Bassman AA864 Build Problem (no sound at all)

[Jima321]

  I have built from scratch a Bassman AA864 (no mods or tweaks intended!).  I am using all new iron.  Tubes are out of another Bassman amp (working). I have absolutely no sound whatsoever.  I have power lamp and all tubes heat up.Here are my voltages at the tube sockets.  I can also upload pics of the build if need be.
 V1 (12AX7)                       
1. 180v        2. 0v           3. 2.8         4. 3.3vac       5. 3.3vac      6. 342v        7. 0v       8. 2.8v        9.
V2 (12AX7)
1. N/A         2. N/A           3. N/A        4. 3.3vac       5. 3.3vac       6. 342v       7. 0v       8. 2.7v        9. 3vV3 (12AX7)  1. 347v      2. 0v              3. 11v        4. 3.3vac       5. 3.3vac       6. 342v       7. N/A     8. 2.6v        9. 3v
 V4 (12AT7)
 1. 308v      2. 173v           3. 193v      4. 3.3vac       5. 3.3va         6. 345v       7. 73v     8. 193v       9. 3v
 V5 (6L6)
 1.  -37v      2. 3.3vac         3. 414v      4. .4v            5. .4v            6. -37v       7. 3vac    8.                           
 V6 (6L6)
 1.  -37v      2. 3.3vac          3. 415v     4. .4v            5. .4v             6. -37v        7. 3vac   8.           
 Bias Pot
 1.      -58v                      2. -34v                  3. -32v
 

[Colas LeGrippa]

Check this:


-power tubes k connected to gnd
-speaker jack faulty / bad connection
-bad connection at speaker
-input jack not wired correctly
-grids of preamp tubes need gnd ref ( bias)
-faulty guitar jack or guitar
- bad preamp tube , I presume power tubes good
-volume defective
-PI not connected to power tubes control grid  ( pin 5 )

[Colas LeGrippa]

Screen grids voltages are bad. They should be around 400 V.

[Colas LeGrippa]

Screen grids : pin 4

[sluckey]

You also need about -45V on pin 5 of the 6L6s. I highly recommend pulling the 6L6s out and insure you have -45V on pin 5 before putting them back in.

[Jima321]

Thanks  .  I did NOT have pin 6 of the power tubes supplying 429v (corrected now).

amp is producing some sound to speaker but still no signal (guitar).  just some noise when "chopsticking" around looking for bad solder joints.

I do not understand the following suggestion:  "grids of preamp tubes need gnd ref ( bias)"  Can you elaborate a little for this novice..?

[Jima321]

I adjusted bias pot and now have -45v at pin 5 of the PTs

[st]

Phase inverter voltages are far off. Check that area against schematic.

[Colas LeGrippa]

You must supply 429V on the screen grids (pin 4 ) of the power tubes. There is othing on pin 6, maybe no pins at all.  Usually we use pin 6 of the socket as a tie point for the grid leaks and grid stoppers.


Cheers !

[sluckey]

Usually we use pin 6 of the socket as a tie point for the grid leaks and grid stoppers.

Umm, not Fender. Fender puts the 470Ω screen resistor between pins 4 and 6, and puts the 1.5K stopper between pins 1 and 5. Like this...

     https://el34world.com/charts/Schematics/files/Fender/Fender_bassman_aa864_layout.pdf

[Jima321]

 Gentlemen thanks for the expertise. 
Just got back from a TDY and had time over the weekend to work on this amp.

Besides what I listed above, I found my other mistakes I made and I'll share at the risk of being ridiculed. I'll blame it on old eyes-that's my story and I'm sticking to it ; )
I used 100ohm resistors everywhere that actually required 100K resistors on the main board.Both channels are working and sounding pretty good.  There is a very low noise floor,  Other observations are:
1.  I cannot hear an audible difference when I change the bright switch position on either channel
2.  On channel two, when the volume pot is maxed out (to 11)--it cuts out the guitar volume and makes a weird noise.  I've not experience that before.

I also have question about using shielded cable on the input jacks.  I have some Belden 8451 dual shielded cable.  It consists of a black coated wire, red coated wire, and a bare wire inside.  I'm guessing I ground one end of the bare wire to chassis and use either the red or the black wire to make connection from input jack to tube socket.  Is that a correct?  I apologize if there is a thread on this-but I did not see it.   


 

 

[shooter]

used 100ohm resistors everywhere that actually required 100K resistors

you're now wise 
ALWAYS, without exception use a meter to verify EVERY R, saves enough time you start to be come younger