7900GT Voltmod-2

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04-30-2006, 09:35 PM
C-BuZz

Quote:

Originally Posted by xit

Yes so I thought, but Cbuzz says that he only overvolted the GPU and his MEM was at default volts. Why would that cause this mosfet to burn? Could it be burnt running MEM at 800 or 900 MHz even at default volts?

I'm amazed that your mosfets are only at 50 degrees....have you heatsinked them? What GPU / MEM volts have you settled on?

I am looking to get a few of these to do the job of cooling the mosfets. They come in either copper or aluminium, but I imagine that copper is better?
http://www.scorptec.com.au/index.php?prdid=10331

actually I said the only mem mod I had in place was the pencil mod. The mem was highly overclocked @ 505mhz ;)

C-BuZz
04-30-2006, 11:00 PM
xit

Quote:

Originally Posted by C-BuZz

actually I said the only mem mod I had in place was the pencil mod. The mem was highly overclocked @ 505mhz ;)

C-BuZz

Oops, i missed that. Thought you only had GPU mod.

So is the opinion that GPU volt increase alone won't cause those mosfets to heat up much above normal? They do seem to run hot !
04-30-2006, 11:05 PM
John600rr

1 Attachment(s)

Well I managed to burn out a MOFSET also. Not one of the ones that gets too hot either. I dont know what happened. I've attached a pic of the one I burnt. It burnt only in the middle,so I can read the letters on top: "119n03s". Could someone please tell me if there is any more writing on the MOSFET? Thanks.

Also, I found this link http://www.ortodoxism.ro/datasheets/...3S_Rev1.11.pdf

It looks and sounds like the one I need. NOw does anybody know where I can buy maybe just 10 of these? I found batches of 5000. Group buy anybody? lol

Somebody with some info help me. :D

NOTE: Sorry, I borrowed the pic, hopefully no one minds.
04-30-2006, 11:25 PM
t024484

Quote:

Originally Posted by C-BuZz

I should be able to fabricate somthing so the points are all contacting the drain area. Anyway, replacement chips due in tomorrow so i'll see how it goes :) **fingers crossed**

Thx for your help, I understand how it all works now :toast:

C-BuZz

As I mentioned earlier, there are two types of Mosfets in this SO-8 shape, either with 4 drain pins, which is the one that is burnt on your board, or with a solid drain plate under the housing, like Q506 and Q510.
Because your mosfet exploded, you have a distorted view of the original situation.
Inside the Mosfet is a metal carrier to connect the drain to the outside pins, this carrier is normally unvisible.
Because of the desintegration, you got the impression that this plate was connected to the metal surface on your board, which was not the case, only the 4 pins where connected. Look at the 4410 next to it and you see what I mean.

Mind that overclocking the memory and increasing the Voltage like you did, increases the current with at least 70%. So using a heatsink in those cases is mandatory.

You do not have to construct anything. The Mosfet you have ordered has a different shape with only one source pin, one gate pin and a backplate for the drain. Instead of having the gate right and the source left, this fet has its gate to the left side and the source to the right, so be aware of that.

The first step of your investigation should be to find out if your board is still functioning, don't worry too much about things that are only second priority.
04-30-2006, 11:30 PM
t024484

Quote:

Originally Posted by John600rr

Well I managed to burn out a MOFSET also. Not one of the ones that gets too hot either. I dont know what happened. I've attached a pic of the one I burnt. It burnt only in the middle,so I can read the letters on top: "119n03s". Could someone please tell me if there is any more writing on the MOSFET? Thanks.

Also, I found this link http://www.ortodoxism.ro/datasheets/...3S_Rev1.11.pdf

It looks and sounds like the one I need. NOw does anybody know where I can buy maybe just 10 of these? I found batches of 5000. Group buy anybody? lol

Somebody with some info help me. :D

NOTE: Sorry, I borrowed the pic, hopefully no one minds.

Take the IRF7821 from www.farnell.com They are cheap and upwards compatible, and can be purchased in small quantities.
05-01-2006, 12:09 AM
C-BuZz

Quote:

Originally Posted by t024484

As I mentioned earlier, there are two types of Mosfets in this SO-8 shape, either with 4 drain pins, which is the one that is burnt on your board, or with a solid drain plate under the housing, like Q506 and Q510.
Because your mosfet exploded, you have a distorted view of the original situation.
Inside the Mosfet is a metal carrier to connect the drain to the outside pins, this carrier is normally unvisible.
Because of the desintegration, you got the impression that this plate was connected to the metal surface on your board, which was not the case, only the 4 pins where connected. Look at the 4410 next to it and you see what I mean.

Mind that overclocking the memory and increasing the Voltage like you did, increases the current with at least 70%. So using a heatsink in those cases is mandatory.

You do not have to construct anything. The Mosfet you have ordered has a different shape with only one source pin, one gate pin and a backplate for the drain. Instead of having the gate right and the source left, this fet has its gate to the left side and the source to the right, so be aware of that.

