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K2 #7379 troubleshooting

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Brian Stevens

K2 #7379 troubleshooting

Hi,
I've hit a snag during 40m tx alignment in being unable to peak L1/L2 to give more than about 500mW o/p with the power setting at 2W. I've gone through the troubleshooting procedure & all checks out ok until I get to the LPF,BPF & T-R switch section of the shared circuit testing.

Using the 10Mhz crystal oscillator in the manual with 0.14V at the antenna i/p I get these readings:

LPF o/p @ W1 = 0.004V (expected 0.13V)
T-R sw #1 o/p @ W6 = 0.003V (expected 0.093V)
BPF o/p @ left side of D6 = 0.003V (expected 0.086V)
T-R sw #2 o/p @ right side D6 = 0.002V (0.077V)

I don't know if it's relevant but the current display in rx mode is higher than the suggested values:
11.8V 0.36A (LCD nite, graph bar)
11.8V 0.30A (LCD day, graph dot)

Any advice would be appreciated.
73 Brian
G0WZX

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Don Wilhelm-4

Re: K2 #7379 troubleshooting

Brian,

If the test oscillator crystal is at 10 MHz, it *should* be very
attenuated by the 40 meter Low Pass Filter.
The K2 40 meter LPF cutoff is in the range of 8.5 MHz, so it cannot be
expected to pass a 10 MHz signal.

If you have a crystal in the 40 meter band, you could substitute it for
the 10 MHz crystal and try those measurements again.

If you do not have such a crystal, go forward in the Troubleshooting
procedure to Transmit Signal Tracing and try those steps. Do not skip
the oscillator checks - VFO and BFO that are in the Receiver Signal
Tracing part of the tests.

One thing about the Signal Tracing steps - work in the order listed, one
point depends on the one before it being OK.
Once you come to the first step where the output is significantly
(greater than 10%) lower than the Expected value, stop because you have
just found the output side of the failure point - it will be fruitless
to go on to other check points.

73,
Don W3FPR

On 11/3/2013 3:53 PM, Brian Stevens wrote:
> Hi,
> I've hit a snag during 40m tx alignment in being unable to peak L1/L2 to give more than about 500mW o/p with the power setting at 2W. I've gone through the troubleshooting procedure & all checks out ok until I get to the LPF,BPF & T-R switch section of the shared circuit testing.
>
> Using the 10Mhz crystal oscillator in the manual with 0.14V at the antenna i/p I get these readings:
>
> LPF o/p @ W1 = 0.004V (expected 0.13V)
>

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Brian Stevens

Re: K2 #7379 troubleshooting

Thanks Don, I started on the Transmit Signal Tracing & did the receieve
signal tracing as suggested at point 5 in the preparation for transmitter
signal tracing section. VFO & BFO frequencies checked out ok.
I'll try your suggestion of changing the crystal frequency & carry on with
the transmit signal tracing.

73 Brian
G0WZX
----- Original Message -----
From: "Don Wilhelm" <[hidden email]>
To: "Brian Stevens" <[hidden email]>;
<[hidden email]>
Sent: Sunday, November 03, 2013 9:15 PM
Subject: Re: [Elecraft] K2 #7379 troubleshooting

> Brian,
>
> If the test oscillator crystal is at 10 MHz, it *should* be very
> attenuated by the 40 meter Low Pass Filter.
> The K2 40 meter LPF cutoff is in the range of 8.5 MHz, so it cannot be
> expected to pass a 10 MHz signal.
>
> If you have a crystal in the 40 meter band, you could substitute it for
> the 10 MHz crystal and try those measurements again.
>
> If you do not have such a crystal, go forward in the Troubleshooting
> procedure to Transmit Signal Tracing and try those steps. Do not skip the
> oscillator checks - VFO and BFO that are in the Receiver Signal Tracing
> part of the tests.
>
> One thing about the Signal Tracing steps - work in the order listed, one
> point depends on the one before it being OK.
> Once you come to the first step where the output is significantly (greater
> than 10%) lower than the Expected value, stop because you have just found
> the output side of the failure point - it will be fruitless to go on to
> other check points.
>
> 73,
> Don W3FPR
>
>
>
> On 11/3/2013 3:53 PM, Brian Stevens wrote:
>> Hi,
>> I've hit a snag during 40m tx alignment in being unable to peak L1/L2 to
>> give more than about 500mW o/p with the power setting at 2W. I've gone
>> through the troubleshooting procedure & all checks out ok until I get to
>> the LPF,BPF & T-R switch section of the shared circuit testing.
>>
>> Using the 10Mhz crystal oscillator in the manual with 0.14V at the
>> antenna i/p I get these readings:
>>
>> LPF o/p @ W1 = 0.004V (expected 0.13V)
>>
>
>

