XFX 7800GS intermittant no display on power up

[illtech]

Hi all,

Accidentally stumbled across this site thru my ventures of googling, got intrigued and started reading up. Now after digging through a few posts on here, it seems I may have an old video card that I tossed aside thinking that it was toast, when all it really needed was a few new caps.

Only problem here is that that there are no obvious signs of the caps being blown. They cap types look like they are polymer, which from what I have read dont really "pop" as such.

If I power on the PC with the video card installed (XFX 7800GS), the video card fan spins, but I dont get any output on the display (it doesn't even get the LCD out of standby mode).

Previously I could simply power off the computer, wait a few seconds then power it back on and everything would work fine. The problem started to get worse and worse to the point where I had to power cycle the PC a few times to get the video to display, eventually to the point where it wouldn't display at all. Once the display is up and running, it would stay running till I powered off the pc.

I have since replaced the video card with another model (Gigabyte 6600GT), albit a bit slower, it seems to work fine.

At the moment, I have a few limited tools to test with - cheap iron (will be investing a decent one shortly) & a digital multimeter.

To any of you more experienced techies out there, does this sound like there may be a problem with the cap(s) on this board? In my in-experienced opionion (I could easly be wrong) it sounds like one of the caps may have slowly given up and stopped giving power to one of the chips.

If it seems fixable, I would like to give an attempt at fixing it, and put it back to use :P

Any help/direction here, would be much much appreciated


Cap markings on the attached pic:
(A) PS 5DC, 330, 16V (No brand marks, maybe Chemicon?)
(B) 546, SVP, 1200, 4 (No brand marks, maybe Chemicon?)
(C) 550, SVP, 180, 16 (No brand marks, maybe Chemicon?)
(D) Sanyo, OS-CON, 510, 4, 7A 105oC
(E) Rubicon, YK, 10Y, 100uF
(F) ELNA, 16V, 47uF (M)

[jsog]

Re: XFX 7800GS intermittant no display on power up

The Sanyo at D looks a little bulgy, but that could be the light. This might be one of the famous nVidia BGA problem chips.

[POM_MJ]

Re: XFX 7800GS intermittant no display on power up

(B) and (C) are Sanyo Solid Polymer.
(E) Should be Rubycon YK 10V 100uF

[bigbeark]

Re: XFX 7800GS intermittant no display on power up

So caps B,C, D & E are all reputable brands, and unlikely to fail, which leaves "A".

Are there any marks scribed in the top of those caps, that could be a vent? Sacon and some others frequently disguise electrolytics as solids.

Are the "A" caps through-hole or are they surface-mount?

It's a lot easier to replace through-hole caps than surface-mount.

[yyonline]

Re: XFX 7800GS intermittant no display on power up

The blue caps marked "A" are United Chemi-con PS series. Solid polymer, reliable, very unlikely to fail.

In fact, all of the capacitors on there appear to be reliable brands. I don't think this is a capacitor problem.

Was there any distortion in the graphics, or did it just fail to start? I see it has an extra power connector on the end of the board - what kind of power supply do you have? It's possible the replacement card is not as power hungry and doesn't stress the power supply as much.

[illtech]

Re: XFX 7800GS intermittant no display on power up

Hi guys,

Cheers for all the tips.

The Sanyo at D looks a little bulgy, but that could be the light. This might be one of the famous nVidia BGA problem chips.

Think it may just be the light. Even at first glace the top looks like it may be slightly raised, but if you look at it dead side on, it is flat. nVidia BGA, best I can do here is tin-foil and run a heat-gun over the chip -- is safe to do so? Or could I just ruin it completely?

(B) and (C) are Sanyo Solid Polymer.
(E) Should be Rubycon YK 10V 100uF

Cheers for the updates, I'll try edit my orig post in a sec to reflect.

Are there any marks scribed in the top of those caps, that could be a vent? Sacon and some others frequently disguise electrolytics as solids.

Looks like the top and sides are 1 piece, no vent markings at all.

Are the "A" caps through-hole or are they surface-mount?

A, D, E & F are through-hole. B & C are surface mount.

The blue caps marked "A" are United Chemi-con PS series. Solid polymer, reliable, very unlikely to fail.

Cool thanks, I'll update the original post.

Was there any distortion in the graphics, or did it just fail to start? I see it has an extra power connector on the end of the board - what kind of power supply do you have? It's possible the replacement card is not as power hungry and doesn't stress the power supply as much.

No distortion of graphics. Just became harder to start the PC with the video posting. Before it completely gave up, I sometimes had to turn the pc on and off 4-5 times before the monitor would turn on. It seems as if the video bios wasnt 'posting'?

Cant remember the brand of the PSU (I'll open up the case in the morning and have a look), but it is a 400W one (about 6 years old now). Supposed to be good quality, as I have been told the same company makes power supplies for medical use.

Setup at the moment, is P4 Northwood 3.2GHz, Abit IC7 mobo, 2x 7200RPM HDDs, no optical drive, 2x 120mm fans, m-audio PCI sound card. Previously I've had this card running along side another 2x 7200rpm drives and an optical drive, and it seemed to run sweet.

The 6600GT I've got in there at the moment is running off the same power connector, although I'm guessing it doesn't use as much power.

I was under the impression that the cards didn't need the full ampage to boot - just under load when all the 3D stuff kicked in?


Edit: Ok seems I cant edit my original post to update the cap brand names.

[PCBONEZ]

Re: XFX 7800GS intermittant no display on power up

This might be one of the famous nVidia BGA problem chips.

I agree.

[jsog]

Re: XFX 7800GS intermittant no display on power up

nVidia BGA, best I can do here is tin-foil and run a heat-gun over the chip -- is safe to do so? Or could I just ruin it completely?

DIY reflow is kind of a nothing-left-to-lose thing.

Worst-case, not only does it not fix the board, it destroys the motherboard and power supply of the computer used to test it. Found a report of that yesterday. It was probably an oven-baked board, which ruined the caps and maybe other stuff. The nice thing about an AGP board is that you can probably find a disposable test computer.

[liquidfusion]

Re: XFX 7800GS intermittant no display on power up

Hi. I just oven baked my EVGA 7800Gs card and had to remove the purple cap "D" 510/4 sanyo 105C. Can anyone help me find capacitance? Voltage and where I can buy a replacement? Thanks.

[Th3_uN1Qu3]

Re: XFX 7800GS intermittant no display on power up

That would be a 500uF 4 volts polymer capacitor.

[c_hegge]

Re: XFX 7800GS intermittant no display on power up

Yup, and one of these would do fine as a replacement

https://www.badcaps.net/store/produc...products_id=79