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Old 29th Dec 2004, 5:08 pm   #1
Mike Phelan
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Default Component restoration - how do YOU do it?

Hi Folks
Just interested in how other members restore things like body-tip-spot resistors and old bakelite Dubilier silver-mica caps. I realise there is some availability of NOS for both of these

These are my thoughts on the subject:
Resistors - as new MF types are so much smaller, I thought of moulding a cylinder round these, and making the leads exit radially at the ends, so they could be wrapped around, and lightly soldered, followed by painting. Material - maybe plaster-of-paris with a bit of PVA wood glue in the mix?

Capacitors - Mould brown resin around a modern cap - use an original for a mould male, but what would you use as a mould material? Would p-o-p be fine enough, or would you use one of the latex-based materials? Whatever you used would have to be in a 2-piece mould because of leads emerging.

What does the team think?
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Old 30th Dec 2004, 12:30 am   #2
corvair
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Default Re: Component restoration - how do YOU do it?

For what it is worth ... probably not much! - I always scoop the innards out of old paper capacitors, and install modern devices of at least the original's ratings. Usually not hard to do, as modern components are usually a fair bit smaller.

What I have found is that paper type capacitors have generally become shorter, but the diameter is about the same as the older ones.

Resistors have often gone high in value - but if everything is working well, I don't worry about that too much.

I have a stock of older resistors, but it seems that they didn't need to be in circuit to increase in value - they did it quite happily sitting in boxes doing nothing for decades.

David

Last edited by Darren-UK; 20th May 2007 at 12:11 am. Reason: Edited to bring in-line with soft deleted posts
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Old 30th Dec 2004, 8:38 am   #3
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Default Re: Component restoration - how do YOU do it?

Thanks for your input, guys.

Rich:
Time? what's that?
If it were a later set, then I would not bother with all this, I would just replace the components.
As someone who is also involved in restoring old clocks, I have this thought about us regretting the way we restored a 1930s set in the future. To give an example, a 17c clock may have had new parts made from modern brass fifty years ago, but we would now be replacing them with 70/30 brass which is now made for this job. Not with any intention to deceive - we always put some documentation inside the item, or even mark the replaced parts.

Paul:
I hear what you are saying about choice of material and this was probably the main reason for the question in the first place.
I am fairly sure that there is something I can use with reasonable thermal and insulating properties to coat a resistor with, and AFAIK most epoxy resin compounds would be fine for withstanding 400v or so across a silver-mica capacitor potted in it. After all, many electronic ignition modules are potted in epoxy, and a typical coil primary pulse is 400-500v. I also know that triplers have been successfully repaired with this stuff - I won't tell you how I know

David:
The problem with my resistors is that quite a few of them are missing, due to a 'rebuild' done about 55 years ago. I will be doing the waxies and electrolytics in the time-honoured way.
Dunno about your valve rebuild, but I have made a few solid-state PL802s when they were in short supply!!

I would welcome any further comments, with the risk of being branded an anorak!
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Old 30th Dec 2004, 12:50 pm   #4
Richard
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Default Re: Component restoration - how do YOU do it?

Hi Mike

I agree with you, if I were restoring something a bit special (thinks, must finish my AD36), I would go to the trouble of hiding new caps in the old ones, resistors I would just use new 2W, so they look better.
Mains dropper, smoothing caps etc I would try to repair/repack, or use new components as discreetly as possible.

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Old 30th Dec 2004, 1:26 pm   #5
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Default Re: Component restoration - how do YOU do it?

Lets be honest. There is no right or wrong way of restoring a set....you do whatever you think is right for the set. I spend far more time on restoring an older (30's 40's) sets than a standard 50's set. Mind you if it was an interesting unusual 50's set it would probably get the '5 star' treatment. However there has to be a limit I think. For example in a 1930's radio I have, it uses resistors that are red in colour with the values printed on them. Some of these are quite long and thin. Not sure how you would go about reproducing those.

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Old 30th Dec 2004, 2:03 pm   #6
Mike Phelan
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Default Re: Component restoration - how do YOU do it?

Quote:
Originally Posted by Richard_Newman
Lets be honest. There is no right or wrong way of restoring a set....you do whatever you think is right for the setRich.
Totally agree with that view, Rich. I just try not to make the mistakes that many have made in other fields that I am familiar with.
If only I had kept things I once owned like the Avo sig gen, TV22, Ultra Tiger, and even colour TVs like the Kuba Florence and Philips K70!
You might be able to 'make' your resistors with Letraset, if the writing is white, and they do not get too hot. One problem with white writing is you cannot use a normal printer for it.
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Old 30th Dec 2004, 8:28 pm   #7
Radio_Dave
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Default Re: Component restoration - how do YOU do it?

Hi Mike,

I think most of the resistors in your radio are quite simular in size to modern 1w resistors. I wonder if, simply, painting modern resistors with the old style markings using heat proof paint would create a satisfactory result?

As for capacitors I have often thaught about cutting open an old cap, scanning it into Photoshop, touching it up and then elongating one end so it could be wrapped around a pencil, or something, to produce a cover for modern caps

HTH

David
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Old 31st Dec 2004, 9:00 am   #8
Mike Phelan
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Default Re: Component restoration - how do YOU do it?

Quote:
Originally Posted by Radio_Dave
Hi Mike,
I think most of the resistors in your radio are quite simular in size to modern 1w resistors. I wonder if, simply, painting modern resistors with the old style markings using heat proof paint would create a satisfactory result?
That may be the route I will take, David. For now, what I will try is to encapsulate a modern resistor in ceramic casting material, paint it, and leave it connected to my power supply for a week or so, running it at, say, twice the dissipation it will have in use, and if the coating survives, good!
Quote:
As for capacitors I have often thaught about cutting open an old cap, scanning it into Photoshop, touching it up and then elongating one end so it could be wrapped around a pencil, or something, to produce a cover for modern caps

HTH

David
Most of the cap legends would be fairly easy to reproduce from scratch, and print on paper of the appropriate colour, and then rolled up into tubes as per your idea. Most of the waxies are 'Wego' with red and black labels on the tube.
Some years ago I recapped a TV22 using 'Gumstrip' for tubes!
The silver micas I may try potting in resin with a mould taken from one of the originals.


Alan
I like your idea of keeping originals in a bag - this is fairly standard practice with antique clocks. Sadly, a non-functioning radio, however rare, is no use at all to me - I would either fix it or sell it If I fixed it, I would reproduce any components accurately - if I could not do this to an acceptable standard, it would have to go!
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Old 31st Dec 2004, 5:29 pm   #9
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Default Re: Component restoration - how do YOU do it?

Hi Gents, I have successfully "modernised" a valve. A friend of mine has a 1938 Cossor TV with a dead timebase triode pentode. The base was removed and a small 4/6.3V auto transformer fitted inside; a bracket over the top and a B9A base on the bracket. ECL80 fitted and the set is working like new. If the correct valve becomes available then it can simply be plugged in.
I am looking at other swops like this and will probably write it up for the BVWS bull in due coarse.
It is quite practical to make a 4-6.3v (or any other voltage) transformer in a 1" cube to do the heater conversion; additional components couold be added as well to "tweak" the circiut. I intend to look at the minature RF tuner triodes as a sub for early triodes in AC sets. They will also be plug replaceable(they will need a low value R/C in parallel to reduce the gain or I suspect the set will oscillate like mad!
Further comments and thoughts are invited.
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