Arfa Daily wrote in message
...



Yes, a gentle blue glow is entirely normal ( although a brighter ' hard '
glow can indicate that the vacuum is ' soft ' )

For some interesting stuff on this, see

http://www.jacmusic.com/html/article...w/blueglow.htm

and

http://members.aol.com/larrysb/blue_glow.html

Arfa



Replaced that dual cap and runs cool and no hum after 10 minutes.
But after an hour a hum develops, intrusive but not as bad as before and at
the same time a serious glow forms on the zinc coloured metalwork of one
pair of the EL34s.
All 4 EL34s tested good , otherwise just 2 off 1.5K resistors to the grids
of each EL34, correct values cold.
The push and the pull from the preamp are AC coupled, leaking cap here?
Swap pairs of EL34s to see if the core glowing ones are in the new position
or the original position ?