I picked up an old TC-01 recently and It was working well after replacing I016 and a few capacitors in the PSU. I powered it up the next day and I was greeted with the **EINSTEIN** banner and nothing more. Anyone had an experience with a continuously asserter IRQ line? I've been following the IRQ daisy-chain and thought it was the CTC but finally traced it to the ADC. While I wait on a spare, I've desoldered it and my TC-01 is now working again.
How often do the ADC0844 devices fail? Has anyone fitted catch diodes or TSV devices to protect the analogue inputs?
Hardware issue - stuck IRQ - failed ADC
Re: Hardware issue - stuck IRQ - failed ADC
The ADC had had a reprieve. Turned out to be I051a - the 74LS74 that latches the ADC Mask bit. I was watching Q when nRESET toggled the nPR pin and Q would set then immediately clear. A logic tester verified my findings. I found a similar vintage Nat Semi part and everything is now working properly.
Time to celebrate with a fresh brew
Time to celebrate with a fresh brew