Re: DELL Optiplex 760 power supply issue
Updates:: Replaced the existing IC from the pcb with a new one then I have measured 2.7v across the source and EN pin. Still have no switching but for sure there is some progress on it.
jazzman72
Member
Last Activity: 03-22-2024, 05:33 AM
Joined: 04-11-2022
Location: Niagara
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Re: DELL Optiplex 760 power supply issue
Hello friends,
Isolated the side panel and checked all optocouplers, all were found in good condition then I did another test. On my testing PCB I soldered a brand new TNY280PN. The source pins were connected directly to the negative rail and the drain one to the positive rail of the main cap then I got 1.6v between the source and enable pin. Why is that 36v on the psu's IC then? I'm still waiting for zener diode kit. Please find attached....Leave a comment:
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Re: DELL Optiplex 760 power supply issue
Yes. That makes sense. Yesterday, I measured 0v between the negative rail of the main cap and anode of the new zener. Sounds like, this opto is shorted on its hot side otherwise it's not supposed to be 0v. Will take the side panel away to see where it is.Last edited by jazzman72; 08-14-2023, 05:15 AM.Leave a comment:
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Re: DELL Optiplex 760 power supply issue
I ordered some 3.3v - 36v zener diode kit from aliexpress. As a hobbyist I should have them. Will keep you posted on the progress. Once again, thanks for your help.Leave a comment:
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Re: DELL Optiplex 760 power supply issue
Tested the circuit by installing a few random zeners. With the first one was measured 15v, the second was 36v but the third one got 9v. I think everything will be fine by using a proper zener. I tested again the original one and got no reading. How to test a zener with DC power supply to see what the upper threshold voltage is?...Last edited by jazzman72; 08-13-2023, 03:16 PM.Leave a comment:
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Re: DELL Optiplex 760 power supply issue
No. Resistors are fine but this very small voltage regulator diode Y4W (3 pin diode) near to EN/UV pin has no diode reading on it. its cathode (middle pin) is directly connected to the enable pin of IC. I tried all possible combinations. I am sure is dead. When it was removed from pcb, the measured voltage on En/Uv pin higher up to 36vdc. While waiting this from amazon can I install some zener (let's say with range from 2.2 to 15v) to test?...Leave a comment:
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Re: DELL Optiplex 760 power supply issue
will do later this afternoon. will keep you posted.
All zeners are fine. I am talking about the brown one near to 4.7 (470) ohm smd resistor.Leave a comment:
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Re: DELL Optiplex 760 power supply issue
Thanks bro,
this diode has nothing to do with EN/UV pin. See my drawing. I think there is something wrong with those three smd 1.5 megaOhm resistors. Sometimes I got 1.5 mega, sometimes 6, sometimes nothing (over limit). Also, is the brown smd component a resistor or capacitor?...Last edited by jazzman72; 08-13-2023, 08:12 AM.Leave a comment:
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Re: DELL Optiplex 760 power supply issue
Good afternoon,
I replaced the broken IC501 with a new one (TNY280PN). Now, I have 170vdc between source and drain and 13vdc between source and EN/UV pin. Does this 13v look normal? Not sure if the diode 502 is being replaced with compatible one since was burned out. Anyways, there is no switching coming out from this IC. I have no voltage on secondary side of the STBY transformer. Any clue what else to check?
@CapLeaker this PSU Model is: L235P-01
Also, I found the attached resistor open, it's right...Last edited by jazzman72; 08-12-2023, 03:24 PM.Leave a comment:
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Re: Dell 2405FPW intermittent power fault
My DELL 2405FPW was having similar issues, this problem became worse day by day and one day just stopped working. I found the bulk cap lost its capacitance and one of the power FET got shorted. I ordered 4 from Ebay for $6.15. it's K3502 N-Chanel Mosfet....Leave a comment:
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Re: Haier LCD TV 40D3500M
it's a transistor. I have reading from the base to the collector and base to emitter. All good with components on this board but still while touching it the TV starts automatically.Leave a comment:
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Re: Haier LCD TV 40D3500M
Good evening,
how should I call this board? It's like a junction box. The black cable is going to the main board, one of the small connector with ribbon cable is going to the button control board, and the second one to the IR board. I have noticed that not able to turn on the tv from the buttons, also while touching this board the TV starts automatically. It happened a few times.
Is the black semiconductor a schottky diode or transistor? I can read something like H1A, not sure if it's labeled as Q1 or D1. I have no reading...Leave a comment:
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Re: Haier LCD TV 40D3500M
yep. i see it now. the one near to the cap#154 and heat sink leg.Leave a comment:
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Re: Haier LCD TV 40D3500M
it will be challenging
One thing I would like to add. When IR board takes a proper voltage, I have got 3.3v measured across the micro chip pins if not, 3.3v is not present on some pins....Leave a comment:
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Re: Haier LCD TV 40D3500M
Sorry for the late response. Was out of the city. Let me repeat this again.
If the IR board is energized properly, the LED goes on and almost every time I can turn on the TV from the remote and it works fine. Once the TV turned off from the remote (I disconnected the control button board to simplify the test) I can't turn the TV back on. Sometimes works, sometimes doesn't work but most of the time does not. The resistor#115 (the once across pin 32 or 33 of the processor, not tested) was found out the trace. I removed it then put...Leave a comment:
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Haier LCD TV 40D3500M
Hello friends,
a friend of mine has this old TV. He told me that once the TV is off, needs time to turn it back on and one day just stopped working. I found the issue in the stby circuit and fixed it. Now I have stable output voltages and I am able to see a red LED lit on of the infrared board. Using a remote I can turn the TV on but once turns off I have to unplug the power cord maybe for 5/10 min to get the TV back on (sometimes this led on is not getting on) While checking the main board I found one of the small resistors close to the processor on the logic board out of the track,...Last edited by jazzman72; 07-27-2023, 08:58 AM. -
Re: DELL Optiplex 760 power supply issue
I ordered 10 of them already. Looking at the datasheet and pins soldered on the pcb. I think that's the right one. ThanksLeave a comment:
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DELL Optiplex 760 power supply issue
Hello friends,
I have an issue with this power supply. There is no output voltage on the standby section, the input section is fine, the bridge is fine and have stable 165 vdc on the bulk cap. While checking the stuff I saw IC501 along with the diode 532 (close to it) gets damaged (look at the picture, the one close to stb transformer). it's a 7 pin ic. I think this guy drives one of the mosfet attached to the heat sink. it looks as LinkSwitch-XT series IC but can't be sure as the top surface is destroyed. Any help would be appreciated. Please find attached....Last edited by jazzman72; 07-20-2023, 12:46 PM. -
Re: New Members - please post your introductions here
Hi everyone
50+ years old guy with small experience of repairing old Russian TV's, PSU's, etc.. back in the begging of 90's. I am not a professional. I happy to be part of badcapsLeave a comment:
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