[Elecraft] [K2] KIO2 Malfunction

[Don Wilhelm]

Larry,

Other than that negative voltage supply, the 5 volt regulator, and the 
12 volt line, there is just not other places to look for a problem.  The 
MAX1406 just handles two RS-232 signals in this application, TXD and 
RXD, so there is nothing on the board to stress the chip.

73,
Don W3FPR

KT4G wrote:
> Hello Don,
>
> Thanks for the insight.  I checked D4 and it seemed to be ok.  I went ahead
> and removed U1 and the voltage on the D1 anode rose from -3.3 to -11.5!  U1
> must be bad.  The only question is what made it that way?
>
> I'm going to order a couple of 1406's from Mouser and see if that indeed
> fixes the problem.  If the original chip suffered from a latent defect (in
> other words, was the proverbial "time bomb" waiting to go off), then I
> should be ok.  If the failure was due to another faulty component then at
> least I've got a spare...
>   
>