Repair amd sapphire nitro r9 390

Mat2786

n00b
Joined
Apr 27, 2021
Messages
30
1 Gnd ok
2 Fb 0.8v
3 Vout 0.8v
4 Vout 1.78v
5 vin 3.3v
6 vcntl 5v
7 pok 3.1v
8 en 3.3v
 

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RazorWind

2[H]4U
Joined
Feb 11, 2001
Messages
3,920
1 Gnd ok
2 Fb 0.8v
3 Vout 0.8v
4 Vout 1.78v
5 vin 3.3v
6 vcntl 5v
7 pok 3.1v
8 en 3.3v
The fact that you have two different Vout values on the pins that should be joined is sort of worrisome, but it's probably just a flaky reading. You've got the power good signal coming out, so that one is probably OK.

Try to look up datasheets for each of the ICs that is still unidentified. Look for the ones that are either low dropout regulators or buck controllers, and then check each of those circuits for operation. If you still strike out, you're going to need to figure out where exactly the enable signal for your memory rail comes from, and then work your way back through the card until you find something that should be working, but isn't.
 

cdabc123

2[H]4U
Joined
Jun 21, 2016
Messages
3,162
The fact that you have two different Vout values on the pins that should be joined is sort of worrisome, but it's probably just a flaky reading. You've got the power good signal coming out, so that one is probably OK.

Try to look up datasheets for each of the ICs that is still unidentified. Look for the ones that are either low dropout regulators or buck controllers, and then check each of those circuits for operation. If you still strike out, you're going to need to figure out where exactly the enable signal for your memory rail comes from, and then work your way back through the card until you find something that should be working, but isn't.
Just out of curiosity is it possible to jump the enable single?
 

RazorWind

2[H]4U
Joined
Feb 11, 2001
Messages
3,920
Just out of curiosity is it possible to jump the enable single?
Yes, but it's not always advisable. In this case, the fact that we're missing the memory enable signal is a symptom of some other problem, so while we might be able to get the memory rail working by just feeding it a voltage from somewhere, that wouldn't necessarily help us if whatever mechanism it's supposed to wait for isn't working.

Also, on some cards, if you don't start the power rails up in the proper order, you can actually damage the logic (GDDR5X designs being the most common, where they have this extra 1.8V rail that has to be higher than the main memory voltage at all times).
 
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