1964 Fender Bandmaster with 4 6L6 tubes ?

[bluez]

I have a AB763 Bandmaster with 4 6L6 tubes. I suspect that the amp has been rebuilt to 80-100 watts. Or was they ever produced with 4 power tubes?
When i look up in to the amp, it seems like it has been re-built to 4. Also the transformer is a bit big. This is a pre CBS amp, and i am thinking about building it back to original. Or perhaps i should just leave it?

(only two tubes are present in the 4 sockets)
I also think the transformer looks over sized, i could be wrong.

[Prairie Dawg]

Home brew fo sho. That output's a little tweaked too.

[Wilder Amplification]

I dunno that PT looks to be original. If it is and it's a 50 watt PT you ain't gettin' 100 watts outta that thing no matter how many tubes you add.

[bluez]

Is it hard to get it back to the original?

[Regis]

Sure those are 6L6's? They look like El34's.

And whats the deal with that skewed OT?

[bluez]

After what i remember this are 6L6 or 6v6. The transformer has loosen from the side. It looks big, but by looking at other pictures, it looks original. I can also see from some of the pictures that The Bandmaster had the same chasis as the dual showman (i could be wrong). It had semi stamped out space for two extra tubes. It seems like many have been tempted to re-build the amp to four tubes.

However i don't need the extra power, so i would prefer to get it back to two tubes.

[pdf64]

Pics in this thread
http://music-electronics-forum.com/t20559/
show a BF BM chassis with spare 6L6 holes.
Does the heater wiring to the additional 6L6 sockets look original?
You could check the OT ratio - feed 1Vac into the secondary and measure the voltage across the primary (amp isolated from line) - to see whether it was intended for 2 or 4 tubes.

[Ronsonic]

There are numbers on the transformers, which schematic for which Fender amp do they match? As PDF64 asks, does the wiring look original, it doesn't to me, but the pic is a bit small.

Getting it back to original depends entirely on what was done to it. I doubt anyone went to that much work and didn't change other aspects of the circuit while he was in there. But who knows. Get a map off the Fender Amp Field Guide and start comparing things.

[g1]

I think that is a 100W OT and a 50W PT. I'm looking at a silver face Band Master and the OT is much smaller. I would guess someone saw the extra holes in the chassis (with cover plates) and added tube sockets and a 100W OT. Problem is the output power is limited by the size of the PT and the extra heater draw may also be a strain on the PT.
I would agree with putting it back to stock.

[Bruce / Mission Amps]

It is most definitely NOT a Bandmaster output transformer... from the looks of it, it appears to be some kind of after market OT... probably around +50 watts.
The power tranny in these amps were not 50 watters.... they are a little smaller then the Super Reverb or Bassman power transformer.
The original output transformer is only about 35 watts and is a two screw channel mount, like a Deluxe Reverb OT, only bigger.

Because the chassis is big enough and some amps used a similar sized chassis and had a rectifier tube, if needed or wanted, it was easy remove the hole covers to use it as is.... or punch in one or two more octal socket holes in these chassis.
The "hot" mod at the time however was get the amp to about 35-40 watts using the stock transformers but with four 6V6GTs not four 6L6s. The 6V6s gave the amp similar output power but with that singing violin tone that cranked up 6V6s give up.
I wonder if this is amp is a modification of that old mod and it just has a bigger OT... maybe someone was trying to use four 6L6s with the 40 watt power transformer... not a good thing.
You could try and figure out what the OT is and consider the four 6V6GTs at around 4K primary with a 4 ohm load.....or just find an old Bandmaster, Bandmaster Reverb or Vibrolux output transformer and put it back to the stock setup with two 6L6s.

[bob p]

are you sure someobdy didn't wire up a spare set of sockets for el34, so he could choose between a pair of 6l6 or a pair of el34?

[Stratster1]

4 Tube Bandmaster

I own a Bandmaster (64, I think) and it definitely has 4 6L6 tubes and it looks very original. The chasis and wiring appear to be un-modified from new. The tubes are Sylvania 6L6GC with the code i9 AKK and have been in it for at least 30 years. It certainly is very loud and quite bass heavy compared to my other amps. I am not sure whether the tubes should be replaced. Does anyone know any more about this type of amp?