Ok - I RE-learned a lesson on this radio. I had restored this radio for a friend and they sent it back to me complaining about how noisy it was and how much feedback, etc it produced. It was unstable.

Turns out I had used GLASS tubes for the 12SQ7 and 12 SA7 and I should have used METAL, since PIN 1 on all of the sockets had a ground connection. The necessary shielding wasn't there!!

Fool me once shame on you. Fool me twice , shame on ME!

Lou

:Ok - I RE-learned a lesson on this radio. I had restored this radio for a friend and they sent it back to me complaining about how noisy it was and how much feedback, etc it produced. It was unstable.
:
:Turns out I had used GLASS tubes for the 12SQ7 and 12 SA7 and I should have used METAL, since PIN 1 on all of the sockets had a ground connection. The necessary shielding wasn't there!!

:
:Fool me once shame on you. Fool me twice , shame on ME!
:
:Lou
:
Lou from Lew:
I have heard of manufacturers using glass tubes, and also the unused pin one for a tie point. When a metal tube is inserted, the metal "shield" is then connected to something hot and acts as a capacitor to the tube elements, causing all sort of nutty problems.
Lewis