Vintage Synth Repair

Maybe Jameco.com.  I'll look in my parts bin at work as I might 
have one.   It was a pretty common FDC at the time.

GB

----- Original Message ----- 
From: "djbrow54" <davebr@...>
To: <vintagesynthrepair@yahoogroups.com>
Sent: Sunday, June 04, 2006 7:05 PM
Subject: [vintagesynthrepair] Re: Ensoniq Mirage help - need WD1772-02


Actually, some of the data lines were high and others were right in 
the middle.  I pulled the various ICs that were in sockets and now I 
can see valid highs and lows on the output of the eprom.  Putting the 
chips back in narrowed it down to the WD1772-02 FDC.  I lifted a data 
pin and monitored it with a scope while the CS-0 was high.  It's a 
hard high output.  I tried to pull it to ground with a 3K resistor and 
it's definitely not tri-state.

Anyone know where I can get a WD1772-02 cheap or free?

Dave


--- In vintagesynthrepair@yahoogroups.com, "djbrow54" <davebr@...> 
wrote:
>
> 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
> >
>








 
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