Results:✅ Battery is detected in Fedora and Windows✅ Voltage is stable around 15.4V❌ power_now = 0 (charging current = 0W)❌ energy_now = 26.5Wh, never changes❌ charge_now file missing under /sys/class/power_supply/BAT0✅ Lenovo Vantage shows “Battery failure – replacement required”✅ tlp-stat, upower, acpi -V, udevadm, busctl, and journalctl confirm same status:→ Battery is present, charging, healthy cells, but power transfer = 0🧪 My Diagnosis:I believe the BMS has:Entered a Permanent Failure (PF) lockPossibly disabled both charge and discharge MOSFETsStill reports all values via SMBus, but disables power transferMay require a BQStudio + EV2300/2400, Be2Works, or EEPROM reset❓ My Questions:Has anyone successfully reset the BMS on a similar Lenovo battery?What controller IC is usually inside L21M4PC7 Lenovo packs? (BQ8030? BQ40z50?)Is this battery recoverable via I2C or SMBus commands, or is a replacement the only option?If I probe the SMBus lines on the battery PCB, is it worth attempting a reset using a TI interface?Do chip-level repair shops generally handle this kind of reset, or is it service-center-only?🧰 What I’m Considering:Open battery and attempt controller IDContact local board-level repair tech with EEPROM programmer / EV2300Order new L21M4PC7 battery as fallbackAny advice, war stories, or schematics would be greatly appreciated.I’ll happily share the full logs, battery-report.html, and Fedora diagnostic outputs if needed.Thanks in advance!– Dhanush(Location: India, Tech Background: Software + Linux + Hardware Enthusiast)
Lenovo S130 ideapad motherboard - need capacitor value. - Page 1
Forum section: electronics / repair

author: robbak
author_rank: Contributor
timestamp: March 30, 2021, 05:47:06 am
content: Have an S130 notebook that won't power on, tracked it down to a cracked and shorted ceramic capacitor. Removing the cap has cleared the short, but the cap is in the middle of what appears to be power supply circuitry, so I don't think I can write it off as a redundant bypass capacitor and proceed without it - although it does appear to be decoupling U600, which looks like a switching device to me - lots of power pins shorted together.The notebook is a S130-141GM. Numbers on the board - rather cyptic - are P. & Q 1833 CM-4 94V-0 E162264 P/N:431205215020S130/130S_GLK_MB_LPDDR4_V10S130-4G+128G-08131-4300-2946I'm attaching photos - the capacitor is marked with a big red arrow and a square, on the top of the board. Any way I can identify this capacitor?

author: amyk
author_rank: Super Contributor
timestamp: March 30, 2021, 01:20:22 pm
content: What are the labels on U6001 and U6002?

author: robbak
author_rank: Contributor
timestamp: March 30, 2021, 01:59:02 pm
content: U6001 is marked 'BACAJG', and U6002, 'AWVAKD'. Their surrounding circuitry looks identical, and those numbers look more like serial numbers that part numbers.

author: wraper
author_rank: Unknown
timestamp: March 30, 2021, 02:14:19 pm
content: Desolder nearby capacitor which is connected in parallel to it and measure its capacitance as it should be the same type.

author: gamalot
author_rank: Super Contributor
timestamp: March 30, 2021, 02:35:25 pm
content: AWV*** should be SY8286A and BAC*** should be SY8288A. I only found the data sheet of SY8286, but I guess their external circuits should be similar.https://datasheetspdf.com/pdf/1297122/Silergy/SY8286A/1

author: amyk
author_rank: Super Contributor
timestamp: March 31, 2021, 12:05:47 am
content: Look for "LA-C371P" schematic. Not your laptop but it uses SY8288RAC on 1.5V and 1.05V, and SY8286BRAC on 3V3 and 5V.

author: robbak
author_rank: Contributor
timestamp: March 31, 2021, 12:25:06 am
content: Thanks, everyone:wrapper: OK. Don't really want to be putting unnecessary heat into this board if I don't have to.gamalot : Thanks, that's a big help. So, that confirms that they are bypass capacitors. The datasheet recommends a 10μF ceramic capacitor - This has two in parallel. I thought they were different sizes, but I just double checked, and they are the same footprint, and look to be the same thickness. I don't recognize device sizes at a glance, but with solder it measures 2mm × 1mm pretty exactly. About 0.8mm thick, by my horribly cheap plastic vernier!Would a pair of 10μF capacitors make sense? Now I know they are bypass caps on the input side, I am confident that the value isn't critical.amyk: Hmm.That schematic lists an array of a parallel 2.2n, 0.1U and 10U capacitors.
Lenovo ThinkPad E580 powers on, no display, then turns off. - Page 1
Forum section: electronics / repair