The first step of your investigation should be to find out if your board is still functioning, don't worry too much about things that are only second priority.

Ahhh I see. That explains that then. When I removed the burnt Mosfet it basically crumbled into small pieces as it was totally fried like a piece of charcoal. The metal plate was actually within the Mosfet. I thought it was actually underneath the mofset..

I am aware of the different orientation of the replacement mosfet, I have read your guide how to install it correctly in another thread.

I searched the entire farnell Australia website for a SO-8 version of this particular mosfet but I could not find it in there catalogue :( I hope this replacement will be ok for some basic testing of the board.

I will test the board tomorrow & see if it is still functioning.

Thanks

C-BuZz
05-01-2006, 01:29 AM
xit

Quote:

Originally Posted by John600rr

Well I managed to burn out a MOFSET also. Not one of the ones that gets too hot either. I dont know what happened. I've attached a pic of the one I burnt. It burnt only in the middle,so I can read the letters on top: "119n03s". Could someone please tell me if there is any more writing on the MOSFET? Thanks.

Also, I found this link http://www.ortodoxism.ro/datasheets/...3S_Rev1.11.pdf

It looks and sounds like the one I need. NOw does anybody know where I can buy maybe just 10 of these? I found batches of 5000. Group buy anybody? lol

Somebody with some info help me. :D

NOTE: Sorry, I borrowed the pic, hopefully no one minds.

What mods had you done (GPU and RAM?) and to what voltages?

I'm trying to get an idea of what is 'safe', so to speak.
05-01-2006, 01:43 AM
Vega

Can anyone please tell me which Mosfets I have to cool when I do the 1.4-1.5V mod at GPU? Pics would be nice! :)

Thanks..
05-01-2006, 02:30 AM
John600rr

Quote:

Originally Posted by t024484

Take the IRF7821 from www.farnell.com They are cheap and upwards compatible, and can be purchased in small quantities.

Are you sure it will work? I've compared the two data sheets and they seem simular (albiet I don't know 2% enough to understand anything).

What I need:
http://www.ortodoxism.ro/datasheets/...3S_Rev1.11.pdf
What you advised:
http://www.irf.com/product-info/data...irf7821pbf.pdf

You seem to know what you're talking about so if you're sure, I'll go with it.

Thanks for your help. Someone mentioned a thread about soldering MOSFETs, could somebody link me to it, I'll be needing it. Thanks.

Sorry for being off-topic.
05-01-2006, 02:34 AM
John600rr

Quote:

Originally Posted by xit

What mods had you done (GPU and RAM?) and to what voltages?

I'm trying to get an idea of what is 'safe', so to speak.

I was running 1.5V on the GPU and 2.2V on the ram.

GPU was the double trace mod (I posted about page ago) and the memory was done via pencil. (570ohms)

I ran 725mhz/1908mhz through the card at about 64C MAX load temp.

I dont blame the OC on the burnt MOFSET, I believe one of the wires measuring VGPU or VMEM came loose and shorted the card out. I wasn't there when it happened so I cant be sure. Dont let me result scare anybody.
05-01-2006, 02:37 AM
t024484

Quote:

Originally Posted by Vega

Can anyone please tell me which Mosfets I have to cool when I do the 1.4-1.5V mod at GPU? Pics would be nice! :)

Thanks..

Just do the Fingertest.
Hold your finger firmly a few seconds on every component that is suspect, if it seems to be below 50C don't worry, if hotter you could use a heatsink.
05-01-2006, 02:54 AM
alpha0ne

Quote:

Originally Posted by t024484

Just do the Fingertest.
Hold your finger firmly a few seconds on every component that is suspect, if it seems to be below 50C don't worry, if hotter you could use a heatsink.

Hehehe thats how I originally found the two hot spots

The Fingertest™ is great for troubleshooting hardware and finding the right partner :fact: :eek: :D
05-01-2006, 03:13 AM
t024484

Quote:

Originally Posted by alpha0ne

Ok the Q501 chip on the MSI NX7900GT is slightly different

This one says :
32N03S
GAA604

and its a diff shape.

Are other cards the same ????

Alphaone, the BSC032N03 is a great component from Infineon.
It has a solid backplate for better cooling, the max channel resistance with 3mOhm is 3 times lower as all the others, meaning 3 times less heat dissipation, and it can handle 70 Watt if cooled properly instead of the 2.5Watt of all the others.
This is the best one I have came across so far. The big question is, where can you get it ?

One thing is for sure, MSI had also trouble with heat development
and found this solution !
05-01-2006, 03:50 AM
xit

Quote:

Originally Posted by t024484

Alphaone, the BSC032N03 is a great component from Infineon.
It has a solid backplate for better cooling, the max channel resistance with 3mOhm is 3 times lower as all the others, meaning 3 times less heat dissipation, and it can handle 70 Watt if cooled properly instead of the 2.5Watt of all the others.
This is the best one I have came across so far. The big question is, where can you get it ?

