No video on Otrona Attache

[FishByte]

Problem

Upon turning on, the power supply signals the POK (Power OK) signal and attempts to power the computer, however
when turned on the crt filament will light up for a second and then go dim. I first checked the CPU (Z80) and then
checked the CRT driver (5027). I can't really test all that much because I've only got a multi-meter. The board does
have the High res mod and another little square board, I attempted to power it up without these but that didn't make
a difference. I hooked up a composite screen to the video out to test if it was just the monitor but again with no avail.

Any help would really be appreciated.

 

[Dwight Elvey]

Problem

Upon turning on, the power supply signals the POK (Power OK) signal and attempts to power the computer, however
when turned on the crt filament will light up for a second and then go dim. I first checked the CPU (Z80) and then
checked the CRT driver (5027). I can't really test all that much because I've only got a multi-meter. The board does
have the High res mod and another little square board, I attempted to power it up without these but that didn't make
a difference. I hooked up a composite screen to the video out to test if it was just the monitor but again with no avail.

Any help would really be appreciated.

You are not likely to get far without a scope. ( don't buy a cheap 1MHz scope. it is not fast enough to deal with the video circuit ). There is a schematic on the web.
Dwight

 

[keenerb]

You are not likely to get far without a scope. ( don't buy a cheap 1MHz scope. it is not fast enough to deal with the video circuit ). There is a schematic on the web.
Dwight

https://tinymicros.com/mediawiki/images/0/06/Otrona_Attache_Schematics.pdf

That's a cool looking little machine. I hope you get it sorted out.