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

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Bill Coleman-2

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

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: [hidden email]
Web: http://boringhamradiopart.blogspot.com
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901

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Don Wilhelm

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

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?
>
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Bill Coleman-2

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

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 <[hidden email]> 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: [hidden email]
Web: http://boringhamradiopart.blogspot.com
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901

______________________________________________________________
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Bill Coleman-2

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

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 <[hidden email]> 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 <[hidden email]> 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: [hidden email]
> Web: http://boringhamradiopart.blogspot.com
> Quote: "Not within a thousand years will man ever fly!"
> -- Wilbur Wright, 1901
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

Bill Coleman-2

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

Don, I have one question.

This is the second time my K2/100 has completely toasted D16 and D17. I also have a KAT100 connected at the same time, which has virtually identical SWR bridge.

How is it that a static discharge can destroy D16 and D17, but the diodes D1 and D2 in the KAT100 are unaffected?

With the K2/100 / KAT100 combo, at which time are each of the SWR bridges used?

> On May 24, 2019, at 10:09 PM, Bill Coleman <[hidden email]> wrote:
>
> 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 <[hidden email]> 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 <[hidden email]> 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: [hidden email]
>> Web: http://boringhamradiopart.blogspot.com
>> Quote: "Not within a thousand years will man ever fly!"
>> -- Wilbur Wright, 1901
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>
> Bill Coleman, AA4LR, PP-ASEL Mail: [hidden email]
> Web: http://boringhamradiopart.blogspot.com
> Quote: "Not within a thousand years will man ever fly!"
> -- Wilbur Wright, 1901
>

Don Wilhelm

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

Bill,

Both wattmeters (KPA100 and KAT100) are in-line at the same time. With
the KPA100 installed the KAT100 wattmeter is only used to calculate the
SWR and use that value to light the SWR bargraph. But otherwise they are
electrically equal.

Why the KPA100 diodes get zapped while the KAT100 ones are often
unscathed is a question I do not have an answer for - it may have
something to do with the physical placement of the toroid and the
diodes. The KAT100 has a greater groundplane area around the toroid and
diodes, and I believe that has something to do with it.

I would suggest that you do something like putting a non-inductive
resistor from the KPA100 SO-239 jack to ground to bleed off residual
static. I have used 3 watt 47k resistors successfully for that purpose.
While you are at it, put one across each ANT jack in the KAT100 as well
- if you have the KAT100-1, you can easily solder them on the bottom of
the board - with the KAT100-2, it is not difficult to solder the
resistors directly across the SO-239 jacks.

73,
Don W3FPR

On 5/25/2019 1:24 PM, Bill Coleman wrote:
> Don, I have one question.
>
> This is the second time my K2/100 has completely toasted D16 and D17. I also have a KAT100 connected at the same time, which has virtually identical SWR bridge.
>
> How is it that a static discharge can destroy D16 and D17, but the diodes D1 and D2 in the KAT100 are unaffected?
>
> With the K2/100 / KAT100 combo, at which time are each of the SWR bridges used?
>
>

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Don Wilhelm

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

In reply to this post by Bill Coleman-2

I only partially answered the question about when each wattmeter is used.
If the KAT100 is connected to a QRP K2 (KPA100 physically removed)
through a KIO2, then the KAT100 wattmeter will be used for power control
and SWR display in the K2 display.

As long as the KPA100 is physically connected, its wattmeter is used for
power control and also display of SWR on the K2.

73,
Don W3FPR

--------------------------------------------------------------------------------------------------------------------
Bill,

Both wattmeters (KPA100 and KAT100) are in-line at the same time. With
the KPA100 installed the KAT100 wattmeter is only used to calculate the
SWR and use that value to light the SWR bargraph. But otherwise they are
electrically equal.

Why the KPA100 diodes get zapped while the KAT100 ones are often
unscathed is a question I do not have an answer for - it may have
something to do with the physical placement of the toroid and the
diodes. The KAT100 has a greater groundplane area around the toroid and
diodes, and I believe that has something to do with it.

I would suggest that you do something like putting a non-inductive
resistor from the KPA100 SO-239 jack to ground to bleed off residual
static. I have used 3 watt 47k resistors successfully for that purpose.
While you are at it, put one across each ANT jack in the KAT100 as well
- if you have the KAT100-1, you can easily solder them on the bottom of
the board - with the KAT100-2, it is not difficult to solder the
resistors directly across the SO-239 jacks.

