Seeking Help - V1 & 2 not working

[mwdavis14]

New Bluesmaster 50 build. Was up and running fine, all tubes working, with the exception of a bad impedance switch. Swapped that out tonight and all of a sudden V1 & V 2 are not heating up. There is 3.51VAC at each of the filament poles, and the tubes heat fine if placed in another amp or at the PI slot, so there is no issue w/the tubes themselves. Neither V1 nor V2 was touched when I swapped the impedance switch. Naturally, no sound if guitar is plugged into the input jacks. Plugging in to the effects return so as to bypass the pre-amp yields sound.

I'm at a loss to explain this. Any suggestions or thoughts would be VERY much appreciated!

[ToneMerc]

Based on what are saying, logic points to you interrupting the filament string some how when you exchanged the imp. switch.What does not makes sense is that even though there's voltage at the proper pin locations on the sockets, V1 and V2 do not heat up. It has be localized to that general area as V3&&V7 are not affected.

Although, in your previous post there was no sound when the imp switch was normalized, only when you bypassed it. So maybe you have other issues as well.

TM

[JazzGuitarGimp]

There is an open connection between V3 heater pins and V2 heater pins. If you tested for voltage at V1 & V2 with these two tubes installed, you will infact see approx 6.3V at both heater wires, even though there is an open circuit. This is because the cold filaments in these two tubes will conduct from the live side to the cold side. If you remove V1 & V2 and measure both legs at V2 again, you will see you only have voltage at one of the heater wires. Resolder both ends of the wire on the cold side.

[mwdavis14]

Thanks so much! This build has been a major learning process. I was not aware that the filaments of the tube would conduct current despite the flawed joint and give me misread. Pulling them has indeed identified the poor joint. Thanks again. Don't know how long this would have taken me to figure out w/o the help obtained here. I hope to return the favor down the line!