Power supply caps and related problems

From: simon <simski_at_email.domain.hidden>
Date: Tue, 10 Apr 2007 17:06:51 +0200

A few day's back i fired up my beloved 2/10 to let it run it' regular monthly hours. this to keep the system in shape and the caps in a working order. but after a quarter of an hour, suddenly the lights went out in my place. There was a fuse blown on one of my house groups. It appears that only one of the phases of the lisa is internally fused and a small capacitor in the line buffer section of the power supply had a short circuit. of course this was on the line that was not internal fused...

So lisa owners beware. replace the small decoupling caps in your power supply. especially the 250VAC versions and for the people living in 240VAC countries: the sooner the better.

on my Ref G power supply that means:

c1	0.33MF 250VAC
c2 	0.1 MF 250Vac
c3 	0.01MF 250VAC
c4 	0.01MF 250VAC
c5 	0.022MF 250VAC
c6 	0.022MF 250VAC
c7 	0.33MF 250VAC
c8 	470MF 250V
c9 	470MF 250V
c10 	1MF 250V

the 470MF ones are not critical. a smaller cap is also possible, but the voltage should only be equal or higher. the caps with a 250vac rating are critical and can explode when defective. I've had that on two lisa's. a loud explosion and smoke, but the lisa keeps running as if nothing had happened.

the next three caps are on the output stage and are a notorious source of hum if defective. mRemember that caps can go wrong in two directions. They could short circuit or open circuit, which means that they act as if they where not there.

c24 	4700MF 6.3V
c25 	1000MF 50V
c26 	2200MF 35V


met vriendelijke groet

Simon Claessen

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Received on 2007-04-10 08:21:32

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