[edisonwu]

Hi, all,
Could anyone tell me what tubes are used in HEV90? What are the brands of its stock tubes?

Are those two small tubes in the front two ECC88?

I just have two photos of HEV90 from two owners.
The first one indicates that the two small tubes are JJ's. And the other one indicates they are siemens's. Not a good tube at all.

JJ:

siemens:

 

[kevin gilmore]

Front end tube ecl83 (12ax7)
Output tubes ecl86 (6gw8)

You cannot just tube roll the output tubes without setting the bias.
You may burn up the plate resistors otherwise.

You cannot just tube roll the input tubes either, as the phase
amplitude also needs adjustment.