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15th Sep 2021, 10:55 pm | #1 |
Pentode
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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. |
16th Sep 2021, 10:53 pm | #2 |
Dekatron
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
Posts: 6,574
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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 |
17th Sep 2021, 1:25 am | #3 |
Pentode
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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 |
17th Sep 2021, 11:00 am | #4 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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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. |
17th Sep 2021, 1:04 pm | #5 |
Pentode
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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 |
17th Sep 2021, 4:14 pm | #6 |
Dekatron
Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
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Re: Beocord 5000 (Type 4715) Motor Run Cap
The markings on the capacitor identifying it as "Electrolytic" and "Bipolar" I find somewhat confusing.
David |
17th Sep 2021, 4:36 pm | #7 |
Dekatron
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Re: Beocord 5000 (Type 4715) Motor Run Cap
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17th Sep 2021, 5:31 pm | #8 |
Dekatron
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Re: Beocord 5000 (Type 4715) Motor Run Cap
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17th Sep 2021, 5:50 pm | #9 |
Pentode
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Location: London, UK.
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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 |
17th Sep 2021, 7:16 pm | #10 | |
Heptode
Join Date: Mar 2011
Location: Dorset, UK.
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Re: Beocord 5000 (Type 4715) Motor Run Cap
Quote:
Rich
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21st Sep 2021, 12:24 am | #11 |
Pentode
Join Date: Nov 2017
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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 |