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 Autovox valve car radio
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 Return to top of page · Post #: 16 · Written at 4:20:37 PM on 4 March 2023.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 1267

Rob, has a point.
In the end the set may best be mounted up on wood display stand with a mains transformer in place of the vibrator AC supply.
Would look good with a chrome antenna.
The whole lot could then be run by mains with correct earthing for safety and no need to worry vibrators and critical caps.
A conventional power tranny with 6-volt heater winding would work with the heaters rewired on the chassis.
Much simpler.
If it's going back into a car, well then, it's the whole hog.

Fred.


 
 Return to top of page · Post #: 17 · Written at 5:13:44 PM on 5 March 2023.
Wodbore's Gravatar
 Location: Nowra, NSW
 Member since 19 February 2023
 Member #: 2539
 Postcount: 12

Confusion reigns. Some of the component labels on the schematic (thanks GTC) are confusing (to me). For example, some capacitor labels used are 250, 0.1, or 8.(full stop), while some resistors are labelled 0.27, or. 1. or. 47.k(full stop).
Can’t find a Google answer, except that conventions seemed to change over the years. Touched one capacitor to check identity, and it fell apart.


 
 Return to top of page · Post #: 18 · Written at 5:14:37 PM on 5 March 2023.
Wodbore's Gravatar
 Location: Nowra, NSW
 Member since 19 February 2023
 Member #: 2539
 Postcount: 12

......


 
 Return to top of page · Post #: 19 · Written at 5:23:55 PM on 5 March 2023.
Wodbore's Gravatar
 Location: Nowra, NSW
 Member since 19 February 2023
 Member #: 2539
 Postcount: 12

......


 
 Return to top of page · Post #: 20 · Written at 8:00:33 PM on 5 March 2023.
BringBackTheValve's Gravatar
 Location: Linton, VIC
 Member since 30 December 2016
 Member #: 2028
 Postcount: 472

Yep, you are in a pickle, the schematic is 'screwy', but we can work through this.

First job---do nothing till you take pictures, as Maarc suggested. Focus on resistor colours. Draw diagrams. Lots of coloured diagrams.

There will be other members now searching I'm sure for the correct schematic, so hang in there mate, patience required.

The vibrator is Australian, a good hint.

You must treat this one as a long term project.


 
 Return to top of page · Post #: 21 · Written at 8:05:01 PM on 5 March 2023.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 1267

Wow!
your post stuttered a bit!

Circuits used to rate caps in microfarads.
like 0.1 .
That is 0.1 mf.
Known as 100n now.

Similarly resistors were rated in megohm.
Like 0.5
Known now as 500k.

Yes it's a convention thing and old fossils like me just do conversion in the head.

You will get used to it and after looking at lots of circuits you will get used to likely values anyway.

Cheers, Fred .


 
 Return to top of page · Post #: 22 · Written at 6:26:21 PM on 6 March 2023.
Wodbore's Gravatar
 Location: Nowra, NSW
 Member since 19 February 2023
 Member #: 2539
 Postcount: 12

Almost there?? Looking at other circuits, and using some logic, I think this is the translation for components.

Capacitors:
.005 .01 .04 .1 .5 are all uF
50 100 250 425 are all pF

Resistors:
.27 = 270k .47 = 470k 1. = 1M

The only mystery now is the 8. capacitor near the 2 x 2200 resistors below the 6M5. Could this be an electrolytic doing a bit of filtering, but not correctly classified as such by the symbol drawn?


 
 Return to top of page · Post #: 23 · Written at 7:56:26 PM on 6 March 2023.
BringBackTheValve's Gravatar
 Location: Linton, VIC
 Member since 30 December 2016
 Member #: 2028
 Postcount: 472

Yes, it is on a HT rail, and forms a pi filter with the 30μF electro. Can you see it? An inspection will soon reveal if it's an electro cap or not.


 
 Return to top of page · Post #: 24 · Written at 8:25:22 PM on 6 March 2023.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 1267

By George, I think he has got it!!!

(apologies to My Fair Lady and Rex Harrison)

Yes there is a lot assumed in many circuits, the 8 would be 8μF .

Fred.


 
 Return to top of page · Post #: 25 · Written at 9:22:16 AM on 7 March 2023.
Wodbore's Gravatar
 Location: Nowra, NSW
 Member since 19 February 2023
 Member #: 2539
 Postcount: 12

Thanks guys. Now for some careful progress.


 
 Return to top of page · Post #: 26 · Written at 1:49:37 PM on 7 March 2023.
Wodbore's Gravatar
 Location: Nowra, NSW
 Member since 19 February 2023
 Member #: 2539
 Postcount: 12

Another of the seemingly endless queries. Where to buy capacitors in the range 50 - 425 pF (as shown on schematic) in Australia? Assume they would be high voltage (up to 600v), and for use on AC?


 
 Return to top of page · Post #: 27 · Written at 10:53:37 PM on 7 March 2023.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 2405

Au.element14.com, for one.

But they would be mica caps and don't need replacing, usually. Just do the electros and the papers.

The 425pF is the padder. Leave it alone.

Watch out for that special cap I mentioned previously.


 
 Return to top of page · Post #: 28 · Written at 7:32:15 AM on 8 March 2023.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 2161

You might want to contact Kevin Chant and purchase one of his solid state vibrators. Much more reliable.
Check his website kevinchant.com for contact details.


 
 Return to top of page · Post #: 29 · Written at 7:19:34 PM on 9 March 2023.
Wodbore's Gravatar
 Location: Nowra, NSW
 Member since 19 February 2023
 Member #: 2539
 Postcount: 12

I have sent 2 pics to Brad. One pic is view of the underside of the chassis - other pic is view of the station pointer mechanism.

Firstly, the underside pic (and inspection) shows all components are original - no replacements. Perhaps the components should be left untouched, and left as a historical item for future generations - give it a careful clean-up, and do some preservation. Repaint the case.

I have been removing rust on some parts of the case in a 9/1 molasses bath - it has also removed most of the original paint. Looks like the steel has been copper coated prior to painting. I will repaint gunmetal hammertone - close to original.

Other pic is looking down on the pointer drive mechanism - what a piece of engineering!! Gear drive on the right turns brass rod at bottom which has a machined spiral. As the rod turns, the pointer follows the spiral across the station plate - pointer supported by the top brass rod. Note also the globe is permanently soldered into position under the spiralled rod - no lamp holder - globe replacement would have been a pain!

I have identified all components using the schematic. Some adjustments to schematic needed - probably some production changes not documented on the schematic? The 47k resistor on the triode grid of the 6AE8 is actually 27k. The 0.005μF across the 470k resistor of grid No. 1 of the 6M5 is not fitted. There is an extra capacitor connected separate from others across the oscillator coil - jammed up against the side of the case (on the left of the chassis) - value illegible, and measuring in-circuit is useless. The 8. capacitor is electrolytic - symbol on schematic incorrect.

Opinions?

Should I treat the radio as a historical item, and leave components intact??

If so, what to use to preserve components??

Any other suggestions??

Autovox car valve radio
Autovox car valve radio


 
 Return to top of page · Post #: 30 · Written at 7:26:04 PM on 9 March 2023.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 2405

You are talking about a museum grade restoration where you melt the insides out of the paper caps and put new caps inside the sleeves. Seal the ends with hotmelt and you have a new cap that looks original.

I would only consider such an effort for a radio that was truly rare and "desirable".

Sadly, yours is neither.

Unless you have the '50s Morris Minor, of course! Or maybe an FJ Holden.


 
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