Replacing link cable in 1950s Blaupunkt Car radio

[Mark Hennessy]

Presumably, the replacement vibrator continues to use the step-up transformer that is part of the set? I've limited experience of these things, but this is the only type I've met before. But forgive me if I'm wrong...

However, if I'm right, it won't be anything like 1MHz as the transformer won't stand a chance of working at that sort of frequency. For something running at 1MHz, it will be using its own magnetics - in other words, it'll be a switched-mode boost converter or similar. That's almost certainly how their voltage boosters will work, but actually, 1MHz is on the high side for such a thing. Having had a quick look, I can't find any reference to 1MHz operation on the website, but I did find this paragraph:

Mechanical vibrators use points similar to those used in ignition systems of older cars. These points are subject to wear, pitting, and oxidization. Solid State vibrators switch electrical current with transistors similar to modern automobile ignition systems. While mechanical points have a life of about 100 million operations, transistors can operate reliably at 1 million operations per second for years!

From: http://www.radiosforoldcars.com/vibratorsadvantages.htm - my emphasis.

Either way, it'll be very easy indeed to determine the switching frequency. Literally 30 seconds with a 'scope

If you still haven't lugged that Philips 'scope down to your workshop yet, one of those cheap Aneng multimeters that I reviewed a while back will measure frequency - to 1MHz and beyond

[Old Sparky]

Mark, I've since checked on 'Antique Electronics Supply (Tubes and more) website, and they state that thesolid state vibrators produce a 115Hz square wave output, which will indeed be easy to measure. I haven't yet lugged that scope you kindly provided to my workshop, though I occasionally use it here at home. Oddly enough there's a similar Philips 'scope which has been in my 'getaround to it' jobs pile for ages, in the cellar in town, but I may invest in one of those Aneng Multimeters. I do, though, have a Frequency counter in the workshop, which should be quite capable of measuring the vibrators o/p frequency. I did (mis)read that same paragraph about solid state vibrators which you quoted, which is why I erroneously assumed the vibrators ran at 1Mhz. Silly me!!

[Murphyv310]

Hi.
The fact its a square wave output means it will be rich in harmonics and filtering will have to be improved. I'll now say that the problems you have are unlikely to be the same issue I had many years ago that I did. In saying that I'd still try decent bonding between the two units and see if any improvement occurs.

[Old Sparky]

I've checked the PSU/output unit again, and remember that I put one capacitor on the small piece of veroboard with the 4 x 1N4007. I had also replaced all the capacitors including the Buffer caps associated with the vibrator, as well as just about every component which needed replacing in the head unit, so it's now a case of obtaining and fitting a new reservoir/smoothing cap (the original was 16 +8uf- a Tesla TO521, btw - rated 450/500v, screwmount type measuring 24mm diameter x 65mm tall(excluding the screwmount part & tags). AFAIK the replacement I fitted was 32 +32uf, but earlier this year I used it to replace a duff can in a record player, which has long since gone back to it's owner, so I now have to source a replacement.