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TheDeath

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Hey Guys,
MY STV mobo just decided to fuck me off for no reason. It was working the last year when i played a few games with the multi-bios, then, as i always do, i've stored it inside a box in my house where all my pcbs are.
I've bought a new game so i've pulled it out the box after this year and it just gave me a black screen with white-noise sound.
The Battery was dead so i've replace it (again, there were not leaks) but to what do i know this is just for keep the settings.
Then i've read about this problem and i have complitely reflowed the 2 Sh2 Cpu asics, being sure that none of pins were lifted or bridged by using a digital microscope, the result was the same.
Tryed to raise my +5 very far away till 5.20 and still nothing. Cleaned CN5 socket, Cleaned Bios Socket, all with elecrolitic solution.
Just Nothing changed..
What the fuck happened? 8|
 
Ive had TWO boards do exactly the same, including the "stored in a box" part.

Cleaned them with a pcb cleaning solution, same deal.

The next day, both decided to wake up and are working flawlessly to this day, and the mystery remains unexplained.
 
I've heard that STV boards are worse than CPS3 boards. I'd check around the CPUs to make sure there are no issues there.
 
And the best part is that i've bought a non-working board for cheap 2 days ago, it was booting but was not able to read carts until i've cleaned and bent few pins here and there. I have played for an hour, power it off, and today guess what? Same as the other one, black screen and no response at all, and this was played elsewere on another set-up. They just DIE for no reason.
I'de like to try change the working rams but i was not able to figure out wich are of them (there's tons here)
 
I've found that it is something related to the discarghe/overheat side.
I've left it apart for few days and when i plugged it, as usual, it boots straight away. I wasn't aware about the extra Test screen by pressing before power up, i have tryed booting it again but it was dead again.
Then i said to myself let's just change those damn caps, after an hour of work, the board boots again the first time. This time i have properly set test to on and i was able to go directly to the extra test. I've did all the available tests and all the results were marked as good. After trying to boot it up again, the board was dead again. At this point i thought i was going into the right direction (?) and i realize that there were 3 more caps to be changed, the tantallium ones (2x10Uf 1x1Uf all 16v), after a 3 minute work the board booted again, and to my surprise, it did twice, again being able to extra test one more time (same result).
Then it went dead again. So this is defenetly something that is slightly overheating/defect or this has to do with caps unable to discharge quickly. If i leave the board for 15mins it will boot again and keeps going until the power off.. what to check next is beyond my comprension by far..
 
it's usually bad solder jounts on large surface mount chips causing intermittant problems.
it's common on pcb's that are too damned big and get flexed a lot.
 
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