Old RCA 12ax7

[momo]

Hello everyone, I just discovered this forum and I must say its &?(&?(_ awsome!
So I dismantled an old Revere 16 mm projector and found a working almost new( the projector was not used alot) RCA 12ax7. Now I have a fender Performer 650 that uses a 12ax7 on the second channel. Can I swap the tubes and use the old one? What should I look for in the sound that would tell me that its better than the "New" chinese tube that was in the performer?
Also I ended up removing 4 old RCA 50b5, are these valuable for guitar amps, if not what can I use them for?

Thanks for the replies!

[stokes]

What to look for?Just that it sounds better to you.As for the 50b5,I never saw one used in a guitar amp.

[Rob Mercure]

50B5s became 50C5s for safety reasons

The reason that very few 50B5s are seen is that the UL made the EIAA/RMA change (or have the manufactures) change the basing. If the B5 were accidentially plugged into one of the other tube's socket in the "all American Five" style heater string radio - the 35W4 socket if I remember correctly but I'm too lazy to look at the basings - then a live chassis could result no matter which way the power plug was inserted. The 50C5 is identical to the 50B5 with the base "scrambled." If you're familiar with how to design around series heater strings then the B5 is about as useful as the C5 now that we use isolation/power trannies (lotsa junk box transistor power amp trannies have +/- 50V windings).

Rob

[bluesman60]

schematic

what model revere was it?you dont happen to have the schematic do you?i have one id like to convert but need to find out how its supposed to be as someone got to it first.

[kvflyer]

what model revere was it?you dont happen to have the schematic do you?i have one id like to convert but need to find out how its supposed to be as someone got to it first.

Are you asking how to rewire a tube socket that was for a 50B5 to use a 50C5? Note that the thread is over a year old. I will try to help if I can...