Future Filmosound Project....

[Khristophorous]

This is from a part of the thread to my post on the Introduction board that kinda veered off topic. It is going to be a while until I get into this project but I thought if I got some input now it would give me a few things to think about until then. This is actually where my foray into tube amps began. There is a B&H Filmosound 185 that has PP 6V6 and that is the chassis I thought I was getting. Anyway what was delivered was Part # 05311, another amp assembly that is used by the 185 and 179 - so there is no PT and it uses 25L6 PP as I'm sure many of you already know. However since my initial disappointment I started brushing up on how much of this works and I think I have found a way to use most of this chassis. I am going to rebuild it using a hybrid of the attached Danelectro Leader schematic and the B&H original design as my general road map. I found a PT that will provide the needed AC for a 25Z6 to produce the HV. It also has a 6.3v winding which will come in handy for the preamp and PI. I'd like to use a 12AX(Y)7 preamp and a 6SN7 PI. I'll be sticking with the 25L6 PP so I can reuse the OT and because it will be part of what will make this amp a little different. I found another smaller PT to provide the heater voltages for the two 25L6 and the 25Z6. Both of these PT are Antek. I am still learning so while this is my general idea as of now, it is of course subject to change. If need be for simplicity's sake I'll stick with the preamp and PI shown in the Danelectro schematic but the transformers I found should still work. I have a 5E3 kit to assemble before I get into all this and even then there is still a lot of reading I wanna do before I work on either project. One of the attached schematics is the Danelectro I am going to draw inspiration from, the other is the B&H amp's original diagram.

[Carlsoti]

I'm working on one of these for a guy at work. It's using an Antek AS-05T320 and the circuit is leaning generally in the direction of a Matchless Clubman. It will be the last time I bother with one of these chassis. The vintage (heavily oxidized) aluminum makes grounding a chore, and they're pretty tightly packed to begin with which makes stuffing all the guts into it a p.i.t.a, as well. The "easy" way to do it would be to find a 1:1 Iso transformer and leave the amp more or less stock. My future efforts will be better spent building in appropriate chassis. YMMV.

[Khristophorous]

That is a route I still may wind up going with  - to just use a 1:1 and keep original design. It took me forever to find a clear schematic of this chassis then I found a PDF that appears to have first scans of just about all the Filmosounds - first as in not a scan of a scan of a scan...... The reason I like that Danelectro is it uses the 25L6 too and is pretty basic. So I hope that coupled with the removal of the unneeded circuits like that PEC and its supporting components that I will be able to make everything fit without it humming or worse. I sure wish I could score one of the good Filmosounds - for a good price. Do you have a schematic of what you were drawing inspiration from? I pulled up one using that name you mentioned but I am unfamiliar with them so I don't know if what I am looking at is what you were talking about.

[SEL49]

I found a PDF that appears to have first scans of just about all the Filmosounds

Would you post that pdf on the forum? Just attach to a message. If it's too big post a link where you found it.

[Khristophorous]

No problem. It's 45MB so I don't know if that is too large a file or not. Anyway the link is.......

https://phsc.ca/repair/Bell-Howell/bh_projector_filmosound-wiring_diagram.pdf

If your amp/chassis is Part# 05311 as used in a Filmosound 185 then page 127 is going to be the one for you.  The clarity versus all the other instances of this diagram online is like night and day. The artistry in the hand drawn schematics is a treat all by itself.

[SEL49]

Thanks!

[Khristophorous]

I'm just glad I could contribute something. Are you working on one as well? This PDF is fairly extensive.

[SEL49]

I'm not working on one, but I see these filmosound projects come through the forum occasionally. Always good to have some schematics.

[Carlsoti]

Do you have a schematic of what you were drawing inspiration from? I pulled up one using that name you mentioned but I am unfamiliar with them so I don't know if what I am looking at is what you were talking about.

I don't have anything drawn out. There are two Matchless Clubman schematics I've seen. One has a 10k plate resistor on the input, the other 18k. Additionally, a member here that goes by bmccowan built an amp he called the Octal Unmatched Fat Guy and posted up docs for that in a Matchless Clubman build thread here in the forum. If I can get it tidied up and tweaked this weekend, I can probably scribble out something that looks vaguely like a schematic.

[bmccowan]

Do you have a schematic of what you were drawing inspiration from? I pulled up one using that name you mentioned but I am unfamiliar with them so I don't know if what I am looking at is what you were talking about.

I don't have anything drawn out. There are two Matchless Clubman schematics I've seen. One has a 10k plate resistor on the input, the other 18k. Additionally, a member here that goes by bmccowan built an amp he called the Octal Unmatched Fat Guy and posted up docs for that in a Matchless Clubman build thread here in the forum. If I can get it tidied up and tweaked this weekend, I can probably scribble out something that looks vaguely like a schematic.

BTW - no regrets on the Octal Unmatched Fat Guy build. It is a fine sounding amp. I've made no mods and the schematic I posted is current.