Vintage Synth Repair

I just picked up an Ensoniq Mirage for parts and would like to see if 
I can coax some life out of it.  Everything appears dead.  Power 
supplies are good.  I'm trying to see if the processor appears 
functional.  I found one bent over pin and thought perhaps that was it 
but it is still dead.

I'm having trouble finding a datasheet for a 68B09 processor.  Does 
anyone know where one is posted?

The G- (pin 20) of the 2732 seems to follow the system clock (1MHz) 
which is screwy.  Anyone have a ecopy of the logic portion of this 
part of the schematic?  I'm starting to think the processor may be 
bad.  I don't want to invest in a full set of schematics since this 
whole unit may be junk.  I'd like to at least see if the processor is 
trying to read data from the eprom.

Dave

> I'm having trouble finding a datasheet for a 68B09 processor.  Does 
> anyone know where one is posted?

Just look for 6809 or MC6809 or M6809.  It's a standard Motorola
8-bit microprocessor from the 1979 onward.  The B is just a slightly faster
crystal.  If there is an E on the end, then it has a different clock drive
circuit.  There's going to be RAM chip too in order for the stack to
work, so if the RAM is toast, the program is too.
 
> The G- (pin 20) of the 2732 seems to follow the system clock (1MHz) 
> which is screwy.  Anyone have a ecopy of the logic portion of this 
> part of the schematic?  I'm starting to think the processor may be 
> bad.  I don't want to invest in a full set of schematics since this 
> whole unit may be junk.  I'd like to at least see if the processor is 
> trying to read data from the eprom.

Yeah, sounds like it's just cycling the data and/or address lines.  The
2732 would be mapped to the top of the 64k so there should be
some decoding like a 74138 or discrete logic.  It may include the
R/W* line.  Also check the RESET signal.  Does the wave at G*
change when the ROM is removed?

GB

I'm got much more Intel than Motorola experience.  Here's what I found 
so far.

With the eprom removed, the G (and E) pins cycle more like what I 
would expect with a lost processor.  With the eprom installed, they 
are perfect replica's of the clock.

BS and BA are low - normal mode.
Reset is high - check.

Q and E look good - 90 degree phase shift between them.

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?

Now, to go find the system ram ...

Dave


--- In vintagesynthrepair@yahoogroups.com, "GB" <grantbt@...> wrote:
>
> > I'm having trouble finding a datasheet for a 68B09 processor.  
Does 
> > anyone know where one is posted?
> 
> Just look for 6809 or MC6809 or M6809.  It's a standard Motorola
> 8-bit microprocessor from the 1979 onward.  The B is just a slightly 
faster
> crystal.  If there is an E on the end, then it has a different clock 
drive
> circuit.  There's going to be RAM chip too in order for the stack to
> work, so if the RAM is toast, the program is too.
>  
> > The G- (pin 20) of the 2732 seems to follow the system clock 
(1MHz) 
> > which is screwy.  Anyone have a ecopy of the logic portion of this 
> > part of the schematic?  I'm starting to think the processor may be 
> > bad.  I don't want to invest in a full set of schematics since 
this 
> > whole unit may be junk.  I'd like to at least see if the processor 
is 
> > trying to read data from the eprom.
> 
> Yeah, sounds like it's just cycling the data and/or address lines.  
The

> 2732 would be mapped to the top of the 64k so there should be
> some decoding like a 74138 or discrete logic.  It may include the
> R/W* line.  Also check the RESET signal.  Does the wave at G*
> change when the ROM is removed?
> 
> GB
>

> 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

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
>

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
> >
>

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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