Properly seated valves.

Hi

I have almost completed my st120 build.
I recently purchased the KT88 and 12au7 Gold Lion Genelex? Series and I tried to insert them into their respective sockets.
I found the valves to be a tight fit, especially the 12au7 valves.
How far into the sockets should the valves be seated?
Thanks

The bottom of the tube should sit flush on the socket with no tube pins exposed.

Hi

I recently completed my ST120 build and noticed one of the resistors from V7, pins 1-8 to earth was damaged.
It was when I tried to set the bias voltage that I discovered there was an issue.
A closer look at the tubes and their sockets confirmed that the KT88 valves do not sit flush on their sockets.
The hardware used to secure the sockets to the metal case does not allow the tubes to be fully inserted into their respective sockets.
There are sections cut out of the tube base. Unfortunately they are a millimeter too small.
I was thinking of using a Dremel tool to enlarge the cutouts a millimeter so that the tubes can be fully inserted into the sockets.
Is this doable?

Gabriel wrote:

Hi

I recently completed my ST120 build and noticed one of the resistors from V7, pins 1-8 to earth was damaged.
It was when I tried to set the bias voltage that I discovered there was an issue.
A closer look at the tubes and their sockets confirmed that the KT88 valves do not sit flush on their sockets.
The hardware used to secure the sockets to the metal case does not allow the tubes to be fully inserted into their respective sockets.
There are sections cut out of the tube base. Unfortunately they are a millimeter too small.
I was thinking of using a Dremel tool to enlarge the cutouts a millimeter so that the tubes can be fully inserted into the sockets.
Is this doable?

Don't bother dremel. The tubes fits fine !
Octal tubes will grip on the sides of the pins, there is no need to get the base flush.

Hi

I decided to give it a go.
I’m not saying it was necessary, but for me it put my mind at ease.
The 10 ohm resistor V7 to earth, was previously damaged.
I’m suspicious that the socket might have contributed to this situation.
Thanks.

My KT88s have been sitting high up - on the screws for years - I never noticed a thing. No problems at all. In my new rebuild (M125s) - I accidentally bought new tube sockets (Fender Drop in) which match exactly the old ones - but they are surface mount - I found this will be nice as the tubes will now sit flush and a tad bit higher. Not that it matters - you shouldn't have any issues with them sitting on top of the screws - I'm speaking from 10+ years experience with these amps.