Re: Zeta v1.1 The "Chernobyl" Ed.

[Sergey <skis...@gmail.com>]

Interesting... Any noticeable damage to the tantalum capacitors? How
about polarity of these tantalum capacitors, is it correct? (see this
picture for the reference: http://n8vem-sbc.pbworks.com/w/file/50221014/POLARITY.JPG).
Note that in Zeta version 1.3 I added polarity (+) signs near MAX232
capacitors, but I also rotated some of the capacitors (to make their
orientation consistent), so don't rely on Zeta 1.3 silkscreen, use the
picture above instead.

BTW, the frequent failure mode of tantalum capacitors is "short
circuit", which might happen if capacitors polarity was not correct:
http://en.wikipedia.org/wiki/Tantalum_capacitor#Polarity
http://en.wikipedia.org/wiki/Tantalum_capacitor#Thermal_runaway_and_self-destruction

That might explain the burned VCC trace.

The short life comment is more about electrolytic capacitors. Tantalum
capacitors (if used correctly) usually more reliable.

Thanks,
Sergey

On Jun 21, 4:49 pm, "..I'd rather be coding ASM!" <uri...@deviate.fi>
wrote:
> G'day Sergey,
>
> Some useful info's thanks! I didn't know tantilum's had a shorter
> life-span than ceramics and that changes the way I view things. I'm not
> sure where the short is then. I'll have to get the magnifying lamp out and
> go over every square centimetre. Odd that it happened during "normal"
> operation.
>
> Al.