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

Timbucus · 2nd Mar 2021, 8:23 pm

they look fine - as long as you do see something on Pin 20 it is possible that code is not executing very often or even at all. That is a finding.

The difference in signal height is from different devices driving the line. While the signal is high on the second capture to the left something is driving up to 4v which is typical of a TTL device (it does not go full 0-5) the 5v you see later is because either something with a 5V pullup is let onto the bus or it is a CMOS drive which does go rail to rail.

2nd Mar 2021, 8:23 pm	#759
Timbucus Octode Join Date: Mar 2019 Location: Barry, Vale of Glamorgan, Wales, UK. Posts: 1,364	Re: Non-working Commodore PET 3016 they look fine - as long as you do see something on Pin 20 it is possible that code is not executing very often or even at all. That is a finding. The difference in signal height is from different devices driving the line. While the signal is high on the second capture to the left something is driving up to 4v which is typical of a TTL device (it does not go full 0-5) the 5v you see later is because either something with a 5V pullup is let onto the bus or it is a CMOS drive which does go rail to rail.