Thanks for providing another point of reference. If the motors were
truly hysteresis-synchronous, that would not be the case, would it? I
guess they could un-lock, but it was my understanding that they were
induction motors and, yes, the fan assembly on the capstan motor and
the air ducts to the spooling motors is something to behold.
I'm glad Pabst got the spooling motor dissipation down by the time
the ReVox A77 came along <smile>.
At 05:22 AM 2009-11-05, you wrote:
>I don't think the speed stability of the Magnetophon K series could
>be taken for granted, anyway. The BBC acquired a pair of K7s in the
>late 'forties to play European tapes for the Third Programme, and
>there was a row about a broadcast of Dalibor which went out a few
>per cent sharp. This led, we are told (in Pawley), to the
>installation of frequency monitoring and speed correction facilities
>for recording channels - but a BBC greybeard told me once that the
>adjustment of pinch pressure on those Magnetophons was critical and
>could easily throw the speed the wrong way on its own. Either way,
>it wasn't something to set your watch by...
>----- Original Message ----- From: "Shai Drori" <[log in to unmask]>
>To: <[log in to unmask]>
>Sent: Thursday, November 05, 2009 5:40 AM
>Subject: Re: [ARSCLIST] power line frequency
>>You're correct. Jack had magnetofons. They used synchronous motors
>>but had a huge blower on the capstan motor to stabilize speed and
>>cool the spooling motors. A very interesting design.
>>Richard L. Hess wrote:
>>>At 02:08 AM 2009-11-04, Shai Drori wrote:
>>>>The solution is very simple. The capstan of the Tonschreiber did
>>>>not run off the incoming AC but had an oscillator and amplifier
>>>>as a servo. It could run at any speed from I think 9 to 130 cm/sec.
>>>That is true, but I don't think Jack Mullin's machines were the
>>>Tonschreiber model and were lacking the oscillator and amplifier,
>>>but also, I do not believe them to be true Hysteresis-Synchronous
>>>The point here is that if Tonschreibers were used (or the
>>>circuitry associated with them was put into a studio recorder)
>>>then George's discussion of mains frequency would need another footnote.
>>>Richard L. Hess email: [log in to unmask]
>>>Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
>>>Detailed contact information: http://www.richardhess.com/tape/contact.htm
>>>Quality tape transfers -- even from hard-to-play tapes.
Richard L. Hess email: [log in to unmask]
Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
Detailed contact information: http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.