problem with new tubes for my 91A

Tube DIY Asylum

Do It Yourself (DIY) paradise for tube and SET project builders.

Just got a pair of 5A/157D tube from Russia. They test ok, but when I put them in the 91A in place of the EF37A's I had in there the volume takes a bing jump and it is noisy until you place your finger on the grip cap wire of either tube. Then the volume drops down a bunch and the noise goes away. This does not happen with the EF37A's. The grip cap wires are shielded with the shielding be connected to the ground on the chasis end of the cable. Again, this is the same as for the EF37A.
SAnyone have any idea what might be happening here?

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Topic - problem with new tubes for my 91A - vinnie2 09:52:12 06/12/15 (1)

update - vinnie2 10:27:43 06/12/15 (0)

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