No Voltage at Terminal 9 [resolved]

[GJW123]

Hello everyone. Just finished assembling the crack for the first time. I have followed the steps in verifying resistance...everything checks OK. LEDs are both lit. Voltage check was going well until I came to terminal 9, which i understand to be the left channel. At this location I have 0 volts, as well at B6. All others are within the normal ranges as published. I have rechecked my wiring and all solder joints to make sure I did not miss anything, and I have re-seated the tubes as well for good measure. The 6080 tube appears to be fully lit on both sides.

Any suggestions as to what may be causing this? Thanks in advance for the help. Any input is appreciated.

[Paul Birkeland]

I'd be interested in seeing photos of your build.  I would strongly suggest not running the amp (as you said, the left channel isn't working anyway )

[GJW123]

Thanks for your reply.  Here are some photos as requested.

[Paul Birkeland]

This could be as simple as a flaky joint on B5.

[GJW123]

Thanks again for your help. I cleaned up the connections at 9, 10, B6 and B5 and re-soldered. Still hitting the same wall. Took the following voltage measurements referencing 12U...

1- 77 V
2- 190.5 V
3- 0 V
4- 190.5 V
5- 74 V
6- 0 V
7- 110.5 V
8- 0 V
9- 0 V
10- 0 V

B1- 77 V
B2- 191 V
B3- 110.5 V
B4- 74 V
B5- 190.5 V
B6- 0V
B7- 0V
B8- 0V

[kgoss]

PB is the amp designer and provides the best tech support you can get for the Crack amp so I'm not hijacking his support work with you.  But I must say you have done an excellent job building your Crack.  You have crimped the wires and your solder work looks good.  So the reason I'm posting is the possibility of nicking a wire while stripping and then it breaking under the insulation after being bent.  Paul said the joint at B5 could be the problem.  Just check for a broken wire as well as the solder joints themselves.

PB will get you up and running.

[Paul Birkeland]

Ken is correct, what I see in your build shows me that you took your time and definitely paid close attention to the manual.

What resistance do you see between ground and terminal 9?

[GJW123]

Thanks guys! I appreciate all the help and respectful comments. Also...thanks for sticking with me here. I checked the wiring to and from B5 again, couldn't tell if I had a break or not, so I replaced it. Voltage measurements still the same. Resistance at terminal 9 is 2.9K.  Checked all the resistances and they look in line with the listed resistances. 

[Paul Birkeland]

In the absence of other possibilities, it might help to try a different 6080.  While we do test every tube before we ship a kit, you have all the conditions that should allow for proper voltage to develop at terminal 9.  The possible causes of something like this would generally be:

Loose wires on B4, B5, or B6
Loose connection at terminal 9 for the 3K resistor or wire going to B6
Backwards 100uF cap
Wire going to the HP jack connected to T9 instead of T10 (this would come with other major problems)
6080 that isn't conducting on one side

[GJW123]

I'll give it a shot. Any chance that it could be something within the tube socket itself?

[Paul Birkeland]

This is somewhat possible, but the sockets are brand new.  If you rocked the tube around a little in the socket and the voltage came up, that might be an indicator.  The tube itself could have oxidized pins too which might be preventing one from making contact with the socket.  You can clean off the pins or just pull the tube out and put it back in the socket four or five times to cut through any potential corrosion.

[GJW123]

VICTORY!!! It was the tube. I managed to get a new 6080 in relatively short order. Replaced and all is good. Sounds Awesome. Dead silent, no noise, music just emerges. Very pleased.  Thanks for your help.