Not correct speed on turntable

Junolab

Active member
Jul 14, 2021
6
2
25
Hi,
I have a very nice but older Michell Gyrodec turntable with a DC motor. The issue is that it's not turning fast enough and right now I have a small "hack" where I expand the belt just half a centimetre, which makes it sound correct. Is there any way to alter the speed or what can cause this "slowness" in a motor?
 
Hi,
I have a very nice but older Michell Gyrodec turntable with a DC motor. The issue is that it's not turning fast enough and right now I have a small "hack" where I expand the belt just half a centimetre, which makes it sound correct. Is there any way to alter the speed or what can cause this "slowness" in a motor?
Surely expanding the belt will make it slower?
Have you tried a new belt?
is it consistently slow or just on some LPs?
Have you tried phoning Michell Engineering?

"Call us now on

+44 20 8953 0771"
 
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nopiano

Well-known member
Feb 15, 2009
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20,070
What is ‘expanding the belt’ exactly? I am imagining you stretching the belt, but that doesn’t alter the gearing. Expanding the pulley would make the platter turn faster but that’s hardly a fix.
 
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What is ‘expanding the belt’ exactly? I am imagining you stretching the belt, but that doesn’t alter the gearing. Expanding the pulley would make the platter turn faster but that’s hardly a fix.
it's a pity he doesn't seem to have returned with any answers.
if he has overstretched the belt this would account for the slowness in RPM unless the DC motor is kaput, which I doubt.
I am wondering if it is anything to do with the electricity supply wherever he is.
 

Junolab

Active member
Jul 14, 2021
6
2
25
Sorry for the slow response. Was moving to a new house and wasn't able to test it properly before now. I did try with a brand new belt some time ago, but it didn't change anything. And sorry my bad, the speed is a bit too fast.
I made a short video about it:
View: https://youtu.be/5T4uOSTRU1o


I have not called Michell yet as it's pretty expensive to call outside the European Union, but that's ofc the backup solution if there's no obvious fix. The increased speed is the same across all records.
 

bigfish786

Moderator
Jan 29, 2013
381
202
19,270
Something like having the wrong hz motor for your electricity supply could be causing this.
Not sure where you are, or what hz you have, but it’s something worth checking.
 

abacus

Well-known member
Sep 24, 2008
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Check on the back of the Power supply as I believe some had a speed adjustment knob or screw. (If it needs a screwdriver you may have missed that it is there)

Bill
 

abacus

Well-known member
Sep 24, 2008
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I thought the normal power supply was a simple wall wart affair, is it not?
Possibly, but the Gyrodec is a high end turntable (One of the best ever made) and a lot JA Michel (Transcriptor) turntables do usually have some type of speed control (Even going back to their70s models) which is the reason I mentioned it. (Plus it was available with various different power supplies)

Bill
 
Possibly, but the Gyrodec is a high end turntable (One of the best ever made) and a lot JA Michel (Transcriptor) turntables do usually have some type of speed control (Even going back to their70s models) which is the reason I mentioned it. (Plus it was available with various different power supplies)

Bill
It is indeed and we are still waiting for the OP to come back with some more information on that. Any speed correction would possibly be screw adjustment pots on the motor itself but these are unusual in DC motors, see below.
He doesn't mention any upgrade power supply
1627551958304.png
 

Junolab

Active member
Jul 14, 2021
6
2
25
I don't know if its an upgraded power supply or not as I bought it used several years ago. There's no place to change the speed, but it's possible the small blue one (cannot remember the name) can be calibrated to fix it. I'll contact Michell about it.

PXL_20210730_094719843.jpg
PXL_20210730_094724030.jpg
PXL_20210730_094919066.jpg
 

abacus

Well-known member
Sep 24, 2008
637
336
19,270
If you can only adjust the speed with the cover removed (Assuming the blue variable resister shown is for that) adjust it 1 turn and place the cover back on, then plug in and see if the speed is now correct, if not then unplug and do the same once more. (If the speed changed the wrong way then turn the opposite way)
It may seem long winded to keep taking the cover on and off, but it is the safest way unless you are competent in working by mains voltages.

Bill
 
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If you can only adjust the speed with the cover removed (Assuming the blue variable resister shown is for that) adjust it 1 turn and place the cover back on, then plug in and see if the speed is now correct, if not then unplug and do the same once more. (If the speed changed the wrong way then turn the opposite way)
It may seem long winded to keep taking the cover on and off, but it is the safest way unless you are competent in working by mains voltages.

Bill
indeed, safer the have a qualified engineer have a look at it.
do you have a strobe disc or anything that will show the actual speed of rotation?
Any Michell dealers where you live?
 
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