The radio works quite well. The dial movement is good and smooth. The set is moderately sensitive, but only has a medium audio output level.
This was the only model "Radiola" that looked like this. The cabinet shape is more like the "Radiolette" mantle set which had several models (28, 29, 30, 31, 32, 37, 54) from 1934 to 1937. The ARTS&P sticker has brown writing on a light brown background and the number is E7451. The colour must have been blue once, as the number dates this radio as being made in 1938. The model number is R48G and the serial number is B0090221.
The left hand knob is the VOLUME control, and it has no ON/OFF switch. The right hand knob is the TUNING knob, which has a spring loaded split gear drive to the under chassis tuning capacitor. The dial is a 270 degree circular type, visible through a square window. There is a toggle switch on the back for the TONE control.
DESIGN
The radio is a tall design, made to fit inside the tall cabinet. To do this, the speaker is high on the top, and the tuning capacitor is under the chassis. It is a very cramped radio. The chassis is plated and most parts are painted dark blue. There are several gold stickers on the back covering patents and the location of components. The valve types are screen printed in red.
The electrical design uses a reflex circuit, to save on the cost of one valve. It also save chassis space. The reflex circuit combines the functions of the IF amplifier and the audio preamplifier in the one valve. It also has 2 diodes in the valve which act as detector and AGC, thus using the valve for four functions. The Radiotron Designers Handbook has a section that covers the theory of reflex amplifiers. The author, Fritz Langford Smith, actually worked for AWA when he wrote the book.
The circuit shows a valve line-up slightly different to the ones in my example. The mixer oscillator is a 6A7G with AGC, the IF/detector/AGC/audio preamplifier is a 6G8G, the audio output is a 6F6G and the rectifier is a 5Y3GT. It has an IF frequency of 460 kcs.
RESTORATION
I replaced the mains cord and all the capacitors. Some were difficult to replace as it was very cramped under the chassis. Of the 2 tall wet electrolytic cans, one was missing, and there were 2 electrolytic capacitors under the chassis. These were very old and I replaced these as well. I checked the resistors and found one open circuit and bypassed by 2 in series. I replaced all 3 with one of the same style. The original resistors were the body/tip/dot style of marking, and 2 replacements were the 3 band type. I replaced these with the original style. I cleaned the chassis, and tightened the loose aerial terminal. I lubricated the dial drive, and replaced the dial lamp. There is a small hole burnt in the top of the dial. This is normal for this series of radios, and there are even replacement dials available, for this very reason. I left the dial as it was, but used a 12 volt bulb, so that it would not be as bright.
I ran the radio up on the VARIAC and all the voltages were OK, except the set was dead. It had HT, all the valves were alight but nothing, not a sound! This proved to be an open circuit field coil on the speaker. I was wondering where I would find a replacement, when I decided to look more closely. Through the magnifying glass, I could see the wires from the tags on the field coil going into the winding. I checked with the meter and moved them around till I found which one was the problem. It came off as I touched it. The coil proved to be OK so I reconnected it. The radio now worked, but had a bad speaker rattle. The spider support for the voice coil was broken on one side, so I glued this back together. The radio worked well so I didn't realign it.
The case had several cracks in it, which had been repaired previously. They were not good repairs and it seems like yellow contact cement had been used as the glue. I rebroke the cracks, scraped off the old glue, and clamped and glued it again. I used a 2 part epoxy glue and loaded it with brown bakelite dust. I made the dust by using a file on an old brown electrical fitting and catching the filings. After clamping and gluing, I scraped off the excess glue. There were 2 small pieces of the cabinet missing, so I used some 2 part epoxy putty to fill these. The instructions on the epoxy putty tube said that I could colour it with paint. When I did so, it didn't cure very well. So I did it again and then painted it. The cabinet was the buffed using car polish.
REFERENCES
AWA Radiolettes 1932-1949, 2nd Edition 1998, Peter Hughes, Historical Radio Society of Australia Inc. P.O. Box 2283, Mt. Waverly, Victoria 3149, Australia.
Copyright
Ray Robinson
