50's car radio repair. Smith and Sons 200X.

[robreddog]

picked up this car radio it says it is a smith and sons 200x,it has a separate power supply.
hoping someone can help me with a diagram and info about it, it's a weighty piece of kit, is it 6 or 12volt.
looks complicated any thoughts about how to go about restoring this?
pics attached.

[Cobaltblue]

Pretty certain this is the same as the Radiomobile 200X available top right

https://www.service-data.com/product...69/6899/a15469

Cheers

Mike T

[robreddog]

wow.. apologies did not realise car radios were in the database,downloading now !!

[Radio Wrangler]

It was considered a very high quality set in its day. Dad had one in his car in the early sixties, I can still hear the hum of the vibrator in the power supply/audio amplifier box.

Well worth restoring.

Smiths, later Smiths industries, used Radiomobile as the brand on their car radios. It's the same Smiths who were makers of car gauges, speedos etc and moved on to military avionics. Still on the go as Smiths Group PLC.

Oh, and they made those Sektric domestic clocks.

David

[robreddog]

So I will attempt a restoration, will have to find a battery, would anyone explain the power supply cct I have to admit to having no idea of how to check it except connect it up and see what I get out and then fault find it but some basic understand would help.
And i'll start a search to see what info I can find.

[Cobaltblue]

Rather than type it all out there are plenty of explanations on the web.

Ignore it says 6V it can be designed for any supply.

https://www.radioremembered.org/vpwrsup.htm

You can think of vibrator supplies as an early form of switch mode supply.

There are solid state replacements for vibrators available as after all this time they suffer with poor contacts.

Cheers

Mike T

[Ed_Dinning]

Hi Rob, note that if you use a vibrator the transformer will need to be a special type.
If you simply want to run the set from the mains a normal transformer will do.
They are good sensitive sets, I had one many years ago

Ed

[G6Tanuki]

At least you've got both the radio and the PSU/audio-stages: the power-supplies were often left in the car when someone removed the radio!

[Julesomega]

Well worth restoring imo, it must be the first generation of proper 'car' radios, designed throughout to be used in a car, unlike earlier car radios which were just domestic radios for fitting in a car. Here we have permeability tuning, with mechanical presettable buttons and a cordless scale mechanism, replacing a tuning gang

[robreddog]

do i assume correctly that the capacitors on the schematic being marked as mf are microfarads.
are the capacitors circled in the atatched pic bipolar
thanks.

[TonyDuell]

I think you're right on both points.

'mF' would be microfarads here, millifarads makes little sense (and is very rarely used anyway).

The capacitors are bipolar so that the thing will work with either battery polarity (+ve earth or -ve earth cars). I suppose you could fit normal electrolytcs if you know what polarity it will be used with, but it could cause confusion in the future if the radio is moved to another car so I'd not do it.

[robreddog]

thanks for confirming, much happier not to start off with too many unknowns (as someone famous said).

[Radio Wrangler]

It was a feature that was rather handy at the time. With a vibrator power pack using a separate rectifier (some 'synchronous' vibrators had additional contacts for rectifying the HT and can't do this trick) it doesn't matter whether the set is installed in a positive-earth or negative earth vehicle.

The valve heaters and the dial light don't care which way the current goes, while the HT rectifier fixes the HT polarity. The only issue is the electrolytic capacitors on the 12v side.

Smiths fitted bi-polar electrolytics to allow either polarity operation with no need for a polarity switch. Rather a neat trick.

You can use ordinary polarised electrolytics if you get them the right way round for the intended vehicle... and you label the set clearly!

David

I had a valve car radio when I was about 12 or so, the whole thing was the standard DIN size, I am sure it was all valve.

[barrymagrec]

In the fifties and early sixties there were many car radios using valves for all the low level stuff using 12 volt HT and an OC16 or similar as the audio output, thus eliminating the need for a vibrator supply.

Most of them were ordinary single units.

[robreddog]

hi, started looking at the radio power unit this afternoon,was worried that the fixing screws undid yesterday came off very easily, someone probably had a look and declined, not worried that all the capacitors will need changing (according to my tester) but the transformer secondary T102 (the primary fed by the vibrator) is open cct, smells burnt and is shot.
this to me seems a major problem i am hoping someone is going to say "not at all", the output transformer tested ok resistance wise.

[PaulR]

If it is open circuit I am sure that Ed Dinning off here can rewind it. He has done a couple for me with excellent results.

Talking of electrolytics I restored a similar set for a friend. Without thinking I connected the negative to the chassis and got a bang as I set it up to test with positive earth as that was the polarity of the car in which it was to be used.

[robreddog]

here is a pic of the xformer, that is good news i can get it rewound, going to look over the tuner and make a few checks, before making contact for a xformer rewind.

[Heatercathodeshort]

Manufactured by EMI at Hayes for Smith and Sons. J.

[PaulR]

I would replace those wax capacitors and at least check the smoothing electrolytics for leakage at working voltage before fitting the rewound transformer in case one of them caused the transformer failure.