[Amps] QRO 2500DX MARK lll 4CX800

[Bob Gibson]

After sending all three tubes down to be checked at D&C Electronics all three tubes came back bad..the test showed..that once the tube comes up to operating temperature there is a resistive cathode to grid short present possibly indicating a warped grid or screen.. My question is why would all three come back the same..I knew one tube was bad but to have all tubes test the same was a little odd..Anyone have any ideas..Bob W5RG