B-52 AT-100 reverb problem

[ShredHed]

Hi all,
I'm new to tube amps and I have a problem with my reverb not working. The light on the footswitch lights up, as well as on the head, but no reverb. It uses a 12AT7 for the reverb. The next message is a diagram of what I have. The 12AT7 seems out of place to me and it is one of the tubes that glow on standby. Are my tubes mixed up? Also, does anyone know the tube assignment on this head? I mean, what tubes are for what? The diagram is just the pre-amp section.

Thanks for any help!

Shred

[ShredHed]

11 22 33 44 55 66 77
11 22 33 44 55 66 77
11 22 33 44 55 66 77

Tubes 1-3 = 12AX7EH (1 & 2 have metal covers over them)
Tube 4 = 12AX7B
Tube 5 = 12AT7 (Tubes 4-7 glow when on or in standby)
Tube 6-7 = 12AX7B

I have no clue what tubes are for what. I should have:

pre-amp - 4 12AX7
phase inverter - 1 12AX7
reverb - 1 12AT7
effects loop - 1 12AX7

[artsaudioinc]

B-52 AT-100 reverb problem

The complement for the AT-100 according to B52's website http://www.b52pro.com is this:
AT-100 Tube Chart
Power: 4 – 6L6 / 5881
Preamp: 4 – 12AX7
Phase-Inverter: 1 – 12AX7
Reverb: 1 – 12AX7
Effects-Loop: 1 – 12AX7
Rectifier: 1 – 5AR4

However the unit currently in our shop has a 12AT7 in the 5th position. The 12AT7 is a medium gain tube and does have the same pin-out as the 12AX7 high gain tube. Usually the two tubes can be interchanged without extremely adverse affects (things burning up, it may distort), however i am not suggesting this course of action. I would suggest you try another reverb tank, any will do for testing (might not sound right, but you'll know if the tank is bad). Looks like this post is a bit dated, but i figured id reply anyway.