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Sharp UW-122

Sharp-UW-122-front.jpg
The Sharp UW-122 is a radio from the early sixties or the late fifties. The circuit is based upon American designs, but with Japanse adaptations. I liked it because it is the first Japanese radio with valves I have ever seen. It is, however, not my prettiest radio.
Usually, if you talk about Japanese radios, you are talking about transistors. References to Japanese valve radios are rare. This must be one of the last Sharp radios using valves. It has a distinct "space age" look but it must have been quite cheap, with its small plastic case and small speakers. Because the Japanese were very eager to apply the transistor in their electronic stuff, the Sharp-UW-122/15 would probably not be older than 1960. But I don't have any real data on this.

This is a straightforward superheterodyne with only MW and SW bands. The IF of 455 kHz is embossed on the side of the IF transformers. There is a circuit diagram on a piece of paper glued inside, but it's barely readable. The circuit looks like an AC/DC radio for 110 V using valves with 150 mA heaters. There is one big difference, though: it has a step-down transformer for 220 V operation so it cannot be used on DC mains. The advantage is that there is no hot, energy wasting dropper resistor in this plastic case. The step down transformer is an autotransformer, so there is no separation between primary and secondary and its electrical safety is as bad as any AC/DC radio.


     The type number badge

The type number badge

All the original valves were by Japanese brands. The valve line-up is:

The 30A5 output valve is interesting because it seems to be an original Japanese design. The majority of references to it on Internet are by Japanese sites, although Philips has also produced it under the Pro-Electron type number HL94. The Hitachi data sheet I found on Frank's electron tube data site states that it is an improvement over the 35C5, having a 5 V lower heater voltage. It provides an output power of 1 W to the two speakers in this radio. The punch line "Wide Sound Personal" on the front of the radio seems to be referring to this dual speaker configuration.


     The inside of the UW-122

The inside of the UW-122

I bought this radio as non-functional. When I received it, I got a suspicion about the cause. The valves all had a shiny top (mirror inside the glass formed by cathode material) except for the 12AV6. After I pulled it, it became obvious it was leaky: the getter mirror had become white and there was a crack in the base. So I went for a spare 12AV6, which normally is not so easy in the Nederlands, but I happened to stumble across an advertisement on an auction site offering one for a really decent price. After it arrived in the mail, I tried it and all was just fine!

The radio gave acceptably good sound, and I was really satisfied. Unfortunately, it still has a few cosmetic problems. The top of the case has a lot of small pits and the knob of the band switch is missing, as one may observe from the photographs. Maybe I'll find a replacement, some time.

Copyright © 2006 by Onno's E-page         published 2006-11-27