The Amp Garage

I seem to remember that it's a 'BAD THING' to apply B+ to cold tubes - cathode poisoning was the issue maybe? Pete.

Also try searching for PEM nuts. Pete.

Regarding screen grid resistor size, from 470R to 1K there is some local negative feedback happening with EL84 IME. That's my understanding also. My thinking to limit screen dissipation is, rather than fit such large screen grid resistors to each tube, to 'common' them up then bypass to ground and ...

So, for the screen supply, that's three 1k resistors in total?
Thanks for the info - Pete.

According to the link, the GA-20 was made between 1950-1954. About 5,000 were made.
http://www.superiormusic.com/page199.htm

Check further down the page, GA-20 carried on till 1961, in 2 tone styling. Pete.

As you've found, fast blow fuses aren't suitable for high inrush current applications. 1/2 amp slow blow are available (long link as don't know what size fuseholder) http://uk.farnell.com/jsp/search/browse.jsp?N=500006+1001439+5446152&Ntk=gensearch_001&Ntt=500mA+fuse&Ntx=mode+matchallpartial&No=0&ge...

How are the screen supply resistors arranged on your JTM45? Like a regular plexi, 470 or 1k per screen grid, fed from the choke output node? Or like the Iss7 of the bluesbreaker RI, with a 1k from the choke output, then splits into 2 470ohm resistors to the screen grids http://www.marstran.com/1987T...

Have you got grid stoppers on the output tubes? Pete.