[Elecraft] K2: KPA100 fan issue + current question

[Bob McGraw K4TAX]

At 13.8 volts, 11amps is about 152 watts input. 100/152 = .658 * 100 for about 66% efficiency.  

All in all , looks about right to me. AKA - I wouldn't be concerned.  


Bob, K4TAX


Sent from my iPhone

> On Nov 9, 2018, at 10:46 AM, Jim KO5V <ko5v at earthlink.net> wrote:
> 
> Well, after checking that all of the components in the fan circuit were correct, I decided to follow Don's usual advice about checking my soldering, so I re-flowed all of their joints. None looked bad, but now the fan works as it should, so...
> 
> I'm still curious about my 11A @ 100W measurement. I think I'll borrow a friend's DMM and see if I get the same voltage measurement across R1 
> (unless 11A is in the ballpark).
> 
> 73, Jim KO5V
> 
> -----Forwarded Message-----
>> From: Jim KO5V <ko5v at earthlink.net>
>> Sent: Nov 8, 2018 2:11 PM
>> To: Elecraft List <elecraft at mailman.qth.net>
>> Subject: K2: KPA100 fan issue + current question
>> 
>> I just finished building and testing the KPA100 that goes with K2 #7225. This kit was a rev C, and I have brought it up to the latest specs. U1 says PA 1.1.
>> 
>> #1: It has passed all of the tests, except it apparently has no low fan speed. I have set the temperature of the heat sink using CAL tPA, after measuring it with an IR thermometer, and I have set and re-set the fan parameters in the secondary menu. On "nor" and on "LoHi" the fan is off. On "Hi" it runs. I have tested the amp's output into my power meter at 100w, but I haven't transmitted long enough to really heat anything up.
>> 
>> When I first applied power to the KPA100 for the initial tests, I believe the fan ran at low speed, so I have probably broken something...
>> 
>> #2: When I key the amp at 100w, through the power meter, and into a dummy load, I measure about .055v across R7, so that's ~11A. I expected higher current. Does that seem about right?
>> 
>> Any insight would be appreciated.
>> 
>> Thanks in advance, & 73,
>> 
>> Jim KO5V
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