TV / Amplifier conversion - 1954 RCA Victor

Discussion in 'Amps and Cabs' started by TEN Effects, May 28, 2015.

  1. TEN Effects

    TEN Effects Member

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    I'm not a regular poster on here, but I just finished a custom amp build, and I needed to share with other gearheads. I wrote this up for my personal FB page, so I'm just cutting an pasting for reference.

    --

    This is a 1954 RCA Victor television that I picked up here in town... the audio worked, but the picture tube was kaput, so for $50 I figured I could do something with it, and naturally it sat in the shop for 2 years until I was inspired.

    I did a custom build on an amp for a guy in Oroville, and I loved the circuit so much that I knew I wanted one for myself... and that TV was just sitting there, mocking my laziness... so I got out my Sawzall and taught it a lesson.

    First I gutted it, then I measured the inside dimensions and had John Mergili (if you need a cabinet, THIS IS THE GUY... incredible workmanship www.mergili.com) make a pine insert with a baltic birch baffle, cut for a 15" speaker (I had recently acquired a mid-60's Jensen 15", it had come out of a little old lady's organ - yes I harvest organs from old people. ‪#‎noshame‬)

    Then I chopped up the chassis (I used a modified Hammond A0-29, again out of an organ) to fit, re-skinned it with new sheet metal so I could have a clean canvas for the component layout, designed the fiberboard layout for the circuit, dry-fit the tube sockets and transformers, built the fiberboard circuit, and did the final assembly on the chassis.

    Then came the hard part... I had to cut down the metal cowling without screwing it all up... and I wanted to re-use as much of the original facade as possible, so I dry-fit the pine insert with the picture tube bezel in place. Then I marked it, cut the cowling, grinded and sanded until it was flush with the insert, then I used SS screws and finish washer to attach the cowling to the pine box, so that nothing would rattle. The other hard part was placement of the handle... it looks like it's off center, because it is - I got a long dowel, placed it underneath the amp along the long axis, and rolled it back and forth until I found the equilibrium point, and marked it - then I did the same thing for the short axis, and that marked the center of gravity... the transformers are HUGE, and very heavy, and it would have been completely lopsided otherwise, but now when you lift it, it's perfectly balanced.

    I also ended up painting the insert flat black - it just looks better from the rear, and from the front I was worried that there was too much contrast between the speaker and the surrounding baffle... especially because the wife and I picked out a really cool, but VERY sheer material for the grillecloth.. it's a cream color, with little shiny gold circles... I was on the fence about it, but she said "that's the one", and she was right, it really tied the room together.

    I also wanted to use the original knobs, but I had to make a compromise - I used the original OUTER knobs, and fixed them in place, but I ground then down very thin so they could serve as a panel on which I could mount the potentiometers. The I happened to have some new Marshall-style knobs, and they work pretty well. The left knob is the volume, and the right is the tone - however, since the 'Tone' knob is where the original channel selector would be, I dug up an 11-position detented pot - so as you change the tone, it feels like your changing channels lol.

    The little panel in the front (at the bottom, it says RCA Victor) flips down, that used to house the horizontal controls, etc - that's where I put the power switch, jewel light and input jack. One challenge was having the long wires necessary to mount the panel controls so far outside the chassis.. I had audio signal running alongside 120V AC, as well as 6.3V AC for the tube filaments. It took a little experimenting, but overall it's pretty quiet, and I was able to fish the components through the baffle and facade pretty easily.

    The circuit is based on a Masco ME-18 - that's the circuit I did the original custom build on, and it sounded incredible.. apparently the Masco is the Holy Graile of harmonica amps, so I wasn't expecting it to sound great for guitar, but as my friend Gary Yeoman said, 'there are no good harp amps - there's just good guitar amps that someone used for harmonica'... and looking at the Masco circuit, he's right - it's similar to an early 50's Fender Deluxe, in that is uses a single 6SJ7 for the preamp, a 6SC7 for the phase inverter... but the Masco specified two 6L6 power tubes, which makes it insanely loud compared to an old Deluxe.... there are a few other important differences as well.

    Anyhoo, this thing sounds incredible.. I was worried about it possible being too bassy (it's a 15, after all), so I left it completely open, but it's not - so I made a vintagey back panel for it. View attachment 1947 View attachment 1948
     
  2. garret

    garret Member

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    That looks great!
     
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  3. Darkness

    Darkness Member

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    Very cool. Nicely done.
     
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  4. zenas

    zenas Member

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    That is cool as heck !


    I never find TVs that old every "old"one I see for free is newer the the one in my living room. And that's solid state !
     
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  5. Torren61

    Torren61 Member

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    That is REALLY nice! I want one, lol.
     
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  6. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

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    Love it!! Thanks for sharing with us.

    - T
     
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  7. Baxtercat

    Baxtercat Member

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    As a longtime Jetson TV amp owner/builder, I say you won the 'net stakes this month. :)

    [​IMG]
     
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  8. joeprs

    joeprs Member

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    Very cool! Enjoy
     
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  9. TEN Effects

    TEN Effects Member

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    Thanks! It was definitely a labor of love. It got its maiden voyage tonight, outdoor, unmiced, performed like a champ... But louder haha.

    Interestingly, the original masco circuit specified a 5y3 rectifier... Which just seems silly to me, especially considering the original circuit (masco me-18) was a 1950s public address system, the type used in department stores.... Why in the world would you use such a weak rectifier, with such a large voltage drop on a circuit that had to 6l6 tubes in it? So I put a 5u4 in there, it sounded great. I'm hoping in the next week or two to have some time to knock out a nice little video demo of it.

    Oh, and that Jetson TV amp? That is awesome...
     
  10. Kristen Marshall

    Kristen Marshall Member

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  11. zenas

    zenas Member

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    In the early 50s late 40s the 5Y3 must have been the "big" rectifier tube. Real common in PAs of the time.
    People had better hearing then.

    Somewhere I've got an old book from about 1950 with plans for a "high power PA" two 6v6s, a 5Y3 and a couple of octal preamp tubes.
    It specified a Jensen P10R speaker and talked about the power with out distortion.
    Old Newcomb PA I redid had a Jensen P10S in it. (maybe a P10P forget now)

    So not only were the tubes low powered in the early 50s the speakers were too.

    As far as 5Y3s Leo built at least one early "high power" amp with a pair of them.
     
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  12. corn husk bag

    corn husk bag Silver Supporting Member

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    That thing is really nice. Your wife is to be congratulated for her part in the design. Can't wait to see and hear the video production of it. Have fun!

    Kind Regards,
    Steve
     
  13. THiwaTT

    THiwaTT Member

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    That looks amazing!
     
  14. e???

    e??? Member

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    Really cool. The jetson amp too. Is there anybody that makes something like this that you can buy? If either of you decide to, PM me, I may be a customer. I don't own a tv, and always put an amp or two where the entertainment center would usually go in the places I've lived. So it would be perfect. Thats some serious art guys...
     
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  15. ripple

    ripple To keep fresh, keep capped & cold. Silver Supporting Member

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    Beautiful and inspiring work Ten Effects!

    I love it - Nice job!
     
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