Re: 2245A mains filtering

Chuck Harris
 

Hi Brian,

As far as I know, Schafner is a bad brand during the
80's, through early 2000's. They work ok in the USA,
but in the 240V world, they like to let their smoke out.

The RIFA sort that are a problem have a yellowish clear
molded epoxy outer coating, over a paper dielectric
capacitor. The epoxy shrinks, cracks, and lets moisture
into the paper capacitor, where it can become explosively
leaky.

Generally, tektronix scopes are made of good stuff. You
can leave most of it alone, until it fails, without setting
yourself up for great collateral damage.

The exceptions are SMD electrolytic capacitors in some units,
and Schafner filters when used in 240V land..

-Chuck Harris

Brian Cockburn wrote:

Chuck,

The caps in my 2245A's PSU that I'm considering changing are the filtering after the Corcom and before the bridge rectifier. The three Y class look a bit RIFA, although without taking them out I can't be sure. The two X class are yellow Philips units. And as I said this is a first step. PSU electrolytics are next if/when there are DC level or ripple problems.

I have had an X class fail - actually went bang in my hands. Although that was on a router (power tool, not network infrastructure).

Ah, Schafner, is that the only brand to worry about?

Here, tonight, it's 240.2 VAC, so yeah I live in a 'high voltage' area. And my 'scope served its time in the UK as far as I'm aware (ex Uk military).

Thanks, Brian.



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