My Pioneer PL-50 is having a hard time getting up to speed. If I manually assist, it will hold the speed fine. I tried to remove the motor to clean it, but unfortunately the screws to the motor mount do not want to cooperate. I tried liquid wrench to no avail. Using the brute force method I only managed to partially destroy the top of the screws.
The platter spins and spins if unconnected to the motor, so that seems not to be the problem (I cleaned the belt and rim of the platter just in case.)
Upon examination the oil tubes to the motor have oil in them and the motor makes no noise (other than a soft whir when running). It occurred to me that the motor capacitor is now about 50 years old and may be out of spec. Which leads me to my two questions:
1- Is the capacitor solely for changing the phase of the ac (the motor is a 4 pole ac motor) or does it also give a jolt to get the motor running?
2- If the latter, does anyone know what would be a good replacement? The service manual lists the cap as 1 uF 1,000W V.
Thanks for any help anyone can give me on this.
Jazzzman
The platter spins and spins if unconnected to the motor, so that seems not to be the problem (I cleaned the belt and rim of the platter just in case.)
Upon examination the oil tubes to the motor have oil in them and the motor makes no noise (other than a soft whir when running). It occurred to me that the motor capacitor is now about 50 years old and may be out of spec. Which leads me to my two questions:
1- Is the capacitor solely for changing the phase of the ac (the motor is a 4 pole ac motor) or does it also give a jolt to get the motor running?
2- If the latter, does anyone know what would be a good replacement? The service manual lists the cap as 1 uF 1,000W V.
Thanks for any help anyone can give me on this.
Jazzzman
LINK: Need to start Pioneer PL-50A by hand. | Audiokarma
(There is a plastic nub in the bottom of the hole. I don't know this machine, but old-old plastic gone bad makes more sense than a 1,000V cap gone bad on 120VAC.)
(There is a plastic nub in the bottom of the hole. I don't know this machine, but old-old plastic gone bad makes more sense than a 1,000V cap gone bad on 120VAC.)
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Not an expert on this TT, but I read elsewhere that the capacitor is there to help the motor start in the right direction.
I don't know why the voltage rating has to be so high, but a here's a replacement candidate: https://www.newark.com/avx/sv09ac105kar/ceramic-capacitor-1uf-1000v-x7r/dp/09R2468
I don't know why the voltage rating has to be so high, but a here's a replacement candidate: https://www.newark.com/avx/sv09ac105kar/ceramic-capacitor-1uf-1000v-x7r/dp/09R2468
Thank you PRR and Galu.
PRR-I replaced that disc a few years ago when I purchased the TT. Now it spins very smoothly. If I spin it by hand (without the belt) it will keep rotating for quite a long time.
Galu-I will give the capacitor a try. Thank you for a suggested replacement part. I will take a look at it.
PRR-I replaced that disc a few years ago when I purchased the TT. Now it spins very smoothly. If I spin it by hand (without the belt) it will keep rotating for quite a long time.
Galu-I will give the capacitor a try. Thank you for a suggested replacement part. I will take a look at it.
Does the motor pulley, without the belt on, come to a gradual stop when switched off?
Or does it stop abruptly, indicating gummed up bearings?
If it's a synchronous motor, it should stop smoothly, and rock back and forth a bit if the synchro magnet is still strong.
A lot of those old motors require a complete flushing with solvent, and resaturating of the sintered bearings with light oil.
Or does it stop abruptly, indicating gummed up bearings?
If it's a synchronous motor, it should stop smoothly, and rock back and forth a bit if the synchro magnet is still strong.
A lot of those old motors require a complete flushing with solvent, and resaturating of the sintered bearings with light oil.
I haven’t checked how the motor stops. I will remove the belt, turn the motor on and off and report back.
I would look at replacing the belt. A synchronous motor by definition has only 2 speeds: 100% or 0% when the cogging torque is exceeded.
I had a Pioneer PL12DII table back in the 70's; the belt slowly stretched out until it ran ~10% slow. When I replaced the belt, the speed was correct again. When the belt stretches, it slips.
I had a Pioneer PL12DII table back in the 70's; the belt slowly stretched out until it ran ~10% slow. When I replaced the belt, the speed was correct again. When the belt stretches, it slips.
