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Thread: Old School Gates CB-77 Turntable Question

  1. #11
    Assuming the motor turns freely (now?)...

    Perhaps the capacitor has dried out? The manual shows there should be one in there.

  2. #12
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    Quote Originally Posted by Grounded Grid View Post
    Assuming the motor turns freely (now?)...

    Perhaps the capacitor has dried out? The manual shows there should be one in there.
    That's a good point.

    A general question, since I've only worked on cart machines, tape decks and turntables with hysteresis-synchronous motors: A couple of engineering texts I have indicate that such motors, particularly in the smaller sizes, may not need a cap to start as there is enough of a "kick" to push the motor into rotation with just applying power to it. Is that true with the kinds of motors we see in old mechanical devices?

    P.S. If you have the actual manual for a CB-77 or any of the CB series (like the 16" transcription monster!) I would love to have a scan for the catalog section of the below-mentioned website. I have the CB series sales brochure, but no manual.
    www.americanradiohistory.com
    Broadcasting Magazine and Yearbooks, Billboard, Cash Box, R&R, Record World, Music & Media, Audio, Television/Radio Age, R&R, Duncan's American Radio, Popular Electronics, Studio Sound, Broadcast Engineering, db, and more.

  3. #13
    Quote Originally Posted by DavidEduardo View Post


    That's a good point.

    A general question, since I've only worked on cart machines, tape decks and turntables with hysteresis-synchronous motors: A couple of engineering texts I have indicate that such motors, particularly in the smaller sizes, may not need a cap to start as there is enough of a "kick" to push the motor into rotation with just applying power to it. Is that true with the kinds of motors we see in old mechanical devices?

    P.S. If you have the actual manual for a CB-77 or any of the CB series (like the 16" transcription monster!) I would love to have a scan for the catalog section of the below-mentioned website. I have the CB series sales brochure, but no manual.
    I spoke to a tech at Ashland Motor in NH. He tells me this model motor has bronze sleeve bearings with a felt wick and the felt has dried out and all it really needs is more oil. He suggested putting in a couple of drops everyday until the wick is re-saturated and it should go back to normal startup once that happens. As far as the manual goes it is fairly easy to find on a google search:

    http://steampoweredradio.com/pdf/gat...0cb77%20tt.pdf

    I also have an original manual if the above link isn't usable.

  4. #14
    Quote Originally Posted by Kelly A View Post
    I remember the Techniques servo direct drive turntable, (can't recall the model #) the one with the square start/stop button, used to start an LP and have it up to speed in one eighth of a turn. The rubber idler, gearshift turntables would require at least one full turn, or slip cueing.
    The Gates CB77 would start in 1/3 turn when properly adjusted. The Russco/QRK would get going in about 1/8 turn. They all rumbled like crazy.

    The original Technics SP-10 was not a fast starter, it was a consumer device, but still got used in broadcast quite a bit because, well heck, it didn't rumble. Then McCurdy produced a modified unit that was quicker to get to speed (IIR, they doubled the motor somehow), and that was followed by the SP-10 MKII that had plenty of start torque. McCurdy also made a suspension mount with adapter plates for several TTs that sprung about 40 lbs of steel weight on rubber isolation mounts.

    My memory -which is not to be fully trusted- the SP-15 and SP-15 were less expensive models, with somewhat less torque than the SP-10 MKII, but still plenty.

  5. #15

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    Do you remember the BQ51? They would start and stop on a dime. I remember airing AT40 (when it was on vinyl LPs!) and they had about 5 seconds of silence between segments. I would simultaneously hit the CART start and the TT stop (when then jingle outro finished) to run the local spots. When the last spot finished I could hit TT start and it would go into the next segment. Never got wow on the air!
    Some of the other guys were recueing the show every time.

  6. #16
    No oil for long periods of use , or improper oil can cause this problem. If regular engine motor oil with detergent has been used it will form a glaze that displaces regular oil in bearing surfaces. If glazing has occurred, regular oil will help but only short term.

    In an internal combustion engine there is enough heat to burn off the detergents, but not in these fractional horsepower electric’s.

    There are probably articles on line about deglazing and treating glazed sintered bearings. The latter requires heat to boil out the impure oil from the bearing collar, but I can’t remember the whole procedure. Sorry.

    LCG

  7. #17
    I was at an FM station where we replaced CB-77 with Technics SP10- MkII. Besides elimination of rumble, SP10 MkII was right on pitch. We did lots of segues. The number of sour or discordant segues dropped dramatically when we went to the Technics. With two copies of an album we could start phasing, and they would stay phasing nicely for the entire album side. We didn't do it on the air, but noted it was possible due to speed stability of the SP10- MkII

  8. #18
    Quote Originally Posted by dc2bluelight View Post
    The Gates CB77 would start in 1/3 turn when properly adjusted. The Russco/QRK would get going in about 1/8 turn.
    Same memory I have when comparing Gates vs QRK--while an LP didn't have to be back-cued that much on a CB77, trying to get a tite Q on a 45 with the Gates was impossible (unless you WANTED a wow). You could always tite Q a 45 on a QRK.
    Save AM radio...kill I-CRAP.

  9. #19
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    Quote Originally Posted by oldiesfan6479 View Post
    Same memory I have when comparing Gates vs QRK--while an LP didn't have to be back-cued that much on a CB77, trying to get a tite Q on a 45 with the Gates was impossible (unless you WANTED a wow). You could always tite Q a 45 on a QRK.
    The problem with the Gates was the requirement of using the aluminum puck or putting 45 adapter thingies in ever record in the station library.
    www.americanradiohistory.com
    Broadcasting Magazine and Yearbooks, Billboard, Cash Box, R&R, Record World, Music & Media, Audio, Television/Radio Age, R&R, Duncan's American Radio, Popular Electronics, Studio Sound, Broadcast Engineering, db, and more.

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