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Brian Stevens

Re: K2 #7379 troubleshooting

In reply to this post by Don Wilhelm-4

Don,
I've had another think & the low readings I get at LPF,BPF & T-R sw o/p's
using the 10Mhz oscillator are with the VFO set so that I can hear the
oscillator signal, not at 40m. Should the signal still be attenuated under
these conditions?

The low power o/p problem occurred while trying to peak the 40m BPF
inductors L1/L2 with the VFO at 7.1Mhz.

73 Brian
G0WZX
----- Original Message -----
From: "Don Wilhelm" <[hidden email]>
To: "Brian Stevens" <[hidden email]>;
<[hidden email]>
Sent: Sunday, November 03, 2013 9:15 PM
Subject: Re: [Elecraft] K2 #7379 troubleshooting

Don Wilhelm-4

Re: K2 #7379 troubleshooting

Brian,

Do you have the K2 completely built? or have you only built it up to the
point where you can receive 40 meters? I guess the point that you said
you had trouble adjusting the 40 meter BPF made me think the 10 MHz
oscillator might not work for you.

If you have it completely built, then the 10 MHz crystal will work. You
must select the 30 meter band.

However, because you have a transmit problem, you should use the
transmit signal tracing rather than receive - you will find the problem
source more easily, and the K2 itself provides the signals require for
signal tracing.

Again, stop at the first point where the RF is substantially lower than
the expected value because you have found a failure point.

73,
Don W3FPR

On 11/4/2013 5:01 AM, Brian Stevens wrote:

> Don,
> I've had another think & the low readings I get at LPF,BPF & T-R sw
> o/p's using the 10Mhz oscillator are with the VFO set so that I can
> hear the oscillator signal, not at 40m. Should the signal still be
> attenuated under these conditions?
>
> The low power o/p problem occurred while trying to peak the 40m BPF
> inductors L1/L2 with the VFO at 7.1Mhz.
>
> 73 Brian
> G0WZX
> ----- Original Message ----- From: "Don Wilhelm" <[hidden email]>
> To: "Brian Stevens" <[hidden email]>;
> <[hidden email]>
> Sent: Sunday, November 03, 2013 9:15 PM
> Subject: Re: [Elecraft] K2 #7379 troubleshooting
>
>
>> Brian,
>>
>> If the test oscillator crystal is at 10 MHz, it *should* be very
>> attenuated by the 40 meter Low Pass Filter.
>> The K2 40 meter LPF cutoff is in the range of 8.5 MHz, so it cannot
>> be expected to pass a 10 MHz signal.
>>
>> If you have a crystal in the 40 meter band, you could substitute it
>> for the 10 MHz crystal and try those measurements again.
>>
>> If you do not have such a crystal, go forward in the Troubleshooting
>> procedure to Transmit Signal Tracing and try those steps. Do not
>> skip the oscillator checks - VFO and BFO that are in the Receiver
>> Signal Tracing part of the tests.
>>
>> One thing about the Signal Tracing steps - work in the order listed,
>> one point depends on the one before it being OK.
>> Once you come to the first step where the output is significantly
>> (greater than 10%) lower than the Expected value, stop because you
>> have just found the output side of the failure point - it will be
>> fruitless to go on to other check points.
>>
>> 73,
>> Don W3FPR
>>
>>
>>
>> On 11/3/2013 3:53 PM, Brian Stevens wrote:
>>> Hi,
>>> I've hit a snag during 40m tx alignment in being unable to peak
>>> L1/L2 to give more than about 500mW o/p with the power setting at
>>> 2W. I've gone through the troubleshooting procedure & all checks out
>>> ok until I get to the LPF,BPF & T-R switch section of the shared
>>> circuit testing.
>>>
>>> Using the 10Mhz crystal oscillator in the manual with 0.14V at the
>>> antenna i/p I get these readings:
>>>
>>> LPF o/p @ W1 = 0.004V (expected 0.13V)
>>>
>>
>>
>
>
> ______________________________________________________________
> 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
>

Brian Stevens

Re: K2 #7379 troubleshooting

In reply to this post by Brian Stevens

Don,
Yes the K2 is completely built & I was at alignment & test part 3 when I had
the low o/p power problem. I started the transmit
signal tracing procedure & did the receive testing to check the shared
circuits as instructed in the manual.

