[sdiy] Prophet 600 diagnostic eprom?

[rsdio at audiobanshee.com]

Have you gone through the calibration steps for the Prophet 600? Any time you swap out a 3340, you'll probably need to force calibration again. I don't know whether the Prophet 600 firmware is anything like the Six-Trak, so I'm not sure whether this advice is appropriate.

In my experience with Prophets, a chip can appear completely dead until the calibration has been performed.

Last time I worked on a Six-Trak, there was one or two voices dead. The owner had a spare 3394, and told me that probably all I needed to do was swap the chip, but he wasn't comfortable pulling and replacing chips. Of course, that's the first thing I tried, and this "brand new" 3394 didn't work. Once I performed calibration, the original chip actually worked, and the owner was surprised that he'd paid for a 3394 when he didn't actually need one. I'm not quite sure how the original chip became uncalibrated. Perhaps the battery glitched.

p.s. I also noticed that the noise source had been defeated on this Six-Trak. That made some of the presets sound dead or almost dead. All I had to do was re-solder a wire that had come loose. Apparently, Sequential Circuits had some manual re-work on certain Six-Trak units to fix some PCB errors, or circuit revisions.


On Jun 19, 2016, at 9:46 AM, Eric Frampton <eric at ericframpton.com> wrote:
> TL;DR: The CPU doesn’t seem to be sending much of anything to the DAC.
> 
> The longer version:
> 
> Front panel buttons on the membrane respond, and all LEDs are working.
> 
> Unison switch seems to work, insofar as if I switch the unit to Unison I get filter control changes on voice 2, and it does track the keyboard; otherwise no response from any other controls besides filter cutoff/res/envelope (which are working correctly).
> 
> Looking at the data lines on the front panel, the unit seems to be reading the keyboard, and looking at the analog output from the front panel it seems to be reading the pots.
> 
> Looking at the data lines from the front panel I can’t tell if all the other switches are working or not, but looking at the oscillator waveform switch lines from the digital to analog board, it appears those switches are working (I can see the lines change state.)
> 
> I’ve only dropped two 3340’s in, but on both of them I’m seeing sub-audible sine-waves only, and they’re not tracking the keyboard. I -am- aware that, since I’m dropping in Rev G 3340’s, that I’m going to go through and change the resistors at some point.
> 
> The DAC is working correctly. I dropped it in to my Prophet-10 to test and it behaved completely normally.
> 
> I’m seeing pulses/activity on all 14 data lines to the DAC.
> 
> I’m seeing activity on all A and D lines from the CPU.
> 
> When I turn up the resonance, as I mentioned above, I do get audio out of one channel (voice 2), so the unit does produce audio.
> 
> Now, if I drop in GliGli, on boot I get random segments frozen on the display, then the unit hangs.
> 
> e
> 
> On Jun 19, 2016, at 8:37 AM, Tom Wiltshire <tom at electricdruid.net> wrote:
>> Ah, now that *is* interesting.
>> 
>> Can you give us a summary of the symptoms/problems you've got?
>> 
>> T.
>> 
>> On 19 Jun 2016, at 00:13, Eric Frampton <eric at ericframpton.com> wrote:
>>> I bought and flashed a Teensy with that exact thought in mind (having previously flashed and successfully installed one into a client's P-600), and it didn’t fix the problem. In this case GliGli just won’t boot, which leads me to think the problem is outside the components that GliGli replaces.
>>> 
>>> e
>>> 
>>> On Jun 18, 2016, at 8:12 AM, Dan Snazelle <subjectivity at hotmail.com> wrote:
>>>> You could just do the gigli p600 teensy update and get rid of the old cpu altogether ;)
>>>> 
>>>> Best half hour I ever spent for my p600 
>>>> 
>>>> On Jun 18, 2016, at 12:31 AM, Eric Frampton <eric at ericframpton.com> wrote:
>>>>> Any of you kind folks have an image of the Prophet-600 diagnostics you’d be willing to share? I think it’s called DIAG6? I’m taking a break from digging through this OB-X to work on my P-600 now that I have 3340’s to drop in there. There’s something going on with the CPU, but I can’t seem to get to the bottom of it, and I’m hoping those diagnostics might help. I’m willing to pay for your time/energy, I just don’t want to deal with Wine Country.
>>>>> 
>>>>> thanks!
>>>>> Eric