The other thing is that, since the trem section is on one side of the field coil, what tube goes in V6 makes a big difference in the strength of the magnetic field generated by the coil and hence the volume of the amp. The more current draw, the more voltage across the coil, the stronger the field. A 6v6 leaves almost no clean headroom and a volume not much above conversational levels; a 6L6 gives reasonable volume with some clean headroom. Neither make the trem work.
This amp, alone among anything I've ever seen, seems to absolutely require a certain tube set to work at all. Wrong power tubes = wrong load which throws the heater voltage on the preamp tubes way off, bias on the power tubes way off (since the DC preamp tube heaters are connected to the bias, which in turn is connected to everything else). Can't substitute rectifier tubes either, only a 5Y3 makes the thing work right. Obviously there is some tube that will make the trem work when inserted at V6, since there are no bad parts in that circuit. Anything else won't cut it.
The other odd thing is, though it is clearly a fixed bias, grounded cathode amp with dissipation around 70% at idle with various 6L6s in the power sockets, it acts a lot like a class A amp in that Ia drops when not at idle, and never goes above idle current.
This amp, alone among anything I've ever seen, seems to absolutely require a certain tube set to work at all. Wrong power tubes = wrong load which throws the heater voltage on the preamp tubes way off, bias on the power tubes way off (since the DC preamp tube heaters are connected to the bias, which in turn is connected to everything else). Can't substitute rectifier tubes either, only a 5Y3 makes the thing work right. Obviously there is some tube that will make the trem work when inserted at V6, since there are no bad parts in that circuit. Anything else won't cut it.
The other odd thing is, though it is clearly a fixed bias, grounded cathode amp with dissipation around 70% at idle with various 6L6s in the power sockets, it acts a lot like a class A amp in that Ia drops when not at idle, and never goes above idle current.
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