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Old 15th Sep 2021, 9:55 pm   #1
Krolroger
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Default Beocord 5000 (Type 4715) Motor Run Cap

Hi all,

I am fixing up a 1970s Beocord 5000 (the one with the terrible reputation) and I have a question about the run cap for the (dual) capstan motor.

The original was a 16uF 40 VDC bipolar cap. I have replaced it with a couple of back to back 105 degree Nichicon PW(M) series 33uF/63V caps (top of left hand photo).

The Matsushita motor runs fine (at about 50 degrees under load) and the new caps are slightly warm.

My question is, given the small size of these compared to the original, are they adequate (each 6.3 x 11mm) for the ripple current they have to handle, and for any power dissipation? They are rated at 250mA ripple current capability.

Thanks for any comments.
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Old 16th Sep 2021, 9:53 pm   #2
DMcMahon
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Default Re: Beocord 5000 (Type 4715) Motor Run Cap

If it is working OK and nothing getting too hot then probably OK.

Was there any particular reason you went for using two back to back electrolytics as against using a single 16uF Run capacitor, the original bipolar cap would have been non polarised.

David
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Old 17th Sep 2021, 12:25 am   #3
Krolroger
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Default Re: Beocord 5000 (Type 4715) Motor Run Cap

Hi David,

I am slightly concerned that the motor is running hot (~55 degrees) and the ac voltages across it in Stop and Play modes are about 50% higher than what they should be, though it doesn't appear to be running fast.

I will reinstall the original (which was in spec) and see where that takes me. I was interested to try two back to back electrolytics as I had seen it done elsewhere in this application.

I have yet to check out the capstan motor servo which may be responsible for the higher voltages.

Thanks,

Simon
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Old 17th Sep 2021, 10:00 am   #4
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Default Re: Beocord 5000 (Type 4715) Motor Run Cap

According to the capacitor data I'm looking at the ripple rating for those Nichicon capacitors is 50mA at 50Hz.

Lawrence.
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Old 17th Sep 2021, 12:04 pm   #5
Krolroger
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Default Re: Beocord 5000 (Type 4715) Motor Run Cap

Looking at the data sheet, I could only find rated ripple handling of 250mA at 100kHz. 50mA is a bit on the weedy side.

I have reinstalled the original. The voltages remain the same across the motor and the capacitor doesn't warm up. I will keep a careful eye on motor temperature. How hot should it run?

Thanks,

Simon
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Old 17th Sep 2021, 3:14 pm   #6
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Default Re: Beocord 5000 (Type 4715) Motor Run Cap

The markings on the capacitor identifying it as "Electrolytic" and "Bipolar" I find somewhat confusing.

David
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Old 17th Sep 2021, 3:36 pm   #7
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Default Re: Beocord 5000 (Type 4715) Motor Run Cap

Quote:
Originally Posted by Krolroger View Post
Looking at the data sheet, I could only find rated ripple handling of 250mA at 100kHz.

Simon
Yes various similar data sheets, some for some unknown reason only listing ripple at 100kHz.

David
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Old 17th Sep 2021, 4:31 pm   #8
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Default Re: Beocord 5000 (Type 4715) Motor Run Cap

Table at bottom of 1st page:

https://products.nichicon.co.jp/en/pdf/XJA043/e-pw.pdf

Lawrence.
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Old 17th Sep 2021, 4:50 pm   #9
Krolroger
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Default Re: Beocord 5000 (Type 4715) Motor Run Cap

Lawrence,

Thanks, so that's what frequency co-efficient means. I now suspect it wasn't entirely happy.

I now have more pressing problems with the Pause Flip Flop..

Simon
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Old 17th Sep 2021, 6:16 pm   #10
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Default Re: Beocord 5000 (Type 4715) Motor Run Cap

Quote:
Originally Posted by Krolroger View Post
I will keep a careful eye on motor temperature. How hot should it run?
Used to get quite a few Beocord 5000's in the workshop having supplied from new, and yes I recall these motors do get hot in normal operation. Same goes for those used in Beocords 1900/2400 etc. Motor run capacitors were a common failure but occasionally the motor bearings could be tight.

Rich
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Old 20th Sep 2021, 11:24 pm   #11
Krolroger
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Default Re: Beocord 5000 (Type 4715) Motor Run Cap

Thanks Rich, that's useful to know.

As for a suitable motor cap replacement, is the CBB61 type fan motor cap any good?

Or should I fit a couple of back-to-back elkos rated at 250VAC or more to handle the ripple current?

Simon
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