[Elecraft] [K2] K2/100 RF power indication not working - Blown D16 & D17?

[Bill Coleman]

OK, I removed D16 and D17, and on the diode setting of my DVM, they both measured the same value both forward and backward - 034. Which means they were totally shorted.

I replaced them with new diodes (which measured 316 forward, and infinite backward), and the RF display is once again working.

Unfortunately, I don’t have a dummy load to do the calibration on page 48 right now, so it will probably have to wait a few more days before I can everything in the same place. 

However, I’m declaring this mystery solved. I am very glad I put machined socket pins in for D16 & D17. Took only a couple of minutes to replace them.

> On May 15, 2019, at 7:30 PM, Bill Coleman <aa4lr at arrl.net> wrote:
> 
> Took me over week to check this, but power is the same whether Tune or Tune/Display — 100 watts! 
> 
> So, the suspects are likely D16 & D17.
> 
> Fortunately, the last time I replaced them I put in a couple of pins from a machined pin socket, so it should be an easy job.
> 
> I’ve had to replace U6 before as well. I think I have a socket there, too.
> 
>> On May 4, 2019, at 12:11 AM, Don Wilhelm <donwilh at embarqmail.com> wrote:
>> 
>> Bill,
>> 
>> Set the power at 50 watts and do a TUNE.
>> Is the output power at 20 to 25 watts?  If so, so far so good.
>> Now try a TUNE/DISPLAY (hold both buttons at once).  Is the power near 50 watts?  If so, you have proper power control and the problem is with the LED display.
>> 
>> OTOH, if the actual power in both cases above goes to 100 watts or more, then the first step is to replace KPA100 D16 and D17.  If that does not fix things, there is likely another problem in the KPA100 wattmeter, likely KPA100 U6 - but get back with the information before replacing it, there are more tests to verify or deny that possibility.
>> 
>> 73,
>> Don W3FPR
>> 
>> On 5/3/2019 10:25 PM, Bill Coleman wrote:
>>> I’ve recently seem a problem with my K2/100. It transmits ok, and the power level out tracks the power control, but the power indication LEDs remain at zero.
>>> No, I’m not in ALC mode, I’m definitely in RF mode for the meter.
>>> I’m using an external wattmeter (a Kenwood AT-250 in passthrough mode), and can definitely see 100 watts being transmitted.
>>> I’m thinking that maybe D16 and D17 may have been fried. Is that a good guess?
> 
> Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
> Web: http://boringhamradiopart.blogspot.com
> Quote: "Not within a thousand years will man ever fly!"
>            -- Wilbur Wright, 1901
> 
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Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
Web: http://boringhamradiopart.blogspot.com
Quote: "Not within a thousand years will man ever fly!"
            -- Wilbur Wright, 1901