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greenkit · 29th Oct 2018, 11:24 pm

I did an impedance test on the faulty transformer's primary with the secondaries open-circuit: the result was 1.9k (mainly loss resistance?), and only a couple of hundred Ohms less with the 600 Ohm load connected properly. The RS Hygrade unit returned >20k under o/c conditions and 9.6k under load. Little wonder that the amplifier's AC load line was a bit depressed. Oddly I can't find any DC leakage between windings or windings-to-core. I don't know the history of this radio, but it has probably had a hard life and Sean's diagnosis is not far off the mark.

I'll post under the 'Wanted' section just in case anyone has an original transformer for disposal, though interested parties have probably read the story here anyhow. Again, thanks to all for your interest and comments.

Noel

29th Oct 2018, 11:24 pm	#19
greenkit Tetrode Join Date: Aug 2007 Location: Belfast, Northern Ireland, UK. Posts: 80	Re: Murphy B40D Audio Output I did an impedance test on the faulty transformer's primary with the secondaries open-circuit: the result was 1.9k (mainly loss resistance?), and only a couple of hundred Ohms less with the 600 Ohm load connected properly. The RS Hygrade unit returned >20k under o/c conditions and 9.6k under load. Little wonder that the amplifier's AC load line was a bit depressed. Oddly I can't find any DC leakage between windings or windings-to-core. I don't know the history of this radio, but it has probably had a hard life and Sean's diagnosis is not far off the mark. I'll post under the 'Wanted' section just in case anyone has an original transformer for disposal, though interested parties have probably read the story here anyhow. Again, thanks to all for your interest and comments. Noel