PS1 Please help! PS1 Repair

[portnoi88]

Hello,
I need help to repair a japanese PS1, model SCPH-7000.
It turns on but shows only a black screen, no video or audio.
The laser start spinning very fast even with the lid opened.
I've tried another board and worked ok. Checked all fuses and reflow the CPU and GPU.
Sometimes works, 1 out of 10.
Is there any way to fix this? much appreciated!

 

[kadorna2]

sounds like a rom problem

EDIT: faulty, improperly installed or badly programmed modchips can also cause this

 

[portnoi88]

You mean a game?
No, it still happens without any disc.

 

[portnoi88]

sounds like a rom problem

EDIT: faulty, improperly installed or badly programmed modchips can also cause this

It doesn't have a modchip.

 

[kadorna2]

no, rom as boot rom, the bios might be corrupted

 

[SKEPTiCK]

Composite port or video card is probably damaged... Could be faulty modchip but less likely.

On the back of the PS1, is it the AV jack that takes the big cord or three separate cables? (double-ended red/yellow/white)

I'm guessing it's the big jack because these are the ones that usually get damaged from being plugged/unplugged.

 

[kadorna2]

Composite port or video card is probably damaged... Could be faulty modchip but less likely.

On the back of the PS1, is it the AV jack that takes the big cord or three separate cables? (double-ended red/yellow/white)

I'm guessing it's the big jack because these are the ones that usually get damaged from being plugged/unplugged.

a bad av multi out wouldn't cause the disc drive go haywire

 

[SKEPTiCK]

a bad av multi out wouldn't cause the disc drive go haywire

That could be a separate problem with the disc drive itself...

I was referring to black screen, no video or audio.

 

[kadorna2]

do you have a cheat cart at hand? AFAIK most if not all gameshark/action replay/codebreaker carts (the ones that plug into the parallel port on the back of the console) hijack the boot process and inject their own code bypassing the bios entirely, i might be wrong though

 

[portnoi88]

do you have a cheat cart at hand? AFAIK most if not all gameshark/action replay/codebreaker carts (the ones that plug into the parallel port on the back of the console) hijack the boot process and inject their own code bypassing the bios entirely, i might be wrong though

No, i don't have a cart.
Sometimes the console boots just fine (1 out of 10) and if i press reset, it resets fine, but if i turn it off and then turn it on i get a black screen again.