I tried the test, I think it passed, it does not stop right away, it continues for a few seconds and does do that rock back and forth at the end. I tried to attach a video so you could tell me what you think, but my iPhone records it as an MOV file, which I cannot upload.
Thanks again for your help.
Jazzzman
Other sources quote a 0.1uF film capacitor and not 1uF as you stated.
Check your service manual again to be sure.
I did replace the belt, the old belt did not seem super tight. What happens if I do not assist it at first is that it takes some 20 minutes or so to get up to speed by itself. I timed 100 revolutions as follows: at initial start 3 min. 14 seconds; after about 5 minutes 3 min. 10 seconds; after about half an hour (or so, it might have been more like 45 min to an hour) almost exactly 3 min.
Interesting. Let me give you some background. The turntable, when I purchased it ran too erratically and the return mechanism did not work. I replaced the the thrust thingy under the spindle, cleaned and lubed the return mechanism, put oil in the motor and replaced the belt. The return mechanism worked and the platter spun smoothly and consistently but too fast. I put back on the old belt with the same result. Seeing that others had had the same speed problem, I used the “add tape to the platter rim” method to slow it down. Everything worked perfectly for a few years. After a period of inactivity the start problem arose. I have been oiling the motor to no avail.
I tried cleaning the belt, removing one layer of tape, and cleaning the tape surface. Then I put the new belt (several years old but unused) on. I thought of removing all the tape as that would presumably speed it up. But since it runs at speed I imagine it will run too fast after 20 minutes or so. The new belt is definitely tighter than the old one. Any suggestions?
Thank you.
Jazzzman
I tried cleaning the belt, removing one layer of tape, and cleaning the tape surface. Then I put the new belt (several years old but unused) on. I thought of removing all the tape as that would presumably speed it up. But since it runs at speed I imagine it will run too fast after 20 minutes or so. The new belt is definitely tighter than the old one. Any suggestions?
Thank you.
Jazzzman
You mention the motor runs fast after 20 minutes.
Merely oiling the motor is not enough.
The old, congealed oil is still in those sintered bearings, and when cold, act as a partial brake against the motor shaft. - when the shaft is "at speed".
Also, using a new, modern oil, and having to mix it with the old oil, is not a good idea.
Because different lubricants can work against each other.
The only reasonable solution is to boil the old oil from the bearings, with solvent to help dissolve the oil - and insure that all of it is flushed out of the pores of the bearings.
I use a clean/new hot soldering iron tip inserted into the bearing, watching for the oil to bubble out, then rinsing with solvent - and repeat the process until I'm satisfied with the result.
Then, heating once again the bearing, dropping it in fresh oil of the proper type, allowing it to cool and absorb the new oil.
It's a tedious job, but the only way.
I've done enough of old motor bearing flushes to know.
Merely oiling the motor is not enough.
The old, congealed oil is still in those sintered bearings, and when cold, act as a partial brake against the motor shaft. - when the shaft is "at speed".
Also, using a new, modern oil, and having to mix it with the old oil, is not a good idea.
Because different lubricants can work against each other.
The only reasonable solution is to boil the old oil from the bearings, with solvent to help dissolve the oil - and insure that all of it is flushed out of the pores of the bearings.
I use a clean/new hot soldering iron tip inserted into the bearing, watching for the oil to bubble out, then rinsing with solvent - and repeat the process until I'm satisfied with the result.
Then, heating once again the bearing, dropping it in fresh oil of the proper type, allowing it to cool and absorb the new oil.
It's a tedious job, but the only way.
I've done enough of old motor bearing flushes to know.
That would indicate the bearing is slowing down the platter. If a synchronous motor is spinning, it is operating at the proper speed. The platter will not spin at the correct speed for two reasons: The belt is slipping or the belt is creeping. Belt slippage is caused by improper tension or a stretched belt. You've eliminated that, so it must be belt creep. Belt creep cannot be eliminated, but it can be reduced. If the bearing oil is thick or the spindle is sticking, it will slow the platter even though the motor is running at the correct speed. All belt drives exhibit this behavior, they speed up over time. Your speed variation is higher than normal (-0.78%) so I would look at the bearing.
Pyramid, thank you for an excellent analysis. However, I am not sure that I understand. The platter is speeding up over time. (3 min 14 seconds to spin 100 revolutions at first — only 3 minutes to spin 100 revolutions after 20 minutes.) Is it that the bearing oil is thinning out as it spins?
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