Problem with MZ80-A CRT
Posted: Mon Jun 20, 2022 8:24 am
HI All,
My first post here - and thank you to the admin for activating my account!
I have picked myself up an MZ80-A and have repaired the main board (just some faulty RAM IC's). That part is now working but I have an issue with the CRT. I have replaced all electrolytic capacitors on the CRT PCB - with the exception of the bipolar capacitor (C2017 - 10uf 25v) as I can't seem to find one - but in another post I read, it was advised NOT to change it?
Anyhow.. what I get onscreen is not quite a horizontal line. It shows the monitor prompt, but the text is printed like a sine wave - and it moves up and down about a 1/4 of the screen in the middle (I hope that I've described that okay!) The text starts about a 1/4 of the way down the screen, is printed on the screen like a sine wave and will roll to about a 1/4 of the way to the bottom of the screen before jumping back up to about a 1/4 of the way from the top and rolling again.. It's really hard to take pictures of the screen - I will try though.
I should add that it looked like this before I changed the capacitors.
Has anyone any ideas what to look for here? My forte is really digital electronics..
Many thanks,
Mark.
My first post here - and thank you to the admin for activating my account!
I have picked myself up an MZ80-A and have repaired the main board (just some faulty RAM IC's). That part is now working but I have an issue with the CRT. I have replaced all electrolytic capacitors on the CRT PCB - with the exception of the bipolar capacitor (C2017 - 10uf 25v) as I can't seem to find one - but in another post I read, it was advised NOT to change it?
Anyhow.. what I get onscreen is not quite a horizontal line. It shows the monitor prompt, but the text is printed like a sine wave - and it moves up and down about a 1/4 of the screen in the middle (I hope that I've described that okay!) The text starts about a 1/4 of the way down the screen, is printed on the screen like a sine wave and will roll to about a 1/4 of the way to the bottom of the screen before jumping back up to about a 1/4 of the way from the top and rolling again.. It's really hard to take pictures of the screen - I will try though.
I should add that it looked like this before I changed the capacitors.
Has anyone any ideas what to look for here? My forte is really digital electronics..
Many thanks,
Mark.