Moog Music Forum

Hi,

I have this problem when playing my Prodigy I hear high clicks, they're in my recordings and on stage you here them also. They don't happen when you press a key but rather random like static electricity clicks in the high frequencies. Here's an example of how they sound, first part is without EQ, 2nd part is with EQ to filter them out.

https://www.dropbox.com/s/82xxuvzlrmkfz ... s.wav?dl=0

(check on decent headphones or speakers)

Someone else on Gearspace describes a similar problem here

https://gearspace.com/board/electronic- ... st16004146

My tech replaced op amps, cleaned the key contacts but the clicks are still there. Anyone knows what might cause this? (btw it's not the VCA offset because the clicks happen randomly)

anyone?

Hi Eklektric,
I’m having the same issue with my Prodigy. Did you have any luck fixing yours?

Is the click visual on a scope? Can it be seen like a kind of needle or similar?

Adjusting VCA BALANCE trimpot?

trimpots do not make any difference on clicking sound

Hi, analogmonster.
Please check attached image of a waveform from oscilloscope. This happens all the time even without pressing any key

dodopop wrote: ↑Sun Dec 31, 2023 12:46 pm Hi, analogmonster.
Please check attached image of a waveform from oscilloscope. This happens all the time even without pressing any key

Picture?

dodopop wrote: ↑Tue Jan 02, 2024 12:26 pm

I would check the audio signal path on board starting at the VCA. It is OTA based (U18 <= CA3080). The input of the OTA (pin 2 and 3 of U18) should show a correct waveform coming from the VCF. If not the VCO signal has to be backtraced to the oscillator core.
To trace this a pure triangle should be selected, and only one oscillator leveled up. The VCF should be adjusted that a rather clear triangle is visible at pin 2 and 3 of the CA3080 (VCA). If the output (pin 6) of the CA3080 is distorted there might be two reasons: The OTA itself is broken, or the control current of pin 5 shows a weird signal. If last the control current must be backtraced etc. etc., so a kind of signal tracking on board has to be performed.
I did this for my own Prodigy. In my case I had to replace the LFO capacity.
Please check the power supply as well. There must not be any distortions on the rails.

I have updated .01uf tubular capacitors with polypropylene film tone capacitors, grounded secondary transformer (grounding was all the way through the audio path) and adjusted VCA balance.
Also found a broken LM3046N which was giving wrong voltages on two pins - this was blocking temperature adjustment because U2#5 was receiving -12 volts.
It is now very clean sounding with no artifacts.
External control now works very stable - before it was constantly rising pitch until pressing lower F and in 5 minutes it was half tone off again.
Thanks for trying to help!