Topic ClosedTube Help : Peavey Mace VT Head

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Direct Link To This Post Topic: Tube Help : Peavey Mace VT Head
    Posted: Aug 08 2012 at 9:19am
  a friend of mine just gave me a mace vt head. he said it wasnt working and if i wanted to mess with it it was cool. it had 5 sovtek 6l6 tubes in it so i put a ruby in the empty socket and it fired right up and sounded great. i did some reading after i got it home and discovered that i could run it with 4 or 2 tubes which i liked better than mixing brands. any-who to the issue, no matter how many tubes i run in it (6 ,4 ,or 2) one of them ends up getting hotter than the others.
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Direct Link To This Post Posted: Aug 08 2012 at 10:25am
 Hi there,
 
Same tube always gets hot if you move it to a diffeent socket, OR does one particular socket overheat any tube you place in it?  Important difference here. 
 
 
When you say overheat, is the plate (outer metal jacket just inside the glass) glowing orange ?
 
 
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Direct Link To This Post Posted: Aug 08 2012 at 10:28am
  different tubes and different sockets
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Direct Link To This Post Posted: Aug 08 2012 at 10:30am
  and the middle of the plate will turn orange and get brighter and brighter
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Direct Link To This Post Posted: Aug 08 2012 at 11:23am
 That is nuking your tubes, btw. If you have multiple tubes doing it , and the problem doesnt stay with any particular socket or tube, then you have a bias voltage problem. That MACE is old enough to need a capacitor replaced in the bias voltage section of the power supply. When the bias voltage starts to sag and cant reach a high enough voltage to keep the tube turned OFF, it will allow the tube to conduct and it starts to overload, resulting int he plate glow.  Its also just possible that the bias voltage is set wrong, but off the top of my head I cant remember if that amp even has a bias adjustment. I think it does, it would possibly be accessible via a 1/4" sized hole in the chassis on the left side of the frame. small flat screwdriver would be needed to adjust it but be careful, over turn it and you will break it easily.  DON'T let the tubes do this for very long or you will take the chance of damaging the high voltage power supply of the amp.   
 
IF YOU ATTEMPT YOUR OWN REPAIR-: TUBE AMPS ARE LETHAL. There is about 500-600 votls inside to drive those tubes. Be careful.
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Direct Link To This Post Posted: Aug 08 2012 at 11:35am
 http://www.6v6power.ru/inf/Amplifier/Peavey/Peavey%20Mace-Deuce%20(VT%20Series)%20Power%20Amp.jpg
Schematic here.
 
Check the voltage on IR26 and IR25 and see if they are the same. If not, this could be where your problem is, as this supplies the voltage to bias each side of the power tubes. Remember what Eric says  TUBE AMPS ARE LETHAL 
 
Take it to Eric and let him check it out for you. It's worth the money to be safe.
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Direct Link To This Post Posted: Aug 08 2012 at 11:58am
 Start with just 2 tubes, divide the sockets in half, 3 on the left make up one group, the 3 on the right are the 2nd group.  This places one tube each on left half and right half. IF both tubes glow, then you have an overall bias voltage issue that is affecting IR25 and IR26 at the same time. Most likely in C11,C12,C13,IR8,IR9,IR10.
IF ONLY one tube glows, add another one on that half and see if they both then glow but not glowing on the other half. That would definately indicate IR25 or IR26, but not both. 
Good Luck!
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Direct Link To This Post Posted: Aug 08 2012 at 12:08pm
its only one on one side so if i use 2,4,or 6 only 1 will glow. im not about to mess with with anything internally. i may just have to bring it to you sometime when i have the money eric.
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Direct Link To This Post Posted: Aug 08 2012 at 12:15pm
 LOL, now I'm really confused..  If you use 6 tubes, only 1 TUBE out of the 6 glow?
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Direct Link To This Post Posted: Aug 08 2012 at 12:18pm
  yes "no matter how many tubes i run in it (6 ,4 ,or 2) one of them ends up getting hotter than the others."
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Direct Link To This Post Posted: Aug 08 2012 at 12:25pm
 OK, and if you pull that glowing tube out, do others start to then glow?
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Direct Link To This Post Posted: Aug 08 2012 at 12:27pm
  a different one will yes
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Direct Link To This Post Posted: Aug 08 2012 at 12:29pm
 on the same half or can it switch from ..say the left half to the right half ?
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Direct Link To This Post Posted: Aug 08 2012 at 12:31pm
  it can from left to right
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Direct Link To This Post Posted: Aug 08 2012 at 12:50pm
 Thats a new one. i think one of your power tubes are bad. The grid is shorted to the cathode -which is grounded and is pulling down the other tubes just into conduction. Best guess answer untill you get it looked at. I don't charge for estimates. I will charge you $15 to test your power tubes. I'm out of town till next week. Email me sometime and come over, I'll help you.
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Direct Link To This Post Posted: Aug 08 2012 at 1:01pm
  it does it with the rubys and the sovteks ive tried 2 sets of tubes
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