Filmosound 285 Projector Amp Conversion Help

[Mason]

I just bought an old Filmosound 285 projector tube amp off Reverb and I'm hoping to convert it into a guitar amp.  I don't have the amp in front of me yet but I do have the schematic, which is attached below.

Right now I just need to figure out what in the amp I can keep, and what I'll have to add.  I know there's some kind of oscillator circuit that I can remove completely. I'm really just aiming to make something simple.  I know this model isn't as adaptable as other Filmosound models, but I think I can make something out of it. I love the look of the chassis, and even if I have to gut the entire thing and put in a completely new circuit it'll be worth it to me.

Any help is greatly appreciated!

[sluckey]

There's no power transformer. B+ is made directly from the AC line. IMO this is a bad candidate for a guitar amp conversion.

[Mason]

Yeah, I had figured that one out.  So besides having to add a power transformer, what other issues do you foresee? Or would you suggest just gutting it and using what parts I can from it to build something else?

[sluckey]

I don't see anything on that schematic that I would use for a guitar amp. Maybe some actual pics would speak to me.

[PRR]

Agree: this is a Death Trap, get proper isolation transformer before you get any fingers near it.

(I recently saw a UK B&H which cleverly powered all the small stages from the exciter, had the power stage transformer IN and out, and was nominally "safe" at the user jacks. That does not mean I would touch it.)

5879 and 6SL7 may amplify guitar, but there is SO MUCH crap there, that I *in this case* agree it begs for a rip-out.

And still loose ends. You do not need the 25L6 exciter, but you need its heater to make-up the series-string.

Obviously "M" is the old "K". (This is a very late drawing to still use M for 1000.)

Let's get the whole muffin on one page.

[DummyLoad]

farm the OT and the tubes - scrap the rest.


--pete

[Mason]

Bummer, I was hoping for more from this amp.  There's another version of the 285 that is powered by 6v6's and has an actual power transformer that seems like it would have been a better candidate. Unfortunately, that's not the one I have though.

So you think I can still salvage the OT?

[sluckey]

The OT should be usable for a small push/pull amp. The 5879 and 6SL7 are usable too.