Collins 20V-2 wiring help needed

Discussion in 'Amplitude Modulation' started by N6YW, Jun 16, 2019.

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  1. N6YW

    N6YW Ham Member Volunteer Moderator QRZ Page

    828DBDD6-E83F-4FB6-9F92-016029AF7C17.jpeg F32E7640-9B75-4E72-BD09-4205F01E3059.jpeg Greetings
    After acquiring this beautiful transmitter it became readily apparent that documented wiring numbers were not in place like it used to be a few years ago when I helped move it.
    After installing the iron and capacitors I became a little confused about the blocking cap C-163.
    On the schematic it’s shown as a series blocking cap with respect to L-111 modulation choke.
    However, comparing to a photo from the WJ6W
    20V-2, one side of C-163 is grounded.
    In the photo, C-163 appears in the lower right.
    You can see that all 3 of the caps are grounded on the same leg. Hence, my confusion.
    Compare this to the schematic and you’ll see what I mean.
    http://www.steampoweredradio.com/pdf/collins/manuals/collins 20v am transmitter.pdf
    Considering what I have, being very cautious is a good practice. These photos are not of my transmitter.
    Any ideas?
     
    Last edited: Jun 16, 2019
  2. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

  3. N6YW

    N6YW Ham Member Volunteer Moderator QRZ Page

    Glen
    Thanks. I didn’t realize the difference between the two. It now makes sense.
     
  4. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    Collins Radio was always making changes in production and those changes could be very simple to very complex.

    Art Collins just could not help but come up with modifications and he insisted that all of the modifications be implemented before the product went out the door. Sometimes, before one set of modifications were made, he came up with still more modifications. That resulted in products not being shipped and that meant no income to the company.

    During my tenure here, at the "new" Collins Radio Company corporate headquarters in Richardson, Texas, every division, in fact every division at all 4 of the Collins Radio locations, had an "Art project" to keep Art Collins occupied making his modifications. Those projects were never intended to have products that actually shipped, just to keep Art away from units in production so that they could be shipped to the end customer and funds coming into the company.

    During the 1960s, the Wall Street Journal had a major article on the Collins Radio Company. In that article was the statement that the Collins Radio Company survived "in spite of Art Collins" and not "because of Art Collins". Needless to say, "officially", the Wall Street Journal was not welcome within the Collins Radio Company.

    My first job, after graduating from Georgia Tech, was with the Collins Radio Company. My job was the liaison between the engineering department and the production departments of the Process Division. I first met Art Collins the 2nd, maybe 3rd, week after being employed. I got to know him better after we both had left the company. Art was a brilliant technical person and a lousy businessman!

    Glen, K9STH
     
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  5. N6YW

    N6YW Ham Member Volunteer Moderator QRZ Page

    67935CEF-DE97-460C-9461-06D0BF61E17F.jpeg 4F37877C-CDCA-4602-99F1-93CB7DC6939B.jpeg 5D0E410E-BEB5-4562-9B67-26BD620654CF.jpeg AB89BCAB-F996-4E1E-BA1E-B5A9D7352262.jpeg
    Glen
    Once again, a very fine post! I have read many posts similar yours regarding Art and his ways.
    After downloading and reading the schematic from the CCA site, it became very clear that the schematic on Steam Powered radio is not correct.
    My reason for wanting clarification is because the way my mind works... it’s a visual thing. If I can’t correlate the object in sight with respect to a document, I always take caution because you only have one chance to screw it up. Alas my judgement won out again.
    Thanks for your contribution, and fine business on you being a “Yellowjacket “!!!
    I’m originally from Georgia and have driven past the GA Tech campus 1000’s of times.
    Here’s a few pics of the new transmitter.
    Enjoy,
    Billy N6YW
     
  6. K4KYV

    K4KYV Subscriber QRZ Page

    A perfect example (slightly off-topic) is shunt-feed to the mechanical filters in the 75A-4 receiver. The original circuit had the full B+ flowing through the input coils of the filters to the plate of the 6BA7 2nd mixer. If the plate of the tube ever shorted internally, somehow wiring to the plate circuit shorted to ground, or insulation internal to the coil inside the filter broke down, it would result in the full B+ voltage across the coil, likely destroying the filter. Later productions of the receiver used an RF choke as a plate choke for the tube, with a 62pf capacitor in parallel to broadly resonate at 455 kc/s. The filters were isolated from B+ using a 1000 pf blocking capacitor C144, and the cold ends of the filter coils were grounded directly. This upgrade was designed to prevent damage to the filters in the event of the above failures. Collins regularly published "service bulletins" to the receiver, incorporating the latest production changes, and often the required components for service updates could be purchased as a kit directly from Collins. This production change appeared on later schematics, but was never the subject of a service bulletin nor have I ever heard of the components being offered as a kit.

    I'm not totally convinced of the effectiveness this modification, since a shorted blocking capacitor (C 144) would produce exactly the same effect as the failures mentioned above. The capacitor used in production was a nondescript 1000 pf 500v disc ceramic, and I have seen many failures in equipment where disc ceramic capacitors developed a dead short. In my 75A-4 I replaced the stock blocking cap with a .001 mfd 3 kv disc ceramic, after first testing it for leakage current at 2 kv using my hi-pot tester. I figured that the likelihood of a 3 kv capacitor testing good and then developing a short with only 200v DC was pretty slim, even though that still would not be beyond the realm of possibility. A more fool-proof approach might be to wire two .002 mfd 3 kv disc ceramics in series, on the theory that simultaneous failure of both capacitors operating so far below the nominal working voltage would be unlikely.
     
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  7. AD5HR

    AD5HR Ham Member QRZ Page

    The transmitter is a beauty, but I really like the resonator guitar!
    What make, age, etc.
    This inquiring mind would like to know.
    Jon
     
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  8. AC0OB

    AC0OB Subscriber QRZ Page

    That's quite an impressive guitar amp behind ya there Billy!

    Billy with Guitar amp.jpeg




    Pheel
     
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  9. W8KHK

    W8KHK Ham Member QRZ Page

    Billy don't need no stinkin' audio generator. He uses the guitar to execute proof of performance tests. No two-tone tests here, how about all six? No distortion analyzer either, just lend an ear to that sweet sound! Rock On, Billy!
     
    N6YW likes this.
  10. K5UJ

    K5UJ Ham Member QRZ Page

    It is important to have some knowledge of the times for Art Collins's formative years. Men such as Edgar Johnson, Art Collins, Bill Halligan, James Millen et al. were part of the spark and pre-WW2 CW period during which radio's technological development was full speed ahead. It was an extremely exciting time with research taking place on many many parallel fronts. Journals and magazines reported new circuit ideas, new antennas, new insight about phenomena not previously understood all that well, seemingly with each issue. It was a time when a Ph.D. or a basement tinkerer could come up with some new idea for a transmitter, receiver or something else. Many young men were under the spell of this radio thing and a few started businesses and got them off the ground. Many are forgotten but the ones who manufactured products in high volume that lasted are known to us. That Collins was a tinkerer and modifier isn't surprising given the radio period he grew up in, a time when a lot of ham gear was homebrew. Bill Halligan was dreaming up receivers and transmitters and ordering photo shoots of prototypes and running ads in QST before production runs, which drove his people nuts. These were radio guys, not business executives in the modern MBA sense, and they were constantly trying to stay ahead of each other.

    This is one reason why I laugh at the "everything must be stock and original" Collins collector crowd. How ridiculous. If anyone favored improving Collins gear it would have been Art Collins.
     
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