Can anyone identify this radio (Stromberg Carlson Maestro 4A20)

[Mullard_Nut_74]

I have searched the radio museum by valve numbers and nothing matches this radio.

Its a 4 Tube set with a 4" Rola speaker.
There is a metal plate front end with the dial glass on a 45 degree angle to the top.
Looking from the front, both control knobs are side mounted.
On/Off/Volume on the Left and Tuning on the Right

Tube Numbers: ECH33, 6ARTGT, EL33B and a 4th tube that only says Radiotron made in Australia.

The seller told me its a Stromberg Carlson but I can find no matching pictures on the net or radio museum so I tried doing the Tube numbers search.
Every radio with an ECH33 & 6AR7GT is a 6 Tube radio and this unit seems not to exist.

Bought as a chassis only so would like to see if there is a case for this radio somewhere in the world.
No markings on the chassis either but the design looks universal so they could mount the controls at the front for a different body case

See photos for more details.
5th picture is the Radiotron tube I think it is a rectifier but markings have worn off.

[paulsherwin]

The valve lineup sounds very Australian and the tuning scale is certainly Aussie. Australian radio design was surprisingly idiosyncratic for a country with a relatively small population at the time, with makers using an odd mixture of American, European and British practices, combined with some home grown ones too.

SC did have an Australian operation.

[Mullard_Nut_74]

All the other 3 tubes are Philips Miniwatt and at least 1 of them say Australia on there.
But as for any other identification marks on the radio, there just isnt any.

[paulsherwin]

Philips did sell their Miniwatt brand in Australia, and they may have manufactured valves there too. A 6AR7 would not be a valid Philips designation in Europe at that time (it's a 1935 American design).

Aussie members may have more info. Australian made valve radios are a rarity here in the UK, so knowledge is limited.

[G6ONEDave]

Definately a Stromberg Carlson, since it is printed on the painted panel behind the tuning scale, as can clearly be seen in the third photo. Might be worth looking behind the tuning scale for the model,if not already done so. A rather rare set to my mind, not even heard of the manufacturer. Good look finding info for it.

[paulsherwin]

SC were a major American manufacturer, but didn't operate in the UK or Europe.

[Mullard_Nut_74]

Thanks Paul,
It doesnt seem to match any of the Stromberg Carlson or Philips radios on radio meuseum.
Any idea what that 4th Valve is.
I mean I am guessing its a rectifier but I am still fairly inexperienced at this.
Perhaps if I had all 4 tube names I would have more luck tracking it down.
I might do a quick flick through Youtube to see any radio restos with side mount controls.
Both sides have extensions on them too that must need to be removed to get the chasis out of a bakelite case.
Total guess though.

Neil

[Mullard_Nut_74]

Originally Posted by G6ONEDave

Definately a Stromberg Carlson, since it is printed on the painted panel behind the tuning scale, as can clearly be seen in the third photo. Might be worth looking behind the tuning scale for the model,if not already done so. A rather rare set to my mind, not even heard of the manufacturer. Good look finding info for it.

OK I think I better get back to Specsavers.
I completely missed that with my glasses on and a magnifying glass.

Thanks Dave I will do some more investigations

[paulsherwin]

The 4th valve is almost certainly a rectifier. The radio appears to be a 'short superhet' with only 3 amplifying valves instead of the more common 4. Short superhets were quite common in Oz.

[Mullard_Nut_74]

SOLVED

Its a 1950 Stromberg Carlson Maestro 4A20

Knobs are side mounted in the pics and dial glass is a match.
Looks like they used quite a variation of tubes in its production which probably fouled the search engine up.

https://www.radiomuseum.org/r/stromberg_4a20.html

If I cant find a case for this radio I may just build a wooden cabinet for it.

[paulsherwin]

The ECH33 and EL33 could be service replacements. They are near equivalents of the types listed on Radiomuseum.

[Mullard_Nut_74]

Cant seem to find a diagram on radio museum for the radio.

They say it is on page 300 of Australian Official Radio Service Manual AORSM Vol 9 1950/51.

Guess I am going to be scouring through old book shops for a whike to find a copy.
Or wait till our state library is open again as it seems they have a copy

[paulsherwin]

There are only a small number of standard AM radio designs. Anything with a 6AR7 inside is likely to be a short superhet with the 6AR7 providing the IF amplifier and detector/AGC diodes. (Most similar UK designs put the diodes inside the output pentode by using an EBL31). If you search for a circuit using a 6AR7 then it will be very close to this radio.

[Mullard_Nut_74]

Thanks Paul.
I did wonder if that would be the case.
This would mean I should be able to find my way through the set using either the Air Hostess 4A19 or 4A19-A Diagrams.
Will just have to study the differences in any of the tubes so I dont mess up if there is variances in the pin outs.

Most of the components on my chassis are in good shape and still have their markings which makes life a bit easier in that respect.

Thanks again.

Neil

[Graham G3ZVT]

Originally Posted by paulsherwin

Australian radio design was surprisingly idiosyncratic...

So if this is a MW only radio, how does that elaborate dial work?

Do the large numbers refer to a band-spread switch, and if so, why do the lower two scales each have two numbers, and why no scale '1', Is that for a PU input?

And no wavelength or frequencies, just station callsigns, was that normally done?

[paulsherwin]

The tuning scales are divided up by states, so you only need to look at the section for your state. The smaller states like Tasmania usually share a division with another less populous state, while biggies like NSW or Vic have their own. Tuning scales do normally have a frequency scale at the top or bottom though.

Remember that Australia is very big and far from anywhere else, so the chances of receiving anything foreign on MW are quite remote. Some dials do have a section for NZ in case anything makes it across the Tasman.

There seem to have been more short superhets made in Oz than Europe, presumably because you could only hear the stations from your local city no matter how sophisticated the radio was, and a short superhet was adequate. They used SW to cover rural areas.

[petervk2mlg]

I've just seen this thread. I can provide a circuit diagram for that radio no problem.

P

[Mullard_Nut_74]

Thanks Peter,

I managed to get one from Trevor as well.

Anyone know how common this model was?
Do you think there is much chance of me finding a case for the radio?

[petervk2mlg]

I'd say the best bet is to keep an eye out on ebay for a complete one.

[Mullard_Nut_74]

If I cant find the exact case for it then I am tempted to buy an empty wooden radio shell for $50 and mount it in that instead.
Wont be original but still be nice as a working radio.
If that were to happen I would also be tempted to throw an FM stage in the cabinet and switch it through the phono input.