[Elecraft] KBT2 charging question

[Don Wilhelm]

John,

While that method is used in many instances, remember that 'the transistors
will always protect the fuse!'

I have seen (and created myself <G>) instances where that parallel diode
will open as soon as it sees a large current impulse due to the reversed
polarity (and before the fuse reacts) and the protection mechanism itself is
gone.  The series diode is much safer for the equipment.

The K2 does have that type protection circuit (RF Board schematic D12) as
well as the series diode, D12 is after the self-resettable fuse, so if you
want to try it, all that is necessary is to bypass D10 with a bit of wire
(not on my K2 please) <G>

73,
Don W3FPR

> -----Original Message-----
>
> Don et al:
> I've never tried this, but I've been wondering if any protection would
> be given the K2 if there were a reverse-biased diode running from the
> +13.8V input to ground.  Put a 5 amp fuse in the positive line between
> the diode  and the power socket and it should immediately blow if the
> diode senses a reverse hookup.  With a correct hookup, the K2 would get
> the full voltage from the power supply.  My guess is the K2 might still
> experience some damage before the fuse blew, but I'm not smart enough to
> know that for sure and I'm definitely NOT going to try it on mine!  I
> haven't noticed any problems with the series diode.
>
> Just some food for discussion, but let's not have a food fight
> over it (hi).
>
> 73's,
>
> John AA0VE
>