7900GT "dead" ?!

[andL64]

hi there

i modded the 7900GT board which i ve done correctly, but i got lazy and didnt check the 10kohm vr exactly only turned to full resistance, but this poti was damaged and now the card is, its a vmem mosfet i got a nice pic of it, its half burned on one site i cant read the numbers exactly for datasheet, but i think it is 4420 - BD6B12 or something

i m good in soldering so if it s possible i can do it but i m not that good in electronics so what chance i got?

i know theres was going a lot of volts through it so maybe the gddr memory is damaged too but i dunno exactly

thanks in advance!

[andL64]

so thanks to SF3D i know now how the chip is called

4420 BE6A15

i cant find a datasheet for it maybe you can help me searching would be great i try to ask my eletronic dealer about the mosfet, thx

[s e t h]

on my gainwad reference card it's a
4420
BE6B11

and the logo on it looks like a fancy AP

maybe this batch has a new one due to problems with your one
my pcb has 0906 as the date stamp just above the 'made in taiwan'

[andL64]

hmmm thx for information but that didnt make things clear/easier for me

i dunno much about electronics so that is definetly a bit difficult.

i found no datasheet for 4420 BE6A15 or 4420 BE6B11 just found this but dont know if its any good....lol

http://www.datasheetcatalog.net/cgi-....pl?text=4420B

to make this clear the card had no problems @ all i just soldered a damaged 10kohm vr for the vmem and i was not paying attention i didnt measure the ohms before soldering, thats what billy would call a "fatal_error".


seEn and thx again

[s e t h]

if you can locate one of those things you might be able to fix it.
it basically depends whether the ram blew first or if that IC blew and maybe protected the ram.

unfortunately locating another dead 7900gt for spares is going to be difficult as it seems fairly likely it will have died for the same reason.
however you may get lucky or even find a suitable component from some electronics distributor.
if you find a replacement i doubt it will be expensive so it would be worth a try imo

was the screen on when it died and did you see artifacts?

[iRoNeTiK]

that IC has gone like that twice on this forum..whats the deal? how to prevent this? lol im starting to worry, i got the 1.5 vmod with a zalman 700cu onit with a PCI fan card on the whole front side of board (so not the back where the IC lie) but i good decent airflow.

[andL64]

thx flytek i hope ure right, and i think also its worth a try!

ironetik you dont have to be afraid my damaged 10kohmvr is was jumping from 1kohm to 10kohm....

and i didnt do anything at all i just bootet the system there was no pic for 2-3secs i had i bad feeling because board hang also....and when i wanted to turn offthe psu i saw some cloud flying behind the card then i saw what it was.

[Chr0n1c]

That is the same IC the caught flame on my 7900GT after the vmem mod. However it burned up so badly that it melted much of the things around it. lol

[andL64]

hmmm yeah i also though about that it maybe burned the chip besides a bit.

we ll see...

i got the card on the same day i damaged it.... it was stock 450/1320 and i got up to 560/1600 (mem not maxed) with stock cooler 63Cmax. so wanted to oc it a bit more

so i m sry to hear your card is gone too, i know you was waorkin hard here for getting the mods.

seEn

[andL64]

so i cant get the ic here in an electronics shop,
cant get the specs of the ic...
"sh33t"


as far as i see only chance is to get an other damaged card with this ic working and soldering on the other card.... like from 2 do 1

[Chr0n1c]

bummer man. GL with your search.

[don wano]

what mthod of vmod did you try?

[Per Hansson]

Not to spread salt in your wounds but placing a resistor after the potentiomter to get a max possible voltage is a very good idea, just something for others reading this to keep in mind...

And also for the ones who pencil mod their cards without calculating what the new voltage with be using a multimeter, this is what will happen...

[andL64]

i know i ve soldered many things....

i took the time and the mods were good but thats the only thing i forgot or i was too lazy for to measure the vr again, well just see the good site i ll sure NEVER forget measuring it again

the idea with the resistor between is a good one :thumbsup:

seEn

[quijonsith]

andL64, do you mind if I use your pic as an example in my guide over at extremeoverclocking so that my readers there can see what would happen if they try the pencil mod and don't care to buy a multimeter. Here's a link to my guide which is on post #4.

