bell & howell projector amp, think twice!

Discussion in 'Tube Audio' started by ke4mcl, Aug 2, 2010.

  1. ke4mcl

    ke4mcl Super Member

    Messages:
    3,745
    Location:
    miami fl
    grabbed this little guy that was gonna get tossed during cleanup at work. looks really cool with the wrinkle finish and very 1940's labeling and such. i was dying to look inside and see how much work it needed.

    well, popped the top and went :yikes:

    look how much crap they packed in there! holy crap that amp is full! needless to say this is definitely an "uh, no" project. its looks too cool though so its gonna sit around for a future date. seems like a good candidate to gut out and start all over inside. i found the schematic courtesy of an old AK post somebody linked to a projector amp question.
     

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  2. kpaxfaq

    kpaxfaq Tube Rectified

    Messages:
    2,384
    Location:
    Erie, Pennsylvania
    Looks like a real rats nest but am wondering with much smaller modern parts if it would be too bad going back together? Kind of hard to tell with such a small pic.

    That is real cool though, would definitely hang onto it!
     
  3. ke4mcl

    ke4mcl Super Member

    Messages:
    3,745
    Location:
    miami fl
    if i gut it and start fresh i would build a simpler PP 6v6 ckt in there. keep in mind right now its got a few inputs and tone controls.
     
  4. kcollins4

    kcollins4 Rocking somewhere

    Messages:
    5,730
    Location:
    Katy, TX
    I've got an old Film-O-Sound out in the garage. I don't recall the amp being nearly that elaborate. Of course they made a lot of models over many years.
     
  5. Endspec

    Endspec Super Member

    Messages:
    1,467
    Location:
    Quinton Ok.
    I got 2 bell & howell film sound amps and they also got 10 pounds of parts in a 3 pound box. Just search b&h recapping in this forum as this puter will not let me copy and paste.
     
    Last edited: Aug 2, 2010
  6. ke4mcl

    ke4mcl Super Member

    Messages:
    3,745
    Location:
    miami fl
    i found a site perusing through old AK posts that has a nice collection of old BH manuals, including the schems. do a search on AK under "bell & howell" in the title and its in like the first or second post.
     

     

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  7. JonL

    JonL Lunatic Member

    Messages:
    13,098
    Location:
    Long Island, NY
    Yup, I bought an old Ampro projector amp a few years ago thinking it could be a good guitar amp project, PP 6V6 and all. It's even worse than your Bell and Howell, actually worse by a whole lot. If I get a new camera soon enough I'll post a picture.
     
  8. coffee123

    coffee123 Well-Known Member

    Messages:
    540
    Wow, why is that so packed? I would think it would be a simple amp in there

    Mark
     
  9. ke4mcl

    ke4mcl Super Member

    Messages:
    3,745
    Location:
    miami fl
    well, it pays to research online. apparently these little filmosound amps have a cult following in the guitar world. some guys are gutting them and building old fender circuits into them then taking the chassis and mounting it in a vintage looking cabinet.

    these amps came with a matching speaker. some where jensens.
     
  10. bobrown14

    bobrown14 Super Member

    Messages:
    2,476
    Location:
    Philadelphia, PA
    Well all is not lost - is that a KenRad 6NS7 sitting there? If that one tests good they draw some good $$ on Eprey.

    Cheers,
    Bob
     
  11. markus

    markus Master Procrastinator

    Messages:
    4,105
    Location:
    Miami Springs FL
    I've had a couple of those come through my hands, and even with original caps they are super quiet - I can only imagine what a recap / hot rodding would do.
     

     

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  12. ke4mcl

    ke4mcl Super Member

    Messages:
    3,745
    Location:
    miami fl
    i think recapping this would turn into a nightmare. the cloth insulation is brittle and the chassis is super packed. it would totally be a labor of love. this is one of the few times i agree with the geetar amp guys, gut it, reuse chassis and iron with a different circuit.
     
  13. steerpike2

    steerpike2 Super Member

    Messages:
    3,355
    Location:
    Transvaal, South Africa
    One part of those amps that adds to the complexity is their 'switched mode' power supply: a 6V6 oscillator driven off the B+, into an RF stepdown transformer. This all to get super-smooth 4.75V DC for the exciter lamp, back when there were no diodes good for 5V, and no practically sized high-uF capacitors.

    Some of the Filmosound amps are live-chassis - not nice.
     
  14. Phototone

    Phototone Super Member

    Messages:
    1,851
    Location:
    Van Buren, AR
    The above is incorrect. There is no "switched mode" power supply. The 6V6 oscillator is FOR the exciter lamp. It is fed a ultrasonic signal, rather than DC.
    The amps were jam-packed because they had to fit inside the cast base of the projector mechanism. The circuitry comprises not only a nice push-pull 6V6 amp, but also has the socket for the phototube (lower right in your photo), and the associated circuitry to bias the phototube, as well as the oscillator circuit for the exciter lamp. Quite a lot to cram in. The example you show is from a "upper" model Bell & Howell. They did make simpler amps that were hot chassis. There was even a model that was a record/play dual magnetic and optical soundtrack model. You can imagine the complexity of that...as it had to fit into the same chassis footprint.
     

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