View Full Version : got a vdd modded 8rda+? Read this!!
RichBa5tard
05-05-2003, 12:28 PM
I killed my first 8rda+ by burning the mosfet near the vdd chip regulator at 2.0vdd.
I replaced the burned out mosfet, and have been running happily ever after at a 'safe' 1.8vdd. I got a little suspicious when a saw a fellow xtreme member burning the exact same chip on his 8rga+, and i immediatly checked out the vdd mod when a friend asked whether it was normal his vdd mosfet chip on his vdd modded 8rda+ looked a little bit melted.
I opened my case, touched the mosfet near the vdd regulator and nearly burned my finger. THIS IS WITH A 120MM BLOWING ON TOP OF IT AND ONLY 1.8VDD!! I can't imagine what kind of damage +1.8vdd and no casecooling does in the long run! Well, actually i can, because my friends 8rda+ mosfet looks melted but still runs...
I can't believe why no-one noticed this before!? Or did i just mis it? :)
Just slap a tiny heatsink on it and you should be pretty safe. No one else noticed this problem?
CodeRed
05-05-2003, 01:39 PM
I brought this up a while ago on AOA. Even presented some calcs showing that these MOSFETS are underrated for the job of supplying the NB and SB :(. Quite a few ppl have cooked this chip already due to too high a Vdd .
Definitely a good idea to put a small HS on it if you're running high Vdd.
XtremepH
05-06-2003, 10:48 AM
well i run an 8RGA+ and am going to put a small heatsink on it but what should i use to hold the heatsink onto the chip? I was thinking of maybe some artic silver epoxy is that what you guys used?
RichBa5tard
05-06-2003, 10:50 AM
i used double sided tape. It doesn't conduct heat as well as thermal epoxy, but it's not like it matters whether the mosfet is 30 or 40°C, i just don't want it to be 90°C. :)
XtremepH
05-06-2003, 11:03 AM
aight so i guess i use the double sided tape as well since i can't seem to find my thermal epoxy.
dykz34
05-06-2003, 03:21 PM
I tried to reach this mosfet... but my vdd mod grabbers and Ti4600 are in the way. :( Im gonna have to pull everything to see this thing, lol. Id assume that mine gets just as hot as yours so putting a small HS on it would be a good idea. :)
rabeb25
05-08-2003, 10:12 PM
if it gets hot with 1.8 I wonder what it gets with my 2.4 going to it :)
dykz34
05-09-2003, 07:18 AM
BTW, I pulled my GF4 off and its not a mosfet under there. Its another chip exactly the same size as the vdd chip. ;) It didnt feel hot either, but I couldnt reach it when it was running.
RichBa5tard
05-09-2003, 07:25 AM
dykz32, it might not look like a regular mosfet because it's a 2-in one mosfet. 2 tiny mosfets in 1 chip. ;)
I can asure you it runs very hot while stressed.
I believe that sink is helping cool the AGP related IC.
M@tt over at TPR blow that IC after a system move and
he said he had vid problems prior to it burning out.
The IC with the added resistor is the VDD IC.
RichBa5tard
05-09-2003, 01:39 PM
I'm pretty sure it's not AGP related. It runs hot if you increase vdd (not vagp), and several ppl who ran at high vdd have melted the chip.
I'm using a PCI VGA card and the IC still gets hot, does this convince you? ;)
dykz34
05-09-2003, 09:47 PM
Hmm, this is the one right next to the vdd chip, right? Looks exactly the same? If so, Ill have to put a lil' heatsink on it just to be safe. :D
saaya
05-10-2003, 06:03 AM
but you have to be carefull that the heatsink does not have contact with the copper wires on the board right?
ppctx
05-13-2003, 02:44 PM
thanks, i epoxied a little heatsink on just to be safe. touch more things and let me know if any of them burn you finger :)
i'm sure this has been seen but this thread is a good place for it.
8rda+ Thermal Images (http://homepage.ntlworld.com/bubo/index.html)
ppctx
05-13-2003, 02:49 PM
I think the smaller of the two boxes showes the mosfet in question vdd mosfet (http://homepage.ntlworld.com/bubo/Southbridge/southbridge.html)
dykz34
05-13-2003, 03:41 PM
According to those thermal images, a heatsink would be useful on both the vdd and the mosfet right next to it.... Ill have to check into fitting some. :D
RichBa5tard
05-13-2003, 09:43 PM
Originally posted by ppctx
thanks, i epoxied a little heatsink on just to be safe. touch more things and let me know if any of them burn you finger :)
i'm sure this has been seen but this thread is a good place for it.
8rda+ Thermal Images (http://homepage.ntlworld.com/bubo/index.html)
63.7°C at 185FSB and 1.6vdd... most of us run at 200+ and >1.8vdd. Can't be to healthy.
Lastviking
05-14-2003, 02:22 PM
Anyone know if NF7-S have same heat problem? And were are the mosfet located on the NF7-S board?Are it there it´s placed on the Epox board?
//Sorry for my bad english ;)
RichBa5tard
05-14-2003, 02:28 PM
Originally posted by Lastviking
Anyone know if NF7-S have same heat problem? And were are the mosfet located on the NF7-S board?Are it there it´s placed on the Epox board?
//Sorry for my bad english ;)
probebly not. in contrary to the 8rda+, the abit was designed to handle higher vdd from start.
PimpJack
05-15-2003, 04:43 AM
I own a nf7 so this isn't for me but could u replace that mosfet with a one that has higher ratings. I'm not exactely sure what a mosfet does... is it just a chip that converts voltages? Putting one in that can easily handle the load would seem like a logical idea especially since u already have the skill of replacing one in the first place. I would say get one thats meant for the cpu but then again i'm sure compatibility problems would arise and again i don't know what exactely goes on in a mosfet