Need ideas for New Build/Old Chassis

[lexluthier72]

Hey Folks,
I figured Mods might be a good place for this one....I have an old Bell and Howell Filmosound amp chassis, that Im looking for build ideas on. It has 7 tube sockets, and what Im assuming to be a pretty decent OT. I will need to find a PT approximately the same size as the old one....Anyone have ideas on what might suit this layout?
-Erin

The inside is pretty much gutted due to a PT gone horribly bad....

[lexluthier72]

Bump....More info...The original tube compliment is: 5y3, 6v6(3), 6sl7. It also has a couple misc sockets, that I likely will not use....anybody got any cool ideas?
-Erin

[Chuck H]

I can't imagine where you might find one, but a schem would be helpful at this point. Three 6V6s is an odd arrangement for any amp. I think Gibson used a 6V6 for voltage regulation in a small bass amp once. But it's still an obscure arrangement. So lets assume that two of the 6V6s are the power tubes. You have plenty of preamp tubes and a standard rectifier tube. So you could ignore the use of the odd "third" 6V6 and just build any 2 x 6V6, tube rectified amp you like. The unused socket won't mind. You may even end up using it for an octal preamp tube.

Just pick a 2 x 6V6, tube rectified amp you like the sound of and try to find a schem and or layout for that amp. That would be a good place to start.

Chuck

[lexluthier72]

I have not found any smaller chassis amps that use 2 6v6's although, I may have overlooked an obvious canidate. I do have the schematic...I am hoping for something fender-esque.
-Erin

[Chuck H]

If you can arrange to post the schem here it would help. Then we can al see what we're starting with. I personally am interested to see what kind of amp uses three 6V6 tubes and series chokes.

Chuck

[J Martin]

The third 6V6 was for an oscillator circuit. There are a whole bunch of circuits that would fit that chassis. It looks from the photo that it has all octal sockets. Use a 6SL7 for an input tube and maybe an octal pentode for a second channel. One interesting circuit would be the Brown Fender Deluxe.

[lexluthier72]

For some reason, I could not clip the individual schematics, but its a model 179. The schematics are at the link below....keep in mind the chassis is only 11"x4" It looks like a fender deluxe power tranny from antique electronic supply is a direct drop in for this chassis, and is close to the spec of the orig....Looking at schematics....how bout the 5c3? Will the above tranny work with the early deluxe? Id rather not drill holes or mod for 12ax7s

http://www.film-tech.com/warehouse/manuals/AMPS.pdf

[Chuck H]

Well... It's kind of a PITA trying to follow the schem when it can only be seen in small pieces at a time on this PDF. But I can tell you that as far as the schems show, there are no chokes used in the audio amps power supply. You may have chokes there, or maybe not. In any case there are other trannies in the schem that will be of no use to you in this build. The only trannies suitable for the amp you want to build are the OT and PT. Other than that I would suggest that you simply salvage whatever film caps, pots, switches, tube sockets, etc. from this chassis to use in a different build. The way the chassis is layed out is not ideal for a guitar amp. If you will be pushing it into overdrive or using a pedal in front you may get oscillations because of the layout you would be forced to use.

JM2C

Chuck

[lexluthier72]

Chuck,
Thanks for looking at the schem. I think Im going to build a 5c3 out of it. looks pretty simple, and it should fit fine in the existing chassis.
-Erin

[petemoore]

I drew 10 layouts when '18-watting' an RCA amplifier, after reading much about how to avoid oscillations and hum, star grounding etc.

[lexluthier72]

Thanks for all the input guys....So far, I have one question (probably in a long line of questions...) On a 5c3, How does one get rid of the extra inputs? Is it as simple as removing the last input from the end of the board, that whole circuit up to the 6sc7 and pulling the second input and the 75k resistor from the board? Also, I have a crazy Idea of using the "photo tube" as the "on light" Anybody ever do this? Any insight would be great.
-Erin
Btw....I ordered the power tranny this morning...it is the exact drop in measurements with no mods to the chassis...and is correct for the 5c3

[lexluthier72]

Bump...Any thoughts on questions in previous reply would be great. Im thinking of the one volume one tone layout. I could do 2 inputs as I have space for them, and just do away with the second volume (it looks as if this is a second channel, and not a master vol) someone correct me if Im wrong. These ideas based on looking at the schematic for the 5c3. I dont want to drill extra holes in the chassis. The new power tranny arrived today, dropped right into the chassis. I am wanting to use the original output transformer, The orig schematic states 300v to the middle lead (red) and brown and blue going to the pair of 6v6s. Where is the best place to get the 300v from?

[lexluthier72]

Bump....Anyone....???

[Fred2202]

I have modded one of these filmosound amps for guitar use and they sound pretty good with minimal changes. I think it was the 385 chassis with 6V6 output tubes. The chassis are so small and tight that it is a royal pain in the neck to work in them. There is almost no room for additional pots if you want to put in a gain control and a two or three knob tone stack. Since you have the guts stripped out it might be easier to transfer what you have into a larger chassis and work from there.