Garrard motor
 

I am servicing a radiogram fitted with a Garrard RC110 turntable.


The motor started to run very hot and burnt itself out. I tried using a motor from another later Garrard deck I believe an AT 6 but although it would fit, the motor ran too slowly.


I thought these were all designed to run at the same speed.


Does anyone know which motor I could replace it with?

Re: Garrard motor
 

Maybe a motor pre autoslim, RC209/210 type as pictured.

Alan

Re: Garrard motor
 

That was the motor I fitted, so either there's something wrong with the motor or I need a different type.

Re: Garrard motor
 

It's all very strange. It's very unusual for a record deck motor to burn out in the first place - makes you wonder what's going on. I've no idea what's wrong in this instance, but I bet I'd work it out if it were sat in front of me - it'll be interesting to see what the outcome is.

Re: Garrard motor
 

I've just had a thought - the original motor could have been set for 110 volts and uses part of the gram mains transformer primary as an auto transformer so that the main voltage selector on the radiogram controls both the gram and the deck motor (I've come across this arrangement before) and someone at sometime has connected the motor straight across the mains and ruined it. Now you've fitted a replacement motor, which will be set at 240 volts, it won't run properly, as its supply is half mains from the original primary tap on the mains transformer - I bet that's the answer.

Re: Garrard motor
 

The radiogram concerned is a Cossor 522.

The motor was always connected directly across the mains. When I tested it, I connected it across the mains. The links in the motor connection box was set for 240V

Re: Garrard motor
 

Well that rules that one out - lucky I didn't have a real bet!

I was wondering how the links on the original motor were connected and you've now confirmed that they were set for normal mains.

So the mystery remains and I guess you've confirmed that there definitely is 240 volts at the motor - or as near to it as you are able to connect the meter probes. It's unlikely that there would be anything to drop the mains other than the supply coming via the transformer, but always worth checking just to rule out what might seem to be ridiculous.

I think it was on an old Columbia that I first came across the gram motor connected across a tapping on the mains transformer - on this occasion the transformer was burnt out.

Re: Garrard motor
 

If you've still got the deck that the replacement motor came from it would be interesting to re-fit it and see if the speed is correct for that particular deck, if so, it would confirm that it must just be that the deck being worked on requires a specific motor - perhaps the stepped pulley can be swapped over from the old motor, which I did once on an American Garrard RC80 that needed to be changed from 60 to 50 Hz.

The circuit for the Cossor 522 that I'm looking at doesn't seem to show the gram motor as far as I can see, just the 'gram' position on the wave change switch.

Re: Garrard motor
 

I have some old Garrard motors - you are welcome to one if it fits.

Re: Garrard motor
 

Is it the motor running slow or the platter turning slow?

If it is the later case, did you check if the stepping pulley and the platter inner rim diameter matched between the original motor and deck with the replacement motor and deck?

Regards,

Anwesh

Re: Garrard motor
 

Good point.

Re: Garrard motor
 

Its the motor running slow. I swapped the pulley which is a 3 speed from the original to the donor.

I will measure diameters tomorrow.

Re: Garrard motor
 

I've made some measurements. The pulley that was fitted to the original motor and which is now fitted to the new motor is slightly larger in diameter.

So to be clear

The 'new' motor is a pre autoslim, possibly from a 209/210

The original motor had a 3 speed pulley fitted to it, its replacement had a four speed pulley.

I've fitted the original 3 speed pulley on to the new motor that I installed in the deck.

The three speed pulley is larger in diameter than the 4 speed one.

Re: Garrard motor
 

One possible reason could be that the original motor was a 2 coil/2pole, while the replacement is a 2coil/4pole. The 4 pole motor shall run at half the speed of the 2 pole motor.

Regards,

Anwesh

Re: Garrard motor
 

I think it's starting to look like its something to do with the number of poles making the difference, seeing as everything else has been ruled out.

Re: Garrard motor
 

How does one tell the difference?

Re: Garrard motor
 

The difference would be as seen in figure B and C of the attachment. If you take off the pulley and the top bearing that is bolted across the stator frame, you can compare both stators. If any doubt, please upload pics here so we all can have a look.

Regards,

Anwesh

Re: Garrard motor
 

It will run at half speed. What do you estimate your speed to be?

Re: Garrard motor
 

Will removing the bottom bearing be sufficient


I'll also take pictures and post on here.

Re: Garrard motor
 

The original motor is no longer installed so should be easy to dismantle and check, photograph the stator. The other one you can inspect from the bottom.
I am quite sure that the RC210 motor is 4 pole. I do not know anything about the RC110.

Regards,

Anwesh