[sdiy] Prophet 5 rev2 conundrum

[brianw]

Indeed. Tests have confirmed that the EPROM chips (I think there are three) have the full and uncorrupted tuning subroutines in them, because the same digital CPU board can tune a known-good analog Voice board.

You're lucky to have spare working P5R2 boards for these diagnostics (despite the frustration so far).

Brian

On May 3, 2023, at 3:45 PM, g m montalbano wrote:
> All very true. However, the problem isn't on the CPU board, since that board works correctly with another Voice board.
> The power supply, front panel,CPU board and 60 pin cable are all good --the fault is on the Voice board.
> 
> On Wed, May 3, 2023 at 2:49 PM Jay Schwichtenberg wrote:
>> For somethings not in the analog realm.
>> 
>> One of the first things to check in old systems like these after the 
>> power supplies is the reset circuit.
>> 
>> If I remember correctly there are multiple EEPROMs in it. Could be the 
>> tuning code in one of them could of gone bad. EEPROMs don't last forever 
>> and if the code is bad the processor would wonder off into oblivion.
>> 
>> Might very carefully pull the EEPROMs and reseat them to see if a socket 
>> connection might of gone bad too.
>> 
>> These are they types of problems logic analyzers are good for. Big pain 
>> to setup but the problem maybe a lot easier to find.
>> 
>> Jay S.
>