Not sure if it came up in chat, but your grounding strap should NOT show clear conductivity. It should have a high resistance. Usually 1 Megaohm. Be sure to measure resistance instead. If it was shorted to ground, that might be a good way to get a good shock! The idea is that charge bleeds off slowly (still only takes microseconds) through a high resistor.
You were seeing bus contention likely due to the internal ROM and the cartridge being selected at the same time. When you remove the ROMs the conflict goes away. Tip that would have led you to the bad PLA much faster: In Ultimax mode the internal ROMs should never be selected. Pins 15, 16, 17 of the PLA select the CHAROM, KERNEL, BASIC ROM so they should never go low while the dead test cartridge is inserted. If they are low during dead test, or pin 12 (I/O select) never goes low, you know you have a dead PLA.
I built a bunch of the gal pla’s and they work perfectly! I also have several dongle style test harnesses that work with the C64 diagnostics program. How do I donate something to you? PO box or something else?
WDC ones are not 100% compatible. If you have to, get and adaptor that converts an old 6502 to a 6510. You can use that with the 65C02, but some software might crash.
Not sure if it came up in chat, but your grounding strap should NOT show clear conductivity. It should have a high resistance. Usually 1 Megaohm. Be sure to measure resistance instead. If it was shorted to ground, that might be a good way to get a good shock! The idea is that charge bleeds off slowly (still only takes microseconds) through a high resistor.
You were seeing bus contention likely due to the internal ROM and the cartridge being selected at the same time. When you remove the ROMs the conflict goes away. Tip that would have led you to the bad PLA much faster:
In Ultimax mode the internal ROMs should never be selected. Pins 15, 16, 17 of the PLA select the CHAROM, KERNEL, BASIC ROM so they should never go low while the dead test cartridge is inserted. If they are low during dead test, or pin 12 (I/O select) never goes low, you know you have a dead PLA.
Awesome live stream, fun and educational. please do schedule another one to fix the remaining machines too!
I built a bunch of the gal pla’s and they work perfectly! I also have several dongle style test harnesses that work with the C64 diagnostics program. How do I donate something to you? PO box or something else?
That 90 Degree power adapter looks like the ones I got from John at Commodore4ever.
WDC ones are not 100% compatible. If you have to, get and adaptor that converts an old 6502 to a 6510. You can use that with the 65C02, but some software might crash.
There is no such thing as a dead Commodore 64.
Only C64s awaiting ressurection.