UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Nascom repair

acollins22 · 29th Oct 2017, 10:26 pm

Hello Folks,

So, a little more progress.

I wanted to know if the character appearing on the screen were coming out of the video memory or were being made up "on the spot" by the fault. I pulled a couple of the chips and saw that the pattern had changed as their corresponding bit had floated high.

I think this means that the problems are related to the addressing logic.

I'm now waiting for a few 74 series chips missing from my spares collection before I work over the addressing logic.

Cheers,

Andy.

29th Oct 2017, 10:26 pm	#16
acollins22 Pentode Join Date: Oct 2010 Location: Melton Mowbray, Leicestershire, UK. Posts: 156	Re: Nascom repair - Looking for clues please Hello Folks, So, a little more progress. I wanted to know if the character appearing on the screen were coming out of the video memory or were being made up "on the spot" by the fault. I pulled a couple of the chips and saw that the pattern had changed as their corresponding bit had floated high. I think this means that the problems are related to the addressing logic. I'm now waiting for a few 74 series chips missing from my spares collection before I work over the addressing logic. Cheers, Andy.