Tweet
adammerah
Junior Member
Join Date: Nov 2008
Posts: 6
5F1 Champ DIY: No sound (Tube/Transformer)
Hey guys this is my first time doing this, and my second time building a fender tweed tube amp (first one was a 5F6A 4x10 Bassman, worked perfectly).
I plugged it in last night (5F1 Champ) and was a little confused about the AC line wiring. So i plugged it in the first time and blew the HOME electrical fuse, not the amp fuse. Did that about 2 more times, (blowing the home fusebox), rearranged the wires, correctly, and then voila, heater wires are on (light) and 12AX7 is warming up. But no sound, none at all, and the rectifier (5Y3GT) and power tubes (6V6GT) are not warming up (no glow). I figured out that my dumb self switched the 5Y3GT and 6V6GT tubes, so i switched them back and the rectifier (5Y3GT) is glowing, 12AX7 is glowing but the power tube isnt. I am wondering with the voltages that the tube must have seen, could it have blown the tube? is replacement necessary? and could a busted power tube completely cut the sound in the amp or is there something else i should be looking for as well (leaking PT)?
also sorry for the long post but could i switch a 5881 for the blown (i dont know) 6V6GT to see if there is any output to the speakers?
and there appears to be no problem with the 6V6GT tube, no discoloration, no obvious problems, a broken key at the pins but am 100% positive, the pins lined up everytime.
MWJB
Senior Member
Join Date: Jun 2006
Posts: 957
You don't say what voltages you have?
Pull the 6V6 and see what heater voltages you have from pin 2 to pin 7 (use clips & connect up with the amp unplugged from the wall). Then, if you have >6.3VAC, reinstall the tube and measure plate, sceeen & cathode voltages.
If the 6V6 is blow then no, you won't have any sound, there's nothing else to transmit sound from the preamp to the OT. Most blown tubes look fine on visual inspection.
I wouldn't leave a 5881 in there for long, plate current will rise as will cathode voltage (usually beyond the 25v cap that most people fit) and the cathode resistor will be stressed. For a quick test to determine wherther the amp works you should be OK.
adammerah
Junior Member
Join Date: Nov 2008
Posts: 6
well the thing is i am looking at 6v6 diagrams and i dont see any reason why the tube would blow under those voltages. I really dont know what the voltages are unless i assume that they are what they are coming out of the PT.
It doesnt make sense that the preamp tube would heat up and the power wouldnt unless there is a problem with that tube. i will try out the 5881 and hopefully something comes out of the speakers. now i know the 5881 isnt a permanent solution thanks.
and i just want to make this clear, the amp makes ZERO discernible sounds.
I am a little confused on how you want me to check the voltages. Unplug the 6v6 and plug in the amp and measure the heater voltages from pin 2 or 7 to ground?
adammerah
Junior Member
Join Date: Nov 2008
Posts: 6
two more things:
MWJB i have read alot of your posts and you are really good at what you do, and definitely know your way around. Respect
and sitting here at work, i just realized that i didnt connect pin 2 AND 7 to 6.3 heater wires, only pin 7, and 2 to ground.
that is one solution but any ideas how that would effect the output (lack of sound)? could i have OT wires crossed for the speaker jack?
MWJB
Senior Member
Join Date: Jun 2006
Posts: 957
You did admit to putting the tubes in the wrong sockets, and that the 6V6 has no keyway...it would be very easy to blow a tube...imagine if a pin expecting 25vdc at low current suddenly gets hit with 6.3VAC at 2 amps, or vice versa?
OK so you want to measure AC volts from 6V6 pin 7 to ground. I trust that you did not connect the PT centre tap (grn/yellow) if the amp had one? This should be insulated & not connected.
If the OT wires are crossed you would most likely have a howling sound coming from the amp, rather than no sound. Check that the actual speaker plug is making good contact.
Measure DC voltages, to ground (chassis), from pin 8 of the 5Y3, pins 3,4 & 5 of the 6V6 and pins 1, 3, 6 & 8 of the 12AX7. The easiest places to measure these are where the wires from the tubes join components on the circuit board, rather than at the actual tube pins (except for 6V6 pin 3). If you are not used to doing this, use a meter with clips and connect up with the amp powered down & unplugged from the wall. After reading power down, unplug rom the wall and make the next connection, always checking connections are good & no chance of shorts.
adammerah
Junior Member
Join Date: Nov 2008
Posts: 6
well i broke the keyway when i was pulling the tubes out so it couldnt have been misaligned. -the big screw up was switching them.
now if pin 2 of the 6v6 was grounded and not connected to 6.3v (while 7 is connected to heaters) could this result in the lack of noise i was experiencing? it doesnt seem like it would.
the OT i have is a hammond fender replacement with no center tap. the output wires are yellow and black (com). i believe the yellow is connected to the circuit output and the black is grounded, that doesnt seem problematic.
i am at work so i will definately jump on the amp as soon as i get home.
i have a feeling i am going to need your back up MWJB. but it might all turn out well.
