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Sharm MZ-80B cassettes - games?

It is looking like there is definitely something wrong with this graphics RAM card doesn't there.

Can you just double check that it is plugged into the correct sockets the correct way around.

The 40 way cable should be plugged into connector CN5 with the little triangles aligned and the 10 way cable should be plugged into CN13.

Might also just be worth disconnecting the cables and reconnecting them again (one at a time of course) just to 'break' any bad connection that may have occurred over the last umpteen years...

Dave
 
This is a good quality print manual: https://original.sharpmz.org/mz-80b/download/Sharp_MZ-80B_Owners_Manual_Sep1981.pdf.

All of the magic appears to be done within the custom chip IC43. The graphics video signal arrives on pin 23 of IC43.

But I am still not sure how the screen display switches from alpha to graphics. It has to do it on a character sell by character cell basis - so I am just wondering whether a control character gets stored into the character cell indicating that the cell should be filled with graphics as opposed to text?

Dave
 
Hi

I checked everything was connected properly. Then I disconnected the two motherboard connections, de-oxit'd them and reconnected a few times to try to remove any oxidisation. When you run the simple square program now it just does nothing and shows 'ready' - no graphics at all.

I'd really love to solve this but I think it's starting to get into the realms of someone who dearly loves the machine and can test on an IC level. Having a second machine to switch out parts would probably also solve it but I doubt that's going to be an economic possibility....

Thanks for the links. I guess I'll just park it for now. It's a shame as the machine is otherwise in such good order now I've fixed all the usual bugbears - I wasn't expecting this curveball!
 
Have you got a logic probe or oscilloscope? It might be worth having a quick look at some of the key signals to see what is going on.

Dave
 
Yes I've got a really good scope. I just don't know what to look for and even if I found it what it would tell me!
 
Ok if you can give me any clues what to look for, I'll set the scope and prod a few pins! Thanks
 
Hi everyone. I'm still trying to source a replacement 'graphyc-1' daughterboard - is this board found in the MZ-80A or any other of the MZ machines? Thanks!
 
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