Sequential Circuits Prophet-5 Repair - DAC Issues

[htongtong]

Very impressive. You can resolve problems with very simple checks. Wonderful

[TheSynthFreq]

Wonderful video! :)

[defzeppardica]

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.

[krmelectronics]

@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.

[waheex]

excellent video,very descriptive and should help a lot with DAC/ADC issues