Classic Hifi Care

I ran across Jordan Pier's interesting simple technique
for assessing if your Magnavox/Collaro motor may be
bad.

I've read that some motors using magnets can lose
their field and cause erratic/slow speeds.

I was worried the W620 I was finishing for the nice
young lady had a bad motor.
It was running a bit slow.

I used the simple screwdriver stethoscope method to check
this motor, and it sounded fine.

The problem actually turned out to be the lower
temp in my house during our Arctic blast this week.

There's also a follow up video of Jordan's where he uses
an EMF meter to attempt to measure the magnetic
field of the bad motor's rotor magnet and compare it to a good motor.

https://www.youtube.com/watch?v=hBsP9zWqrvM

Well, NO, the motor has slowed down a bit again,
after running on speed and warmed up.

I'll have to take it off and check the rotor and
bearing, though it is very clean and lubed
w/turbine oil.

Darn.

I have had three Magnavox motors that were totally seized when I acquired the stereos. The upper bearings were the main cause on all three. The motors are large and beefy, you'd think they would be more robust. They were made in England, and we all know that "Lucas, King of Darkness" lives in England, so maybe there is a connection?

Fortunately I have never come across a bad motor on a collero ... and if I did I never noticed it , as long as it was even close to speed , it was good enough ... now My RCA, on the other hand, runs fast at all speeds .. kinda irritating...

I spun the rotor again, and it seemed to spin for
less time than after initial cleaning.

I dis-assembled the motor, cleaned it again, and
added some more turbine oil to the reservoir pads
in the bearings housings.

I tested speed periodically for 24 hours on/off, and it held speed.

What I surmise is that after heating, some of the old
congealed oil in the housings warms up and wicks
out of the reservoirs.

Then on cooling, it acts to slow the rotor down a bit.

I've seen this on not a few Alliance 2 pole motors.

The changer is back in the young lady's Magnavox,
and she was happy its functional.

Good work, Mr. Mogul, and another happy customer is always a good thing.

Bill

the changer in the magnavox I modified the speed is slow ... approx 2 rpm slow on all speeds, 16 speed is the closest that runs at 15.5 ...cleaned all components including taking apart the motor and lubing it up...and changing the idler from a known good machine, made zero difference.. maybe this is a bad motor?... I tried the screwdriver thing but I couldn't hear any waver in the speed ...oh well.... can't have everything work great on a 60 year old machine ...

It's possible it needs another cleaning and lube job. Sometimes it takes more than once to get all the old oil and grease off.

Bill

William wrote: ↑Sat Feb 03, 2024 12:34 am It's possible it needs another cleaning and lube job. Sometimes it takes more than once to get all the old oil and grease off. Bill

That's right. That's the reason I posted the follow up
about cleaning and lubing the motor again.

I do have another changer identical to it that works great in the smaller barcelona console i have, but that is just kicking the problem down the road, can't really see doing the motor again ... the bearings were really spotless when I re-oiled the felts. and the table takes about 30 secs to spin down when it shuts off other than the slow speed it works flawlessly.

hermitcrab wrote: ↑Sun Feb 04, 2024 1:11 am I do have another changer identical to it that works great

Have you tried switching out the idler from the on-speed changer ?

Idlers usually cause erratic speeds--"wow," and often extreme--when they get slippery from age. If the speed is constant but slow, it's more likely a motor issue.

There's the rub. Induction motors are supposed to run at a speed keyed to the AC line frequency, right?

I have an old Garrard RC-80 that runs fast. I always figured that the motor had been fitted with a spindle intended for 50 Hz Ac instead of our 60 Hz standard. I should probably drag it out and compare spindle diameters to an RC-80 that behaves properly.

Chris Campbell

TC Chris wrote: ↑Sun Feb 04, 2024 6:56 pm Idlers usually cause erratic speeds--"wow," and often extreme--when they get slippery from age. If the speed is constant but slow, it's more likely a motor issue.

There's the rub. Induction motors are supposed to run at a speed keyed to the AC line frequency, right?

I have an old Garrard RC-80 that runs fast. I always figured that the motor had been fitted with a spindle intended for 50 Hz Ac instead of our 60 Hz standard. I should probably drag it out and compare spindle diameters to an RC-80 that behaves properly.

Chris Campbell

I did take the idler off a known good deck , it made zero difference ... I just attribute it to the age of the machine (60 years) ....I use one of those RPM apps on my phone , not sure how accurate they are , I downloaded another app, and it showed even worse results ... playing it today for the first time it sounded more on speed... maybe the oil took time to work into the felt wicks ?... anyways it plays well enough ... most people probably would not notice the speed difference .