Re: Garry's MMC cap failure explained.

["Tesla list" <tesla-at-xxxxxxxxxx>]

Original poster: Terry Fritz <twftesla-at-uswest-dot-net>

Hi Marc,

At 06:14 PM 12/2/2000 -0500, you wrote:
>terry,
>does the construction of garry's caps use that "compressed aluminum powder"
>looking stuff for the foil end connections? the reason i ask is that i had
some
>propylene caps that heated on one end in operation also, after a few burnt, 
>i tore
>them apart and it seemed this powdery stuff had some kind of plastic blended 
>into
>it, (maybe a binder?) this powder end cap actually had nonconductive spots 
>in it
>that my megger wouldn't ring threw. i thought that even though i used a
sink on
>the leads, i overheated the "powdery cappy thingy" and melted the "binder"? if
>this could be what is going on then maybe all the current is going through a 
>very
>small area on the end cap?
>i threw all of them out and i don't remember the make, but i'll dig in my junk
>boxes if you think this is feasible, might still be one lying around.
>just a thought.
>marc

All these caps have "sloupage" (sp?) as an end cap material (I think it is
much like that aluminum solder stuff you see at the hardware store).  This
is some odd metal stuff that will stick to aluminum and the lead and still
conduct electricity (sposed to).  I have never seen a problem with this
stuff but I have seen leads that did not go far enough into it and fail do
to insufficient lead contact area to it.  The attachment of this stuff to
the foil is a common failure point that appears to be due to current simply
burning the connection out.  Apparently, it "sticks" far worse to vacuum
metal films than to the solid foils.

If the caps you threw out are "bad" for Tesla coil stuff, I would love to
list them to help others avoid getting them again!  It appears that the
caps that have ALL the layers as vacuum deposited metal film are far worse
that those that have solid metal foil layers.

http://hot-streamer-dot-com/TeslaCoils/MMCInfo/good-bad.txt

So far only one person has sent me their data but I added my MMC testing
stuff to the list also just now.  All I need to know is the manufacturer,
part number or type, voltage, value, and if it as a good or bad MMC cap in
your experience.

Cheers,

	Terry


>
>Tesla list wrote:
>
>> Original poster: Terry Fritz <twftesla-at-uswest-dot-net>
>>
>> Stan,
>>
>> We are thinking this was either a bad batch or something else is wrong.  I
>> did notice that one seemed to heat on just one side??  Garry had the leads
>> bent pretty close to the case.  I wonder if the end connections were
>> damaged by sever lead bending?  I'll do more tests...
>>
>> Cheers,
>>
>>         Terry
>>
>> >snip
>