[andL64]

ygpm

[DeToNaToR.cl]

That has because the vmem mod? how many voltage you were giving to those mems? :3

[andL64]

i dunno but it was sure a lot if i didnt got a screen on bootup so i think it OVP kicked in but the little IC cant hold it and blewed up.

seEn

[cirthix]

try removing it entirely. it looks like there are two of those chips in paralell. might just double up the load on the second one (which might blow that chip too) and make it work. either way, you have to remove the burned chip.

sorry for the loss

[iRoNeTiK]

I did the pencil mod and I got it to 553 ohms exactly but I haven't measured the voltage yet..i need someone to hold my heatsink fan up while i do it, anyone want to come to my house? lol jk...i cant get to the vmem measure point otherwise STUPID XP-120! lol

[Per Hansson]

I did the pencil mod and I got it to 553 ohms exactly but I haven't measured the voltage yet..i need someone to hold my heatsink fan up while i do it, anyone want to come to my house? lol jk...i cant get to the vmem measure point otherwise STUPID XP-120! lol

Just solder a wire to the measure point so you get easier access too it?

[t024484]

try removing it entirely. it looks like there are two of those chips in paralell. might just double up the load on the second one (which might blow that chip too) and make it work. either way, you have to remove the burned chip.

sorry for the loss

The component that is destroyed is a N Channel Mosfet.
It is one of four switches of the two phase bucket convertor.
A replacement part is the IRF7821PBF costing roughly $1,-.
There are no chips in parallel, but there is a second 4420 that should also be replaced to keep things in balance.
One could even replace all four Mosfets with the IRF7821PBF if they are suspect.
I hope that this is all that is damaged, although I fear that the 7900 GPU had a voltage applied that was much too high.
AndL64, where the hell did you connect the 10K VR to. This was wrong from the beginning, since the 7900 should be modded differently.

[andL64]

The component that is destroyed is a N Channel Mosfet.
It is one of four switches of the two phase bucket convertor.
A replacement part is the IRF7821PBF costing roughly $1,-.
There are no chips in parallel, but there is a second 4420 that should also be replaced to keep things in balance.
One could even replace all four Mosfets with the IRF7821PBF if they are suspect.
I hope that this is all that is damaged, although I fear that the 7900 GPU had a voltage applied that was much too high.
AndL64, where the hell did you connect the 10K VR to. This was wrong from the beginning, since the 7900 should be modded differently.

hmm thats good news, first....

u said there s an other 4420 do you mean the chip besides? here its 4410 and 4420...if you mean it
i ll get the mosfet tomorrow and see what i can do

heres the pic where you see the mod i did and which pic i used:

[andL64]

I did the pencil mod and I got it to 553 ohms exactly but I haven't measured the voltage yet..i need someone to hold my heatsink fan up while i do it, anyone want to come to my house? lol jk...i cant get to the vmem measure point otherwise STUPID XP-120! lol

i cut a molex from psu stick it on the end of the card and solder the measure point to the wire just stick in multimeter on the upside and voila no problms and best method

[t024484]

hmm thats good news, first....

u said there s an other 4420 do you mean the chip besides? here its 4410 and 4420...if you mean it
i ll get the mosfet tomorrow and see what i can do

heres the pic where you see the mod i did and which pic i used:

I did not interprete your picture correctly yesterday since it only displayed a very small part of your board, and I assumed it was the Vgpu that you had modded.
Having a better picture now, I can see that it was the Vmem that you tried to mod, and hence the 10K Vr that you used.

Since I am abroad at the moment, I cannot see the part nr of the voltage regulator (U501) , so please tell me this part nr.
With this part nr I can see if this voltage regulator is using two N channel Mosfets or a complementary pair of Mosfets and give you the proper advise.

Forget what I told you before about the four Mosfets and the possible damage to the GPU.