generel motor questions - speed and heat

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baek47 Posted: Sun, Aug 23 2020 6:41 PM

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Hi

I have been fixing beogram 3400 with the intention to listen to 4ch and sq.

I had to buy a few to get lucky to have one with the built-in decoder….

I have been playing with the beogram some days - i just did some cleaning and lubrication inside (motor spindle/idle whell and some mechanic parts)  + I changed the roedenstein caps on the decoder.

I didnt do anything to the motor, yet.....everything worked well (even the cd4 diode was lit)

After some days to bg 3400 went down in speed, 26-27 rp...At least one of the others did the same.!!??

Im planning to buy new belts - but i dont think they at related to this problem - the old belt are not that bad.

Now I have cleaned and lubricated the bottom motorbearing lightly (without taking it totally apart) - but i only reached speed after 1 hour. Which is good, and now it starts at the right speed.

Now my questions

• Is it ok to completely take the bearing apart? Doesnt it have to be reassembled very precisely (i mean beyond my skills)
• The motors I have lubricated Bg3400 and Bg1000 (round motor) runs very hot (especially the bg1000) - is that normal?

Mvh baek47

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Dillen replied on Mon, Aug 24 2020 8:48 AM

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Yes, you need to take the motor apart and treat the bearings.
The bearings cannot be oiled by simply adding oil as drops, regardless where you add it it will only be a short-lived solution. The motor will run slow again
as soon as the oil is pressed away (or evaporated).

The bearings are "self-lubricating", they have the oil sitting in pores inside the "hollow" metal material, oil is then sucked out from the pores by capillary action by the rotation of the spindle, forming an ultra-thin film for the spindle to run in.
A felt reservoir around the bearing holds additional oil for the bearing to suck from.

You need to clean out the remains of the old oil from the pores of the bearing (and from the felt washers). I use an acetone bath for this.
Then infuse fresh oil into the bearing material using vacuum and oil with the right additives.

It has been discussed here many times and Beolover shows how on his blogspot page (though Beogram 4002, but the principle is the same).

The belt, if still the original, will be bad by now but is most likely not the reason for the slow speed in this case.

Martin

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baek47 replied on Tue, Aug 25 2020 11:27 AM

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Thanks a lot Martin

I will try - and let you know how it went :-)

Torben

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baek47 replied on Sun, Oct 11 2020 10:31 AM

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Hi again

I tried infuse the bearings. They were in acetone for 2 nights, then dried 1 night, then in vacuum for days and only bubles the first night…..The BG1000 run run stable on correct speed, but the round motor it self runs hot (I can have my fingers there but its not nice).

I could only do the lower bearing in BG1000, the upper is stuck…..perhaps thats why…..

I use lawn mower oil sae30 - perhaps its too thick or wrong additives...

Br Torben

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baek47 replied on Sun, Oct 11 2020 10:31 AM

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Hi again

I tried infuse the bearings. They were in acetone for 2 nights, then dried 1 night, then in vacuum for days and only bubles the first night…..The BG1000 run run stable on correct speed, but the round motor it self runs hot (I can have my fingers there but its not nice).

I could only do the lower bearing in BG1000, the upper is stuck…..perhaps thats why…..

I use lawn mower oil sae30 - perhaps its too thick or wrong additives...

Br Torben