RE: Fixing the C900 power supply

From: Martin Hoffmann-Vetter <>
Date: Fri, 9 Jan 2015 17:12:07 +0100
Message-ID: <005801d02c27$04d5c6d0$>
Hello Michau,

>> Well, there are a few things that would be good to know.
>> - What are they using as the primary switching transistor?
> There is someting that looks ike a big transistor which reads
> "BUV47A". 
>> - What are the ICs on the vertical board?
> They are a 4006 and a LM339N.

The 4006 can be a UAA4006 (see The typical application example ( shows a BUV45 for the switsching transistor. So i think this can by your power supply! Can you check it?

>> Also, all capacitors with an 'ROE' logo should be regarded as suspect
>> and at least checked if not replaced. They tend to mutate into a
>> short circuit internally. I see a few of them on the righthand side.
> There are some labeled "ROE" and some labeled "FRAKO". I tested with
> an ohmometer without unsoldering them, and it indicated a short
> circuit everywhere but I am not sure whether is is from a bad
> capacitor, or from some other circuitry in the PSU?

You can't measure the resistance without unsoldering. The next problem is, all these capacitors have a lower capacity over the time. When this value is too low, the PSU don't work.

So i would change all electrolyte capacitors. But you need low-ESR types on the secondary side!


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Received on 2015-01-09 17:00:03

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