Type 111 capacitor replacement

Craig Sawyers <c.sawyers@...>
 

Hi all

I've uploaded a couple of pics to the pictures section of the Tekscopes site
showing the replacement of the 40+40uF @ 450V smoothing cap in the Type 111
pretrigger pulse generator. The original was a Sprague unit, with a nylon
insulating sheath. At least one lister contacted me reporting a similar
failure with a Sprague cap in his oscilloscope, so perhaps this isn't
unusual with these Spragues.

The replacement is a JJ cap (Slovakian) that I got from a local supplier in
the UK (although they seem to be available in the US and elsewhere too, just
trawling google). JJ are a part of Tesla, who manufacture audio tubes.

I used a 50+50uF @ 500V cap, and is exactly the same diameter as the Sprague
unit, but a trifle shorter.

What I did was remove the old cap from the mounting plate by twisting the
locating tabs and pulling it off. I then trimmed the plastic sheath off the
new cap at the bottom revealing the metal can, and give the adhesive
something to grip to. Superglue was then used to glue the new cap to the
base.

As you can see, it almost looks as if it is original (which was part of the
exercise!).

JJ's site is at http://www.jj-electronic.sk/.

Craig

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