Trs-80 model 1 -5v

[joeatact]

the -5v mine is reading -5.22 volts? Could this cook the ram? Could this be a defective zener?
Am exsperiencing burn finger ram chips?
Thanks
Joe

 

[ajacocks]

@joeatact no, -0.22vdc off is not nearly far enough to cause an issue. +/-20% is often the tolerance for voltages on 5 and 12vdc. Are you saying that you have some very hot DRAMs on the model 1? If so, they may well have failed, and need replacing, as that is a common symptom.

- Alex

 

[Eudimorphodon]

If the machine is working fine and the other voltages are fine you’re probably just par for the course. 4116s, especially early ones, were nasty power hogs.

 

[joeatact]

Thanks for the help one more problem, I believe this is a video ram issue with the roms removed shouldnt it be @9's?
Joe

 

[Eudimorphodon]

View attachment 1271636
Thanks for the help one more problem, I believe this is a video ram issue with the roms removed shouldnt it be @9's?
Joe

When in 32 column mode the machine only displays every other character, so there probably are a bunch of 9’s there you can’t see in the hidden odd addresses. You may well have some sticky bits since it’s not all @‘s, but considering the behavior you’re going to get with the ROMs pulled isn’t guaranteed to be completely consistent I would suggest this is a lower priority than getting the machine to the BASIC prompt. (Which it should be able to do with bad VRAM.) Once it’s booting you can properly test it.

Just backing up… does this machine actually not work when the ROMs are plugged in?

 

[Someone]

Note the@9's only appear if the CPU is executing repeated RST 38Hs (op code FFH).