oh turds! compressor motor starting cap's 'blown out' but it's a "non-standard"

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:

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

That is a common value, either of these two will work at about $8 each

CDE bought the Mallory capacitor business. Take a look at this catalog page:

Thus looks to be the closest size:

460-552 MFD PSU46015A 110/125V 1-13/16" 3-3/8"

$6.15 each, 42 in stock.

--
The movie \'Deliverance\' isn\'t a documentary!

On Thu, 08 Oct 2009 21:03:20 -0400, dave put finger to keyboard and composed:

- Franc Zabkar

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Please remove one \'i\' from my address when replying by email.

On 10/8/2009 7:03 PM KD7HB spake thus:

That can't be safe, can it--running AC through two polarized capacitors?

(Hey: two explosions for the price of one!)

--
Found--the gene that causes belief in genetic determinism

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.

You shouldn't have too much trouble finding a suitable replacement from an electrical jobber supplier.. Johnstone, or local independent electrical supplies dealer.

If you have a local motor repair shop, they will know what you need by referring to the 120VAC motor voltage and 4 HP motor rating.

Start capacitors need to be for AC usage, and are typically sized at about

500uF per HP. The numbers on the original cap indicate that the actual value of that series can be as low as the minimum value, or as high as the maximum value shown. The actual measured values (microfarad, or uF, or mfd) of start capacitors can vary widely, as much as about 30%, especially on parts that are decades old.

The voltage rating for start caps is generally higher than the AC line voltage, and different manufacturers choose to use different rating numbers. Another common marking is 377VAC.

The other source of problems in split-phase motors would be the centrifugal switch for witching between the start and run windings.

-- WB ......... metalworking projects

Why? You have no idea how it actually works. Look up 'Electrolytic Rectifier'. What happens when you have two series connected rectifiers, with both cathodes connected? Nothing, if you don't exceed the PIV of either diode.

Sorry, but you're the biggest loser. :(

--
The movie \'Deliverance\' isn\'t a documentary!

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Roy, you're probably right, however, I wonder that if you skew the value to the higher end if you pay a price by decreasing the life of the contacts on the centrifugal switch.

Air compressors . Pull too much power , makes me wanna put a 13hp gas engine , Atkinson the engine , which is easy since the cam has an advance .

Or hyd pump , driving a 3 stage piston , any pressure you want .

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It was NOT a movie , no one remembers it . ------------- Any Monte Python fans out there ... ---- Time Bandits had a few Monte Python characters and some very talented dwarfs . I can allways watch Time Bandits , without falling asleep . Robin Hood " Is that REALLY necessary ? Oh yes mastu .. Then Robins man slugs a poor old lady for accepting stolen property .. from Robin Hoods Righteous thieves . . Sean Connery played a good character . The ogre .. "More foot powder , dear ? " ---- Life of Brian was OK , A few laughs .. ---- Holy grail was the WORST , most boring t ive ever seen .

Jackie Chan Shanghai Noon . very good Shanghai knights bad . Tuxedo . mediocre . Who am I OK , not boring , they changed scenes enough to catch a wide audiance . But some parts , i had to FForward.

Forbidden kingdom? was very good . Color and photography and sets were very good .. Almost Nat' Geo'

Wild Wild West had some really good props and scenery and color and lighting was Star Wars quality . Spies like us was OK , Scenery was bright and colorful , Unlike other Chevy Chase movies .. The gods must be crazy had the same fast scene/theme change and i had to FF some of it , but the rest is OK . Eddie Murphy in Harlem nights ... not bad , but Eddie played in another where he got to sing more . forgot the name but it was very good . Papillon Steve McQueen .. The only part i liked was when he escaped to native village ,, live with the girl.. The rest was too cruel , Sand pebbles , too "dark" and serious ... tragic . Great escape lots of top actors , good acting , good scenes .. Germans were depicted in a good way .

Wise guys , Danny DeVito and ? Piscopo . Not real hot . ? ? somethin somethin of the "rose" Sean Connery = Bad

African Queen , B&W see it once every 10 years is OK Toyko joe B&W no . casablanca B&W much better . good acting

Dirty rotten scoundrels NO

Rush hour wasnt very good

Hi!

Funny you'd mention that. I bought an old furnace fan assembly ($10) and found that not only was the motor rusty inside, but the start cap was bad. The motor cleaned up well and that got it starting a lot better, but it was still stubborn at times.

So I popped the cap out and looked at it. Turned out it was a Mallory capacitor. I took another look at it and said "that's been a long time". What I took as a date code suggested 1983 or 84 (don't remember which). I'm sure that little motor started up lots of times between then and now.

I'm going to have to remember that! (Or at least remember to try it and see the next time a capacitor drops out.)

I'd have thought that finding a replacement capacitor for my fan would have been easy. (Find one at the hardware store, right?) Nope. Struck out at various hardware stores, Farm and Fleet (now, come on!) and only had any luck at a little hole-in-the-wall motor repair shop.

$7 later I had a slightly larger "Rotom" ("motor" spelled backwards-- clever, huh?) capacitor and everything was fine once again. I was fortunate in that it did fit the capacitor compartment perfectly.

If the OP can't find an exact replacement, mounting it elsewhere on the motor should be acceptable.

William