Hi Alan,
thanks for the tip, I will keep an eye open for RIFA PHE428 or PHE450
which seems to be the newer version of that capacitor type.
In my PA, I used two .1 uF caps in series to make .05 uF, then three
of these in parallel to make .15 uF hoping that the currents will be
distributed, however I think, once one of them gave up the ghost, the
others immediatelly followed suit, so I ended up with one in every
two-in-series capacitor being busted.
By the way, that self-healing effect is quite useful if you ever want
to create a bunch of lower value caps with non standard values :-) I
now have a77 nF, 45 nF, 16 nF and even a 0.3 nF out of my .1 caps! I
am kidding of course. :-)
73, Dimitris VK1SV
2012/8/9 Alan Melia <[email protected]>:
> Hi Demitris, I am not sure of the types codes but I used 1000v or greater
> rating, the problem often is that the caps are not rated for high pulse
> currents. The best kind of caps that are used are rated for pulse operation
> in switch-mode power supply. Normal caps will not take the current
> pulses.....the individual plates get disconnected from the lead wires.
> One of the caps I used has come to hand its a RIFA PHE428 rated 2000v. I
> used this on 36v Class E running about 300W. I believe WIMA make similar
> caps but I am not sure of their type numbers.
>
> Alan
> G3NYK
>
> ----- Original Message ----- From: "Dimitrios Tsifakis"
> <[email protected]>
> To: <[email protected]>
> Sent: Wednesday, August 08, 2012 11:03 PM
> Subject: LF: Caps for Class-E amp
>
>
>> Hello LF group,
>>
>> I am building a 200 W Class-E transmitter for LF but keep killing the
>> capacitors in the output circuit (both C1 and C2 according to the
>> schematic in Sokal's QST article). I have used a mixture WIMA
>> polypropylene MKP10, MKP4 and FKP1 caps and I haven't damaged any FKP
>> ones so far. Should I not bother with MKP and use only FKP caps or is
>> there any other type of capacitor what will do the job? I need a
>> couple of hundred of nanofarads. The voltage rating of the caps I
>> destroyed was 400 VDC or 250 VAC. I can see that these caps have a
>> decreasing AC rating as the frequency goes up, but that's what I had
>> in the junk box at the time...
>>
>> The mode of failure of these MKP10 0.1 400 VDC caps is interesting
>> too, they seem to go down in capacitance as the damage progresses.
>>
>> Any advice is appreciated.
>>
>> 73, Dimitris VK1SV/SV1DET
>>
>
>
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