Circuit Symbol

Probably the tube filaments.

Incidentally, I have seen people selling solid-state plugin replacements for vibrators.

Splendid suggestion, John. I must admit that never occurred to me. I'm afraid this chap is a stickler for originality and wants everything done with old parts. I did venture to suggest a modern, monolithic converter but that was rebuffed most vociferously. Sigh...

Those are the valve heaters.

The valve books I read while growing up used the word filament for a directly heated valve where the filament was the cathode. And heater for a heater which heats a cathode (indirectly heated).

I'd stick a transistor radio behind the old knobs.

It may have a dynamic speaker too, which could be hard to replace.

Buy the vibrator replacement and rub some dirt on it, or stuff it into the ugly old can.

Oh, I found the problem! It says "Made in the UK" on the label! HEH

They are the filiments (heaters) for the tubes (valves). It is very common for the tube circuits to put all the filiments in one area of the schematic. It makes it simpler to look at when they are all in a series or parallel circuit. The numbers at them are the pin nubers of the tubes. As there are 8 tubes in the radio they will be labled V1 to V8 with the V standing for the Valve they are in.

Ralph ku4pt

FWIW, the ARRL equivalent is shown in the uppermost-rightmost corner on this schematic symbol sheet:

Danke,

Naturally an American valve radio would still be working perfectly after 86 years, it's fair to assume?

Joseph Lucas, the inventor of darkness, died in 1902. His legacy lasted another century.

Cheers

Phil “former TR7 owner” Hobbs

That's what I'd do if it were my car. You can get AM radios on 1/2" square boards; just add your own L and variable C and a TDA2611A for the audio. All sorted out. I told him I'd do it that way for free, but if he wants to do it the hard way I can only offer guidance and whatever vintage spares I have.

Oh dear. I feel your pain, Phil. The only vintage TR7 I'd want to own would be a Drake. ;-)

I recall that vibrators weren't reliable. Finding a replacement would be tricky.

Post a pic of the Bentley!

Well, we needed something to lubricate the roadways.

Simple enough to contrive a replacement using an old telephone exchange relay if he'll accept that. It's miraculous they functioned for as long as they did, given the hammering they took due to the way they were wired.

I'll see what I can do....

I vaguely recall that they oscillated at somethig over 100 Hz. I powered an old car radio with 60 Hz instead of the vibrator, and the radio's step-up transformer ran hot.

The early designs were a bit unreliable but it was often due to contact damage when the suppression capacitors failed. Later designs were much better engineered, with extremely ingenious mechanical arrangements to minimise contact bounce and ensure that everything worked correctly at the resonant frequency.

The later ones were surprisingly quiet, both mechanically and electrically. They carefully arranged the centres of mass of the vibrating parts so that they didn't translate the vibations into unwanted modes.

If the set was specifically designed to only work with a vibrator, the rectifier could be omitted and a second set of synchronously-vibrating contacts would do the rectification. That more than made up for any efficiency losses in the vibrator itself.

There is a story that, at his retirement party, a German motor industrialist was asked by a journalist what single factor he thought made the most important contribution to the supremacy of the German motor industry. He hesitated and then said "Joseph Lucas & Co. of Birmingham".

They ran at a frequency as high as reasonable for a mechanical device. This allowed for a smaller transformer.

Vibrating contacts were the first switching regulators. Auto generators - before alternators - used a hysteretic oscillating contact closure to drive the field coil. That was very efficient and not especially reliable.