UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Suspect Mains Transformer in 1930s Radio P.S.U.

'LIVEWIRE?' · 25th Apr 2018, 11:15 am

Apologies for any confusion, Jerry. T.B.H. it's beginning to confuse me, but the first list - VU39(L5), SP4(L1) ML4(L3),, PM24M(L4), and MS4B (L2) are the valves which were in the 274A about 3 years ago, when I received it. They were in the positions I've indicated above, according to some notes I made at the time. According to an original printed label affixed inside the back cover, the valves should be (in the same order), 1821, MM4V, 994V, PM24M, and S4VB. As mentioned, I've already obtained & fitted a N.O.S. 1821, which is working well, at least, with no other load besides the new reservoir & smoothing caps and filter choke. If I'm correct in thinking that the ML4 (the smaller of the valves with the set) is the triode, that's the one which somehow got broken, whilst the SP4 (a gold colored Mullard one) has the later type of top cap. The MS4B may need replacing, whilst a substitute for the ML4 (994V) will be needed.

25th Apr 2018, 11:15 am	#82
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Re: Suspect Mains Transformer in 1930s Radio P.S.U. Apologies for any confusion, Jerry. T.B.H. it's beginning to confuse me, but the first list - VU39(L5), SP4(L1) ML4(L3),, PM24M(L4), and MS4B (L2) are the valves which were in the 274A about 3 years ago, when I received it. They were in the positions I've indicated above, according to some notes I made at the time. According to an original printed label affixed inside the back cover, the valves should be (in the same order), 1821, MM4V, 994V, PM24M, and S4VB. As mentioned, I've already obtained & fitted a N.O.S. 1821, which is working well, at least, with no other load besides the new reservoir & smoothing caps and filter choke. If I'm correct in thinking that the ML4 (the smaller of the valves with the set) is the triode, that's the one which somehow got broken, whilst the SP4 (a gold colored Mullard one) has the later type of top cap. The MS4B may need replacing, whilst a substitute for the ML4 (994V) will be needed.