Ok so got in a nice set of NOS 150V reg tubes with GE logo, made in Holland. They look almost new,
and was told they are a matched set.
Upon putting them in noticed not all lit. Swapped a couple around, then they all lit. That made me inspect the sub chassis
they were mounted on. Most the 1959 solder looks still great but Johnson used stiff buss wire on everything here and one wire was straight against the sharp edge of the terminal of the wire next to it , on 2 of the sockets. The heat from that pin
over the decades, melted a groove into the insulation, and the terminal was loosely touching the exposed wire as shown in the arrows
Now all the tubes stay lit very solid, but still I had the odd idle current on the cathode of the 4-400A's in CW or LINEAR mode and the VR tubes would extinguish in those modes as I measured a little over 100mA draw on the dropping resistor
which the tubes being only 40mA rated clearly would not tolerate.
Removing the tubes restored proper screen voltages. So clearly the tubes were biased, though my standby voltage was being generated ok, but is it making it to the control grid?
Sure enough , no.
After tracing why, I found L8 , a 2.5 mH RF choke open.
The wire on one end is completely vaporized - I guess a souvenir from the unstable condition that oil cap had , perhaps
making the grid bias too unstable.
Without at least -150V on the grid, I guess these tubes can still behave like a forward biased diode from screen grid to cathode.
Now to locate a new or good used choke. The Tbolt used these same ones in 3 different parts of the chassis.
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