more PPG 2.3 boot failure

[Paul Maddox]

Sandro,

>I'll be very patient (i'm just dealing a Rhodes Chroma with bad Dual
Channel Boards ...) and I know these things are NOT easy to fix also ...

Hehe, early poly synths were a nightmare!

>Anyway , you're assuming I mean that "the cursor scrolls left to right,
then goes to second row scans left to right and then back to the start "
>It's not exactly so. In fact , at the boot , the cursor scrolls left to
right the first row without finishing it - it stops at 3/4 of the first row
without going to >second one at all.

OK, its usually the same problem.. make sure all the eproms ae seated in the
sockets properly...
You may need to replace these...


>You also said about PROZ boards,  to have ordered a complete set of chips
to replace the whole lot as a quicker way to repair it .
Yeah, its a complex board..

>Then , may you confirm is PPG 2.3 repairable in these boards just replacing
chips ? Or it has also "custom" components so that I'd sink in muddy waters
???
>

There are no custom chips anywhere in the synth, BUT....
there are some PALs which I have the JDEC files for, these dont usually go
wrong..
the fault you are describing is typeical of the CPU board not botting
correctly.. it could be a loose eprom or a faulty eprom.
PROZ board problems are anormally related to the picth of the playback or
the playback sound being wrong..

>At last , it's an expensive repairing ?

The one chip that is next to impossible to find is ;- 74F189,
its a 16by4 dual port SRAM chip.. Philips still make them, BUT you have to
buy 550 of them at least!
(anyone know where I can get a lower quantity at a decent price?)
The rest of the board is standard 74LS logic... so it shouldn't be too
expensive..
Like I say, you have what would appear to be a CPU board problem... find
someone with another 2.3 and try swapping the CPU
board if reseating the eproms doesnt work..

Good luck

Keep it blue,
Paul Maddox
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