73,
Don W3FPR

On 5/25/2019 1:24 PM, Bill Coleman wrote:

> Don, I have one question.
>
> This is the second time my K2/100 has completely toasted D16 and D17.
> I also have a KAT100 connected at the same time, which has virtually
> identical SWR bridge.
>
> How is it that a static discharge can destroy D16 and D17, but the
> diodes D1 and D2 in the KAT100 are unaffected?
>
> With the K2/100 / KAT100 combo, at which time are each of the SWR
> bridges used?
>
>

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Post: mailto:[hidden email]

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Bill Coleman-2

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

So, if you turn the KPA100 off via the menu, the KPA100 SWR bridge is still used in any case?

I’ll plan to add 50-100 kOhm resistors across the output, as you suggested. I’m also going to re-do the calibration of both SWR meters, just make sure no damage was done to the KAT100.

> On May 25, 2019, at 1:52 PM, Don Wilhelm <[hidden email]> wrote:
>
> I only partially answered the question about when each wattmeter is used.
> If the KAT100 is connected to a QRP K2 (KPA100 physically removed) through a KIO2, then the KAT100 wattmeter will be used for power control and SWR display in the K2 display.
>
> As long as the KPA100 is physically connected, its wattmeter is used for power control and also display of SWR on the K2.
>
> 73,
> Don W3FPR
>
> --------------------------------------------------------------------------------------------------------------------
> Bill,
>
> Both wattmeters (KPA100 and KAT100) are in-line at the same time. With the KPA100 installed the KAT100 wattmeter is only used to calculate the SWR and use that value to light the SWR bargraph. But otherwise they are electrically equal.
>
> Why the KPA100 diodes get zapped while the KAT100 ones are often unscathed is a question I do not have an answer for - it may have something to do with the physical placement of the toroid and the diodes. The KAT100 has a greater groundplane area around the toroid and diodes, and I believe that has something to do with it.
>
> I would suggest that you do something like putting a non-inductive resistor from the KPA100 SO-239 jack to ground to bleed off residual static. I have used 3 watt 47k resistors successfully for that purpose.
> While you are at it, put one across each ANT jack in the KAT100 as well - if you have the KAT100-1, you can easily solder them on the bottom of the board - with the KAT100-2, it is not difficult to solder the resistors directly across the SO-239 jacks.
>
> 73,
> Don W3FPR
>
> On 5/25/2019 1:24 PM, Bill Coleman wrote:
>> Don, I have one question.
>>
>> This is the second time my K2/100 has completely toasted D16 and D17. I also have a KAT100 connected at the same time, which has virtually identical SWR bridge.
>>
>> How is it that a static discharge can destroy D16 and D17, but the diodes D1 and D2 in the KAT100 are unaffected?
>>
>> With the K2/100 / KAT100 combo, at which time are each of the SWR bridges used?
>>
>>
>
>

Don Wilhelm

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

Bill,

Yes, as long as the KPA100 is physically connected to the base K2, its
wattmeter will be used for power control. The base K2 provides power to
the critical circuits and MCU in the KPA100 even though the PA is turned
off in the menu or not powered via the APP connector.

You MUST connect the antenna/dummy load to the KPA100 SO-239 ANT jack -
you cannot use the base K2 BNC ANT jack unless you physically remove and
disconnect the KPA100. If you try, the base K2 will think there is no
power being produced and will increase drive to maximum - as high as 19
watts uncontrolled power output will result no matter where you set the
power control.

73,
Don W3FPR

On 5/26/2019 2:56 PM, Bill Coleman wrote:

> So, if you turn the KPA100 off via the menu, the KPA100 SWR bridge is still used in any case?
>
> I’ll plan to add 50-100 kOhm resistors across the output, as you suggested. I’m also going to re-do the calibration of both SWR meters, just make sure no damage was done to the KAT100.
>
>> On May 25, 2019, at 1:52 PM, Don Wilhelm <[hidden email]> wrote:
>>
>> I only partially answered the question about when each wattmeter is used.
>> If the KAT100 is connected to a QRP K2 (KPA100 physically removed) through a KIO2, then the KAT100 wattmeter will be used for power control and SWR display in the K2 display.
>>
>> As long as the KPA100 is physically connected, its wattmeter is used for power control and also display of SWR on the K2.
>>
>> 73,
>> Don W3FPR
>>
>>