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

[dl9hda at dl9hda.de]

Dear Don,

thank you very much for your answer. I checked it with an wattmeter and 
a dummy load. Nothing.

But I checked the voltages at the diodes especially D11, D12, D13 and 
D14 in receive-mode:

D12 and D14 have the right voltages at the anodes and cathodes when I 
switch from low-power to high-power and vice-versa.

But the voltages at D11 and D13 are wrong. The voltages at the anodes 
and cathodes are always 13,8V. There are no voltages about ~140V. At D12 
and D14 I can measure this high voltages at the cathodes.



best regards
Holger, DL9HDA




Am 2014-05-05 21:55, schrieb 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
>> 
> 
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