16 Jan 2019

Wrestlefest - Technos 1991 (repair log)

This board was bought by Kelvin as working but on arrival it was clearly not. Luckily for him he got a full refund.
This is the Korean version of the game, not sure what are the differences outside of the "KOREA ONLY" text in the intro.

I powered the board and found the following issues:
- wrong colours
- horizontal lines in the background
- garbled/misplaced sprites
- no sound
Not bad for a working board... 😒

Wrong colours:

Found one of the colour RAMs (IC55, 6116 narrow type) faulty:

Horizontal lines in the background:

Found a severed trace due to a poor previous reflow job on the custom chips. I used the core of some kynar wire on few millimetres making it almost invisible.

Garbled/misplaced sprites:

Found both sprite RAMs (IC26/IC27, 6116 narrow type) were bad:

This revealed an other issue, sometimes sprites had "holes":

Found mask ROM IC15 bad (27C080 compatible):

No sound:

Found sound RAM IC41 (again 6116 narrow type) was faulty. However replacing it gave me activity on buses but sound was still absent.
Using an audio probe I could hear both music (from the YM2151) and samples (from the M6295) were generated correctly before amplification. However nothing came out of the two pre-amps IC74/75 (Fujitsu MB3615, silkscreen says M51516). I replaced them and sound was fully restored.

To complete the repair I replaced a cap hanging by one of its legs.

Game fixed.

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