The UK’s first transistor radio. Manufactured in 1956. Designed in the Pye research laboratories, using transistors essentially hand-made in-house by Pye, via its “Newmarket” subsidiary. (The more common Mullard OC71 and OC72 transistors did not become available even in sample quantities until later in 1956).
Tuning was 176-568 metres (Medium Wave) plus a preset 1500m setting for BBC Light Programme.
A low IF of 120KHz was used instead of the originally designed standard 470KHz due to production changes in the IF transformers. In addition, the transistors had poor gain and the radio’s sensitivity was not great. Output power was only about 50mW, but it would run for 750 hours on a small set of batteries, a big improvement on valve sets.
At over £30 including a hefty £8 of purchase tax, it cost nearly twice as much as an equivalent portable valve radio, and still weighed 5lbs due to a generous 6”x4” loudspeaker. It was powered by 4 U2 (D Cell) batteries, as still still used in many modern radios.
Transistor line-up: V6/R3, V6/R3M, V6/R3, V6/R2, V6/R2, V10/30A, V10/30A, V10/30A. Push-pull output with no transformer but using instead a centre-tapped 120 ohm loudspeaker.
The brochure, which makes fascinating reading, highlighted the use of a printed circuit board and stated that “as far as is known, the transistor will last indefinitely”.
These photos, plus a very good write up of the Pam 710 and its development are contained in the book “Radio! Radio!”. (See Links)
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