MSX newbie here and I've acquired a Sony HB-75B but it's stuck at black screen.
Only multimeter voltage tests done so far and power looks good and going to chips including ram OK also no visual damage anywhere and nothing running very hot etc.
Have switched out CPU with another but no change.
Mentioned in another thread that the eproms could have degraded over the years?
This appears to have 2 UV erasable ones HB EXP i and ii BASIC (there's no change of black screen if removed).
I do have an eprom programmer so can replace but would need good rom bins to compare them, either the originals or custom variants (ie can http://openmsx.sourceforge.net/ be used on the real thing?) if ever made but is that highly likely to cause black screen or would it be more likely other parts of the system?
I also have parts from a Toshiba HX-10 which has a corroded PCB and could be beyond repair in case there's any other swap out parts that could be of use for my diagnostics.
*Any* help extremely welcome.
Cheers
The only difference may be the pound key. I suppose, not checked that... 
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