maybe it's not the gpu , maybe it's not getting enough power (I am just thinking out -loud) , did you try without the 4 pin plug? or cold solder joins at the 4 pin connector... hmm . So many things to check . it's definitely a project.... I would probably Recap the card first.... (after the hot iron thing before the reflow) those 470uf 10V may seem fine but may not be ... however you need skill to change them all.

ediflorianUS wrote on 2023-06-04, 09:56:

LE. BTW most of the times if GPU is 100% blown it won't have power on the fan rails , so I am not sure that it's 100% dead. (it's a good sign you have power on fan rails).

Nope.
The old design Radeon 9800 is based on APW1175, which is powered by two phases of 3.3 and 5V.
The fan is powered directly from the 12V bus.

ediflorianUS wrote on 2023-06-04, 10:46:

maybe it's not getting enough power

Again no.
There is a diode from the 3.3V bus to the 5V phase.
When an additional wire from the PSU is not connected, about 2.7V comes to the second phase and the GPU starts up.
Depending on the VBIOS, it either issues a warning and stops, or continues to work as if nothing had happened.

PS. It all starts with measuring the voltages coming to the card and after the converters. And not in poking a soldering iron into a GPU.

shevalier wrote on 2023-06-04, 11:12:

Again no. There is a diode from the 3.3V bus to the 5V phase. When an additional wire from the PSU is not connected, about 2.7V […]
Show full quote

ediflorianUS wrote on 2023-06-04, 10:46:

maybe it's not getting enough power

Again no.
There is a diode from the 3.3V bus to the 5V phase.
When an additional wire from the PSU is not connected, about 2.7V comes to the second phase and the GPU starts up.
Depending on the VBIOS, it either issues a warning and stops, or continues to work as if nothing had happened.

PS. It all starts with measuring the voltages coming to the card and after the converters. And not in poking a soldering iron into a GPU.

post a picture with the converters circled so we all learn something.

This?
https://fccid.io/M698836/Schematics/Schematics-414550
page 21
or this?
download/file.php?id=165581
page 8

Diode from rail to rail - is D25 for 9800 pro old design.

And most importantly, ***, in which no one believes.

Played a little more with my dead 9800PRO AIW this weekend and stil can't figure out what is wrong, using a PCI card in conjunction I can see the 9800 is recognized in Windows and even by the Catalyst driver. Using ATI DOS flash tool I was able to access it, save the original VBIOS and flash a VBIOS I downloaded from techpowerup. Computer boots but no signal on the monitor, it only has a DVI conector, so I used a DVI-HDMI to my monitor.

Anyway, very different issue from OP's apparently, I don't wanna hijack his post, just sharing my pain with another 9800PRO.

Pino wrote on 2023-06-05, 17:17:

Played a little more with my dead 9800PRO AIW this weekend and stil can't figure out what is wrong, using a PCI card in conjunction I can see the 9800 is recognized in Windows and even by the Catalyst driver. Using ATI DOS flash tool I was able to access it, save the original VBIOS and flash a VBIOS I downloaded from techpowerup. Computer boots but no signal on the monitor, it only has a DVI conector, so I used a DVI-HDMI to my monitor.

Anyway, very different issue from OP's apparently, I don't wanna hijack his post, just sharing my pain with another 9800PRO.

AIW has TV tunner on it , will that chanel posts into the TV turner app? (instead of DVI monitor maybe you should try mounting a old compatible TV , CRT or old LCD).

Looky what I found today (I totally forgot I had in a few shue boxes - from my old GPU collection , probably need's fixing ) :

PowerColor CN-R98-PC3B-1B-467-005K A00 - so that's a Radeon 9800 Pro right? (unknown status)

Black PCB Sapphire(has a hologram?) - Radeon 9800SE 128M DDR V/D/VO - samsung 434 memory R360 chip

Radeon 9800 Atlantis (It's calling...) 128M 128-bit DDR V/D/VO - hynnix 411A memory R360 chip

Powercolor and Atlantis - probably dead GPU. Sapphire with Black PCB could be repairable after memory replacement.

The Serpent Rider wrote on 2023-06-16, 15:35:

Powercolor and Atlantis - probably dead GPU. Sapphire with Black PCB could repairable after memory replacement.

Tnx , I will check in the day's to come.