K2/100 kaputt

[Raimon-3]

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
[hidden email]


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 [hidden email], 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
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[Don Wilhelm-4]

Raimon,

If your diode voltages differ from the chart by more than 20%, that may
indicate a problem.  The chart was created from readings on one KPA100
which was working properly, but that KPA100 may not have been exactly
typical (meaning component tolerances  were not checked for
mid-tolerance values), so some variation is expected and is not an
indication of a problem.

The oscillation possibility is an 'educated guess', so do change C31 and
then if a problem persists, we can offer additional assistance if you
give us data and your observations/conditions.

73,
Don W3FPR

raimon wrote:

> 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
> [hidden email]
>

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