7300GT smd cap knocked off causing instability

[Koda]

I have a customer with a 7300GT PCI-e card. I found one smd capacitor (very small one) missing. The cap is on the back side connecting one of the pins of the card with the core. The cap is connecting the trace so it's not put there just to filter ripple but also provide continuity. I haven't checked the card yet but the customer said the system would lag and lock up randomly so I guess this is the cause of the problems. I just need your confirmation on the defect. I don't know if my soldering skills are up to the task but I will give it a go so any advice on how to go about this is appreciated. Also would like to ask if going for a cap with the same size from another board would work. I have some closeups but they are kinda blurry.

[Th3_uN1Qu3]

Re: 7300GT smd cap knocked off causing instability

These caps are almost always 100n. You can just grab a similar one from another board. I've done this on several occasions, worked every time. But if you have a multimeter with capacitance function i'd advise you to measure one of its neighbors (you might have to lift it from the board tho) and be double sure about it.

They are actually really easy to solder once you get past the "omg how small they are" phase.

[mockingbird]

Re: 7300GT smd cap knocked off causing instability

Are you sure that it's not the caps on the card causing instability? I recently re-capped a 7300GS.

[Koda]

Re: 7300GT smd cap knocked off causing instability

Are you sure that it's not the caps on the card causing instability? I recently re-capped a 7300GS.

Caps are quality panny's and no visible defects.

BTW can I change the smd cap to a ceramic one?? there are free circular pads above and below the place where the cap should be and it'd be a lot easier to solder on a ceramic there.

[Agent24]

Re: 7300GT smd cap knocked off causing instability

Might work, might not too. At the high clock speeds the PCI-E interface works at, the added length of the non-SMD capacitor's leads could cause issues by affecting the trace impedance\length.

Of course, I don't know a huge deal about such things so I could be tallking rubbish. Give it a try and see if it works I guess!

Otherwise, check this out: http://www.youtube.com/watch?v=66GV4OuShzI and have some fun (?)

[Th3_uN1Qu3]

Re: 7300GT smd cap knocked off causing instability

BTW can I change the smd cap to a ceramic one??

Caps in that format are ALWAYS ceramic, so yes, you can use a regular leaded ceramic there, but cut the leads as short as possible.

[Koda]

Re: 7300GT smd cap knocked off causing instability

Gess what, the card is perfectly stable even without the capacitor (ran furmark for an hour with no problems). Guess that pin is not critical to the card. The card is passively cooled though and it gives really high temps 78C at idle and that might have been the cause for instability. When will people learn not to buy passively cooled cards. I hate the damn things.

[Agent24]

Re: 7300GT smd cap knocked off causing instability

Could be, if his case doesn't have good airflow.

That said, my old 8600GT was passive cooled and it never lagged or locked up. I didn't stuff it in a tiny case with no airflow but it did run about high 70s during gaming too.

[Koda]

Re: 7300GT smd cap knocked off causing instability

Well the thing died on mean hour ago. I mounted a PSU fan on the heatsink to try it out and see what temps I'd be getting, it was running 49C idle and 78 full load with furmark. Left it to run for about 2 hrs and things were just fine. Fired up HL2 and played on the thing for about a hour and half (I was bored ) againg everything fine. Restarted the system and after about 1-2 min in windows the screen went dark. Restarted and while loading windows it happened again. After that no more display at all. Any idea as to what might be the problem??

[Agent24]

Re: 7300GT smd cap knocked off causing instability

Maybe it really did need that capacitor?

Or perhaps the capacitor didn't matter, and the GPU or a RAM chip (or something else!) was going faulty and your stress testing finished it off.

[Newbie2]

Re: 7300GT smd cap knocked off causing instability

The 7300GT is old and slow anyway; an inexpensive NVIDIA GeForce 8400GS or ATI Radeon HD 5450 replacement (cards in that class) don't cost much.

[Koda]

Re: 7300GT smd cap knocked off causing instability

Maybe it was the capacitor or something else, I added a capacitor after it died but it was already too late (stupid me...) I guess it doesn't matter now. I'm not that good at electronics to troubleshoot other smd components so I'll just return it to the owner. BTW a 5450 here is atleast 60$, uset 7300 goes for 30$ and I was gonna charge 10$ for the added cooling and the repair (if any needed) so do the math. People here don't buy new things unless they absolutely have to.

[mockingbird]

Re: 7300GT smd cap knocked off causing instability

7300 is a piece of junk, even slower than a 6600... Is that the best you can get there? I got a Radeon 4890 off eBay for $20.

[b700029]

Re: 7300GT smd cap knocked off causing instability

That's receiver lane 14 differential pair's negative half AC coupling capacitor.

From the PCI-E specification they are to be from 75 to 200nF.

The card should still work fine without it, but will be reduced to x8 mode operation.

[Koda]

Re: 7300GT smd cap knocked off causing instability

7300 is a piece of junk, even slower than a 6600... Is that the best you can get there? I got a Radeon 4890 off eBay for $20.

Yeah 7300 is a piece of junk but even junk costs money here and I can't order from ebay cause we don't have paypal in macedonia.

That's receiver lane 14 differential pair's negative half AC coupling capacitor.

From the PCI-E specification they are to be from 75 to 200nF.

The card should still work fine without it, but will be reduced to x8 mode operation.

So I guess something else is wrong with the card. The hell with it, I wasted enough time with it.