I removed the L17, L14, L11, L15, L7, L6 smds and I noticed I have a short with those and +5V.
And ground shorts with +5V... WTH! 😀 I hear sound but after a little while it stops.
Other L- short as well but not with +5V, could they be some kind of voltage regulator and supposed to "short" (continuity test)?

Now doesn't boot. No error code, no nothing. 🙁

There are 2 inductors (looks like) close to the cpu, 1@5V + 1@2V connected to a series of capacitors all @2V (12 in total, prolly vrm stuff).
Is that correct?

I'm getting 3.3V on tachometer on fan headers, but I can't find where ground connects to. 🙁 🙁

Correction, of the two inductors one is 5v and in line with some caps (different line than 2V), other is 2V connected to 12 caps all in line.

Those SMD parts with L's are also inductors, and they are supposed to indicate a short between their pads (per each package).

In particular, L17, L14, L11, L15 are directly related to the PS/2 ports, and L7, L6 are related to the USB ports.

Unless either the USB ports or the PS/2 ports have a short between their pins, these SMD parts should not affect the POST procedure.

Have you considered the transistor controlling the fans may be bad?
Often on older boards ground on fan headers is connected to a transistor that switches the fans off i.e. in standby mode.

On another note I really can't follow your reasoning on which components you measure and remove on your board. I'm admittedly no electronics wizard so it may very well be my ignorance, but what happened so far seems pretty random to me and if that's correct you may be causing additional damage.

In fact parts failing give random readings and are unreliable.
Troubleshooting without blueprints is just a guessing game.

-

NPN

computerguy08 wrote on 2020-10-15, 15:57:

Those SMD parts with L's are also inductors, and they are supposed to indicate a short between their pads (per each package).

In particular, L17, L14, L11, L15 are directly related to the PS/2 ports, and L7, L6 are related to the USB ports.

Unless either the USB ports or the PS/2 ports have a short between their pins, these SMD parts should not affect the POST procedure.

I had time to do some more things and there are no shorts. Thanks for clarifying.
I'm sure that one other IC on the board has finally stopped working. I have to check the bios also.

I asked a friend in China to buy all the stuff I need to replace all the components that could be dead.
Unless it's the NB or SB I should be ok replacing parts.

Honestly I just want to have fun with it and learn some soldering.

I have a cheap chinese diag card and it won't even display a number thus I'm not stressing about it anymore.

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Some time has passed and now I have soldered the missing resistors.
I still couldn't get hold of the stuff I ordered as my friend hasn't come home yet.

After some tinkering the PSU i was using blew dramatically (smoked away). I don't have +12V short but +5V short to ground.
Now I get to figure out what is causing it.

Found the same board.
Gonna buy it and compare.

It's frustrating how voltages change w/ or w/o a cpu installed.
Looks like it's shorting but once turned on it's not.

Well. Was a nice couple of hours wasted.

Testing ATX power connectors I have a +5V to gnd resistance of 457 ohms; +3.3V to gnd of 93 ohms.

Doesn't look ok to me and I have 3 tantalums on the board.

What happens if I remove the IC controlling the fans? It's this one https://pdf1.alldatasheet.com/datasheet-pdf/v … 3/NSC/LM80.html
If I desolder pin9 (goes directly to +3.3V) to remove +V and disable it, it should stop any hanging during POST?

One shottky rectifier diode, 1N5817, has a resistance of ≃375 ohms (obviously 0 in the other way).
Goes from 5V to diode to 5VSB.

Maybe this diode is faulty and there are issues between 5V and stanby?

LF110 fuse

Power off, continuity OK
Power on, continuity not present.

I can still probe +5V at both ends, is this normal?

Shottky 1N5817 has resistance both ways,

+ on + and - on ~3700 ohms
+ on - and - on + ~1115 ohms

Doesn't look right either.

In fact all schottkys fail continuity test.

Nexxen wrote on 2021-08-05, 21:43:

In fact all schottkys fail continuity test.

I don't know now, after a few vids, if that's a bad thing.

I don't currently have a 1N5817, can it be safely removed and replaced with a 1N4001???

Ok, now it works and you'll stop reading this stuff.

Issue: LM80 IC, used to control fans and display "system monitor" in BIOS was dead.
I tried lifting the Voltage leg from the motherboard but it did nothing.

I removed the whole IC to see if it changed anything and it booted without the "system monitor" menu.
I guess I have to replace that to have it work again.

I can't find any obvious issue as there are no shorts or anything. I should ask EvilMonkeyz to open it up, but I don't htink it'll be an interesting feat.