Murphy 'A124' - in the pile!

[Yorkie]

I really ought to be de-cluttering - not acquiring yet more sets to take out of someone else's loft to put up in mine, and I'm quite cross with myself for my lack of willpower, but I saw this little 1948 Murphy 'woodie' baffle set, which I think is quite stylish, so couldn't resist it and up in the loft it is, for now. The cabinet is in a state that would send Colin into raptures - it's typical of post-war sets in that the front of the cabinet is veneered in nondescript sapele veneer which has chunks out of it so will have to come off and be re-veneered. The sides are separate panels and they too are veneered in a lighter veneer and are probably sound. (The side panels on some versions were painted cream apparently).

It covers long medium and short-wave bands and despite its high price tag in its day (£20 inc PT in 1988 = £600 in 2014), it's evident that some thought went into economies of production, and also with serviceability in mind - it's probably most accessible chassis to work on that I've ever seen. Once the combined back and base panel has been removed, both sides of the chassis are accessible. Performance wise it won't set the world alight - it's basically 3 valves plus rectifier and uses a PEN45DD which is double diode triode for the AVC, detection and AF amplification.

It's AC only and uses an auto transformer so the same precautions as with a live chassis need to be exercised. They probably did this as an economy measure but it does have the advantage of not having a mains dropper, unlike the AC/DC model - the U124 so doesn't generate heat in the cabinet. The maker's instructions state: "Note: The A124 and U124 receiver chassis are connected directly to the mains.... An efficient earth is necessary for satisfactory operation of the mains filter and as a safety precaution against electric shock if the scale lamp is touched by the hands". (Exposed metal parts such as the scale lamp cursor rail and sockets, loudspeaker socket, and exposed metal parts are all connected to earth - not to the chassis).

I've attached the circuit and it will be evident that the earth socket is isolated from the chassis with a .01 cap, 'C3', listed as 1,000 VW. I'll replace that with a Class X or Y (never sure which is which - I know one is for going directly across the mains input of sets such as the DAC90A). Given that the maker's instructions call for 'an efficient earth' for the reasons stated, presumably there's no reason which I shouldn't use the mains earth connected to the earth socket?

Any thoughts?

There's a picture of an A124 here:

http://www.classicwireless.co.uk/Murphy_U124.htm

This A124 isn't going to get any attention any time soon - I've got a Dynatron GR8 record player to restore first, and for now, my Ekco AC77 restoration has stalled due to so many other commitments but I'm itching to get on with it.