Sinclair ZX80 / ZX81 / Z88 Forums

I received my boards

Now I just need to solve an annoying display problem before I can try them out
And a little MtM adapter because it seemed usedful

EDIT: Originally I thought I had a display problem. It turns out my RAM keeps failing. No display Is just how it shows itself. ORIGINAL POST: I just got some new toys to play with - and I can't because my display says "No Signal" - again. Symptoms: 1) The signal looks terrible (see attached pic) 2) ...

is The value of the capacitors calculated in any way? Line filter capacitors (in this configuration) act to short out high frequencies, while passing through lower frequencies and usually have a capacitance in the range between .1µF and 10µF They basically act as a short across the +Vcc and GND unt...

Welcome.

I'm in the Bay Area, having fun messing around with Ts1000 myself. If you have any questions this community is great.
Glad to have you as part of it.

Cheers,
Matthew

You Mark =

This seemed relevant to some here
https://hackaday.com/2020/08/17/3d-on-t ... ctrum-48k/

Cheers,
Matthew

Mystery Solved It was switching noise. :oops: :oops: :oops: I hadn't added the bypass caps to the 74xx chips :oops: :oops: :oops: Lesson learned. Never underestimate the power of the bypass cap across Vcc & GND to clean up switching noise. Ignore them at your own peril and frustration. BTW: The hint...

First I'd try putting the old RAM back.
That will narrow the problem.

It looks like miss-attribution rather than no attribution. The person received the Gerber files from Klaudiusz Fatla and attributes the design to him with a thank you. Likely the correct attribution got lost in the handoffs. It would be kind to let them know of the error as they seem to want to give...

I've tried increasing [C13] up to a 10uf cap and it still faults. But, at least now I feel like I'm making progress IC4b, C13, and D1 are clearly not doing their job. Increasing C13 is supposed to help it work more effectively. I started think about the purpose of C13. I did silly thing and moved C...