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Re: FSP300-60GTF repair - blown transoptor, resistors, worth it?

Posted on 2025-03-07, 17:04

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

LOL that ain't right either. 390 Ohms --> 330 Ohms is about 15% reduction in resistance, but 5.8V to 4.6V is a little more than 20% reduction, which doesn't make much sense. R13 value shouldn't be that sensitive at all, once there's enough current to drive the LED in the optocoupler. So might need …

Re: FSP300-60GTF repair - blown transoptor, resistors, worth it?

Posted on 2025-03-07, 16:21

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

So I've replaced the R13 (only one near opto coupler which was 390 ohms) with an 330ohm and the voltages are bellow spec (4.56-ish volts). Which is a good and bad thing :) I'll try an 360 ohm next when the PSU discharges. If that doesn't help then idk what will. It didn't help, only made this worse …

Re: FSP300-60GTF repair - blown transoptor, resistors, worth it?

Posted on 2025-03-06, 17:21

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Okay with an 1k in the voltages are down to 5.5v. Still to high though.... And besides now there's an funny smell inside. I cannot describe it but it's like plastic melting or something like that but veery light. Maybe it's from the outside but I can only smell it when there's power to the PSU.

Re: FSP300-60GTF repair - blown transoptor, resistors, worth it?

Posted on 2025-03-06, 16:58

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

You need some big enough load on the output for voltage to get in spec, i.e a few LEDs or something like a 100 ohm resistor. Unloaded SMPS outputs are rarely if ever in spec. Actually, on a second thought this doesn't sit right with me... The PSU after replacing all the bad parts for the first time …

Re: FSP300-60GTF repair - blown transoptor, resistors, worth it?

Posted on 2025-03-06, 16:03

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

1k ohm (for good measure) resistor on 5vsb to gnd. Got it.

Re: FSP300-60GTF repair - blown transoptor, resistors, worth it?

Posted on 2025-03-06, 14:44

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Okay I've replaced that diode with the one above and..... 5VSB IS BACK! ...but again without a catch.. It's waaay out of spec (5.8v!).... I have no idea what else now is screwed. Caps were replaced on both the primary and secondary side... At least the sec. aux. rail is okay (10.20v).

Re: FSP300-60GTF repair - blown transoptor, resistors, worth it?

Posted on 2025-03-06, 13:35

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Okay for the PS106R I found an FR107, which should be 1A 700V. It's legs are a tad bit short but I think soldering some copper wire to one pin should be okay. At least for testing. As for the opto coupler I'll just replace it with a new one. Have like 20 of them I forgot about😆

Re: How to disable the charging circuit on an old 486 motherboard?

Posted on 2025-03-06, 10:17

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I think putting an diode on the positive pin should do the trick. Just make sure to put it correctly

Re: FSP300-60GTF repair - blown transoptor, resistors, worth it?

Posted on 2025-03-05, 19:40

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Case 1 shouldn't be the culprit. C8 was replaced and doesn't show a short between the pins, D5 still shows around 500mV in bias and nothing in reverse bias. R61 is the one I couldn't locate using the pictures DAVE86 provided and my own PSU (the pcb got scorched too much). I don't think I have any …

Re: FSP300-60GTF repair - blown transoptor, resistors, worth it?

Posted on 2025-03-05, 16:09

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

1) snubber circuit (consisting of ceramic cap C8, HV diode D5, and resistor R61) might have a bad component. Most likely either C8 is leaky, D5 is leaky, or R61 is open. Check R61 first. Should be 22k according to what @DAVE86 wrote (and what I see from the pictures too.) If that checks out on …

Re: FSP300-60GTF repair - blown transoptor, resistors, worth it?

Posted on 2025-03-04, 18:56

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

And now there's close to nothing on 5vsb (0.2v) and the bulb stays halfway/ 1/3rd of the full brightness when power is applied.....

Re: FSP300-60GTF repair - blown transoptor, resistors, worth it?

Posted on 2025-03-04, 14:53

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Okay the R16 is replaced (somewhat smaller but it should be enough for testing) and we have 5VSB! ...if we skip over the fact that in the beginning it was going up to around 2v (me cutting power due to hearing "sizzling" noise may also be the culprit) and the fact that the whole PSU dies after a …

Re: FSP300-60GTF repair - blown transoptor, resistors, worth it?

Posted on 2025-03-03, 19:35

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Okay so the low value resistor R16 (which according to band markings (yellow,purple,gold,gold) is an 4R7) seems to not let anything through it. Even in diode mode I get nothing. I only have an bulky 22W one but it's too big to fit... High resistance resistor R14 is good (680kOhms). Primary winding …

Re: Test and troubleshoot PC@LIVE motherboards

Posted on 2025-03-03, 10:19

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

I saw this exact same issue on my socket A board with nf2. In my case the board wasn't playing nice with an 100mHz FSB CPU. An athlon xp fixed the issue. Maybe it's the CPU in your case too? Although you might have tried it already..

Re: FSP300-60GTF repair - blown transoptor, resistors, worth it?

Posted on 2025-03-02, 14:22

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Okay with the small TO 96 transistor on the primary side 5vsb rail replaced (it burnt itself so badly one of the legs fell out) and the MOSFET inplace and without Q4/5 and J12 and the two pull up 1k resistors I get absolutely nothing on 5vsb and the sec. aux. rail has -0.27v according to my metex MM …

Re: FSP300-60GTF repair - blown transoptor, resistors, worth it?

Posted on 2025-03-02, 09:26

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Okay in my parts bin I also found an SVF2N65D, although this one has only 2A continuous drain current..... Should be OK... if nothing else, for a test. I suspect it will be fine, though. Same as CEF02N6 which isn't an MOSFET but an N-chanel enhancement mode field effect transistor... Although the …

Re: FSP300-60GTF repair - blown transoptor, resistors, worth it?

Posted on 2025-03-02, 08:23

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Okay in my parts bin I also found an SVF2N65D, although this one has only 2A continuous drain current..... Same as CEF02N6 which isn't an MOSFET but an N-chanel enhancement mode field effect transistor... Although the datasheet shows its internal structure as an MOSFET. Then there's the IRFS730 N- …

Re: FSP300-60GTF repair - blown transoptor, resistors, worth it?

Posted on 2025-03-01, 21:38

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Okay I corrected my mistake and it lives! Yay, congrats, one up for the count... well almost there anyways. ;) Was hoping the tagan would get fixed firstly, but I take whatever I can fix. But still, knowing my skill it's a very big leap in the PSU repair stuff :) Although the rails are a tad bit of …

Re: FSP300-60GTF repair - blown transoptor, resistors, worth it?

Posted on 2025-03-01, 20:20

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Okay I corrected my mistake and it lives! Although the rails are a tad bit of... 12v is 11.84v, 5v is 5.34v, 3.3v is within spec (3.4v), -5v is -4.60v and -12v is -10.6v. All are unloaded. That might be due to the small primary caps going dry and/or the dim bulb protection being to powerful for this …

Re: Logic Concept LC-B300ATX 5Vsb too high, not starting

Posted on 2025-03-01, 17:49

in Marvin \ General Old Hardware

in Marvin \ General Old Hardware

Sorry for reviving this thread. Since I had my deer lc350w PSU become unstable with the 5vsb rail I got the chance to test this PWM chip and it works inside my deer PSU. And since I scrapped this PSU I have no longer the chance to trace what could've been wrong, but it might be due to missing sec. …

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