Vintage Synth Repair

I recapped my Moog prodigy a few years ago and one challenge was finding electrolytic capacitors with radial leads. Most are PCB mount these days.




On 1 Aug 2016, at 1:57 AM, Kirk Slinkard kslinkard@...<mailto:kslinkard@q.com> [vintagesynthrepair] <vintagesynthrepair@yahoogroups.com<mailto:vintagesynthrepair@yahoogroups.com>> wrote:






  Electrolytic capacitors can change their value over the years, which can alter the sound. But that's pretty rare. Electrolytics usually have a slightly higher distortion in the audio path than better materials, which supposedly can be heard. I've never come across any actual evidence of that, although I suspect that there are some people who actually can hear the difference in a direct A/B listening test. There have been claims that some electrolytics sound better than others, but I've never heard of ANY support for that.


  There is one tech that I have conversed with that says he fixes all the problems in his vintage gear just by replacing the electrolytics. But with me and all the other techs I've conversed with, changing electrolytics almost always makes no difference at all. There is a greater chance of really cheap electrolytics failing that decent quality ones, but Moog doesn't use cheap components. Electrolytics are said to have a life span of a certain number of years, which is specified in parts catalogs. One example: "guaranteed lifetime of 20000 hours" (more than 2 years). But getting back to real life, the oldest piece I've worked on was a Rickenbacker amp from the 40s, and the original electrolytics in that were all just as good as new. So I personally go by the rule: "if it isn't broke, don't fix it".


  But on the other hand, there DEFINITELY are some people that you can impress by telling them you changed out all of the electrolytics. So it really depends on what your goal is.




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From: "gk.box@...<mailto:gk.box@hotmail.com> [vintagesynthrepair]" <vintagesynthrepair@yahoogroups.com<mailto:vintagesynthrepair@yahoogroups.com>>
To: vintagesynthrepair@...m<mailto:vintagesynthrepair@yahoogroups.com>
Sent: Friday, July 29, 2016 3:23:21 PM
Subject: [vintagesynthrepair] Moog Prodigy: do capacitors model/type affect the sound?






There are 6 electrolytic capacitors on the Moog Prodigy circuit board. And as I understand the schematics, 4 of them are in the audio circuit. And after 30+ years, I assume their performance is compromised. And since it *seems* to me that the sound of the synth has been slightly changed over the last time, I'm thinking to replace all electrolytic capacitors, using the same capacitance/voltage replacements, of course.




The question is, do the capacitors affect the actual sonic characteristics of the output signal? At least, in a case with Moog Prodigy?




My concern is that the modern capacitors (different series, different characteristics) will make the sound different. And I would like to keep the "original" coloration of the sound as much as possible.




I would greatly appreciate any input..




Thank you!






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