Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old August 23rd 20, 01:11 AM posted to sci.electronics.repair
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Default can bad cap = hot motor?

On Friday, 21 August 2020 18:27:09 UTC+1, wrote:

I know modern caps are much better than old caps. However, why do you
suppose it is that motor run caps are so big for their voltage and
capacitance ratings compared to other non-polarized caps? I'm serious.


That is not a bad question at all:
a) Because they are AC-rated caps.
b) Because the nature of a motor starting puts a tremendous load on the cap for a very short time, so they must be robust enough to absorb that shock, repeatedly and reliably, in addition to the actual voltage involved. So, whereas the actual operating voltage may be say.... 240 VAC, the start-cap must be rated (at a minimum) of 150% of the operating voltage.
c) Typical NP caps are used a great deal in audio applications, where the voltages are small, and the frequencies high.
d) Motor Run caps start around 370V, or so, are typically of much lower capacitance than a start-cap (and whereas replacement voltage may be higher, replacement capacitance should remain very close or identical to OEM).

Hope that helps.

Peter Wieck
Melrose Park, PA


Of course motor rated caps have advantages. So do higher rated non-motor caps.
But the key point the op appears to have not noticed is that his crude paper cap has already lasted over 70 years. That is more than good enough.


NT

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Old August 23rd 20, 04:20 PM posted to sci.electronics.repair
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Default can bad cap = hot motor?


But the key point the op appears to have not noticed is that his crude paper cap has already lasted over 70 years. That is more than good enough.


We do not know that at all. What we do know is that *FINALLY* Eric has gotten around to dealing with it.

Peter Wieck
Melrose Park, PA
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Old August 24th 20, 02:08 AM posted to sci.electronics.repair
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Default can bad cap = hot motor?

On Sat, 22 Aug 2020 16:11:03 -0700 (PDT), wrote:

On Friday, 21 August 2020 18:27:09 UTC+1, wrote:

I know modern caps are much better than old caps. However, why do you
suppose it is that motor run caps are so big for their voltage and
capacitance ratings compared to other non-polarized caps? I'm serious.


That is not a bad question at all:
a) Because they are AC-rated caps.
b) Because the nature of a motor starting puts a tremendous load on the cap for a very short time, so they must be robust enough to absorb that shock, repeatedly and reliably, in addition to the actual voltage involved. So, whereas the actual operating voltage may be say.... 240 VAC, the start-cap must be rated (at a minimum) of 150% of the operating voltage.
c) Typical NP caps are used a great deal in audio applications, where the voltages are small, and the frequencies high.
d) Motor Run caps start around 370V, or so, are typically of much lower capacitance than a start-cap (and whereas replacement voltage may be higher, replacement capacitance should remain very close or identical to OEM).

Hope that helps.

Peter Wieck
Melrose Park, PA


Of course motor rated caps have advantages. So do higher rated non-motor caps.
But the key point the op appears to have not noticed is that his crude paper cap has already lasted over 70 years. That is more than good enough.


NT

So you suggested that I stuff the old cap with a new cap(s). I knew
new motor run caps were too big to fit in the old cap case. You
suggested I use modern caps with the same ratings. I wondered why
motor run caps are still so much physically larger than caps with the
same specs but which are not motor run caps. Then you post the answer
above. I am not sure why you even bothered.
Eric

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Old August 24th 20, 02:11 AM posted to sci.electronics.repair
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Default can bad cap = hot motor?

On Sun, 23 Aug 2020 07:20:43 -0700 (PDT), "
wrote:


But the key point the op appears to have not noticed is that his crude paper cap has already lasted over 70 years. That is more than good enough.


We do not know that at all. What we do know is that *FINALLY* Eric has gotten around to dealing with it.

