EI EL 84s

tralfax19645

Member
Messages
581
Hi.
I need to know if I have a defect batch of these. Pin 1 according to every tube pinout I have looked at says that this pin should be open,but on the EIs they are tied to pin 2. I like to solder the screen resister to pins 1 and 9 just for conveinience sake.JJs work fine, but put the eis in and they just hum and conduct way too much current, from the high voltage going to the screen grid resister being fed strait to the control grid. Has anyone ever heard of pin 1 of a 6BQ5/el84 being connected to an internal funtion of the tube ???????
Thanks,
Rob
 

tralfax19645

Member
Messages
581
Well,
I think I answered my own question. I bent pin 1 out of the way on this set and reistalled them, the tubes work great now. For some reason these 2 sets I bought definately have pin 1 and 2 tied together.
If you get some ,better check em!
Rob
 

fullerplast

Senior Member
Messages
6,781
Pins 1, 6, and 8 may be connected internally to other pins, depending on manufacturer. It's not unique to EI.
 

fullerplast

Senior Member
Messages
6,781
I would expect that the EL84 is not the only tube with unused pins tied internally, other than an actual N/C. Best to check a few manufacturers pinouts on a case by case basis if you are planning on using a pin as a tie point, IMHO.
 

tralfax19645

Member
Messages
581
Thanks for the info, I did know tube pinouts would vary from company to company. learn something new everyday. Guess I wount be socket mounting the screen and control grid resisters on theses anymore ! Rob
 

fullerplast

Senior Member
Messages
6,781
You're not the first one to get burned doing this. Laney had the same problem on some of their EL84 amps, except I think they used pin 6 IIRC....
 

tralfax19645

Member
Messages
581
Hi,
I meant to say I DIDNT know, sorry I misspelled.
So as I dont look too dumb, the guys at CE and mojo that I talked to didnt know either.
God this sucks.
Rob
 

Blue Strat

Member
Messages
30,066
AFAIK, Sovteks are the only EL84s which don't have internal connections to pin 1. Most or all NOS EL84s have this connection.

It's a good idea NOT to use pin 1 of the socket as a tie point.
 

tralfax19645

Member
Messages
581
Hi,
The jj EL 84s are not tied to pin 1 either. Been using them and it is only when I had the special request for the EIs is when is got blind sided by this snafu.
I am not going to use any tie points on the PT sockets anymore.
thanks for the info guys !
rob
 




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