5 Oct 2017

Heated Barrel - TAD 1992 (Repair log)


Game booted but with a dominant green tint (forgot to take a picture) and was silent.
Concerning the colour issue I probed the colour RAMs (2 of them) and the one @ E4 (U096) had weak data signals. Piggybacking it cleared the issue so I replaced it:



For the sound problem I found the audio RAM @ C5 (U118) was dead too altough piggybacking it didn't make any change. This game uses a weird custom chip noted YM3931 (not sure it's linked with the Yamaha brand) for sound. I was sure of it cause it's connected to the audio RAM, the YM3812 and the OKI M6295. Anyway, many of what I thought were outputs were silent. This also isn't normal, the chip is a SDIP64 (shrink DIP with a pitch of 0.07" instead of 0.1" for standard DIP) and very few legs were active. Luckily my friend Kelvin found the chip somewhere online for $8 IIRC:



I replaced it and sound was brought back to normal.



Game fixed.



2 comments:

  1. Well done.Anyway, the YM3931 is not a Yamaha chip.As you can read in MAME source it's the main/sub cpu interface, similar Taito's TC0140SYT.It also provides the Z80 memory map and interrupt control.

    Caius

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    1. Thanks for the information Caius. I've hacked few more systems since our last discussion, I should really send you an email.

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