volume control question

[cromag]

i just bought a 76 model T.   it needs some TLC.   new tubes etc...    but i was able to fully crank it today and noticed that once the volume knob is at about three through seven the volume doesn't get much louder.   then from seven through ten the volume actually seems to get quieter.   any suggestions as what the problem might be.   could it be the tubes?  bad volume pot?  oh yeah, after just a few minutes the tubes were extremely hot.   what is the deal?   thanks for any help.

[Dave73]

So the amp actually went down in volume as you increased volume?
Was it the master or the bright/normal?
The tubes get hot because there on and your cranking the amp.
Mine get hot ass hell to the touch even biased around 40 mA
wich is kind of a conservative point for 6550's.
Tubes are alway suspect so start there. If you have extra 12ax7's switch
um out one by one two find a possible bad one. You can aslo pull the two
inside power tubes to check the power tubes two at a time.

[JoeArthur]

http://www.dangpow.com/~sunn/phpBB2/viewtopic.php?t=2810

[cromag]

joearthur,

 i did see that article you posted after i posted my questions.   very informative.   after i get it re-tubed, i'm going to cut that wire.   i am still kinda concerned that even before that "7" level, the amp isn't really that loud.   the other various amps i have, when i crank them, i have to plug my ears (i wear ear plugs to play with everytime.  so when no plugs are in, anything is too loud for me).   any idea why it isn't really that loud at around 3 and above?

[Isaac]

If a Model T isn't too loud when cranked, then either you're doing something wrong, or there's somethign wrong with it.

[cromag]

that's what i think too isaac.

[JoeArthur]

The tubes will get hot and I got the burned fingers to prove it!!  But it could indicate that the bias is not adjusted correctly.  Since you mentioned this amp needs some TLC... include adjusting the bias into that.

If it has been sitting for a while chances are good the electrolytics need replacement.  They may be leaking more voltage than desired.  This is a pretty simple process with a Model T - but make sure you get at least a 600V rating for the two primary electrolytics - accept no substitutes of a lower voltage!

Then clean all controls including the output jacks and impedance selector.  These are excellent dust collectors.

[cromag]

hey joearthur,

would you be able to post a 'list" of what to replace the caps with and all the numbers and stuff.   just so when i take it in i kinda have some info to talk to the tech about instaed of looking like more of an ass than i actually am.  as well as things that you would check out while giving some TLC.   i may miss a few things.

thanks