[Elecraft] Issues with KPA100 (K2/10 is 100% OK)

[Don Wilhelm]

Holger,

Those resistance values indicate that D16 and D17 in the KPA100 are 
faulty.  The resistance in the forward direction should normally be much 
lower.  You can check to see if your ohmmeter is reading properly by 
measuring a new or known good small signal diode.

I believe if you check the power output with an external wattmeter and 
connected to a dummy load, you will find a higher than normal power even 
though the K2 display and LED Bargraph indicate no power.

You might want to check D1 and D2 in the KAT100 as well.

73,
Don W3FPR

On 5/5/2014 3:09 PM, dl9hda at dl9hda.de wrote:
> Hi,
>
> my K2 works well but I have issues with my KPA100. KPA100 and KAT100 
> are both situated in an external enclosure but the KAT100 is 
> permanently disabled (cal-mode). I used the KPA100 to drive my 
> tube-amplifier ...
>
> I cannot exactly say what happend but for a year or so the maximum 
> output power on all bands has been only 60W. It's enough for the 
> tube-pa but now the output is zero.
>
> If I change the band or hit the antenna-switch the relays are working. 
> So the communication seems to be OK.
>
> While pressing tune the K2 says high current and there is absolutely 
> no output-power an the K2 and of course at the KPA100. (The K2 without 
> any connections to the second enclosure works pretty well!!!).
>
> So the first guess was to check the diodes D16 and D17. I did not 
> desolder them but I made some measurements with mit Fluke 177.
>
> D16: Diode-Voltage zero and the other direction shows 0.390 V. The 
> resistor-values are 95.7 KOhms and 104,6 KOhms
> D17: Diode-Voltage zero and the other direction shows 0.387 V. The 
> resistor-values are 95.5 KOhms and 105,2 KOhms
>