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Old 14th Jun 2018, 5:38 pm   #11
Studio263
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Join Date: Apr 2007
Location: Hampshire, UK.
Posts: 1,574
Default Re: Philips radio ID? Philips 170A

This was their first post-war set in the UK. The odd valve line up is partly to do with the non-availability of double diode triodes at the time (this type was not made for services use), hence the RF stage to make up the gain.

Not a hard set to get working, but lots of gain before the detector makes for touchy stability if anything is amiss. In particular, the metallised paint on the EF39s has to be in first class condition and properly bonded to the relevant pin or the whole thing just oscillates at its IF frequency and you get -20V (or more) of AGC bias, meaning that sensitivity effectively drops to zero. I fixed the last one by wrapping the EF39s in cooking foil with a loop of wire wrapped around between the 'hip' of the glass and the plastic base. This was then soldered externally to the pin on the base. It worked a treat, but I'm sure there are more elegant ways of doing it...
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