[Elecraft] K2/100 kaputt

[raimon]

Dear Don
Many thanks for your prompt reply and information.
C31 in my KPA100 is 0.033 mf, I did not receive it with the upgrade kit 
and I forgot to change it.
I will try to get it from a local supplier, either .22mf, .2 mf or two 
.1 mf as you suggest.
Most voltage diodes readings agree with the new chart, but there are 
still notable deviations.
If you believe that my problem is caused by an oscillation, I will wait 
until I can substitute C31.
If you suspect any other reason, I will send the voltages chart again in 
a more intelligible way.
Many thanks again, I hope to have soon my K2/100  working again.
73
EA3EZO
Raimon
rfuidio at telefonica.net


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