UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Non-working Commodore PET 3016

SiriusHardware · 17th Mar 2021, 7:18 pm

In the first instance, just to see if there are any suspicious differences in the signal levels on the data connections from the RAMs. As each RAM IC has one bit input and one bit output and shares its single-bit connection with only one other RAM, any visible anomaly on one of those nodes will hopefully narrow it down to 2 RAM ICs and the associated 74LS244 buffer.

Then there is also the possibility of either swapping the high and low banks in the hope that one is working, and / or switching off one half to see what difference that makes.

We also have Slothie's test code, and I've also found another diagnostic ROM image which looks quite comprehensive and may also attempt to identify the actual faulty area. Obviously both of these will require EEPROMs or EPROMs to be programmed and an adaptor from the programmed device to the pin outline of the original PROM to be made, so that won't be the first line of attack, although it may not be far behind.

17th Mar 2021, 7:18 pm	#1098
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,558	Re: Non-working Commodore PET 3016 In the first instance, just to see if there are any suspicious differences in the signal levels on the data connections from the RAMs. As each RAM IC has one bit input and one bit output and shares its single-bit connection with only one other RAM, any visible anomaly on one of those nodes will hopefully narrow it down to 2 RAM ICs and the associated 74LS244 buffer. Then there is also the possibility of either swapping the high and low banks in the hope that one is working, and / or switching off one half to see what difference that makes. We also have Slothie's test code, and I've also found another diagnostic ROM image which looks quite comprehensive and may also attempt to identify the actual faulty area. Obviously both of these will require EEPROMs or EPROMs to be programmed and an adaptor from the programmed device to the pin outline of the original PROM to be made, so that won't be the first line of attack, although it may not be far behind.