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Idler wheel turntables: 60 to 50hz
- Thread starter SFM-Ptgal
- Start date
I believe on the idler drive QRKs, you'll need to swap the motor pulley to the proper one for the line frequency. The older ones at least used a synchronous motor.
SFM-Ptgal said:
I don't think so. The capacitor is probably used to start the motor. It should be changed, but that won't alter the speed. If you look at the shaft of the motor, I think you will see a machined sleeve attached to it. It has two diameters, one for 33, the other for 45. Those sleeves can be changed to compensate for the line frequency. If you could find out what diameter the 50 HZ sleeve is supposed to be, you could have one machined.
It is probably easier and cheaper to find some turntables that actually are setup for 220 volts 50 HZ.
Back in my touring sound days, we faced similar speed problems with Hammond B-3 organs which used a mechanical tone generator. At 50 Hz, they would run slow, so the organ would be off pitch. The cure was to use an audio oscillator and a large power amplifier to run the motor. Macintosh amps were popular, since they even had a 115 volt output. You could also mono-strap a Crown DC-300 and get the motor to run. You could do that for your turntables, but it is probably way more trouble than it is worth, unless you just happen to have the right stuff lying around.
"motor pulley' is what a couple of manufacturers called the sleeve. They were available for 50 and 60Hz operation. And for the Truly Suave, a couple of outfits machined them slightly larger, so you could speed up your music just a bit. If you had a steady hand you could do the same with a bit of splicing tape wraped onto the pulley.
I had forgotten the B-3 tone wheel. If the act had the Leslie with it, did you run it up too, or just let it run a bit slow? Sime if them were multispeed anyway.
I had forgotten the B-3 tone wheel. If the act had the Leslie with it, did you run it up too, or just let it run a bit slow? Sime if them were multispeed anyway.
littlejohn said:
I never saw a rock act with a B-3 that didn’t use at least one Leslie. As I recall, those motors were just some shaded pole versions, very similar to the ones used in cheap Alliance turntables. They were inexpensive and not particularly speed critical. We never ran them off of a separate 60 HZ source, but I remember that they would run quite hot on 50 Hz if left on for a long time.
Usually, the keyboard player had them switched off, and turned them on for a short effect. (Think: Sugarloaf – Green Eyed Lady).
When used like that, they worked fine. Normally, the bottom motor ran continuously in slow speed, but sped up when you hit the Leslie switch. There were plenty of Leslies that the low-end motor only worked on high speed and nobody seemed to notice. The top motor which was used to spin the horns was either stopped or spinning. (I have seen modified versions where it was two-speed). The speed difference wasn't particularly noticeable, so there was no point in powering them separately.
The upper motor was the one I referred to. MOst of the ones I've seen were dual speed. That was an aftermarket setup? Never knew. Although, got to wonder if someone just put one of the lower motors up to drive the horns.
B-3s bring a nice price these days.
B-3s bring a nice price these days.
littlejohn said:
You're right. Now that I think of it, the stock Leslies spun quite slowly, then kicked in high speed when the switch was engaged. For most rock purposes these things were highly modified. A lot of keyboard players liked the effect of the abrupt start from the stopped position. That tended to exaggerate the effect.
There were a lot of variations and everyone had their own pet modifications. The original Leslie set up used a "repeater relay" to run a second cabinet. They were very problematic, and also became quite a shock hazard as they aged and the Amphenol connectors got flaky. When only one cabinet was used, it got its AC power through the Amphenol 6 pin tube socket connector, which took power, audio and control from the B-3. When you used two or more cabinets were used (what self respecting rocker wouldn’t?), the repeater relay was used to power the additional cabinets through its own power cord. This daisy-chain effect caused lots of problems, since the associated circuitry seemed overly complicated. Worse yet, many of the early versions used two pin non-polarized AC connectors. To keep things reasonably quiet, they sometimes had capacitors running from one side of the power line to chassis ground. (Lots of guitar amps did this too and often had a “hum” or “ground” switch on the back). In theory, that should be OK, but in practice things could get quite "festive" when the caps leaked and the two cabinets were plugged into opposing legs of a 220/110 volt service.
I remember changing out the Leslies that I owned to just a simple low voltage relay, and powering each Leslie directly from its own U-Ground AC connector. The low voltage part was good, because people would occasionally get shocked by the Leslie speed switch mounted on the keyboard console. Of course, that was frequently caused by operator error. Things like losing the plastic insulating knob, dumping beer in the switch, or maybe getting your drug paraphernalia caught in the slot in the switch housing.
Ah, the good old days.
Since these turntable are "rim drive" you could also speed them up by adding layers of tape to the inner rim of the platter itself.
A regular maintenance item for this design was the 'puck' idler wheel: the rubber would age, and the rumble would get worse until replaced.
Re: Leslie/Hammonds, I recall watching Gregg Allman in action. Man, he was a master at getting the most out of two speeds! I could see the horn spinning, and it was fascinating to see where in the songs he would accelerate, and then let it coast.
Kind Regards,
David
A regular maintenance item for this design was the 'puck' idler wheel: the rubber would age, and the rumble would get worse until replaced.
Re: Leslie/Hammonds, I recall watching Gregg Allman in action. Man, he was a master at getting the most out of two speeds! I could see the horn spinning, and it was fascinating to see where in the songs he would accelerate, and then let it coast.
Kind Regards,
David
Yeh, on the QRK and CueMaster 'stick shift' tables, if you didn't take them out of gear, the drive idlers died fairly rapidly. When the tumpTHUMPthumpTHUMP got louder than the kick drum, we replaced them with new ones.
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