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 Valve car radio, advice appreciated
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 Return to top of page · Post #: 1 · Written at 9:43:05 AM on 22 August 2019.
Valvejob's Gravatar
 Member since 11 August 2019
 Member #: 2378
 Postcount: 3

I have acquired an old car radio, believed to be an AWA CRUISER, probably a 935A. I'm new to this forum so not yet sure if I can post pictures. The radio has a "fitting" on one side that is labelled " POSITIVE TO FRAME". This fitting is a plug-in unit into a socket similar to a small valve. While the cap can be turned I suspect that that is only because it is secured to the base by a centre-mounted rivet and the turning does not have any functional use. Can anyone enlighten me as to the purpose of this unit? I don't want to test the radio until I'm sure it is indeed a 935A (positive eth).

2nd question: There is a nob (pot handle) on the other side which would appear to be difficult to access when the radio is mounted, which makes me wonder what it may be for? I cannot read the value of the pot but will include a photo if I can.

Looks like I cannot post photos but hope someone out there is familiar with this unit.

Regards, Richard.

Radio valve
Radio valve
Radio valve

 Return to top of page · Post #: 2 · Written at 10:12:54 AM on 22 August 2019.
Sirwin's avatar
 Location: QLD
 Member since 10 April 2009
 Member #: 465
 Postcount: 101

I'd say that the radio is definitely positive earth, but you might have to trace out the circuitry to be sure. If the output transistor emitter resistor connects ultimately to the case then it is +ve earth.

The adjustment at the back is the aerial trimmer. It is adjusted for maximum signal when tuned in to a weak station near the top of the dial. It normally only has to be adjusted on installation.

Cheers, Stuart

 Return to top of page · Post #: 3 · Written at 11:46:20 AM on 22 August 2019.
GTC's avatar
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 5836

 Return to top of page · Post #: 4 · Written at 5:05:37 PM on 23 August 2019.
Valvejob's Gravatar
 Member since 11 August 2019
 Member #: 2378
 Postcount: 3

Thanks for that Stuart, I have forwarded a few photos to the administrator so they may soon be available. Although the dial mentions it is a transistor radio I've yet to locate any thing resembling a transistor. if it's an output transistor I presume it is wired to the speaker? I am unable to sit or stand for long at the moment so my inspection has been a quicky. just trying to catch up on small jobs from the back burner while I'm recovering.

regards, Richard

 Return to top of page · Post #: 5 · Written at 5:32:57 PM on 23 August 2019.
Redxm's avatar
 Location: Tamworth, NSW
 Member since 6 April 2012
 Member #: 1126
 Postcount: 443

If you get stuck, get in touch. I'm only up the road from you in Tamworth


 Return to top of page · Post #: 6 · Written at 6:45:55 PM on 23 August 2019.
Arty41's Gravatar
 Location: Brisbane, QLD
 Member since 18 September 2010
 Member #: 102
 Postcount: 294

Richard, it's a hybrid car radio, the output is a transistor 2N301 usually located at the back with a protective cover, the rest are valves.


 Return to top of page · Post #: 7 · Written at 7:45:35 AM on 24 August 2019.
Brad's avatar
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6181

Photos uploaded.

A valve a day keeps the transistor away...

 Return to top of page · Post #: 8 · Written at 12:16:33 PM on 27 August 2019.
Valvejob's Gravatar
 Member since 11 August 2019
 Member #: 2378
 Postcount: 3

Rudolf, you are right about the 2N301. I've had a quick look to see if I could find out a bit more about it but no joy. I learnt the theory of transistors and valves many years ago but have had very little practical experience, and even that was last century. Can you confirm that this would definitely be a positive eth unit? The transistor is mounted on the heat sink and rather cacky to get at with aging blunt fingers. The radio will be up for sale when I determine it's working status, along with a couple of other valve amps (record playing units) and a few text books on old TVs. I think I even have some old radio mags tucked away somewhere. An area I've always wanted to dabble in but never got to and it's time to clean out my sheds. I'll post details of anything that may be of interest when the SALE/SWAP link opens and I've had time to sort and list what I've found. I suppose there are sites that have valves and their equivelant brands on line somewhere? I do have a booklet of such information somewhere I can probably add to the forum if this info is not readily available.

Thanks Ben, I may take you up on your offer. Is your speciality by any chance 2 way radio coms? We may have met in the past.

Regards, Richard.

 Return to top of page · Post #: 9 · Written at 9:27:12 AM on 30 August 2019.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4184

Try Kevin Chants site for a circuit.

Re Photos: Refer to Brads comment & my reply.

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