Badcaps.net Forum
Go Back   Badcaps Forums > Motherboards with Bad Capacitors > Other Devices with Bad Capacitors
Register FAQ Calendar Search Today's Posts Mark Forums Read

 
Thread Tools Display Modes
Old 10-27-2019, 01:42 PM   #1
saronno
Member
 
Join Date: Jan 2012
Posts: 22
Default XFX R9 380 No Ram Voltage.

Hi, I am trying to repair this R9 380 by XFX.

Fans works, no video .... but it's not the gpu ... there is no voltage
on the ram.

Looking at the board, there are two APW8722 near the two PCI-e power connector.

Checking the datasheet, there are two interesting pins: BOOT and COMP.
If COMP is pulled down, the IC shut down.
The BOOT honestly I am not sure, but it should give a voltage bump at
the beginning to initiate the voltage regulation.
VCC is presente. The two MOSFET connected to the IC are good.
There are not evident shorts checking here and there with the multimeter .. and also checking with a finger if something is hot results in nothing obvious.

Any idea? I was guessing the APW8722 was faulty but since both of them have the same behaviour I am inclined to think there is something else who stop them to regulated the voltage, maybe pulling down COMP ...

At the beginning I also guessed there was something wrong with the bios but I check the chip with my ch341 and the bios was ok ... but there is no voltage to the chip when you star the board !!
Attached Images
File Type: jpg P_20191027_140155.jpg (540.9 KB, 7 views)
File Type: jpg P_20191027_140142.jpg (581.7 KB, 8 views)
File Type: jpg P_20191027_140117.jpg (700.4 KB, 7 views)
File Type: jpg P_20191027_140108.jpg (768.9 KB, 6 views)
File Type: jpg P_20191027_140056.jpg (679.5 KB, 6 views)
File Type: jpg P_20191027_140044.jpg (770.8 KB, 6 views)
File Type: jpg P_20191027_140029.jpg (712.4 KB, 5 views)
File Type: jpg P_20191027_101442.jpg (507.5 KB, 5 views)
File Type: jpg P_20191027_101358.jpg (596.1 KB, 4 views)
File Type: jpg P_20191027_101347.jpg (606.2 KB, 5 views)
saronno is offline   Reply With Quote
Old 10-28-2019, 08:08 AM   #2
SMDFlea
Moderator
 
Join Date: Jan 2018
City & State: York
My Country: UK
I'm a: Knowledge Seeker
Posts: 3,053
Default Re: XFX R9 380 No Ram Voltage.

Check the voltage on the gate of 2N7002 (Q3 in the Typical Application Circuit in the datasheet) when you power up .

Last edited by SMDFlea; 10-28-2019 at 09:25 AM..
SMDFlea is offline   Reply With Quote
Old 10-28-2019, 11:36 AM   #3
saronno
Member
 
Join Date: Jan 2012
Posts: 22
Default Re: XFX R9 380 No Ram Voltage.

.

Last edited by saronno; 10-28-2019 at 12:25 PM..
saronno is offline   Reply With Quote
Old 10-30-2019, 06:58 AM   #4
saronno
Member
 
Join Date: Jan 2012
Posts: 22
Default Re: XFX R9 380 No Ram Voltage.

Finally I have some spare time to keep analyzing this board.
It seems the problem has nothing to do with the APW8722.
I check the pci-e voltage and both of them are presente (12v and 3.3v).
But GS7103 near the eprom has a very low VCC. So I find what component
is responsible for generating VCC .... and it's a adjustable voltage regulator (bm1117).
But the Vin there is very low too.
Anyway there are no low-impedence paths on the Vin and Vout line .... but nearby there is this little component who looks very suspicious.
One pin is attached to bm1117 Vin the other one is attached to 12v line (present).

Since the Vin should be more or less in that range (20v max) and Vout should be in the range 3.3v-5.0v (GS7103 VCC) I think think the problem is that little component ...
it's a fuse or something else (it's not open and it's not short ....)

Are you able to identify it?
Attached Images
File Type: png Screenshot_2019-10-30_12-55-52.png (332.9 KB, 13 views)
saronno is offline   Reply With Quote
Old 10-30-2019, 07:06 AM   #5
piernov
Moderator
 
Join Date: Jan 2016
City & State: Valbonne, 06
My Country: France
I'm a: Knowledge Seeker
Posts: 1,677
Default Re: XFX R9 380 No Ram Voltage.

I see a 0 ohm resistor on a picture found on the web. Seems reasonable. On the board it says "R401" so it's supposed to be a resistor.
What you have on your board doesn't look like a 0 ohm resistor at all, and looks broken. Did someone work on this before and put the wrong component?
Attached Images
File Type: jpg xfx-amd-radeon-r9-380x-review-back.jpg (460.0 KB, 8 views)
__________________
OpenBoardview http://openboardview.org | IRC #openboardview@irc.freenode.net
piernov is offline   Reply With Quote
Old 10-30-2019, 07:29 AM   #6
saronno
Member
 
Join Date: Jan 2012
Posts: 22
Default Re: XFX R9 380 No Ram Voltage.

Quote:
Originally Posted by piernov View Post
I see a 0 ohm resistor on a picture found on the web. Seems reasonable. On the board it says "R401" so it's supposed to be a resistor.
What you have on your board doesn't look like a 0 ohm resistor at all, and looks broken. Did someone work on this before and put the wrong component?
Exactly .. I agree with you but it would be better to have a confirmation before making any damage as you said.
saronno is offline   Reply With Quote
Old 10-30-2019, 09:20 AM   #7
saronno
Member
 
Join Date: Jan 2012
Posts: 22
Default Re: XFX R9 380 No Ram Voltage.

This is from a radeon rx470 ....
http://nekosoftpc.blogspot.com/2019/...-rx470-8g.html



It look more or less the same ... a 0 ohm resistor is a good guess.
saronno is offline   Reply With Quote
Old 10-30-2019, 10:08 AM   #8
saronno
Member
 
Join Date: Jan 2012
Posts: 22
Default Re: XFX R9 380 No Ram Voltage.

Done. Put a 0 ohm resistor in the card ... everything fine.
The only problem is ... it will be enough? It is smaller than the original ... who
knows ... time to test and see.
saronno is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



Badcaps.net Technical Forums 2003 - 2019
Powered by vBulletin ®
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 12:03 PM.
Did you find this forum helpful?