[sdiy] Prophet 5 Q & which z80?

[Paul Wagorn]

HI All:

I've got this P5 that's been driving me crazy - i finally had to bring it
somewhere to get repaired.

basically, right now it goes through it's tuning procedure & looks like it
comes up ok, but when you press a key, you it just makes a click (ie really
fast attack & decay)... the kb scanning *might* be ok (it sounds as though
the clicks are the right pitch, but really hard to tell)

the repair tech tells me that the address lines (a0-a2) from the z80 don't
have any action on them & they *should*.  it seems as though the mux's are
not getting a proper clock -  So, he says the z80 is most likely bad.  the
crystal timing circuit seems to be ok.

2 q's:

- does this diagnosis make sense?
- the cpu is basically just labelled a z80.. .Now, there are a million
different types... what is the right one that goes in the P5?  it's a 40 pin
one.  I think it's ttl - will a cmpos one work ok i i can't find a ttl?

thanks!
paul