PCB Repair Logs Toki
Random crash problem was a dry joint on the crystal, someone had attempted to resolder all 4 joints but hadnt done a very good job. Removed all old solder with desolder station and resoldered the lot. Board was then solid as a rock.
Sound problem was slightly trickier, the amp on board was fine, touching its pins gave a buzzing noise and the volume pot worked too. Made up an audio probe and fed the output of the DAC chip into an external amplifier - I had sound, well the FM sounds, not the samples.
The only thing between the DAC output and the AMP chip input was a custom SIP package, over a dozen pins, its looks like a small PCB covered in black plastic, you can see the component bulges in one face of this board.
Luckily the owner had another Toki that had more serious issues, including no sound. On that board the DAC was dead so I chanced my luck, desoldered the SIP package and moved it to the other board. Flipped the power on and all sounds and samples were restored.
I dont know what this little SIP board does, but I suspect its some form of audio mixer circuit. The FM sounds and samples come from separate parts of the audio section and come together at this chip before the merged audio hits the amp.
Problem fixed tho! Mad game too!
- bad soldering on 20 Mhz crystal near the 68000 - bad epoxy block near the sound amplifier.
I resoldered the 20 Mhz crystal near the 68000 and the board now boots and run flawlessly.
Since I had no replacement for the epoxy block, I removed it and made a 2 channel mixer to mix the ym and oki sound output.
Now the game works perfectly with sound.