Old School Gates CB-77 Turntable Question

Does anyone still have expertise with these old studio turntable motors? I have one that has been sitting idle for a while and is sluggish and slow when first powered on. I added fresh 10 weight oil per the manual and it is still slow until it warms up. Any one have any insights about a option or a solution?

Thanks

DavidEduardo said:

Was this unit stored for a long period of time? The first step in troubleshooting an out of service mechanical device is to determine if the lubricant has solidified. Adding new oil will not eliminate the grungy old lubricant, so the motor may need to be flushed with the proper solvent. I forget what brand of motor those CB-77's used (Bodine, maybe?) but you can probably search for the model indicated on the face-plate on the motor and get some guidance. Otherwise, unless you have experience with motors, I'd take it to a motor repair specialist to be cleaned and re-lubricated.

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The motor is an Ashland D80DZU-2 with spouts at the top and bottom of the motor. How does the flushing process work?

How about the idler wheel? Those things are rubber and dry out.

That's why those were known as 'Gates Rumblemasters'. Always needed to remind the jocks to put the speed in neutral when not in use. Otherwise the rubber idler roller would become dented from the motor shaft sitting on the rubber idler.

The rubber idlers used to get old back in the day. Imagine what that rubber is like 50 year later!

You can get the rubber idler wheels rebuilt. Try: http://www.terrysrubberrollers.com/

frankberry said:

Then Panasonic introduced their direct drive turntables which far out-performed the idler-driven turntables.

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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.

Kelly A said:

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.

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We had a pair of SP-25s back in the mid-'70s at WKXL (Concord, NH)....these replaced the 2 Gates "beasts"....
These worked really well....but you had to be careful; if you were a bit careless (or ham-fisted.....) you could end up accidentally changing speed when you went to cue up.....!
LOTS of torque, IIRC.....we used Stanton 500E cartridges with conical styli......

Assuming the motor turns freely (now?)...

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

DavidEduardo said:

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.

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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/gates harris/manuals/gates cb77 tt.pdf

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

Kelly A said:

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.

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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.

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.

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

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

dc2bluelight said:

The Gates CB77 would start in 1/3 turn when properly adjusted. The Russco/QRK would get going in about 1/8 turn.

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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.

DavidEduardo said:

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.

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The CB77 has a built-in captive pop-up 45rpm adapter. No adapters required in the records, that would have been a deal-breaker, and no separate puck. The Russco, QRK, and subsequent Harris turntables had an adapter built in too, but it was fixed, and the platter was recessed for a 45rpm record so the adapter just stayed in place. Much better operationally.

The CB77 used a mercury switch under that big red rocker, the only TT to do that besides it's big brother, the 16" CB700. The trick to getting a CB turntable to start quickly and not wow was in adjusting the stops on the gear shift so the idler would dig in just enough to accelerate the plater, but not too much so that it over accelerated and wow'ed. The adjustment depended on the current friction coefficient of the rubber idler, so it wasn't stable over time.