Vintage Synth Repair

It's a 68B09EP.

While scoping the data lines of the eprom, D1 - D7 were always high. 
D0 appeared to be always low.  Seems quite suspicious.

I can try and find a programmer at work.  I'll take the ROM image.  
Contact me offlist.

Thanks. - Dave


--- In vintagesynthrepair@yahoogroups.com, "GB" <grantbt@...> wrote:
>
> > Pin 36 is always low. One data sheet says this is MRDY, the other 
says 
> > it is AVMA.  MRDY makes no sense as the processor should be in a 
> > constant wait state.  What is AVMA?  And, why the difference 
between 
> > these datasheets?
> 
> I don't remember for sure but AVMA might be Address Valid.  Which
> means that the address lines have finished wiggling and are valid 
for the
> upcoming access.  I don't recall this quirk being present on the 
6809 but
> I do recall it for the 6502 (VMA).  It was a signal that just needed 
to
> be included in the address decoding.  Annoying.  Do you have a 6809
> or 6809E flavour of CPU?
> 
> You might just have a bad EPROM or SRAM, though anything that 
> hangs the data bus would toast you.
> 
> I have a ROM image if you can find a way to burn a new EPROM.
> 
> GB
>