Re: I got it! The story and the questions...

["Lars Mikael Verholt" <lmv@ostenfeld.dtu.dk>]

Congratulations Theo!
It's a shame with that blown speaker. Be more carefull in 
selecting helpers when you get a console organ... 

I can't help you wiht all your questions, just a couple of them.

1. The bright glow in some tubes at startup is normal. It varies with the
physical lay-out of the tubes, and comes from the heater. The heater works
just like the elektrode in an ordinary light bulb and when the metal is at
room temperature
the resistance of the metal is very low. When the power is switched on, the
heater
will draw a higth current causing it to glow. When the temperature
increases the resistance
drop and the current draw is stabilized. There you have it - pure physics.

2. Yes, vacuum tubes are known under different names in Europe and in the
US.
Here are some common types and their U.S. equivalents:

                      ECC83 = 12AX7 (also 7025 industrial spec's)
                      ECC82 = 12AU7
                      ECC81 = 12AT7
                         EF81  =  6C4
                        EF90  =  6AU6A
                        GZ31  = 5U4 (rectifier, they differ in build but
perform almost identical)

The "E" does not stand for "Europe" but is the code for 6,3V heater
voltage.
 
The 12BH7 and 6V6 tubes are only availible (to my knowledge) in the U.S.
versions.

Best of luck with your new instrument


Take care
Lars Mikael Verholt