I'm working on a late 1965 Magnatone M15A amp, and the output transducer on the presumably-original Gibbs spring tank is open. On this amp, the tank is driven in series with a 100 Ohm resistor from one of the 7189A ultralinear output channels, each of which drives a single 16 Ohm speaker.

The tank has the letter "F" printed on the inside in the same place where I've seen "4V" on other tanks from that era, but the input winding measures 1.2 Ohms DCR, indicating an 8 Ohm input. The F tank is supposed to have a 1,475 Ohm input impedance.

Does anyone know exactly what the original tank specs were for this version of the Magnatone M15A? There doesn't seem to be much documentation on these amps other than the Magnatone site, which I have read thoroughly. I want to make sure I get the correct replacement tank.

The tank has the letter "F" printed on the inside in the same place where I've seen "4V" on other tanks from that era, but the input winding measures 1.2 Ohms DCR, indicating an 8 Ohm input. The F tank is supposed to have a 1,475 Ohm input impedance.

Does anyone know exactly what the original tank specs were for this version of the Magnatone M15A? There doesn't seem to be much documentation on these amps other than the Magnatone site, which I have read thoroughly. I want to make sure I get the correct replacement tank.

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