P.S James,

You can also follow Robert’s advice for a full test of these caps.
If you don’t have an insulation tester is not a problem. You can always rectify the mains voltage and then connect the capacitor under test with a 3 Watt (max). incandescent lamp, then feed it with the rectified d.c voltage and see if the lamp lights even barely but permanently. The normal function is to see some light, but momentarily (until the cap is charged). The smaller the power of the lamp, the better the sensitivity of your test is.
The best of course (preferably after the visual test) would be to connect a d.c mA meter in series with the cap/lamp circuit and see if there is any current flow. If there is, then you have a problem with the cap under test. Simple isn’t it? (Keep your eyes open when working with high voltage anyway)!!

B.R

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Hello James

I think I saw similar failure cases in the web, with those mylar caps defective. Anyway, keep in mind that you can use very safely your ESR meter down to 0,1μF, provided that your meter can measure up to 100 Ohms ESR. The only thing you need is a reference table. You can make your own table by buying a new set of them, starting from this value above and ending in 1μF. Once the table is available, you can go on with testing. No problem at all. I test all bipolar caps down to 0,1μF. This is the down limit, only because the meter cannot measure above 100 Ohms ESR!

Best Regards

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Hi James,

I was thinking maybe you have a bad cap or two also. You need to get an insulation tester to help find bad ceramic, mylar & etc caps. In my article, " Lights of America Shop Light Repaired", I found a bad cap with my insulation tester that checked good on capacitance. What the insulation tester showed was that under voltage the cap was acting like a resistor. That's why we need to check caps at high voltage because if they leak they behave like a resistor in the circuit.

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Thanks a lot for your valuable advise.
I will check the motor separately to identify whether it is the motor problem(e.g., needs lubrication) or electrical problem first.
In the past few days, I've also read some articles about fan motor speed problems, and nearly all of them trace back to a 0.xxuF 3XX volt cap. I think I might have overlooked the several 0.XX uF 3XX volt big mylar caps in my last trouble-shoot (because the ESR meter only target at bigger eCaps and are less effective in detecting small (0.XX uF) caps), I think I will de-solder those 0.XX uF caps and check their capacitance. I think if the problem is not due to the motor, then those caps will be the most probable cause.

Thanks again for your advise and look forward to reading more articles from you and learn from you.

Beat regards,
James

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Hello Ulises

Thanks for your support.

Best Regards

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Hello James

First of all I was working as a Panasonic service technician before 1986. Unfortunately at that time there were no such box fans in production and therefore I cannot give any straight answer to your problem. We had only the classic types of fans, where their speed changing was based upon tapping their internal windings connections and of course there was no louver at all installed on them.
In your case anyway, since there are electronics involved in the speed regulation process, if I were in your shoes, I would first start with checking the rotating mechanism itself. Then, if everything would prove to be in proper operating condition, I would go to the electrical part. In this stage I would try to locate the problem by separating the motor from its circuitry and feeding it directly with power for a given speed. Then I would have the picture of the problem clear. If the motor would work steadily in constant speed, then the problem would obviously be hidden in its electronics. Now, given that you have already done some essential tests, I believe that you are very near to the solution you seek…
The only failure I strongly remember with these fans is that either after extended operation of them or especially at their first try to operate them at a new summer season after being left standing for almost one year, the rotors of their motors were stuck due to the grease used to lubricate the rotor axle within the (sleeve or ball-) bearings having become in a petrified condition. The problem was every time eliminated by thorough cleaning and re-lubricating those bearings. There was no electrical failure with their motors whatsoever

Thank you for your good words.

Best Regards

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Hello Robert

I simply put momentarily my finger on the upper surface of this “post stamp” chip. This was the only place available to measure temperature as there was no heatsink on it before I put the one.
As a following test, I measured the magnitude of the temperature by using the method already described in the article.

Best Regards

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Hi Zed

Thank you too.

Best Regards

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Hello Yogesh

You are always welcome.

My Best Regards to you as well.

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