[Elecraft] K2 parts to have 'on hand' ?

[Don Wilhelm]

Brian,

I believe I can speak with authority having repaired over 1000 K2s in 
the last 15 years.

The one item that fails frequently in the K2 is the headphone jack, so I 
would advise having a spare on hand.

Maybe a set of K2 PA transistors (for the base K2, not the KPA100).  If 
the diodes in the KPA100 or KAT2 are hit by static and the power control 
goes to maximum, the base K2 PA transistors will fail if that condition 
is not recognized and operation is not stopped until the condition is 
corrected.

If the K2 is old, yes the AF Gain and other potentiometers can become 
'scratchy', and since they are sealed, there is no other cure but 
replacement.  If the K2 serial number is less than 3000, make sure the 
Alternate AF Gain Wiring Mod has been installed (and replace the AF Gain 
pot at the same time).

A few 1N5711 diodes can be handy especially if you are not diligent 
about disconnecting the antenna when not in use and static from the 
antenna feedline takes out the diodes in the wattmeter (KPA100, KAT2 or 
KAT100).  For those who do disconnect the feedline(s), be certain to 
short between the feedline center conductor and the shell to discharge 
any accumulated static charge before connecting it to the K2 ANT connector.

Other than that list, I can't think of any K2 part that fails 
frequently.  As Murphy says, if you have the part on hand, it will not 
fail!  Other failures involving ICs and transistors are not common. 
However, if you have an older KPA100 (with red toroid cores at L15 and 
L16), I advise you to install the KPA100UPKT mod and also the shield kit 
KPA100SHLDKT.

If you do not have the current K2 firmware 2.04 MCU 1.09 IOC, you might 
want to upgrade it and save the old firmware ICs in case of a 
catastrophe, but that is not a frequent failure either.  Serial numbers 
below 3000 do require wiring changes for the sidetone source when 
upgrading to the 2.04 MCU firmware.  If the KIO2 or the KPA100 has been 
installed, those wiring changes have already been installed.

73,
Don W3FPR

On 1/4/2020 3:25 PM, Brian wrote:
> I saw a message on 'another list' the other day which was a reply to someone who was thinking about getting a K2 kit while they could. The reply said... "inferior parts.. get spare variable resistors etc."  ---- I am assuming he means potentiometers...
> Anyhow, I'd not seen or heard much about this 'you gotta replace this stuff in a year' kind of view.
> Since I DO have a couple K2 rigs... would I be advised to get a few critical parts to take them into the next decade or two? They probably have more than a decade on them already.
> I must admit that in the VERY early days I asked Eric how long we might expect the microprocessors to last? Meh, never been an issue nor has anything else in them, for me at least, luckily perhaps. Or the norm....
> 
> I realise nothing 'lasts forever' but since almost every thing I have is getting on... and some are pushing MY age from late 50's and early 60's circa some things can last a long time.
> In any case, any wisdom on what to get on the shelf and have at hand while it is possible?... or don't worry and if the time comes just say a fond farewell? Or will I not care if and when a K4 finally landed here sometime (not thinking about that....yet).
> 
> Having Winter fun on CW here...hope you are too.
> Brian VE3VAW