[Elecraft] K27100 kaputt

[Don Wilhelm]

Raimon,

The KPA100UPKT changes the diode voltages in the T/R switch.  There is a
new chart for diode voltages in the KPA100 manual on the Elecraft
website that you should print and add to your older manual.  I am having
trouble following the columns for your measured voltages so I offer no
clear response to those.  Please re-check with the new chart.

If your KPA100UPKT did not contain a replacement for C31, you should
increase the value to .22 uf.  Elecraft will send you a .22 uf 65 volt
capacitor if you send a note to parts at elecraft.com, or you can replace
it with 0.2 or 0.22 uf capacitors that you obtain locally.  I have
paralleled 2 0.1 uf capacitors for use at C31 and that works fine.  Any
voltage rating above 25 volts will work.

Without the change in C31, the updated KPA100 can oscillate at about 660
kHz - not all KPA100s show that behavior, and some work initially, but
then later fail.  The .018 uf bypass capacitor at C31 is no longer an
effective bypass after the new design T/R switch components are added.

73,
Don W3FPR

raimon wrote:
> Hi Friends
> I have got a problem with my K2/100 and need your help.
> I built K2, KPA100, KSB2 and KAT 100 which worked OK for years from 
> the first day until now.
> Recently I upgraded the KPA100 with KPA100UPKT, it passed all tests (I 
> did not realign it), and it worked perfectly for two weeks.
> One day I worked in the morning without any trouble, but when in the 
> afternoon I fired it up again, the KAT100 was unable to tune: relays 
> clicked, diodes did not light, tune was not obtained.
>