One thing is for sure, MSI had also troubles with heat development
and found this solution !

So if the MSI 7900GT has this better mosfet that doesn't overheat, should we be exchanging our other branded cards for MSI's? Or is heatsinking simply better? I may still be able to exchange lol.....
05-01-2006, 06:11 AM
t024484

Quote:

Originally Posted by xit

So if the MSI 7900GT has this better mosfet that doesn't overheat, should we be exchanging our other branded cards for MSI's? Or is heatsinking simply better? I may still be able to exchange lol.....

I have no idea. Maybe the MSI board has been improved on all aspects, can also be that they have changed other details to inhibit too much overclocking
Somebody with this board has to tell us his experience.
05-01-2006, 08:09 AM
alpha0ne

Quote:

Originally Posted by t024484

I have no idea. Maybe the MSI board has been improved on all aspects, can also be that they have changed other details to inhibit too much overclocking
Somebody with this board has to tell us his experience.

Well my MSI NX7900GT was a beast (I have sold it now, buying the Gainward 7900GT 512MB card) though 0502 still got very hot

Optimised freq @1.2V
http://i16.photobucket.com/albums/b2...misedFreq1.jpg

Optimised freq @ 1.4V
http://i16.photobucket.com/albums/b2...ptimalFreq.jpg

'05
http://i16.photobucket.com/albums/b2...05701-9212.jpg

'06
http://i16.photobucket.com/albums/b2...06701-9222.jpg

:D :D :D :D :D :D
05-01-2006, 09:18 AM
madgravity34

Its a nice card, but my EVGA SC hits 590/900+ (havent pushed mem more) w/ stock volts so we at least know the MSI's dont clock better, but they dont clock worse either lol.
05-01-2006, 08:46 PM
sluggo

Quote:

Originally Posted by t024484

Alphaone, the BSC032N03 is a great component from Infineon.
It has a solid backplate for better cooling, the max channel resistance with 3mOhm is 3 times lower as all the others, meaning 3 times less heat dissipation, and it can handle 70 Watt if cooled properly instead of the 2.5Watt of all the others.
This is the best one I have came across so far. The big question is, where can you get it ?

One thing is for sure, MSI had also trouble with heat development
and found this solution !

When you reduce Rds in a mosfet you typically increase the Qg, or total gate charge. That's the case here, as the Infineon part has 3x the Qg of the IR part, and a corresponding increase in the turn-off delay. Dumping the increased gate charge 250k times per second leads to dramatically increased switching losses. Idle temperatures for the Infineon part will be significantly higher. Given that MSI is using it, though, it's certainly okay at stock switching frequencies.

If you increase the switching frequency of the FET, however, switching losses increase linearly. An Infineon part with the frequency mod described here will have switching losses around 6x the IR part at stock switching frequencies. If the IR part is fairly hot at idle, the Infineon part will be very hot when overclocked.

My point is that overclocking the Infineon part will not necessarily be easier or even possible.
05-01-2006, 09:05 PM
alpha0ne

Quote:

Originally Posted by madgravity34

Its a nice card, but my EVGA SC hits 590/900+ (havent pushed mem more) w/ stock volts so we at least know the MSI's dont clock better, but they dont clock worse either lol.

You have totally missed the point

my MSI card ran at 650MHz @ 1.2V but who cares, it means nothing

With coolbits you find the max optimised frequncy at stock V, thats what I was/have shown
05-01-2006, 09:32 PM
quijonsith

that's one amazing OC for stock volts
05-01-2006, 09:36 PM
alpha0ne

Quote:

Originally Posted by quijonsith

that's one amazing OC for stock volts

It was/is an amazing card, by far the best I have ever owned but sold now and waiting for the Gainward 7900GT 512MB version but it looks like the circuitry is totally different on the 512MB model so very unsure ATM :confused:
05-01-2006, 09:57 PM
graham_h

Pics for the Gainward 7900GT 512Mb
Any ideas where to start ?

http://www.tigerdirect.com.au/images...eftsidepcb.jpg

Full card pics here > HI RES > http://www.tigerdirect.com.au/images...llcardback.jpg
05-01-2006, 11:32 PM
onion

Quote:

Originally Posted by graham_h

Pics for the Gainward 7900GT 512Mb
Any ideas where to start ?

Yup. Read at least a dozen books on electrical engineering, study each chip on the card via white papers. After that you should be fine. :D
05-01-2006, 11:42 PM
graham_h

not what I wanted to hear :(
05-01-2006, 11:53 PM
s e t h

thanks for finding that pic graham. i've been wondering what has happened to the new pcb. it looks like they ruined the nice digital vgpu mod.

anyway i should have a 512mb gt in about a week and we can start working on the new mods

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