On Thu, 8 Jun 2017 17:28:02 -0000 (UTC), Cursitor Doom
wrote:

Hi all,

I tore down a Marconi signal generator today. It's been awaiting my
attention for quite a while. Can't recall the model number off hand but
it does 10kHz to 5.4Ghz IIRC. I bought it from some chap who told me it
had a faulty smoothing cap in the PSU 'cos it was generating signals with
ripple on it. He told me he'd been quoted GBP280 ($387 in US dough as of
today's date) for a new replacement from Marconi and I bought it on that
understanding. Anyway, I tore it down today and located the said
capacitor. Here it is:

https://www.flickr.com/photos/128859...in/dateposted-
public/

This is the only pic that came out for some reason, but it's got most of
the important info on it. You can't quite see, but it has 5 terminals for
some reason, but on the board only 2 of them are connected. It's gone
seriously low-res internally, BTW, so *does* need replacing.

Questions: what makes this thing so special as to cost so much?
Why have the designers used such a huge capacity cap in this low current
drain application?
If I can source a generic electrolytic of the same spec or better for
30 quid, why should I not use that instead of the bespoke replacement??

It will be a limited production component that is no longer made and
the remaining stock has a very high price. Replace it with an
electrolytic of the same capacitance and voltage rating. The extra
terminals are probably connections to internal parallel capacitors. I
once worked on a power supply that had a 600 uF capacitor but when it
went I discovered it was made of 8 x 100 uF in parallel all in the
same encapsulation with two terminals. I assume the 600 mark on the
case was a misprint.

Steve

--
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