Old unmarked appliance cable - core ident

[Rockingit]

Old 1950’s appliance with 2 core, no obvious identification except that one core is copper and the other silver - any thoughts as to L & N?

 

[pc1966]

Is the cable still OK for use, or better replaced anyway?

 

[Pretty Mouth]

What is the appliance? And does it incorporate any switching or fusing in it?

 

[Rockingit]

It's an ask from a friend, 1950's reel-reel tape machine so my guess is the worst case would be a motor runs the wrong way, although any valves in it might have an interesting time?

 

[Pretty Mouth]

If wired wrong I wouldn't have thought the operation of it would be affected, it being AC current without a reference to earth?

Try wiring it one way, energise it, but keep the machine itself switched off (or if no switch, don't operate the machine, so it's open circuit). Have a good poke around at the machine with your trusty volt pen. Then wire it the other way and do the same.

You might find wired one way leaves the bulk of the appliance at line potential when open circuit, and wired the other way at neutral potential. The latter presumably being the correct way of wiring.

 

[davesparks]

If it has exposed metalwork a continuity test to each core might reveal that one is connected to the metalwork.

 

[pc1966]

That is a good point, it is probably a Class 0 appliance, not earthed but equally not double-insulated.

Some radios and TVs were "live chassis" so metalwork on neutral and potentially dangerous if metalwork exposed, good job nobody does that now! Oh wait, TN-S-C...

If they plan on using it I would suggest fitting new 3 core and earthing the chassis, assuming it is not connected to one of the live (unlikely here).

 

[Lucien Nunes]

The machine will work fine with either polarity, but as mentioned there might be a preferred way round for the mains lead to put an SP power switch in the line. DP switches weren't unknown. The USA had a convention for terminal screws identified by metal colour. Copper = line; nickel plated = neutral, but I doubt that will apply to a UK tape recorder mains lead.

Many tape recorders were class 0 but I've never met a live chassis (transformerless AC/DC) model. Radios and TVs yes, but the need to interface tape recorders to the outside world at AF rather than RF, and their generally post-dating DC supplies, and generally having induction motors, meant there was no point not having a mains transformer.

Most importantly, if the machine has not been used for a long time DO NOT PLUG IT IN!

Old valve electronics that have stood for decades, almost certainly will have faulty or unformed capacitors due to both age and lack of use. If powered-up without these first being re-formed or replaced as appropriate, knock-on damage often occurs that is far more expensive and time-consuming to fix and sometimes writes the machine off. E.g. a leaky audio coupling capacitor that needs changing could cost £0.50 from RS, but if it toasts the output transformer (even while the unit appears to be working) you have a whole new project to find a suitable transformer, which cannot be bought off the shelf and might be fairly specific to that model, plus possibly a £15 valve.

There is a set routine for preparing and waking up long-dormant valve electronics. TBH I don't know the last time I found a deck of that age that would have worked as-found, unless it has been in the hands of a collector who has kept it in use. I like old tape decks, I have over 100 machines from tiny domestic ones up to studio-quality, but (mainly on account of belts, heads and pinch rollers) they can be expensive and hard work to restore.

What model is the machine, and what is the objective of getting it running?

 

[telectrix]

L or N?? one stings, the other does not.

 

[123]

L or N?? one stings, the other does not.

I've had stings off each of L & N before.