Radeon X1650pro stops motherboard power up

[weirdlookinguy]

Re: Radeon X1650pro stops motherboard power up

That fan looks like a POS...

[pfrcom]

Re: Radeon X1650pro stops motherboard power up

That fan looks like a POS...

But it's now a re-lubricated POS, which seemed to work OK for the very brief times I've had the card powered on


Pyr0Beast,

I did look at Farnell - they said No Longer Manufactured for the Infineon part, and choose a substitute

But their system didn't suggest anything, apart from the Infineon in different packaging, which was also not available

That's why I eventually stumbled on the ST part, which is available from RSComponents

I've lost the original SO8 mosfets - they fell through gaps in my workbench, and I didn't bother searching for them

[pfrcom]

Re: Radeon X1650pro stops motherboard power up

Stick the card in the slot and start it up. If there is nothing (computer still halts), unsolder the other two mosfets on the other end of the card, near the choke, as well. Check if one is connected paralel on the bottom.

With the MOSFETs near the Molex connector removed, it still won't start

Just as before, there's a slight twitch from the CPU fan, and that's all there is

[momaka]

Re: Radeon X1650pro stops motherboard power up

With the MOSFETs near the Molex connector removed, it still won't start
Just as before, there's a slight twitch from the CPU fan, and that's all there is

That means there's still a short and we (read: you ) gotta hunt it down.
Basically, it all comes down to remove components until any short circuit between 5v/ground and/or 12v/ground disappears.
Start with the easy components - D1, D3, D4. Then check for short circuit. If still present, continue with any other mosfets and voltage regulators on the card that measure continuity/0 resistance between output and ground or output and 5v/12v.

Also, referring to the picture I attached below, check resistance between the pads circled in blue and the pads circled in green. What resistance do you get? Now check resistance between the cyan pads and the green pads. Again what resistance do you get?

[pfrcom]

Re: Radeon X1650pro stops motherboard power up

Thanks for the colour coding - I can cope with that (still trying to work out what is the choke, mentioned by Pyr0Beast in post #19 - is it the component marked R68M ?)

Resistance between the blue & green pads is 85.5 ohm

And between the cyan & green pads is 87.9 ohm

[momaka]

Re: Radeon X1650pro stops motherboard power up

(still trying to work out what is the choke, mentioned by Pyr0Beast in post #19 - is it the component marked R68M ?)

Yes.

Resistance between the blue & green pads is 85.5 ohm

And between the cyan & green pads is 87.9 ohm

Good. That means nothing else is shorted down the line.

Next, check for continuity again between the 5v pin and ground on the power connector. Also check for continuity between 12v and ground. If you're still getting a low reading on any of these, proceed to remove D1, D3, D4. Then check for continuity again at the power connector. If you still get a low continuity reading, remove the MOSFETs Pyr0Beast mentioned (one is on the front of the card, near the choke R68M, the other is in the back, right under the first one).
Then, yet again, check for continuity at the power connector. Post a log of the results you get here.

Once the short circuit between 5v and ground or 12v and ground is removed, the computer should hopefully start. After this, all you'll have to do is get replacements for the components you removed, and you may get a working video card.

In the meantime, keep the old components (or try not to loose them ) - some of them, like the diodes, may still be good.

[Pyr0Beast]

Re: Radeon X1650pro stops motherboard power up

Thanks for the colour coding - I can cope with that (still trying to work out what is the choke, mentioned by Pyr0Beast in post #19 - is it the component marked R68M ?)

Yes.

Remove both mosfets. One is on the upper side of the board. Otherone on the bottom.

With mosfets removed and short still detected I would check tantalum capacitors on input.

Also replace the PSU if they are shot - as seems voltage surge killed them.

I did look at Farnell - they said No Longer Manufactured for the Infineon part, and choose a substitute
If they are in stock, no problem with that.

[pfrcom]

Re: Radeon X1650pro stops motherboard power up

Next, check for continuity again between the 5v pin and ground on the power connector. Also check for continuity between 12v and ground. If you're still getting a low reading on any of these, proceed to remove D1, D3, D4.

Was still getting a continuity beep between 12v & ground, although removal of the first set of MOSFETs near the Molex connector had fixed between 5v & ground

Removed the diodes on the back, as per this pic, but no change

[Pyr0Beast]

Re: Radeon X1650pro stops motherboard power up

Remove the small green electrolytic capacitor below white molex connector (if it is for 12V)

[pfrcom]

Re: Radeon X1650pro stops motherboard power up

Then check for continuity again at the power connector. If you still get a low continuity reading, remove the MOSFETs Pyr0Beast mentioned (one is on the front of the card, near the choke R68M, the other is in the back, right under the first one).
Then, yet again, check for continuity at the power connector. Post a log of the results you get here.

