Tube Amps / Music Electronics
For current discussions, please visit Music Electronics Forum. New: view Recent Searches.
New: visit Schematic Hell!
The sunn still shines online!

Listen to great tunes streaming live right now!

ampage archive

Vintage threads from the first ten years

Search for:  Mode:  

Heater voltage in a JTM 60?

3/20/2004 10:12 PM
Heater voltage in a JTM 60?
The schematic says it's 6.3vac. I'm getting 7.1 vac.Could the tranny be getting bad? Thanks
3/21/2004 6:21 PM
Bruce /Mission Amps

"The schematic says it's 6.3vac. I'm getting 7.1 vac.Could the tranny be getting bad? Thanks"
With all the tubes inserted?  
Book Of The Day The Ultimate Tone, Volume III by Kevin O'Connor
Have you ever wondered if there is a better way to build a Bassman, Champ, Plexi, an 800, AC-30, Bulldog or Portaflex? Or you wanted to build an SVT with off-the-shelf parts? How about a master-volume amp that doesn’t change tone with the master setting? Everything you need to know is right here, including: proper grounding techniques, wiring methods, and mechanical considerations. Eighteen chapters cover the “iconic” amps everyone knows and loves, with schematics and layouts for each, along with the technical history of the product. Eyelet-board and chassis-mounted tube socket construction is used throughout, for easy servicing and modding. TUT3 is very accessible even if you cannot fully read a schematic and is a "must have" if you are going to build an amp for your self.

Note: The Ampage Archive is an Amazon Associate site. A small commission is paid to the site owner on any qualified purchase made after clicking an associate link such as the one above.
3/21/2004 7:18 PM

Thanks Bruce thats with all the tubes in. Thanks pb
3/22/2004 10:13 PM

What's your applied AC from the wall at? Do you have a variac you could try to see what primary AC voltage will give you 6.3V heaters?  
I did an experiment once on a tube mic that had adjustable heater voltage. Above spec. introduced a lot of noise.
3/23/2004 4:02 PM
Not a problem.  
Consider: slightly  
excess line voltage  
or 6.3Vac winding  
3/23/2004 4:56 PM
Le Basseur

In fact,this IS a problem.  
The "slight excess" getting to a "6,3 VAC winding variance" means that the ECC8x tubes' filaments will worn out much faster than they should.This is not happening with the output tubes' filaments though,these being much more tolerant about over-voltage.  
I had enough trouble with stunned customers coming with their freshly-retubed amps wich after 20-30 days (read:a few dozens of hours of playing the amps) proved to have some unexplainable low cathode emission on the preamp/PI tubes.  
If you're using some expensive tubes,be prepared to loose them relatively soon...unless you don't do something and improve the situation.  
Does your amp have a primary voltage selector for the PT?If yes,you'd might want try adjusting (lowering) the filament voltage by choosing the appropriate primary winding.This will also lower the B+ to a certain ammount (20-30 V) and it's up to you to decide what's more important.  
3/23/2004 10:02 PM
Baloney. If this was the case  
every darn amp made in the tweed  
to bF days would eat tubes prematurely.  
(Since line voltage ratings were diff.  
Most guys don't "use" tubes long enough  
for this to become an issue anyway.
   Page 1 of 2 Next> Last Page>>