Boogie IIB tube question.

[dancullinane]

Just scored a IIB (60watt, reverb, eq) head from the bay. I'm in the process of changing tubes since a few preamp tubes seemed noisy especially with the reverb on. My chassis is labeled 1982. The sharpie marks for my V1 and V3 indicate that this should be a 12AT7 tube. Does this sound right? I thought V1 was supposed to be a 12AX7? Also another wierd thing was the reverb knob was acting like a gain knob, no reverb added just gain. I think this was a loose connection as this returned to normal once I checked the connection. I think this amp was originally a combo since the reverb pan seems longer thann the original slot in the bottom of the head. Looks like someone cut the hole larger.
Thanks
Dan

 

[Boogiebabies]

Does it have the fetrons? It should have 12AX7's in those positions.
You may have one with a change reverb tank. I believe it should be an Accutronics 9AB2A12 3 spring.

 

[Boogiewan Kenobi]

You can use any or all combinations in the amp.. Ususally V1 is 12AX7, BUT you can use a 12AT7 to tone down the gain a little.

12AX7 has 100% output (or 'gain')
12AT7: 60%
12AU7: 40%
12AY7: ...I think 20-30% output.

You will have more effect in the first 3 tube positions. If you are trying
to soften the gain, put it in V3. V1 will cause the whole amp's input and
tonal response to have only 60% output.... no harm, no foul. check it out.

BWK

 

[dancullinane]

Ok, Thanks Ian and Boogiebabies. Here's what kind of moron I am. Had the amp out of the cab, upside down on a bench. It's actually V2 and V4 that are marked 12AT7. the V2 might just be bad printing. the manual I downloaded shows the AT7 in V4 for the reverb.

tried an AT7 in V4, really didn't notice any difference.
Thanks guys
DC