Posted by
Chris Kantarjiev K6DBG on
Oct 06, 2007; 5:57am
URL: http://elecraft.85.s1.nabble.com/KPA100-KAT100-trouble-tp453506p453508.html
Don,
It's taken me several weeks to get to this, but tonight was the night. I had
tested and determined that the base K2 was fine, but neither the KPA nor KAT
controlled power correctly. The parts folks had sent me diodes.
Boy, what a nuisance these are to replace! Julius N2WN had suggested putting the
KPA's diodes on the underside of the board, where they are easier to get at, and
I followed that advice. For the KAT, there's just no good way to get at the
backside of the board w/o removing all the connectors. I used a stainless dental
pick to clean out the holes from the front, and soldered from that side, too.
Power control works great now. Both bridges seem to want to be recalibrated -
the max output is about 75W, even when I have 100+ dialed in. I didn't do the
original calibration on these, so I'm not certain of how close they were ... and
I guess I'm not sure that I measured for full power out when I bought them.
I suspect that it's a calibration issue, because output is low across the entire
HIGH range. The bargraph is showing about the right number of bars for the POWER
setting.
Or is there some other problem I should be looking for that might cause this?
Thanks again.
73 de chris K6DBG
Don Wilhelm wrote:
> Chris,
>
> As your first step, you need to obtain some 1N5711 diodes - obtain 5 of
> them if you have to order any.
>
> First remove the KPA100 and check the base K2 into a good dummy load.
> Do you have good power control over the entire range? If yes, the base
> K2 is working, but if no, replace RF Board D9 and re-check.
>
> Once you have verified that the base K2 can control the power output,
> add the KPA100 - operate into a dummy load (no antennas please because
> there are too many variables to deal with). If the K2 with KPA100
> properly controls power and displays a 1:1 SWR, then you will have 2
> more extra diodes. OTOH, if the KPA100 produces full power output no
> matter where the power knob is set, then replace D16 and D17 in the
> KPA100. The K2 with KPA100 should now properly control power output.
>
> Lastly, add the KAT100, but set the ATU menu to CAL and connect the
> dummy load to the KAT100. If all works well, you have extra diodes, but
> if all is not well, then replace D1 and D2 in the KAT100.
>
> After all is working fine into a dummy load, then you can connect an
> antenna and try it out - you should find normal behavior.
>
> OK, this has been simplistic and considers only that the lightning
> zapped the wattmeter diodes. This is usually the only consequence, but
> if at any point, normal behavior is not restored after replacing the
> diodes, there is some other problem that must be investigated before
> attempting to proceed any further with the testing.
>
> 73,
> Don W3FPR
>
> Chris Kantarjiev wrote:
>
>> I may be having my first run-in with lightning damage.
>>
>> A thunderstorm rolled through the SF Bay Area last night. I didn't
>> disconnect my antennas until I *saw* the first lightning flash.
>> Oops, I think.
>>
>> I turned on the radio later in the evening, and was getting very
>> high SWR indications on the KAT100, and HiCur on the K2. Hitting
>> TUNE caused a lot of clicking and clacking, and eventual tune to
>> about 1.5:1, but SWR was still high on transmit - and the indicated
>> power on the bargraph was lower than dialed in. This is on both
>> antennas - a vertical and OCF dipole - both more or less resonant.
>>
>> I turned off the rig and called it a night.
>>
>> This morning I pulled out my LP200 dummy load/power meter. The ATU
>> tunes it to 1.1:1. Power out does not change appreciably
>> in response to the POWER knob - if set for any value less than 10W,
>> the power is about 4W; if set for values about 10W (PA on), power out
>> is always about 30W. In neither case is the LED indication on
>> the K2 correct.
>>
>> I also notice that the SWR LEDs no longer display anything when the
>> power is set below 10W, but indicate as expected when POWER is
>> above 10W.
>>
>>
>
>
>
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