Blackface Bandmaster modding

[khaled011]

Hi all,
This is my very first post although I have joined this forum for some time.
I recently bought a fender blackface as a repair project of mine, it is now fixed and running, but since it has a tremolo channel which really I do not like, was thinking of modding it, without gutting a lot of its inside, to a Trainwreck topology by adding one half of the tremolo section tube. also changing output 6L6 into a 6V6 to go with it.
Any thoughts on this that might help me?
Other suggestions than the Trainwreck?
Thanks'

[pompeiisneaks]

Hi all,
This is my very first post although I have joined this forum for some time.
I recently bought a fender blackface as a repair project of mine, it is now fixed and running, but since it has a tremolo channel which really I do not like, was thinking of modding it, without gutting a lot of its inside, to a Trainwreck topology by adding one half of the tremolo section tube. also changing output 6L6 into a 6V6 to go with it.
Any thoughts on this that might help me?
Other suggestions than the Trainwreck?
Thanks'

First off the output transformer is designed to have an impedance for 6L6's and 6V6's need completely different impedance. 6L6GC's want about 5600 ohms impedance and 6V6 want about 8000 at that same range. (this will vary on plate voltage of course, but that's the general ballpark) do it will make the 6V6's not be in their optimal range. Also the 6V6 tends to like lower plate voltages, say 300VDC and the 6L6's are often closer to 600V. Then you may need to adjust the bias circuit to give the right plate current for 6V6's. The 'right' thing to do is to swap out the power transformer and output transformer for a setup for 6V6's which seems like a travesty to an old blackface.

As for the other mods, I don't know how to respond usually without looking at a suggested schematic. If you don't have a planned schematic to build to, it's too hard for anyone to speculate at what you 'might' be able to do with it.

~Phil

[Stevem]

A well set up blackface ( up to 1967) Bandmaster with good filters and strong output tubes will put out 36 to 42 watts of clean power, and thru 2 good 12" drivers is loud.

If you want to tame it down I would check out a power scaling kit from London power which will run you a little less cost wise then a new OT for running 6V6 tubes and allow you to bring the amp down to 2 watts should you want to.

There's plenty of spare room in the amp for the added circuit for this.

You will need to add a master volume control for the power scaling mod so now your last unused Tremolo pot will be the perfect spot for it.
Please note that if you use 1/2 of that Tremolo 12AX7 for a added gain stage be sure that it's used in the signal stream and not jumped in before one of the previous gain stages unless you want a unusable oscillating monster on your hands!

Getting this right is more then just a simple rewire of the amp for a beginner.