Apache TX-1 question

[Robert & Linda McGraw (K4TAX)]

In resolving a problem with a TX-1 I observed that when only one of the two 6146's is in the PA I have no grid drive.  This occurs with the left tube in and the right tube out.  Swapping tubes always shows grid drive on one tube being in the left socket.  When the tube is put in the right socket, no drive. Confirmed that tube(s) are individually good.  Also noted that no plate current is indicated when tube in right socket but normal (at 1/2 value) when a given tube is in left socket.

I've checked the schematic and it appears that the two 6146's are connected in parallel.  Seems normal.  Thus it would seem that the tx would work with only one tube but that's not the case.  Is it by chance that the common connection within the 6146 is in series with the cathode or grid of the 2nd tube?  Without pulling the PA cage and pulling up the two top mounted sockets to check the wiring, a lot of work, can someone give me a clue.

All this started when observed that the plate of the left tube was glowing red and the right tube not.  Also observed the after a couple of minutes in transmit the grid current begin to decrease.  

Conclusion, with one tube in the left socket, plate current 125 ma,  3 ma of grid current and 75 watts output.  Move the tube to the right socket and na da, nothing, no grid current, no plate current no output.

Thanks in advance.

Bob, K4TAX

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