Removed one MOSFET on the back, as per this pic - was already suspicious of this one, because previous testing showed a continuity beep between the centre (ground?) and right legs

No more continuity beeps on the Molex connectors, so on to the acid test ...

... and motherboard powers up with this card in its AGP slot

Now I'll need handholding for replacements of the diodes and the MOSFET(s) - am I correct in thinking the one still in situ should be replaced also, being a pair ?

Anyway, the diodes are marked with a W logo, and underneath that M72, and underneath that 383 or 3B3

The removed capacitor is marked D452 and BA627H

The capacitor still in situ, on the fan side of the card, is marked D472 and BA632G

[Pyr0Beast]

Re: Radeon X1650pro stops motherboard power up

Seems ok now ?

I would then replace one rail by one. They both work independently.
First the SO8 mosfets.

[pfrcom]

Re: Radeon X1650pro stops motherboard power up

I'm looking to buy all the replacements at one time, to minimise shipping charges

[Pyr0Beast]

Re: Radeon X1650pro stops motherboard power up

Yes yes.

[momaka]

Re: Radeon X1650pro stops motherboard power up

... and motherboard powers up with this card in its AGP slot

Nice. Next step, replacement parts .

Now I'll need handholding for replacements of the diodes and the MOSFET(s) - am I correct in thinking the one still in situ should be replaced also, being a pair ?

Yes.

As a matter of fact, check the rest of the large MOSFETs as well (circled in blue, see attached images). That is, get their datasheets first, see which pins are Source and which are Drain, then measure resistance between Source and Drain. Those that show very low resistance (less than 20 Ohms) should be removed from the board and measured again. If they measure normal out of circuit, you can put them back on the card.

Anyway, the diodes are marked with a W logo, and underneath that M72, and underneath that 383 or 3B3

Check them for continuity with your multimeter. They should show continuity only in one way, but open circuit/infinity when the probes are reversed.
If they pass this test, you can put them back on the card.

The removed capacitor is marked D452 and BA627H
The capacitor still in situ, on the fan side of the card, is marked D472 and BA632G

Are these tantalum capacitors? Where were they located?
If they aren't shorted, I think you can put those back in as well (though it would be good if someone else could confirm that this is okay).

[pfrcom]

Re: Radeon X1650pro stops motherboard power up

The removed capacitor is marked D452 and BA627H

The capacitor still in situ, on the fan side of the card, is marked D472 and BA632G

Are these tantalum capacitors? Where were they located?
If they aren't shorted, I think you can put those back in as well (though it would be good if someone else could confirm that this is okay).

Sorry, Senior moment on my part, plus wife on my case to get off the bl.... computer

Should have read:

The removed MOSFET is marked D452 and BA627H

The MOSFET still in situ, on the fan side of the card, is marked D472 and BA632G

[pfrcom]

Re: Radeon X1650pro stops motherboard power up

To me, the D452 and D472 MOSFETs appear functionally equivalent (datasheets attached)

If that's correct, would 70T03H MOSFET(s) which I can cannibalise from a dead motherboard, also be OK ? (datasheet attached)

[Th3_uN1Qu3]

Re: Radeon X1650pro stops motherboard power up

Yes the 70T03H should work.

[pfrcom]

Re: Radeon X1650pro stops motherboard power up

That is, get their datasheets first, see which pins are Source and which are Drain, then measure resistance between Source and Drain. Those that show very low resistance (less than 20 Ohms) should be removed from the board and measured again. If they measure normal out of circuit, you can put them back on the card.

The removed MOSFET marked D452 has been replaced, as per picture, by one marked 70T03H cannibalised from a dead motherboard

I wasn't sure what normal should be for "measure normal", so I selected a 70T03H which gave a short beep for Continuity/Diode test between Drain & Source (which, in my limited experience, indicates a working MOSFET)

Afterwards, no continuity beeps between 12v or 5v and ground pins on the card's Molex connector

And a motherboard still powers up with the card in its AGP slot

[pfrcom]

Re: Radeon X1650pro stops motherboard power up

Check them for continuity with your multimeter. They should show continuity only in one way, but open circuit/infinity when the probes are reversed.
If they pass this test, you can put them back on the card.

The three diodes passed this test, so they're back on the card, as per picture

Again, no continuity beeps and motherboard powers up

Now I have to buy some replacement SO8 MOSFETs and see what happens - those parts don't seem to be used on motherboards, and possible to cannibalise

Pyr0Beast, I haven't disregarded your advice about replacing the electrolytics - it's on my list of things to do

[Pyr0Beast]

Re: Radeon X1650pro stops motherboard power up

Check voltages on that rail to see if it works.