Junior Member
Join Date: Nov 2008
Posts: 6
5F1 Champ DIY: No sound (Tube/Transformer)
Hey guys this is my first time doing this, and my second time building a fender tweed tube amp (first one was a 5F6A 4x10 Bassman, worked perfectly).
I plugged it in last night (5F1 Champ) and was a little confused about the AC line wiring. So i plugged it in the first time and blew the HOME electrical fuse, not the amp fuse. Did that about 2 more times, (blowing the home fusebox), rearranged the wires, correctly, and then voila, heater wires are on (light) and 12AX7 is warming up. But no sound, none at all, and the rectifier (5Y3GT) and power tubes (6V6GT) are not warming up (no glow). I figured out that my dumb self switched the 5Y3GT and 6V6GT tubes, so i switched them back and the rectifier (5Y3GT) is glowing, 12AX7 is glowing but the power tube isnt. I am wondering with the voltages that the tube must have seen, could it have blown the tube? is replacement necessary? and could a busted power tube completely cut the sound in the amp or is there something else i should be looking for as well (leaking PT)?
also sorry for the long post but could i switch a 5881 for the blown (i dont know) 6V6GT to see if there is any output to the speakers?
and there appears to be no problem with the 6V6GT tube, no discoloration, no obvious problems, a broken key at the pins but am 100% positive, the pins lined up everytime.
MWJB
Senior Member
Join Date: Jun 2006
Posts: 957
You don't say what voltages you have?
Pull the 6V6 and see what heater voltages you have from pin 2 to pin 7 (use clips & connect up with the amp unplugged from the wall). Then, if you have >6.3VAC, reinstall the tube and measure plate, sceeen & cathode voltages.
If the 6V6 is blow then no, you won't have any sound, there's nothing else to transmit sound from the preamp to the OT. Most blown tubes look fine on visual inspection.
I wouldn't leave a 5881 in there for long, plate current will rise as will cathode voltage (usually beyond the 25v cap that most people fit) and the cathode resistor will be stressed. For a quick test to determine wherther the amp works you should be OK.
adammerah
Junior Member
Join Date: Nov 2008
Posts: 6
well the thing is i am looking at 6v6 diagrams and i dont see any reason why the tube would blow under those voltages. I really dont know what the voltages are unless i assume that they are what they are coming out of the PT.
It doesnt make sense that the preamp tube would heat up and the power wouldnt unless there is a problem with that tube. i will try out the 5881 and hopefully something comes out of the speakers. now i know the 5881 isnt a permanent solution thanks.
and i just want to make this clear, the amp makes ZERO discernible sounds.
I am a little confused on how you want me to check the voltages. Unplug the 6v6 and plug in the amp and measure the heater voltages from pin 2 or 7 to ground?
adammerah
Junior Member
Join Date: Nov 2008
Posts: 6
two more things:
MWJB i have read alot of your posts and you are really good at what you do, and definitely know your way around. Respect
and sitting here at work, i just realized that i didnt connect pin 2 AND 7 to 6.3 heater wires, only pin 7, and 2 to ground.
that is one solution but any ideas how that would effect the output (lack of sound)? could i have OT wires crossed for the speaker jack?
MWJB
Senior Member
Join Date: Jun 2006
Posts: 957
You did admit to putting the tubes in the wrong sockets, and that the 6V6 has no keyway...it would be very easy to blow a tube...imagine if a pin expecting 25vdc at low current suddenly gets hit with 6.3VAC at 2 amps, or vice versa?
OK so you want to measure AC volts from 6V6 pin 7 to ground. I trust that you did not connect the PT centre tap (grn/yellow) if the amp had one? This should be insulated & not connected.
If the OT wires are crossed you would most likely have a howling sound coming from the amp, rather than no sound. Check that the actual speaker plug is making good contact.
Measure DC voltages, to ground (chassis), from pin 8 of the 5Y3, pins 3,4 & 5 of the 6V6 and pins 1, 3, 6 & 8 of the 12AX7. The easiest places to measure these are where the wires from the tubes join components on the circuit board, rather than at the actual tube pins (except for 6V6 pin 3). If you are not used to doing this, use a meter with clips and connect up with the amp powered down & unplugged from the wall. After reading power down, unplug rom the wall and make the next connection, always checking connections are good & no chance of shorts.
adammerah
Junior Member
Join Date: Nov 2008
Posts: 6
well i broke the keyway when i was pulling the tubes out so it couldnt have been misaligned. -the big screw up was switching them.
now if pin 2 of the 6v6 was grounded and not connected to 6.3v (while 7 is connected to heaters) could this result in the lack of noise i was experiencing? it doesnt seem like it would.
the OT i have is a hammond fender replacement with no center tap. the output wires are yellow and black (com). i believe the yellow is connected to the circuit output and the black is grounded, that doesnt seem problematic.
i am at work so i will definately jump on the amp as soon as i get home.
i have a feeling i am going to need your back up MWJB. but it might all turn out well.
Comment