[Boatanchors] EF Johnson thunderbolt

[KA2PTE]

Ok got brave and put the tubes back in, lit their filament, and tested my 
new plate switch on the front panel,
and I am getting a peg on the panel volt meter which means I have >3KV 
coming in from the Heathkit KS-1
power supply which is good. ( I dont plan on leaving the meter pegged like 
that, just a fast way to test for HV)

I put in a new plate switch on the front panel that feeds 115V back through 
the unused pin on the 220V input jack,
and goes into the KS-1 via the octal plug, which puts power to the plate 
relay which is connected to neutral on the other side.

This way if indeed I run into smoke, sparks or zorching its easier to kill 
the plate power from the front panel , as per the original design.

Got braver and checked for grid and or screen current on the panel meter. 
Zero, which is good in either CW, TUNE or LINEAR.

(no RF input and nothing on the amps outpur coax, and the bias cable is in 
blocking (standby) mode)

Checking for idle plate current, nothing when in CW or LINEAR , but in TUNE, 
I get a little draw. About 1 notch on the meters scale,
which comes to about 25Ma.

I had seen this all the while from the getgo and figured it was normal , as 
another owner of a Tbolt said theirs draws a "needles width" of
current in TUNE as well in the same config.

However they are using a stock Tbolt in AB2 config with the typical plate 
volts applied. I am AB1 with around 3400V, so I guess its
understandable more current is drawn with more plate volts, but I am not 
100% sure current ought to be drawn in TUNE mode at idle?
Or is this perhaps the first sign of the parasitic osc? Strange when you go 
to LINEAR mode , its gone, no draw at all.

VR tube config is the VR75 for the bias tube, (2) VR150's and (2) VR105's 
which is the default factory config.

Most updated schematic of my chassis in pdf , here: 
https://www.mediafire.com/file/c59nbazluuk0tqk/TBOLT_KA2PTE_.pdf/file


--
Steve Hearns [ KA2PTE ]