[Heathkit] Help with SB-401

[Dave]

I have an SB-401 with the accessory crystal pack installed.  I cannot get the transmitter to operate independent of the 301, e.g, use the internal crystal pack rather than the 301 crystal pack.

I have reveiwed the schematic and done the voltage checks.  The hetrodyne oscillator tube is a 6AW8, a triode (V8A)/ pentode (V8B) combination.  In the circuit descriptions located within the manual, it states that I should get voltage at pin 9 of V8B only when the mode switch is in the transceive position.  This is true, measured voltage at pin 9 is indeed 149.8 volts.  However, the manual also states that when the mode switch is in the standby/ transmit/ or spot positions the 150 vdc should be absent at pin 9 of V8B, and appear at pin 3 of V8A - the 6AW8.  This is where I have problems.  The B+ voltage is removed from pin 9 of V8B, but never appears at any time at pin 3 of V8A regardless of mode switch position.  So, the natural conclusion is that I have a wiring problem.  So, I figure, no sweat I can track this down, easy enough.  I grab for the schematic.

My problem is this:  I look at the schematic and I cannot for the life of me figure out how B+ voltage gets to the plate (pin 3) of V8A.  It literally stops at the rear side of the second wafer on the bad swtich.  The cathode is at ground, and I get proper voltage at V8A pin 2.

This is driving me up a wall.  Can anyone help with some advice on how the plate of V8A receives B+ voltage?  Since I can use the receiver's crystal pack in transmit, I am certain that once I restore the B+ voltage to V8A, e.g, correct the wiring problem where ever it is, the thing will oscillate independent of the receiver and all will be well.

Any help is appreciated.


Dave, W8QW

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