Sequential Circuits Prophet-5 Repair - DAC Issues
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- เผยแพร่เมื่อ 2 ต.ค. 2024
- Description of a common failure mode of the Prophet 5 (the DAC and related circuits), how to diagnose it, and how to fix it.
#prophet5 #repair #sequentialcircuits #synth #synthesizer
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The world needs more skilled synthesizer doctors like you. Thank you for saving her!
Mr. Keith are you a general repairman for synths? Just want to know to add you to contacts if you are for future work. TY
+skyprop
Yes, I do repair work on synths, and studio gear in general.
@defzeppardica
Hi.
Before replacing the DAC, I would check the data lines going into it (like in my video). If any of them are stuck high or low, work backwards from the DAC until you find the fault.
Another thing to do is to look at the output of the DAC with an oscilloscope. You should see a 'stairstep' where all of the knobs are being sampled. If you turn one of the knobs, you should see one of the 'stairs' raise or lower. This could give you clues on what's wrong.
Does a problem with the dac can cause the panel to activate different functions than usual ? I get random activation of numbers
Excellent instructional video! Thanks from a P5 owner!
Hey,
I uploaded a video of the problem with my Prophet 5. The LEDs and display either aren't cycling or are cycling so fast it looks like they are blinking. Also, the only audio output is what you hear on the video. They keys and knobs don't affect the sound at all. I don't have a logic probe but I have my trusty Fluke DMM. I'll run though the diagnostics that you suggested. But if you have any other ideas, please let me know.
Cool video! I wanted to do a sysex dump of my P600 patches. I have a 6-08 rom to do midi sysex. the manual says to press record and program 2 in order to do sysex with a computer. I'm using sysex librarian for mac. It doesn't seem to be working. Do I hold down record and then press 0 and 2? And should the preset light be on? I'm really confused on this. Any help would be appreciated. Thanks
I like how the last 2 chords you played sounded like "Tadaaaaaaaaaa, the synth is now working" :-D
The hard to find parts on the Prophet 5 are the SSM or Curtis chips, and the DAC. Depending on the version of the synth (rev 1, 2, or 3) the chipset is slightly different.
Great video. I have an early revision 2 with a dead front panel and no sound. However there is some life to the front panel when switching the grey switch near the bottom of the logic board on the LHS of the synth inside. Then the preset buttons would work and the synth panel would respond to front panel patch selection 11 through 18 but not the others.. I had someone here in the UK look at it but we couldn't find the precise fault.
Thank You ! I'm trying ho repair a Polaris using digital tester and a scope !I Never thought to test the ADC 0804 with a probe !!'
Very impressive. You can resolve problems with very simple checks. Wonderful
excellent video,very descriptive and should help a lot with DAC/ADC issues
z-80 Processor......Same as used in the Ol TRS-80 computers from Radio Shack. Actually called "ZiLog-80"
+skyprop The Moog Source Uses the same Z-80 Processor!
Great info. Thanks!
Wonderful video! :)