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From: Denis G. on 8 Oct 2009 21:48
On Oct 8, 9:03 pm, dave <tool_...(a)weirdstuffcox.net> wrote:
> my ancient 4hp sears craftsman air compressor needs a starting
> capacitor, I've determined (through a process of elimination). I still
> have the original owners manual, and the capacitor is "part of the
> motor", not shown in the parts blowup, or parts list, as a seperate
> orderable part. further, the friggin' thing seems to be a 'non-standard'
> mfd rating, too (it doesn't 'fall into' any capacitor size-groups of any
> maker's starting cap's I can find online. matter of fact, it's not even
> close):
>
> the one in it now is
> 110 volt, 485-580 mfd
> mallory #139852-49
> seems a slightly non-standard SIZE as well:
> diameter: 1 13/16ths inch, and
> length, overall, excluding 'spades': hair over 4 5/16ths (but clearly
> under 4 3/8ths)
>
> atttempts to locate same by the mallory part number on it entirely
> unsuccessful. so (physical size and 'look' issues aside) can I "daisy
> chain" two cap's and achieve the same net effect, somehow? appearance
> "not an issue", I just need a working compressor. I know I can replace
> the cap with a higher voltage cap, and that'd be fine (maybe even
> desireble) but what about the mfd rating? if I must, is it best to go
> 'bigger mfd numbers' or lesser?
>
> thanks for tips on this, guys :-)

It looks like the value of the cap is not that critical. They give
you a range 485 to 580 microfarads. The average value is
approximately 540 microfarads. If you order from McMaster Carr, this
should work: http://www.mcmaster.com/#7245k114/=3z7b3b

From: KD7HB on 8 Oct 2009 22:03
On Oct 8, 6:03 pm, dave <tool_...(a)weirdstuffcox.net> wrote:
> my ancient 4hp sears craftsman air compressor needs a starting
> capacitor, I've determined (through a process of elimination). I still
> have the original owners manual, and the capacitor is "part of the
> motor", not shown in the parts blowup, or parts list, as a seperate
> orderable part. further, the friggin' thing seems to be a 'non-standard'
> mfd rating, too (it doesn't 'fall into' any capacitor size-groups of any
> maker's starting cap's I can find online. matter of fact, it's not even
> close):
>
> the one in it now is
> 110 volt, 485-580 mfd
> mallory #139852-49
> seems a slightly non-standard SIZE as well:
> diameter: 1 13/16ths inch, and
> length, overall, excluding 'spades': hair over 4 5/16ths (but clearly
> under 4 3/8ths)
>
> atttempts to locate same by the mallory part number on it entirely
> unsuccessful. so (physical size and 'look' issues aside) can I "daisy
> chain" two cap's and achieve the same net effect, somehow? appearance
> "not an issue", I just need a working compressor. I know I can replace
> the cap with a higher voltage cap, and that'd be fine (maybe even
> desireble) but what about the mfd rating? if I must, is it best to go
> 'bigger mfd numbers' or lesser?
>
> thanks for tips on this, guys :-)

The capacitor values are a range because the caps are made with a
large tolerance. Even if you got one marked exactly 580 mfd, it could
actually be much smaller or much larger. I don't think Mallory has
made capacitors for many,many years.

One trick we used to do in a emergency is to get two DC electrolytic
capacitors of twice the needed AC capacity and connect them in series,
either both + leads or both - leads together and wire the remaining
leads to the motor to replace a single AC capacitor. Gets you going
while you look for the correct replacement.

Paul
From: Bill Noble on 8 Oct 2009 23:44
That is a common value, either of these two will work at about $8 each

http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=3363840&PMT4NO=72152023

http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=3363841&PMT4NO=72152023


"dave" <tool_box(a)weirdstuffcox.net> wrote in message
news:rZvzm.94198$u76.12432(a)newsfe10.iad...
> my ancient 4hp sears craftsman air compressor needs a starting capacitor,
> I've determined (through a process of elimination). I still have the
> original owners manual, and the capacitor is "part of the motor", not
> shown in the parts blowup, or parts list, as a seperate orderable part.
> further, the friggin' thing seems to be a 'non-standard' mfd rating, too
> (it doesn't 'fall into' any capacitor size-groups of any maker's starting
> cap's I can find online. matter of fact, it's not even close):
>
> the one in it now is
> 110 volt, 485-580 mfd
> mallory #139852-49
> seems a slightly non-standard SIZE as well:
> diameter: 1 13/16ths inch, and
> length, overall, excluding 'spades': hair over 4 5/16ths (but clearly
> under 4 3/8ths)
>
> atttempts to locate same by the mallory part number on it entirely
> unsuccessful. so (physical size and 'look' issues aside) can I "daisy
> chain" two cap's and achieve the same net effect, somehow? appearance "not
> an issue", I just need a working compressor. I know I can replace the cap
> with a higher voltage cap, and that'd be fine (maybe even desireble) but
> what about the mfd rating? if I must, is it best to go 'bigger mfd
> numbers' or lesser?
>
> thanks for tips on this, guys :-)

From: Franc Zabkar on 9 Oct 2009 01:41
On Thu, 08 Oct 2009 21:03:20 -0400, dave <tool_box(a)weirdstuffcox.net>
put finger to keyboard and composed:

http://www.instruction.greenriver.edu/avery/activities/tech/images/Shift_Key.jpg

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
From: Roger Shoaf on 9 Oct 2009 04:06

"dave" <tool_box(a)weirdstuffcox.net> wrote in message
news:rZvzm.94198$u76.12432(a)newsfe10.iad...
> my ancient 4hp sears craftsman air compressor needs a starting
> capacitor, I've determined (through a process of elimination). I still
> have the original owners manual, and the capacitor is "part of the
> motor", not shown in the parts blowup, or parts list, as a seperate
> orderable part. further, the friggin' thing seems to be a 'non-standard'
> mfd rating, too (it doesn't 'fall into' any capacitor size-groups of any
> maker's starting cap's I can find online. matter of fact, it's not even
> close):
>
> the one in it now is
> 110 volt, 485-580 mfd
> mallory #139852-49
> seems a slightly non-standard SIZE as well:
> diameter: 1 13/16ths inch, and
> length, overall, excluding 'spades': hair over 4 5/16ths (but clearly
> under 4 3/8ths)
>
> atttempts to locate same by the mallory part number on it entirely
> unsuccessful. so (physical size and 'look' issues aside) can I "daisy
> chain" two cap's and achieve the same net effect, somehow? appearance
> "not an issue", I just need a working compressor. I know I can replace
> the cap with a higher voltage cap, and that'd be fine (maybe even
> desireble) but what about the mfd rating? if I must, is it best to go
> 'bigger mfd numbers' or lesser?
>
> thanks for tips on this, guys :-)

Take the old one to the Grainger's nearest you and walk out with a suitable
replacement Easy.

If no Grangers nearby, look in the yellow pages under motor rebuilding and
they can set you up also.


--

Roger Shoaf

About the time I had mastered getting the toothpaste back in the tube, then
they come up with this striped stuff.


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