[sdiy] PPG Wave 2.3 Boot Problem

Hermann Seib him at hermannseib.com
Thu Jun 20 06:58:00 CEST 2002


> I'm in the process of repairing a non-functional PPG Wave 2.3. The problem
> is, that the PPG refuses to boot. When powered up, the backlight of the
> display goes on, and the top line of the display shows a long
> black bar and
> that's it. The unit is in good shape, the only thing is, that the machine
> doesn't have a battery installed on the I/O board. As the battery is used
> for keeping patches and sequences in memory, the missing battery shouldn't
> affect the booting sequence IMO. I've done several tests on the unit
> (checking voltages, reseating IC's, watching MCU pins on o-scope,
> etc.) and
> came to the conclusion that either the MCU has died or that the EPROM code
> is messed up. I'm thinking it's the EPROMs, but until I've made myself an
> EPROM reader, did anyone of you have a similar experience with
> your PPG and
> if so, what did you do to fix the problem?

The battery is indeed unnecessary for booting, although it might be a good
idea to put one in :-)

The boot process of the Wave 2.3 is very simple.
.) Initialize Stack
.) reset the 3 DACs on the I/O board
.) reset all work memory areas
.) initialize the OF4s
.) set all sequencer channels to 3
.) check whether 2.2 or 2.3 and set up for 8 or 12bit
.) test RAM / EPROM
... and at that point, it already initializes the display and displays the
"R/T,A,C,E" boot diagnostics. So this leaves us with the following
(non-esoteric :-) possibilities:

.) +5V line doesn't deliver ... you said you checked that, right?

.) E or C EPROM gone bad, which would cause the CPU to go into Neverland

.) Reset logic on the motherboard defective, so that the Wave doesn't even
try to boot. My personal favorite :-)

.) TAS board or LCD connector broken... since it got no battery, it got no
sounds, so you won't hear anything even if it boots correctly and just
doesn't display anything. In that case, the Group A LED should be lit, and
pressing the GROUP button should toggle between A/B/Both.



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