Compressor problem / electrical question

I've got a Campbell Hausfield hobby type compressor I won in a contest back a bit. Anyway been working fine, shut it off for a few months and when I went to
use it again, no joy. (Fortunately I have a backup).
Fuse was blown so I put in another one. Bzzt! Hmm, let's try that again. BZZT! OK, there's a dead short somewhere. Got thing completely disassembled. There is no obvious fry or melt anywhere. The motor brushes, etc look fine no visible shorts, not even sure you could have one.
The only electrical components are the power switch, the pressure switch and on the PCB itself are a Metalized Polyester Film Cap 104K/630V and a KBPC1-10 Bridge rectifier. Oh and the fan leads, a standard 120V type cooling fan.
Now I am definitely not a real electronic gearhead. I can solder/desolder, use a meter and I sort of know what the components are for. So my question is could a rectifier fail sufficiently to cause a dead short without any external evidence. I'm pretty sure it isn't the cap since it's just in and out 2 leads, but the rectifier has 4 legs and from the data sheet I looked at I could definitely see where an internal short could develop.
And no I haven't metered anything yet, I just got it disassembled for the preliminary exam and wanted to ask this.
Frank
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Frank, I'm not familiar with the brand and I don't know if you've already looked at this, but it seems to me that the motor or compressor might be siezed from sitting, hence the overload and blown fuse. If possible, see if you can turn anything by hand. If you've already done this, ignore me and continue with your investigations. I mention it because my Paasche compressor suffers from the same thing at times, which is usually cured by a quick slap upside the head. :)
RobG (The Aussie one)
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Hmm, that's an idea. I'll check.
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I have a 13 gallon sized CH compressor I use for handyman work. If I use an extension cord more than 50 feet long the breaker will trip when the motor gets hot (underpowered due to increased resistance of the cord and the resulting voltage drop.) Shouldn't your compressor have a overload breaker rather than a fuse?
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Remove\disconnect the brushes. Power up and see if it still blows. If it does then you know the problem is in the limited drive components (rectifier, capacitor) etc.
If not then it doesn't necessarily rule out those components but it is more likely to be a problem with the motor (armature winding, or motor seized etc.).
The rectifier is a bridge rectifier with 4 diodes to do full wave AC to DC rectification. If you look here
http://en.wikipedia.org/wiki/Diode_bridge
it is possible that if one or more diodes were to fail closed circuit then you could get a short on the AC side. However, I've never known one fail like this - but there is always a first time.
The capacitor is either a smotthing capacitor (if it is a big electrolytic) or more like a suppresor to stop the generation of RF noise that would interfere with radios etc. Unlikely for that to be the problem.
Cheers,
Nigel

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Resending as something appears to have gone wrong with my first post. Apologies if you can see this twice.
Remove\disconnect the brushes. Power up and see if it still blows. If it does then you know the problem is in the limited drive components (rectifier, capacitor) etc.
If not then it doesn't necessarily rule out those components but it is more likely to be a problem with the motor (armature winding, or motor seized etc.).
The rectifier is a bridge rectifier with 4 diodes to do full wave AC to DC rectification. If you look here
http://en.wikipedia.org/wiki/Diode_bridge
it is possible that if one or more diodes were to fail closed circuit then you could get a short on the AC side. However, I've never known one fail like this - but there is always a first time.
The capacitor is either a smotthing capacitor (if it is a big electrolytic) or more like a suppresor to stop the generation of RF noise that would interfere with radios etc. Unlikely for that to be the problem.
Cheers,
Nigel
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Thanks, both times.
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Gray Ghost wrote the following:

A common problem is the check valve.that prevents backflow from the tank to the compressor head. It can be disassembled and cleaned which may work, or a new check valve might be needed. Go to the Campbell Hausfeld manuals site and enter your model number for a diagram and parts list. http://www.chpower.com/webapp/wcs/stores/servlet/XManuals?langId=-1&storeId 051&catalogId001 or http://tinyurl.com/5jexo4
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Bill
In Hamptonburgh, NY
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Yep, I did that. Unfortuneately all the parts I want to see are marked "Not a shown". But I'm pretty sure it's the bridge rectifier by now.
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Gray Ghost wrote the following:

OK, but here's some clues for a bad check valve from their FAQs.
Q: My compressor motor hums and then trips my breaker, should I replace the motor? A: There could be several causes for the motor to hum but the most common would be because of a bad check valve. The check valve is located at the bottom of the exhaust tube where it goes into the tank. It is a one-way valve that keeps pressurized air from backing up onto the pump head. When the check valve fails, the compressor pump is trying to start under head pressure and the motor is not designed to handle this type of load. It will then draw high current until either the circuit breaker trips or the motor overload trips. The easiest way to diagnose a bad check valve is to listen to the compressor when it shuts off at max pressure. You should hear a short hissing sound coming from the unloader valve on the pressure switch that will stop after a few seconds. If the hissing sound does not stop, the tank pressure is leaking through the check valve onto the compressor head and also through the unloader valve. Upon restart of the compressor, the motor will start humming. Using too small of an extension cord or low line voltage could also cause a motor to hum at start.
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Bill
In Hamptonburgh, NY
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I saw that. I took the whole bloody thing apart. I turned in on with the pipe removed on the advice of a friend who is a electronics engineer among other things. Pump never even had a chance to start, the fuse blows the moment I click the switch.
Thanks.
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Gray Ghost wrote the following:

No problem. Well, at least the clues will be in Google news forever for others who may have trouble with their compressor. :-)
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Bill
In Hamptonburgh, NY
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