Search found 166 matches

by TMAOne
Sat Aug 18, 2012 7:04 pm
Forum: Hardware
Topic: 16K RAM Pack Schematic / Chip Layout
Replies: 71
Views: 28271

Re: 16K RAM Pack Schematic / Chip Layout

Thank-you Mark. That's just the kind of insightful guidance I need, and I appreciate the time and thought that goes into laying that out for me. I will follow your advice next time I work on this (soon). Strangely, the problem came back after I boxed the RAM pack back up in its case and put it back ...
by TMAOne
Sat Aug 18, 2012 6:31 am
Forum: Hardware
Topic: 16K RAM Pack Schematic / Chip Layout
Replies: 71
Views: 28271

Re: 16K RAM Pack Schematic / Chip Layout

Success! I think. But I don't understand it. When I explain, you guys are going to think I'm bullshiting you, but I'm not. To review, I had a pack with 1 bad bit. Its measured voltages were low, but it seemed to run fine except for that one stuck bit. Then I started replacing the electrolytic caps, ...
by TMAOne
Fri Aug 17, 2012 9:58 pm
Forum: Hardware
Topic: 16K RAM Pack Schematic / Chip Layout
Replies: 71
Views: 28271

Re: 16K RAM Pack Schematic / Chip Layout

Argh. I realized I haven't changed the caps in this particular unit, since I didn't think a cap could be responsible for one bad bit. But given that the voltages were off, I started with the big 100uF and replaced it with one from my salvaged parts supply. Suddenly, no boot. Okay, maybe that was a b...
by TMAOne
Fri Aug 17, 2012 8:07 pm
Forum: Hardware
Topic: 16K RAM Pack Schematic / Chip Layout
Replies: 71
Views: 28271

Re: 16K RAM Pack Schematic / Chip Layout

No, the 4116 chips that I have are not "known good". In fact, I don't even remember what I pulled them out of, or when. They've been in an anti-static mat in the "IC drawer" of my small parts box for ever. Sooo,... I did get around to checking the voltages of my 3 non-functioning or semi-functioning...
by TMAOne
Fri Aug 17, 2012 8:47 am
Forum: Hardware
Topic: 16K RAM Pack Schematic / Chip Layout
Replies: 71
Views: 28271

Re: 16K RAM Pack Schematic / Chip Layout

Thank-you for the welcome and the great information. It was some time ago I did my searching for a schematic. My bad. I found this forum and got a little excited, and posted without doing a renewed search to see if anything had changed. I'm glad I found you nice knowledgable Zeddy folks! The diagram...
by TMAOne
Thu Aug 16, 2012 10:40 pm
Forum: Hardware
Topic: 16K RAM Pack Schematic / Chip Layout
Replies: 71
Views: 28271

16K RAM Pack Schematic / Chip Layout

Hello, new poster in Canada here. I bought the ZX81 kit when it first came to Canada in May 1982 and cost $150 plus taxes and separate power supply. My soldering skills were poor back then, but got the job done. 30 years on, that one has been Frankenstein'd in various ways, but still beats me at che...