Peter Wieck
Melrose Park, PA

I was going to go back in time to replace that cap but my time machine
was serviced byb me after a few gins so instead I waited until I
bought the grinder in real time, used it for a couple years, posted a
question about it here and now I have a new cap coming.
Eric

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Old December 31st 20, 03:48 PM posted to sci.electronics.repair
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Default can bad cap = hot motor?

On Sunday, August 23, 2020 at 8:11:26 PM UTC-4, wrote:
On Sun, 23 Aug 2020 07:20:43 -0700 (PDT), "
wrote:


But the key point the op appears to have not noticed is that his crude paper cap has already lasted over 70 years. That is more than good enough.


We do not know that at all. What we do know is that *FINALLY* Eric has gotten around to dealing with it.

Peter Wieck
Melrose Park, PA


I was going to go back in time to replace that cap but my time machine
was serviced byb me after a few gins so instead I waited until I
bought the grinder in real time, used it for a couple years, posted a
question about it here and now I have a new cap coming.


Good stuff with orange juice and 2 or 3 banana liquors. I wonder what an 80 year-old gin bottle would fetch today.
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Old December 31st 20, 06:15 PM posted to sci.electronics.repair
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Default can bad cap = hot motor?

On Sunday, August 23, 2020 at 8:11:26 PM UTC-4, wrote:
On Sun, 23 Aug 2020 07:20:43 -0700 (PDT), "
wrote:


But the key point the op appears to have not noticed is that his crude paper cap has already lasted over 70 years. That is more than good enough.


We do not know that at all. What we do know is that *FINALLY* Eric has gotten around to dealing with it.

Peter Wieck
Melrose Park, PA

I was going to go back in time to replace that cap but my time machine
was serviced byb me after a few gins so instead I waited until I
bought the grinder in real time, used it for a couple years, posted a
question about it here and now I have a new cap coming.
Eric


If you get that time machine working, go back to 1964 and tell Ford to use galvanized sheetmetal on the Mustang. Thanks.

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Old December 31st 20, 08:15 PM posted to sci.electronics.repair
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Default can bad cap = hot motor?

On 31.12.20 15:48, bruce bowser wrote:
On Sunday, August 23, 2020 at 8:11:26 PM UTC-4, wrote:
On Sun, 23 Aug 2020 07:20:43 -0700 (PDT), "
wrote:


But the key point the op appears to have not noticed is that his crude paper cap has already lasted over 70 years. That is more than good enough.

We do not know that at all. What we do know is that *FINALLY* Eric has gotten around to dealing with it.

Peter Wieck
Melrose Park, PA


I was going to go back in time to replace that cap but my time machine
was serviced byb me after a few gins so instead I waited until I
bought the grinder in real time, used it for a couple years, posted a
question about it here and now I have a new cap coming.


Good stuff with orange juice and 2 or 3 banana liquors. I wonder what an 80 year-old gin bottle would fetch today.

How do you teach a gin bottle to fetch?????
  #29   Report Post  
Old January 1st 21, 12:02 AM posted to sci.electronics.repair
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Default can bad cap = hot motor?

On 12/31/2020 11:15 AM, Sjouke Burry wrote:
On 31.12.20 15:48, bruce bowser wrote:
On Sunday, August 23, 2020 at 8:11:26 PM UTC-4, wrote:
On Sun, 23 Aug 2020 07:20:43 -0700 (PDT), "
wrote:


But the key point the op appears to have not noticed is that his
crude paper cap has already lasted over 70 years. That is more than
good enough.

We do not know that at all. What we do know is that *FINALLY* Eric
has gotten around to dealing with it.

Peter Wieck
Melrose Park, PA

I was going to go back in time to replace that cap but my time machine
was serviced byb me after a few gins so instead I waited until I
bought the grinder in real time, used it for a couple years, posted a
question about it here and now I have a new cap coming.


Good stuff with orange juice and 2 or 3 banana liquors. I wonder what
an 80 year-old gin bottle would fetch today.

How do you teach a gin bottle to fetch?????


You can't teach an old gin bottle new tricks.



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