D.G. Nova update -- crapacitors strike again

[Christian R. Fandt]

Upon the date 03:32 01-04-05, Tom Jennings said something like:
>Well I identified the failure, fixed it, and the disk pack is
>formatting right now. Whew!
>
>Another crapacitor -- looks like a tantalum, but it's only .01uF,
>a dipped-looking bright blue axial part, about the size of a 1/8W
>resistor. I think these were discussed recently; not necessarily
>tants, but some short-lived process.

Oh yeah, these are likely monolithic ceramic caps. We used them in various 
products as logic supply bypass caps where I used to work. I personally 
have not seen any failures like this in my own experience. I have a bunch 
of 0.1 uF parts on reels around here somewhere.

However, disc ceramic capacitor failures were a recent topic of discussion 
on one of the old radio email lists. Failure mode was migration of the 
capacitor plate material through the disc because of flaws or cracks. High 
leakage current or outright shorts were the problems observed. I can see 
that happening with axial monolithic caps if there were manufacturing 
quality problems with the ceramic materials used to make the parts.


>Man, there's hundreds of those little blue bastards in this
>machine. I hope future shorts are so benign. Gulp.

May be just the only one you'll ever see but at least you've learned by 
experience a failure mode of these parts.


Regards,   Chris F.

NNNN


Christian Fandt,    Electronic/Electrical Historian
Jamestown, NY  USA      cfandt at netsync.net
         Member of Antique Wireless Association
         URL: http://www.antiquewireless.org/