Can I replace a HV Capacitor with a slightly higher capacitance?

Thread Starter

jonlim

Joined Mar 18, 2019
28
Hi! I have a Samsung microwave oven in which everything is working except it is not heating. I have a very limited knowledge with electronics, so everything that I will be telling here is based on research i did on the internet. I have checked using a multimeter tester the HV Diode by connecting it to a 9v battery and it was okay (I watched a video how to do it). I also checked the magnetron by checking for continuity its power supply pins and each power supply pin against the body using a multimeter tester and it was also okay (I also watched a video how to do it). When I checked the HV Capacitor using resistance test, it only tested 1.6 ohms wherein there is supposed to have a 10M ohms resistor inside it, also in the capacitance test, it shows 0 mF. I believe the HV Capacitor is shorted.

The HV Capacitor BiCai CH85-21068 and rated as 2100V-AC, 0.68uF, 10M ohms. I wish to replace it but the closest the online sellers have is a generic HV Capacitor with a rating of 2100V-AC, 0.7uF, 10M ohms. My question is can i use this even though this has a slightly higher capacitance? (0.68uF vs 0.70uF). This HV Capacitor is the big one connected from the power supply in one end and to the HV Diode and magnetron on the other end so I know, I cannot take chance on this.

Thanks in advance.
 

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Papabravo

Joined Feb 24, 2006
14,668
Generally speaking you can do this subject to some caveats. If the value of capacitance is used to perform a timing function then results may not be acceptable. In filter applications the value may change the behavior of the filter. In power supplies you can normally do this.
 

Thread Starter

jonlim

Joined Mar 18, 2019
28
Generally speaking you can do this subject to some caveats. If the value of capacitance is used to perform a timing function then results may not be acceptable. In filter applications the value may change the behavior of the filter. In power supplies you can normally do this.
Since this capacitor is connected from the power supply on one end and to the HV Diode and Magnetron to the other end and as far as I know, this is used to power the Magnetron, does it mean this small variance in capacitance is "okay" and will work just fine? Thanks!
 

KeithWalker

Joined Jul 10, 2017
1,296
It should work. The tolerance on the value is probably close to the difference of the nominal values. The tests you did on the magnetron are not 100% conclusive so the capacitor may blow again. Good luck.
Keith
 

Thread Starter

jonlim

Joined Mar 18, 2019
28
It should work. The tolerance on the value is probably close to the difference of the nominal values. The tests you did on the magnetron are not 100% conclusive so the capacitor may blow again. Good luck.
Keith
Thanks! I would take my chances! The only thing I want to be sure of is that this won't create any accident as this is high voltage. Thanks, again!
 

Papabravo

Joined Feb 24, 2006
14,668
Thanks! I would take my chances! The only thing I want to be sure of is that this won't create any accident as this is high voltage. Thanks, again!
For that you pay attention to the working voltage rating. A bit of headroom on that can't possibly hurt and it might help.
 

MrChips

Joined Oct 2, 2009
22,085
0.68μF and 0.7μF are virtually the same value. The difference is in the labeling.
At ±5% tolerance, the actual value can be anywhere between approx. 0.64-0.74μF.
 

dendad

Joined Feb 20, 2016
3,612
Just a thought, did you have the capacitor disconnected from the rest of the circuit when you measured it? If not, you may have measured a shorted rectifier.
 
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