derole
Beginner
Hi there,
I have a later revision sega naomi (837-14258-02) which was previously intermittent (it often took a while to boot or didnt at all, but would eventually and then be rock solid after that). Upon investigation found the GPU fan was not spinning (apparently is the main cause of this as naomi checks the rpm signal).
Ordered a noctua NF-A4x10 5V as recommended elsewhere, specifically the 3 wire version and not the 4 wire PWM one. After it arrived repinned it to match the original fan pinout, power up, and.... nothing. Tried a few times and tried leaving it on for a good 5 minutes does nothing at all but fan does spin now (I guess thats something lol).
Am really stumped on what is causing it not to boot. The following is what ive tried:
I'm not sure if the reset signal has anything to do with it from the watchdog chips, thats currently my suspicion but no clue what is causing them to be held high or if this is normal?
Would greatly appreciate any input/anything I can check etc, would rather not throw ram chips at it if I dont have to, it was passing ram tests with flying colours before it died
Few images attached of the board, one before/after the fan swap, and one of underneath the board (note the heat scortching underneath the cpu/gpu, assume this is normal for a previously publically-operated board?).
I have a later revision sega naomi (837-14258-02) which was previously intermittent (it often took a while to boot or didnt at all, but would eventually and then be rock solid after that). Upon investigation found the GPU fan was not spinning (apparently is the main cause of this as naomi checks the rpm signal).
Ordered a noctua NF-A4x10 5V as recommended elsewhere, specifically the 3 wire version and not the 4 wire PWM one. After it arrived repinned it to match the original fan pinout, power up, and.... nothing. Tried a few times and tried leaving it on for a good 5 minutes does nothing at all but fan does spin now (I guess thats something lol).
Am really stumped on what is causing it not to boot. The following is what ive tried:
- Checked PSU voltages (original sun psu, 3.3 and 5v are adjusted to be spot on and boot a naomi 2 just fine without issues)
- Used both the original naomi connector and the noctua 3 pin connector (both wired to the correct pinout)
- New CR2032 battery
- Tried de-soldering the supercap (which had barely leaked, and doesnt seem to have damaged anything)
- Swapped from multi-bios eeprom back to the standard eeprom that came with it
- Checked for continuity between the altera FPGA and its eeprom, all have continuity as expected
- Took a rather crude measurement of the PWM signal from the noctua with a multimeter (no oscilliscope unfortunately), there is something there
- Tried to research where the rpm signal actually goes, seems to go to a blank area for an MB3773 watchdog IC, cant find anywhere else it goes though? Theres a 3771 just below it which is holding the reset pin high (5v), unsure if this could be the cause? Theres another 3771 right near the altera which also has its reset pin held high
- 10k pull-up resistor between 5v and rpm wire (unsure if this is needed, its needed for dreamcast with these exact noctuas so figured id give it a go, didnt make a difference
- pressing firmly but not excessively on the CPU/GPU heatsink (figured maybe a BGA issue), did not make a difference, also tried gently heating both sides of the board in those areas with a hot air gin, has not helped either
I'm not sure if the reset signal has anything to do with it from the watchdog chips, thats currently my suspicion but no clue what is causing them to be held high or if this is normal?
Would greatly appreciate any input/anything I can check etc, would rather not throw ram chips at it if I dont have to, it was passing ram tests with flying colours before it died
Few images attached of the board, one before/after the fan swap, and one of underneath the board (note the heat scortching underneath the cpu/gpu, assume this is normal for a previously publically-operated board?).