author: Arty30
author_rank: Regular Contributor
timestamp: July 23, 2023, 12:32:01 am
content: Hello, I have a Lenovo ThinkPad E580 That is non-functioning. I got it for almost nothing because it had a corrosion issue. I replaced a peripheral board that had damaged ports. I believe it was stone dead since it had been sitting a while. I cleaned it up as best as I could, but when it comes to testing I did not make it very far. It finished charging, and when I press the power button the power LED and all the num lock/scroll lock/ fn lock lights come on for about 20 seconds, and then it powers off. I hear the fan running while it does this, and when I shine a light on the screen I see it get darker as if it's displaying a "black" screen but nothing more. perhaps the backlight is dead, but I'm not sure that would make it shut down after about 30 seconds. I haven't tried anything yet I just want to hear if anyone has any tips. I wouldn't be too surprised if it's junk.

author: amyk
author_rank: Super Contributor
timestamp: July 23, 2023, 04:15:23 am
content: You can check for activity on the BIOS pins to see if the CPU is reading from it.Schematic seems to be available under reference ID "NM-B421".

author: Arty30
author_rank: Regular Contributor
timestamp: July 23, 2023, 02:26:20 pm
content: OK so I reseated all the cables I could get to and moved the RAM to the other slot and now it seems to work. Windows seems to be acting weird so I'm just going to reinstall windows.
Lenovo Y50-70 not working on power adapter, only on battery - Page 1
Forum section: electronics / repair

author: costivl
author_rank: Newbie
timestamp: May 03, 2020, 04:16:06 pm
content: Hello,Schematics:https://www.laboneinside.com/lenovo-...matic-diagram/Check page 47 on schematicThis laptop is not powering up with power adapter connected, it only works when battery connected, also it does not recharge battery, i did some checks and i have the following with battery disconnected:P2 - 20VVIN - 20,5VP3 - 0,6VAlso i get 20V on both ground pins of PQ301 and PQ302if i connect the battery i get 7V on P3 but battery not recharging.
Lenovo Yoga 3Pro 1370 - Too low voltage at all USB ports - Page 1
Forum section: electronics / repair

author: ra-ma
author_rank: Contributor
timestamp: April 02, 2021, 04:19:18 pm
content: Hi, since a couple of days the USB ports at my Yoga 3 Pro don't work anymore. Whatever device I'm connecting - there's no indication of "life" (no light/no connection). This is the case within Windows, but also while powering up (USB boot), it's not working. Besides that everything else works including illuminated keyboard etc. Also there's no error in the Windows device manager.I measured the voltage and it appears that only 0.3 volts are present at all USB ports.Luckily I was able to find a schematic (attached). Unfortunately no circuit diagram, but main components are labelled on the board (like "U40").When measuring on the board I find that at PJ7 "+5VDX_WALKPORT" (page 29 left) only some 0.3 volts are present. All other voltages like 3.3V, 1.8V etc. are present and even 5V at PJ4. At the capacitor PC42 I measure 8V at the connection towards the ISL.Visually I can't find obvious damages. Does anybody have an idea where to look next?

author: amyk
author_rank: Super Contributor
timestamp: April 02, 2021, 09:39:03 pm
content: The last page of the schematic (power distribution diagram) shows TPS62130s for a few of the power rails, but there are no other mentions of TPS62130 elsewhere. Is it a fake schematic?
Lenze ESMD302L4TXA VFD defect - Page 1
Forum section: electronics / repair

author: gaminn
author_rank: Frequent Contributor
timestamp: October 17, 2023, 12:56:55 pm
content: Hi,I got two ESMD302L4TXA inverters and both are not able to drive my motor:https://youtu.be/WpKo30suBRIThe motor doesn't run smoothly and produces a lot of noise. It is like the motor starts and stop several times per second.The motor runs smoothly on every other VFD I ever had connected to it.Is there any setting in this inverter that will fix it or are both inverters bad? Any idea how to fix it? I noticed both inverters have its plastic enclosure discoloured (brown or yellow) mainly in the areas that are in contact with aluminium heatsink so I'm afraid both VFDs experienced some overheating.

