[R-390] Will they substitute... and work?

[Pete Williams]

Re  R-390/URR.

I'm re- constituting a R-390/URR and can't verify what I found odd in the RF
module, let alone if it had worked in the first instance--- I couldn't check
myself  as the  Rx not  complete.
 V202, second RF amp and normally a 6BJ6, was replaced with a 12BE6 - a
pentagrid converter, and V203 normally a 6C4, had been replaced with a 
6AB4 also a triode.
Also - conveniently, pin connexions check out correctly for both tubes with
essential elements connected to appropriate  supply points .- no internal
mods.
Apart from heater voltage - 12V in the 12BE6- one might suppose the rx
worked,
A small but intriguing technical point and I can't see why a  12BE6 or 6BE6
wouldn't function as a RF amp.
Anyone with a R-390/URR might like to do a substitution and advise.
The 6AB4 has a higher transconductance than the  6C4 which is  a maor
difference