[Elecraft] K2 PA and 232 problem

[Don Wilhelm]

Bob,

Great work. 

The EL5146 can be ordered from Elecraft, and if it has been discontinued 
in the DIP package, the SMD equivalent will be supplied mounted on a 
carrier board to adapt it for thru-hole use.
If you have the K60XV installed in your K2, the use of a non tri-state 
op amp will interfere with the K60XV transceiver output power control.

I really don't know the cause of these failures, I just don't have 
enough information about the circumstances of operation when the failure 
takes place.  I have seen a few of them, but it is a small percentage - 
you were one of the unlucky ones.

73,
Don W3FPR

Bob G3PJT wrote:
> Hi Don
> I was just about to send something to the reflector. Both the 1406 and 
> the 5146 had failed but I do not know why.
> However the solution was :-
> - find out which chip was crowbarring the 5v line. Pull the PIC - it 
> was OK in my case. Cut  pin 16 on the 1406, check and resolder if OK 
> (it was OK in my case) Do the same with pin 7 of the EL5146 which 
> showed that it was that chip which had failed. Extract the 5146 by 
> cutting the pins and clean up the board with desoldering tape. 
> Sacrifice the chip not the PCB. Replace with a 8 pin socket as EL5146 
> is discontinued here. Use almost any op amp with the same pinout 
> except for pin 8 and clip off pin 8.
> - I determined which channels of the 1406 were not working using a 
> prototype board type interface and then rewired the 1406 to use the 
> unused 232/TTL interfaces, only the pin5/12 circuit had failed in my case
> - replace the 78L05 as its not clear how much abuse it had suffered.
>
> 73 Bob G3PJT
>