author: paulvos
author_rank: Newbie
timestamp: October 21, 2023, 05:58:43 pm
content: Not really familiar with Lenze drives, but according to the Type number this model has optional modbus control. You should check parameter C01 , to see if it's really in local terminal control mode ( should be set to 1 according to manualhttps://www.nexinstrument.com/assets/images/pdf/Manual-SMD-V20-0-GB-2016_12.pdf).Could also be electrical problem, maybe the input bridge fried. Happens when running inverters that have been stored for too long ( caps have to be reformed ). You should check connections B+ B- to see if there is a constant DC bus voltage.During run , check these parameters for any abnormalities.C50 Output frequency 0.0 {Hz}C53 DC bus voltage 0.0 {%}C54 Motor current 0.0 {%}

author: gaminn
author_rank: Frequent Contributor
timestamp: October 27, 2023, 09:42:16 am
content: Hi, thanks for your reply.Herehttps://youtu.be/VZ2Sw_vkjVUis a video documenting C53 and C54 parameters behaviour. C53 decreases as output frequency goes higher and suddenly there is run displayed. C54 increases. I can do like 10 Hz output frequency, after that I'm afraid my motor will be damaged. Please turn sound on so you can hear what's happening. Motor is just shaking.C50 is steady during inverter operation.
Leo Bodnar mini GPS Receiver - Page 1
Forum section: electronics / repair

author: C-47
author_rank: Regular Contributor
timestamp: January 17, 2024, 08:07:10 am
content: I have the above unit for some years, no problem, however after several 45 deg C days with the antenna on the shed roof there is no 10Mhz output signal, checked with freq counter, the LED remains red. Measured output voltage and voltage to the active antenna all within reason, the software is showing satellite reception located near the office window, while I initially thought it was an antenna problem, I'm now doubting this based on software readings. I opened the unit up, but things inside are so small I doubt I'd see anything anyway.Any thoughts on this or suitable replacement. Thanks, Alan.

author: tautech
author_rank: Super Contributor
timestamp: January 17, 2024, 08:39:30 am
content: Contact Leo, Alan:support@leobodnar.com

author: C-47
author_rank: Regular Contributor
timestamp: January 17, 2024, 08:58:55 am
content: Thanks mate, already done.
Lesson learn about Agilent E3615A repairing  - Page 1
Forum section: electronics / repair

author: BD1QMP
author_rank: Contributor
timestamp: April 04, 2023, 07:58:17 am
content: Here I will sharing my lesson learn of E3615A repairing.Finally, I found the issue are caused by contacts issue of S1-S5, at least 3 switches have this issue.and when followed the table A-5 for trouble shooting, the higher out put of out+ plus grounding issue of S1-S5 cause the A/D chip (TC14433) in display board fail.Warning:when you are following table A-2 to check the power supply, if you found the voltages of TP6-Point3 and TP6-Point5 are abnormal, but the voltage output of the voltage regulator are fine. you need check the S1-S5 immediately. the ground connection in S1/S5 may cause higher voltage in A/D chip and then burn it.The A/D chip TC14433 is very difficult to find. My play is redesign the display board with MAX1447 (I have 4 chips in hand).service manual is here:https://wiki.physics.wisc.edu/yavuz/images/2/24/E3614a.pdf
lettering - Page 1
Forum section: electronics / repair

author: cncjerry
author_rank: Unknown
timestamp: October 16, 2024, 06:16:13 pm
content: The subject often annoys us, and I was wondering if anyone has figured out a way to apply lettering to projects? This would be silk screened or somehow plastic stenciled lettering, not rub-on, unless it was something new. I have devices that have rubberized coating that is sticky that I want to remove. I want to put the lettering back on after spraying the cases again. Mostly, the lettering would be applied to flat surfaces. Ideally, some kind of precut stencil would be ideal, were you would apply the stencil, spray, remove, etc.As the surfaces are plastic, I wouldn't be able to cure it.Any ideas? Can you paint on 10pt lettering using silk screening?ThanksJerry

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: October 16, 2024, 07:21:48 pm
content: Use a laser cutter (5W diode laser will work on plastic). I use Inkscape and its 'Hershey text' plugin to generate the toolpaths, these are single-stroke fonts.

author: ataradov
author_rank: Super Contributor
timestamp: October 16, 2024, 08:41:17 pm
content: There are a ton of laser engravers out there. They sent a lot of them to YouTubers, so pick the one you trust and check their reviews. They are not super cheap, but if you need to do that regularly, it may be worth the price. I bet it will be cheaper and way easier than a silk screen setup from scratch.

author: cncjerry
author_rank: Unknown
timestamp: October 16, 2024, 10:07:48 pm
content: I haven't invested in a laser yet. My brother has one. he said you have to watch melting plastic as it will cloud the lens. He suggested I setup air extraction if I go that route. I have tons of CNC gear and had a laser setup to cut black tape a while back. I guess I could place tape on the case, cut the tape, lift the sections to be painted and spray it.