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

[Don Wilhelm]

Holger,

That indicates that D11 is shorted.  I would replace D11, D12 and D14 
and remeasure.
Do not substitute - use only 1N4007s.  While those are normally power 
diodes, they work well for switching purposes too, and that is not true 
of most other diode types.

73,
Don W3FPR

On 5/5/2014 4:05 PM, dl9hda at dl9hda.de wrote:
> 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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