Thread: Help needed to find Faulty Capacitor

Not all multimeters will have a capacitance (C) measurement setting but that is what you will need.

To measure them correctly you will need to disconnect the power and wait for couple of minutes so they self discharge.
To be sure the are discharged you can connect a light globe across the end of the cap.

Then disconnect one leg of the Cap from the circuit board and apply the meter leads to each leg - it takes a few seconds to do the measurement so wait a while before removing the lads.

The next problem you might come across is that the Cap might have a capacitance that is too large for the meter to measure.
Then you need to combine other know caps caps in series and this will reduce the overall capacitance to a measurable level.

The total capacitance Ct is related to the individual caps (1, 2, 3 etc) by 1/Ct = 1/C1 + 1/C2 + 1/C3 etc
If 1 is your unknown and you measure Ct, C2 and C3 you can do some maths and find C1.

Repost both you picture so I can read the scales on the meter and the values of the components on your board.

I am not familiar with the Jet Air Filter so don't know what the circuit board does. But a humming motor could be the motor start capacitor. If the start capacitor is the issue, giving the motor a spin then applying power while still spinning should make it run. Warning - only do this if safe to do so.

Peter

I'll give it a try...I know what you mean ...I'll start it spinning with something other than my fingers....stick of celery perhaps.

If it is the Starter Capacitor, it is the one attached to the top of the motor. At least that may eliminate one of the Capacitors in the equation.

Well it doesn't appear to be the Starter Capacitor.......I was able to give the motor a big spin and then turned the unit on and the motor immediately slowed down to it's slow turning & humming again as if a brake was applied to it.

Disconnect the one on the motor & try the same push start trick.

It could be shorted & that will give you the same symptoms.

So instead having the current pass through the Capacitor......join the 2 wires that the capacitor is connected to at the moment and take the capacitor out of the line.

NO definitely not.

1) Start with the Motor off.
2) spin motor by hand
3) remove hand and apply power.

Originally Posted by skot

So instead having the current pass through the Capacitor......join the 2 wires that the capacitor is connected to at the moment and take the capacitor out of the line.

No, disconnect the cap & tape up the ends, then try the push start.

If the cap is shorted, that is the same as connecting the 2 wires.

The Start winding is out of phase with the Run winding, the Cap causes the AC to be moved out of phase.

It is there to start the motor rotating in the same direction each time.

If it was shorted, both windings would be getting the same phase AC & with one winding out of phase with the other, you would get the symptoms you are describing.

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Cliff,

That doesn't appear to be the problem. I tried as per above but it still has the same problem.

There is another capacitor on the board ...2.2uF 250VAC....the big rectangular black one on the PC board image I posted

I saw a Youtube vid that showed a Jet Air Filter with the same problem as mine. The owner replaced that Capacitor and that fixed the problem but when I enquired at Jaycar Electronics, they didn't stock those types.

Any help in where I can source one of those 2.2uF 250VAC capacitors would be appreciated. This will probably be my last attempt in repairing the PC Board components as it should be just a couple of dollars for the Cap. If that doesn't work, I might just have to go to Gregory's and cough up the $165 for a new board. (I think the last one I bought for this unit in 2013 was only $75)

Cheers

Scott

Try Mouser Electronics

Mouser Electronics Australia - Electronic Components Distributor

..

Ignore the value on the pic, it is just a sample to show you what it looks like.
https://www.wagneronline.com.au/moto...250-433/39/pd/
https://www.wagneronline.com.au/moto...250-369/34/pd/

Thanks Cliff...that would explain why the one I removed from the board says 105K 400VAC....going to Jaycar tomorrow with Capacitor in hand to see if they have one...if I can not get one locally tomorrow I will give Mouser Electronics a try as recommended by Big Shed.

This is the one I removed .....


AF Cap.jpg


I am hoping that Jaycar has staff that knows their gear but I have also looked on the net for a conversion table...can you knowledgeable folk tell me the equivalent...is 105K = 1uF ?

Yes. 105k is 1uf. The code equals. 10 *10^5 if I remember correctly.

We buy most of electronic parts from Jaycar or, if they don't carry it, element14 (used to be Farnell)

B32524Q6105K - EPCOS - CAPACITOR POLY FILM 1UF 400V RADIAL | element14 Australia

Originally Posted by Lappa

Yes. 105k is 1uf. The code equals. 10 *10^5 if I remember correctly.

Gnats hairs, but 10x10^5 would be 10^6 or 1 Mega . . . . .
10x10^-5 would be 10^-4
To be 1 uF it would need to be 0.1x10^-5

For some codes see. Capacitor code table | Kaizer Power Electronics