Lew McCoy TV set transmitters from the 1950s..

Discussion in 'Homebrew and Kit Projects' started by W1BR, May 28, 2013.

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  1. W1BR

    W1BR Ham Member QRZ Page

    I've been thinking about collecting a bunch of early homebrew transmitters, based on the W1ICP Lew McCoy novice transmitter projects that appeared in QST Magazines back in the 1950s and 1960s. My goal would be to convert these homebrew rigs back (reverse engineered) into working vintage televisions of that era.
     
  2. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    That would be a very specialized collection indeed!

    The hard part will be gathering original TV dust. ;)
     
  3. KB1WSY

    KB1WSY Ham Member QRZ Page

    When I saw your post I did a quick calendar check to make sure it's not April 1st. I am building the "65 Watts at Low Cost" W1ICP transmitter from QST, March 1961 (which I have codenamed as "LCT-65"). So far I've built only some coils, but will continue as soon as I find the time. Here are the parts:

    LCT65_parts_2.jpg

    (Not shown: the parts for the power supply, which of course was a lot of the reason why it was cheap to use old TV sets.)

    ZJH: we'd better stay out of each other's matter/antimatter fields, eh?

    73 de Martin, KB1WSY
     
  4. K5UOS

    K5UOS Ham Member QRZ Page


    Martin,

    I read most of the transmitter articles from that era when I built my transmitter. At the very least I love to read about the early homebrew gear.
    My original transmitter was similar to the one you are building but I used a homebrew VFO instead of crystals.

    You will have a lot of fun. The TX is part of my main station in the winter. I meet up with a lot of fellas that have built these vintage transmitters. Always lots to talk about.

    BTW: I started with two parallel 6L6’s with +350VDC on the plates. I decided to change to a single 6146 with +750VDC on the plate. Instead of plug in coils I have a roller inductor.

    My tube line up is 5763 buffer, 5763 driver, 2 regulator tubes for the PA screen and the 6146 PA itself.
    I have a IRFXXX (I can't remember which) HEXFET switching transistor in the cathodes of the driver and PA.

    It is simple but complicated - I use the 5VAC winding on my transformer and a PNP keying circuit to provide the bias voltage for the HEXFET. I rectify, filter and regulate the ac voltage and use the PNP switch to apply bias to the gate of the HEXFET which keys the driver and PA.

    This is how I key the TX. Something a little different I did to be able to use my old keyer and paddle.

    I cheated. I bought new Hammond iron. [​IMG]

    I am coming to Massachusetts in September for Needham High School Reunion. Great State MA!

    Good Luck with your project.

    To the OP: If I thought you were serious I would ask .....Why?


    P1010140.jpg

    100_0488.jpg
     
  5. W0AAT

    W0AAT XML Subscriber QRZ Page

    There is a TV repair shop (yes one still exists!) near me that has the dust. I don't think that back room has been cleaned since the 1920's... I already scanned it for goodies, just old TV junk.
     
  6. KB1WSY

    KB1WSY Ham Member QRZ Page

    Thanks Don! I love the pictures in your Photobucket albums, referenced in your QRZ profile. To see them is very encouraging for a total beginner like me. I am in the process of completing my first "Novice era" homebrew project, which is the "Three Transistor Receiver for the Beginner" in the 1968 edition of ARRL's "How to Become a Radio Amateur." Your can see a few pictures here: http://tinyurl.com/lrpkoya.

    After which I plan to move on to all tube-based stuff, starting with the 2-tube Novice transmitter from the same book and the 3-tube "65 Watts at Low Cost" transmitter referenced above, along with a ham bands converter for my BC-453 based on the "Novice Q5er" CQ magazine article from 1956. Another challenge is learning the code; I am up to 18 characters at 20wpm with the Koch method but it is a slow learning process!

    I am determined that when I finally get on the air, every single item in my station will be homebrewed, albeit with a lot of help from long-retired ARRL writers.

    73 de Martin, KB1WSY
     
  7. K5UOS

    K5UOS Ham Member QRZ Page

    Thanks and wow yourself Martin. Awesome metal work! Everyone is a beginner at some time.

    Dang, I am still a beginner! I have just found a comfortable niche with my modest skill level.

    I love those quality variable capacitors. Great for stability. They still make and sell them - http://www.mrshirt.com/technologies
    My last couple receivers use those same type. Can be made very rigid.

    The 1950's and 60's ARRL transmitter projects were great fun. I built several as many of the guys on QRZ have. I still have 3 or 4 of them.

    But receivers are the most fun.

    I have to smile when I remember some of my first projects particularly my receivers. I didn't have any commercial gear to compare how well they worked.

    You will have a great time with your homebrew station. Experience tells me.

    BTW: If you are like me twenty years later you are still working on "finished" homebrew rigs.

    Some things I remembered about my first receiver:

    1. Don't run the receiver too long or the power supply overheated. Once in a while a used filter capacitor popped open and gushed out smelly fumes.
    2. Watch for smoke from the receiver. Many of the resistors and chokes were pulls or used. They could go at any time.
    3. The hum will go away, or sorta will, when the wife is vacuuming. The static from the vaccum covers up that pesky hum.
    4. A 6BA6 fails with +400 VDC on the plate. Measuring voltages became standard in my workshop. Receiving tubes shouldn't need a cooling fan. Who knew?
    5. You can walk away from a +300 to 400vdc shock. Actually, more than one time. But your knees wobble the 1st time and you sweat a little.
    6. Constantly tuning your receiver as it drifts 200+ cycles per minute is all part of the fun. I still can't keep my hands off the receiver knobs.
    7. If your IF is 4MHz you can often pick up your neighbor on 80M using his legal limit amp as you listen on 40M.

    There is nothing like the first projects. They will always be the most fun to build and operate.

    Pity to those who never try to build anything. Miss a lot of good stuff!

    K5UOS
     
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