I'll carry on with the transmit signal tracing & see where I get to.
Thanks
73 Brian
G0WZX
----- Original Message -----
From: "Don Wilhelm" <[hidden email]>
To: "Brian Stevens" <[hidden email]>
Sent: Monday, November 04, 2013 1:03 PM
Subject: Re: [Elecraft] K2 #7379 troubleshooting

> Brian,
> Do you have the K2 completely built? or have you only built it up to the
> point where you can receive 40 meters? I guess the point that you said
> you had trouble adjusting the 40 meter BPF made me think the 10 MHz
> oscillator might not work for you.
>
> If you have it completely built, then the 10 MHz crystal will work. You
> must select the 30 meter band.
>
> However, because you have a transmit problem, you should use the transmit
> signal tracing rather than receive - you will find the problem source more
> easily, and the K2 itself provides the signals require for signal tracing.
>
> Again, stop at the first point where the RF is substantially lower than
> the expected value because you have found a failure point.
>
> 73,
> Don W3FPR
>
> On 11/4/2013 5:01 AM, Brian Stevens wrote:
>> Don,
>> I've had another think & the low readings I get at LPF,BPF & T-R sw o/p's
>> using the 10Mhz oscillator are with the VFO set so that I can hear the
>> oscillator signal, not at 40m. Should the signal still be attenuated
>> under these conditions?
>>
>> The low power o/p problem occurred while trying to peak the 40m BPF
>> inductors L1/L2 with the VFO at 7.1Mhz.
>>
>> 73 Brian
>> G0WZX
>> ----- Original Message ----- From: "Don Wilhelm" <[hidden email]>
>> To: "Brian Stevens" <[hidden email]>;
>> <[hidden email]>
>> Sent: Sunday, November 03, 2013 9:15 PM
>> Subject: Re: [Elecraft] K2 #7379 troubleshooting
>>
>>
>>> Brian,
>>>
>>> If the test oscillator crystal is at 10 MHz, it *should* be very
>>> attenuated by the 40 meter Low Pass Filter.
>>> The K2 40 meter LPF cutoff is in the range of 8.5 MHz, so it cannot be
>>> expected to pass a 10 MHz signal.
>>>
>>> If you have a crystal in the 40 meter band, you could substitute it for
>>> the 10 MHz crystal and try those measurements again.
>>>
>>> If you do not have such a crystal, go forward in the Troubleshooting
>>> procedure to Transmit Signal Tracing and try those steps. Do not skip
>>> the oscillator checks - VFO and BFO that are in the Receiver Signal
>>> Tracing part of the tests.
>>>
>>> One thing about the Signal Tracing steps - work in the order listed, one
>>> point depends on the one before it being OK.
>>> Once you come to the first step where the output is significantly
>>> (greater than 10%) lower than the Expected value, stop because you have
>>> just found the output side of the failure point - it will be fruitless
>>> to go on to other check points.
>>>
>>> 73,
>>> Don W3FPR
>>>
>>>
>>>
>>> On 11/3/2013 3:53 PM, Brian Stevens wrote:
>>>> Hi,
>>>> I've hit a snag during 40m tx alignment in being unable to peak L1/L2
>>>> to give more than about 500mW o/p with the power setting at 2W. I've
>>>> gone through the troubleshooting procedure & all checks out ok until I
>>>> get to the LPF,BPF & T-R switch section of the shared circuit testing.
>>>>
>>>> Using the 10Mhz crystal oscillator in the manual with 0.14V at the
>>>> antenna i/p I get these readings:
>>>>
>>>> LPF o/p @ W1 = 0.004V (expected 0.13V)
>>>>
>>>
>>>
>>
>>
>>
>
>