Moog Prodigy Advice

[roboctopus]

Hi all.

I'm looking for some advice. I have a Moog Prodigy 336A. Cosmetically really nice, only missing one slider, no other real cosmetic issues.

But... I turned it on one day and no sound! (It worked fine one day, stayed in tune, played like a dream, then...nothing. Oh the pains of owning a vintage analog.)

Anyway, I have a Little Phatty that I love, and live in an synth tech impoverished area, so there's not much incentive to fix it.

Anyone have a notion of a fair price to ask for a Prodigy that powers up but makes no sound?

[thealien666]

I'm curious, does the filter make any sound when pushed to self-oscillation ?

Does the synth makes any kind of thump or click sound at the output when you power it up?

If not, I suppose the only indication that the synth is "on" would be the power LED ?

[roboctopus]

It doesn't make any sound at all. The LED lights up.

I have no knowledge of electronics, so I haven't investigated it.

[thealien666]

Since the power LED indicator is only being powered by the negative negative side of the power supply rail, it only confirms the presence of -12 volts. If the positive rail is gone (missing the +12 volts because of a defective 7812 voltage regulator), then major damage elsewhere might possibly have been done.

However, if you're lucky, it could only be the final output op-amp (1/2 of a 4558) that might be defective.
Replacing it would be a small task for an electronics hobbyist like myself (or possibly a friend in your area ). But not for someone who really don't know anything about electronics.

As for the resale value of a defective Prodigy, I don't have any idea.

[EMwhite]

I like your signature 'dead' part.

I don't have any direct advice but can tell you that my Opus 3 is flakey in a similar way.

1/2 the time I power it up it only outputs a faint clicking sound when played. If I power it off for a split second then immediately back on it works fine. The LFO light works in either case.

Prodigy and Opus are very different but were made during the same timeframe and may have similar components (and possibly the same failings).

According to Wikipedia, the later model Prodigys had a Gate in trigger so you might want to try firing the envelopes externally to see if you get anywhere. Eventually I will have to fix mine but it's such a simple synth electronically, I would think it is either power related or some aged capacitors, or dirty contacts.

A few guys here are very good at repair and have seen it all so hopefully can suggest something to check. As for value? A working one in good shape went recently on eBay for 800 or 1,000 USD. Much depends on what types of 1/4" Jacks are onboard as this has changed across the years. Broken, I would say 1/2 that but I'm just guessing. Any repair is going to cost you a few hundred I would think.

[EMwhite]

Question for TheAlien666; I got home today and powered up my Opus to see if the Filter would go into oscillation as you suggested to the OP, mine does. I can either just push it up and get the squeel or switch the LFO to Filter and have it chirp at different speeds and levels of intensity.

What would this indicate to you? Something with the keyboard scanner or sound source triggering circuit or something else?

Thanks.

[thealien666]

Question for TheAlien666; I got home today and powered up my Opus to see if the Filter would go into oscillation as you suggested to the OP, mine does. I can either just push it up and get the squeel or switch the LFO to Filter and have it chirp at different speeds and levels of intensity.

What would this indicate to you? Something with the keyboard scanner or sound source triggering circuit or something else?

Thanks.

Was the dreaded "foam of death" ever removed from yours ? If not, it might be a source of bad contacts in switches, pots, and even onboard connectors inside your Opus 3.
The Prodigy doesn't have that problem, since it was produced before Moog Music decided to use such a "self-decomposing-foam-over-20-years" to protect the slotted openings of the sliders on Opus 3, MG-1, and Rogue from outside dust.

Anyway, the fact that switching the power off-on quickly, resolves the problem makes me suspect a possible cold joint or cracked solder joint somewhere on the main PCB, or on the keyer/power-supply circuit board, or a bad electrical contact in some connector inside.

[EMwhite]

Yes, I had to remove the remnants of the FoD myself and did my best to clean up all of the sliders and the board with q-tips, etc. Lots of labor in that. I bought this from (guess), yes eBay and one of the prior owners apparently dumped kerosene or something nasty inside in order to try and clean up the foam.

I didn't take too close a look at the connectors, just cleaned the pins up, I suppose as you said cold solder joint type issues. I suppose I should take a closer look and float new solder if anything looks suspect. Thanks.

[thealien666]

Yes, I had to remove the remnants of the FoD myself and did my best to clean up all of the sliders and the board with q-tips, etc. Lots of labor in that. I bought this from (guess), yes eBay and one of the prior owners apparently dumped kerosene or something nasty inside in order to try and clean up the foam.

I didn't take too close a look at the connectors, just cleaned the pins up, I suppose as you said cold solder joint type issues. I suppose I should take a closer look and float new solder if anything looks suspect. Thanks.

I'd start by the keyer/power-supply circuit board first, especially the legs of the 3 voltage regulators, since it's powering everything else and generating s-trigger signals for the VCA envelope, uh sorry I meant "Articulator" too.

[roboctopus]

Just to give you guys an update--I sold the Prodigy for $450 via Craigslist in Nashville. You know, if you're wondering what to price a broken synth at in a Southern U.S. Market. Interest was not very high. I had 3 offers (one of them a low-ball "I'll give you $100). *Shrug*.

Now to use the cash to buy other gear! *evil grin*

[Portamental]

So sad to see a Prodigy go down and an Opus 3 on the brink.

Find a good tech, put a little money in your vintage synths. They are unique and totally worth it. I found an Opus 3 a little while ago, had it refurbished. Awesome.

[thealien666]

Just to give you guys an update--I sold the Prodigy for $450 via Craigslist in Nashville. You know, if you're wondering what to price a broken synth at in a Southern U.S. Market. Interest was not very high. I had 3 offers (one of them a low-ball "I'll give you $100). *Shrug*.

Now to use the cash to buy other gear! *evil grin*

Oh well, at least you got something out of it. But Moog prices being what they are, for that much money all you could probably get is a Moog EP-2 expression pedal !
Just kidding.

You already have a good head start on the price of a Minitaur...