Electrolytic caps never fail to disappoint

[Argus25]

excuse the ebay reference but this shows a picture of some 36mm diameter pulse types, used in electric fences. I'm am conducting some experiments to see if I can successfully paint them in a way where the paint won't flake off, to make them look metallic silver:

http://www.ebay.com.au/itm/16uF-900V...sAAOSw3xJVZ~QD

[Oliver35]

They look very useful! I've certainly found the motor caps to be very handy, mostly but not exclusively for smoothing. I've hidden rectangular 8uf examples in a cardboard box coated in wax to make an 8+8+8 block, single cylindrical ones in cardboard tubes to make large axials, and of course the aluminium ones look the part already, if you cut a large hole in the chassis to hide the spade terminals beneath. Vis a vis the ones in your link, could they not be sleeved in aluminium tube or wrapped in that aluminium tape used for ductwork &c?

Oliver

[Argus25]

They look very useful! ... Vis a vis the ones in your link, could they not be sleeved in aluminium tube or wrapped in that aluminium tape used for ductwork &c?

Oliver,
Yes it turns out that these pulse grade capacitors slip neatly inside a metric aluminium tube used for motorcycle air intake couplers, I'd been working on this option too. These capacitors also have fairly closely spaced terminals so they are good for a smaller chassis hole than the bigger oil filled ones with the widely spaced spade terminals.

However, I'm in luck with these pulse capacitors. I did some experiments on the plastic. A small dot of acetone dissolved the surface much to my delight.

So I have spray painted them with a fine silver quick dying paint, like Duco lacquer. It has slightly etched into the surface and given a fantastic bond to the surface, so it won't scratch off or flake and an silver metallic excellent finish. I will post some images soon and explain exactly how I prepared them and how this worked out.

Also its good that these are around 36mm dia, a lot (but not all) of the oil/motor types in the 16 to 22uF range are 40mm and don't look quite right, but I have some smaller ones on order.

Hugo.

[Argus25]

OK, I now have my first attempt at eliminating electrolytic capacitors from my vintage TV's. Photos attached.

This attempt consists of making a capacitor kit using MPP (Metalized polypropylene) caps which are 16uF 900V rated, specifically for high surge currents. So the idea is running these at around 400V they will likely have near indefinite life and they contain nothing corrosive to burst open and damage & corrode surrounding structures like our good friend the electrolytic.

As noted in the post above, I was able to paint them such that the paint etched into the surface, It won't scrape off easily at all, it has become "one" with the surface.

The 36mm diameter capacitor clamps are a thick robust type (There are many thin material gold color pasivated zinc clamps on the market now that don't look as good as they are flimsy). The ones shown have been lacquered so they won't tarnish.

To prepare the capacitors I rubbed them down with 800 grade paper, this removed the white writing which might have reacted with the paint, which is Duco type automotive lacquer.

Due to the fact that there is a small lip on the capacitor case, adjacent to that I used two turns of 1/2" wide Scotch 27 fiberglass tape to allow the clamps to sit flush on the surface.

One thing about these caps is they have a pattern on the top. It looks like the type of pattern that might be at home on the outer casing of a Dalek. I could have put filler in this, but there was the chance that any type of filler or resin could shrink and separate leading to cracks in the paint, so I decided to leave the tops as they were.

My next attempt is with oil filled capacitors. It will be interesting to see which method wins out, but whatever one it is, either will leave the electrolytic capacitor for dead (as they often are)

[MrBungle]

Those look excellent!

I'm currently debating whether or not I should restuff the nice sprague can capacitors in my HP power supply or just stick the replacements in which look very small and lame in comparison to the originals. They are literally 1/4 of the size!

[Oliver35]

These look pretty good, I will bear this in mind. Vis a vis the moulding in the end, it sounds like these caps are cased in some form of styrene, given their reaction to cellulose based products. That being the case, perhaps discs cut from 2mm plastikard or similar could be cemented on to the ends, the edges being sanded round to mimic the pressed end of a capacitor? It would probably give a more satisfactory finish than filling- a punch could even be bought or manufactured to knock 'em ou wholesale.

Oliver

[Andrewausfa]

They look the part, excellent effort. Do you know if these originally come from HK Film Capacitors?

Andrew

[Argus25]

Originally Posted by Oliver35

perhaps discs cut from 2mm plastikard or similar could be cemented on to the ends, the edges being sanded round to mimic the pressed end of a capacitor?
Oliver

Oliver, yes that would work.

The plane of the top surfaces is not completely flat though, the central piece sits a tad lower than the edges. Of course if I knew how thick this this area was it might have been ok to plane off the pattern. I guess at some point I could get a capacitor for sacrificial purposes to find out, but it seems a shame to damage such a nice part to find out.

[Argus25]

Originally Posted by Andrewausfa

They look the part, excellent effort. Do you know if these originally come from HK Film Capacitors?

I don't know where these ones originated, they are supplied by an Australian ebay seller, they could have originated in HK I guess.

The resin inside them is rock hard with an opaque blue look, I have not seen this exact particular resin before on any other caps, must be unique to the company. It looks really nice though.

(The oil filled types I'm trying are coming from the USA, so they take a couple of weeks to get here).

[Argus25]

I'm now on the second attempt to use something to eliminate most of the electrolytic capacitors from all of my vintage valve equipment restorations.

Looking into motor grade capacitors, most in the range of 20uF are around 40mm diameter and don't look right on a radio or TV chassis, though oddly in my searches I found some that had been coated in black material and re-sold as audio grade caps.

Also, the other two problems; mostly the spade terminals are spaced too far apart on motor capacitors for many radio & TV chassis holes and many (not all) have a mounting threaded rod on the top of the can.

But then, the ones in the photos turned up. Made by EPCOS.

They are 30mm diameter and will fit a 22mm chassis hole, they are relatively tall too, resembling a vintage capacitor in external appearance. They are not oil filled but a metalized polypropylene MKP type in an aluminium housing which have very high capacity (20uF in this case) for their physical size.

I was able to get 30mm (roughly about 1 & 1/8") very solid nos vintage mounting clamps which turn out to have the same hole spacing as the standard 36mm clamp. I cleaned them up and lacquered them (with DS117) and also lacquered the clamps to prevent future corrosion. Photos attached.

20uF is a good value and for many circuits and is about the right value for the filter capacitor on the valve rectifier output, without the value being too excessive. Being a 450V AC rated cap I'd expect it would be good for 600V DC without any issues.

So now I'm retro-fitting many of my restored radios and TV's with these capacitors, where possible, because I'm done with the multiple problems of electrolytic capacitors which keep coming back to haunt me relentlessly.