Wiring insulation?

[Geoff 555]

Hi everyone, this is a question about wiring insulation in a pre-war set. Single solid copper wire with which there is no problem but it is encased with a black woven sleeving which is very very sticky and where it touches other wires or chassis metal work it has 'glued' it's self to whatever it has touched. Now this carries both mains and HT and I am wondering if it is still safe.
Purely as a feeling (with out enough experience to be sure) I think it would be safer to replace it. If so, then, what with please?
Calling on your experience gentlemen.
Thank you very much.
All the best.
Geoff.

[wireful3]

Hi Geoff, It sounds as if the sleeving is Systoflex and this is a common problem. In this gluey state it is usually leaky so it would be wise to replace it. I don't know of a modern equivalent. My own approach is to replace it with silicone sleeving. It does not look the same but should be much better.

[Geoff 555]

Thanks very much John , that's what I thought. I couldn't spell 'systoflex' !!
Next question if I may , please where do I obtain the sleeving? I am going to need quite a bit.
Thanks again.
Cheers.
Geoff.

[Skywave]

Hi Geoff,

Wiring carrying mains supply current is a concern; other wiring less so.

My own preference is to replace such wiring that is carrying mains supply current with wire salvaged from old mains appliances - such as toasters, kettles, etc. These devices will have a current rating far in excess of that required in a device such as you have, therefore providing a good measure of safety. Presumably, we are not talking about an appliance that will be used in a hostile environment, such as tropical, salt-laden atmospheres, etc. However, keep the replacement mains wiring away from things that run hot.

Obviously, such salvaged wiring needs to be carefully inspected to ensure that it is not damaged, perished sleeving, etc.

As regards wiring that is not carrying mains-sourced current, wire thickness determines the current capability; thickness (& nature) of sleeving determines voltage insulation. Generally, I use plastic-covered 7/0076 * for general purpose, 14/0076 * for heaters and solid conductor for short runs and where vibration could cause a problem - e.g. oscillators.

Overall, it depends on what you're aiming at. A complete re-wire will substantially change the original appearance - which may be important - and is quite a lot of work. On the other hand, if planned ahead & done carefully, it is my opinion that it often improves the look of the set & aids future fault-finding: for example, by using a consistent colour-coding scheme that indicates the nature of the current that it is passing, e.g. red for highest HT+, orange for next lowest HT+, yellow for a.c. heater supplies, green for valve grids, black for earths, etc.

I'm sure others here will have equally useful comments to make.

(* Or the metric equivalent.)

Al. / Skywave

[kalee20]

See this thread. You want Vidaflex of a suitable diameter - woven glass-fibre braid impregnated with coloured silicone varnish. Doesn't char when touched with a soldering iron, doesn't decay, is flexible, and looks totally the part!

[Radio_Dave]

As far as I know Systoflex is only a fabric sleeve coated with shellac?

I can't see what's there to degrade with the passing of time (unlike rubber coated flex), so as long as it's not cracked I leave it alone. Where it does crack I cover the area with heat shrink tubing

David

[Geoff 555]

Hi, OK the plan is to replace the mains wiring as there is some rubber covered stuff that is bad as well.
Sleeve the HT wiring. Thank you for your help and suggestions.
Cheers.
Geoff.

[Barry Lloyd]

I seem to have a dim recollection of sleeving being made from varnished cambric. I have no idea whether this is the same thing as systoflex.
Also, I see that NOS sleeving of this type is being offered at http://www.vintage-radio-resources.com/wire.htm.

Barry