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Subject: Re: [korgpolyex] Power circuit repair.

From: <backshall1@...>
Date: 2014-03-12

Totally agree with Gordon on that one. Replace only bad caps, not the goodones, and low voltage electrolytics rarely fail. If your multimeter doesn’t havea capacitance range, you should be able to find a cheap one that will work justfine. Power problems on Poly-800’s that I have seen are generally due to D2and/or Q1, except for that one machine I had where Q15 and Q16 seemed to be deadso I ripped everything out and put in the 7805.
Don B.
 
Sent: Tuesday, March 11, 2014 6:50 PM
Subject: Re: [korgpolyex] Power circuit repair.
 
 

On Tue, Mar 11, 2014 at 11:42:21PM +0200, Sami Jumppanen wrote:
> Afterfixing a number of devices by replacing capacitors only, I recommend
> youalways begin with them if it's likely a power issue. Electrolytes, no
>other types. Medium sized, not the smallest or biggest (depending on the
>device, there may not be large capacitors). By the numbers: usually 470to
> 2200 micro F and from 15 to 63 volts.

... and I generallyrecommend people scrap equipment that's been subjected to "re-capping" when theybring it round for me to resurrect.

I've pretty much only ever seen electrolytics fail in cheap crappy switched-mode power supplies (think Amstradsatellite receivers from the 80s and 90s). Of the rest, I've replaced maybe halfa dozen electrolytics that were actually the cause of a fault and only one ofthem in an analogue synth.

Electrolytic capacitors just don't fail thatoften.

DO NOT just start ripping them out because you suspect there'ssome sort of fault. You'll only make matters worse.

--
GordonjcpMM0YEQ