Blues Junior - no sound - tubes light -possible problem with circuit around V1?

[keithpop]

Hi y'all,
A friend of mine asked me to look at a Blues Junior.  I don't know how to tell which version it is.  The schematic at the bottom of this document seems close
(Fender_blues_junior_service_manual.pdf

Initial complaint:  Plugging a guitar chord in and no output..... but I hear some noise out of the speaker). 

I have:
- Checked most voltages (my meter has a problem with millivolts....)
- Continuity along circuit traces are ok.
- Resistor values ok
- Capacitors not shorted
- Swapped 12AX7 with known good tube

I put a clip lead between R2/Input jack to R7 (bypassing the 1st half of V1).  With this,  the amp seems to work fine but this is not the fix.


I attached a picture of where I attached the clip lead.


Why does the amp work like this?  What am I missing with the components or circuit board?


Any and all ideas of what the real problem may be would be appreciated. 


I thank you all in advance.


Keith P.

[shooter]

I've worked on a couple, the main problems have seen;
1. the yellow board with all the parts, sucks
2. the gray with red stipe cables, suck
3. the green board where the tubes plug in, sucks
beside that, not a bad sounding amp 

re-flow solder connections till you can't stand it and it'll probably work, well, till it gets bumped again

[Papa Jim]

Shooter is right. I recently fixed a friends. The green board had bad solder joints on the 2 output tube sockets from getting too hot and melting.

[keithpop]

Shooter is right. I recently fixed a friends. The green board had bad solder joints on the 2 output tube sockets from getting too hot and melting.

I failed to mention that I re-flowed the solder for the complete preamp section and it didn't fix it.  I will look at it again.  Thanks for your help!

[Papa Jim]

Lot's of BJr. repair info on this http://billmaudio.com/wp/

[keithpop]

Thanks for the responses on this posting.   I finally sat down and re-soldered every connection in the preamp section (both boards) and as y'all said....it's working. 


Thanks again for the valuable input.


Keith




by the way....this amp is not my favorite...   
- I hate PCB
- I hate ribbon cable

[Tbone55]

Sounds like you need to convince your friend he needs Doug's Blues Jr. conversion kit. 

[keithpop]

Sounds like you need to convince your friend he needs Doug's Blues Jr. conversion kit. 

Sounds like a fun thing to do but he's doing the smart thing and selling it. 


thanks
kp