I recently picked up a nice boxed Commodore 16 for not too bad a price.
The PLA found in this is a MOS variant of the PLS100 PLA chip. I don’t believe it can natively be dumped as it seems to have its connection on pin 1 severed internally and decapping done some time ago revealed it was neither a PLS100 or 82S100 device either despite the pinout being the same.
I wanted to make a replacement using the NOS PLS100 chips I have because some people like that sort of thing and there doesn’t seem to be anything out there publically already.
I hooked up the PLA to an Arduino MEGA and wrote a small program to count through all combinations of the address pins and log the outputs to a 64KB binary file.
From here I wrote a program that converted the file to a truth table
and finally into equations which I could compile to a PLS100 fusemap using the old easyABEL program.
From here I could program a blank PLS100 and test in a real machine.
Still need to do some testing but early signs are looking good.
Most likely the component was internally faulty so I replaced it with a repro of mine:
Finally the board booted into game but the sound was barely audible also at maximum volume level:
After a visual inspection I found that the component silkscreened ‘PX4460’ was missing from sound section:
Board uses also another little sound custom, the “LPF6K”, here is a picture from another board for better understanding:
Actually you can replace them by installing the parts they are internally made of directly on PCB (there is silkscreening for them) but I wanted to keep the all-in-one solution the so I decided to have a look inside them in order to reproduce both (although the ‘LPF6K’ was not missing on my board).I removed the coating and did an Hi-Res scan;
On the left on the above picture it’s the naked ‘PX4460’ which, like its name suggests, embeds all the parts (minus the 1000uF 16V electrolytic capacitor, this is on the PCB) needed by the typical application circuit of the ‘LA4460’ amplifier as datasheet shows :
On the right of the scan, it’s the ‘LPF6K’ that contains an LM324 OP-AMP and all its required parts, its function is to pre-amplify the sound.
Given the simplicity of both customs it took few time to figure out schematics and route them to a replacement PCB.Here is the result:
Installed on PCB ready for the smoke test:
Success!Sound was restored and both repro worked fine as replacement.
The ‘TC0070RGB’ is a 15-bit RGB DAC (5-bit for each color) used in many PCBs from Taito : Rainbow Islands (Normal and Extra version), Bonze Adventure, Cadash, Continental Circuit, Chase HQ, Operation Wolf, Final Blow, Ninja Warriors just to name few.As many custom RGB DAC of its era it comes in SIL package (picture taken from the net)
I will not go into the technical details since the component has been already analyzed and schematics figured out as well as a reproduction has been excellently realized by Macro (who embedded all logics into two GAL devices) :
What I have done is I simply reproduced the ‘TC0070RGB’ in my way trying to stay as much close as possible to the original design while keeping the same dimensions, color and parts used.The result is quite pleasant: