Re: Interesting observation, question

On Sat, 12 Jul 2003 17:45:28 -0400, "James S. Bright" <james@quarterarcade.com>
wrote:

>
>I have noticed on these Zoo keeper/Qix boards (BTW, the second level of
>Dante's hell) and I've run into now three boards that have had their 12V
>line shorted to ground. In all cases, it's been due to the tant
>capacitors. I've got some new ones in stock, yet in one case merely
>having that cap installed (new cap) will cause the short. That's the
>general observation.
>
>The question part comes down to this: is this pretty common for tant
>capacitors in general? Do they tend to fail short?

Absolutely. It's the number one reason Cinematronics monitors fail -- shorted
tant caps. I think they only need nano-seconds of reverse voltage to short.
They're very temperamental and I swear these things will short out if they've
already seen the Seinfeld episode playing, and you don't turn the channel.

>Since they're used
>only to cut down on noise in this application (4116 chips), I can run
>the board just fine without them. Although if there were designed to run
>with them installed, I'd like to have them installed.

Replace them with electrolytic caps. You'll have to increase the capacitance,
to get the same noise reduction, since tants have better H.F. response at lower
capacitance. My rule of thumb is to double the value. For instance, replace
4.7uf tants with 10uf elects.

-Zonn
Received on Sat Jul 12 15:52:38 2003