one tube hot, one not
Moderators: pompeiisneaks, Colossal
one tube hot, one not
What does it mean when one power tube gets much cooler than the other?. When I switch the tubes it stays with the socket. One tube is hot as usual, the other I can put my fingers on without it burning like it should. There is no sound coming out of this amp. Its a Blues deville that has been abused, its very rusty. Ive tried good working tubes, same result. Thanks for any help
-
Stevem
- Posts: 4570
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: one tube hot, one not
First off unplug the speaker jack from the bottom of the amp and jump a 9 volt battery across it and if the speaker is good you will hear a good popping / crackle sound as the battery makes connection.
Note, this amp has 2 speaker jacks on its bottom side chassis, and the jack on the left as you face the rear of the amp is the correct one for its internal speakers.
I will assume that when you have a tube in the bad socket that the heater elements glows in the tube atleast, no?
If so proceed to below.
Do these D.C voltage checks with output tubes removed from there sockets.
Pin 3 on each socket should have around 400 volts on it as should the red wire feeding the Output transformer, if the red wire checks for power then the output transfomer is bad.
Pins 4 on each socket should have the same voltage as a good working pin 3, if not then that socket has a bad screen resistor.
Note, this amp has 2 speaker jacks on its bottom side chassis, and the jack on the left as you face the rear of the amp is the correct one for its internal speakers.
I will assume that when you have a tube in the bad socket that the heater elements glows in the tube atleast, no?
If so proceed to below.
Do these D.C voltage checks with output tubes removed from there sockets.
Pin 3 on each socket should have around 400 volts on it as should the red wire feeding the Output transformer, if the red wire checks for power then the output transfomer is bad.
Pins 4 on each socket should have the same voltage as a good working pin 3, if not then that socket has a bad screen resistor.
Last edited by Stevem on Tue Mar 21, 2017 12:49 pm, edited 1 time in total.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
-
Stevem
- Posts: 4570
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: one tube hot, one not
Also check that on pin 5 in both sockets you read a minus 48 volts or better, if not do not plug a tube into that socket!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: one tube hot, one not
Or he might get the right amount of bias voltage, but have a loose pin clamp on the grid pin (or even a loose screen pin clamp).
Last edited by tubeswell on Wed Mar 22, 2017 10:55 pm, edited 1 time in total.
He who dies with the most tubes... wins
-
Stevem
- Posts: 4570
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: one tube hot, one not
Assuming it has the heaters on ,No bias voltage while having plate, screen and a good Cathode connection would have the tube in short order roasting from red plating.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: one tube hot, one not
Maybe I'm missing something here. I don't have the amp in front of me. The OP says the problem follows the socket when he swaps tubes. If there is nothing obvious, why not just replace the socket?
Before I replaced the socket, I would:
1) check for continuity on all socket pins; clip on probe to the bottom pin and stick the other probe into the tube end.
2) live circuit check for continuity by taking voltage readings from the top/tube side of the socket instead of the bottom/pin side.
You may find one pin is not adequately tensioned or that its connection from top to bottom is broken.
Before I replaced the socket, I would:
1) check for continuity on all socket pins; clip on probe to the bottom pin and stick the other probe into the tube end.
2) live circuit check for continuity by taking voltage readings from the top/tube side of the socket instead of the bottom/pin side.
You may find one pin is not adequately tensioned or that its connection from top to bottom is broken.
-
frankdrebin
- Posts: 131
- Joined: Wed May 14, 2014 11:40 am
1 others liked this
Re: one tube hot, one not
Screen grid resistor open
Inviato dal mio m3 note utilizzando Tapatalk
Inviato dal mio m3 note utilizzando Tapatalk