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no DDS VFO output/KX1

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wa7bme

no DDS VFO output/KX1

Hello All:
My first time to post to this list.
I am building KX1 S/N 2825 and have progressed to page 43 Alignment and Test Part 2 with no problems. I have completed tests through page 44-keyer.
I have not been able to proceed to the Receiver Alignment section, page 45, because I can not discern any signal from the DDS VFO, so not able to hear any
signals, on either 20m or 40m.
My question is this: should I be able to see the VFO signal at pin 19 of U2? I am using an old TEK 422 scope with 10 x probe. I see nothing at pin 19 or at pin 3 of Z2 the 50 mhz clock. At pin 3 of Z2, clock output, I measure gnd (with power off, of course). I also measure gnd at pin 4 of Z2, but also see 2.7 vdc when the unit is powered up. No VFO or MCLK signals are visible. This is confusing(!)

I’m kinda stymied at this point, and any suggestions are welcome!
Should I be able to hear the VFO signal on an outboard receiver?
Should I be able to see the VFO signal at some point, and where is the best measurement point?
Another note: I am using the directions from Don Wilhelm’s letter of 4 May, 2011 regarding replacement of components for KXB3080 option prior to installing the option. This includes C27,C26,C1,T2. He will know what I am referring to.
Sorry to run on for so long.

Any help or suggestions, please?

Thanks for the bandwidth.

73
Ron Dickerson WA7BME
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Fred Townsend-2

Re: no DDS VFO output/KX1

Ron I have no comments about the KX1. However I do seem to recall the Tek 422 has a 30 MHz bandwidth with a P6006 probe.

73
Fred, AE6QL

-----Original Message-----

>From: [hidden email]
>Sent: Aug 23, 2014 3:50 PM
>To: [hidden email]
>Subject: [Elecraft] no DDS VFO output/KX1
>
>Hello All:
>My first time to post to this list.
>I am building KX1 S/N 2825 and have progressed to page 43 Alignment and Test Part 2 with no problems. I have completed tests through page 44-keyer.
>I have not been able to proceed to the Receiver Alignment section, page 45, because I can not discern any signal from the DDS VFO, so not able to hear any
>signals, on either 20m or 40m.
>My question is this: should I be able to see the VFO signal at pin 19 of U2? I am using an old TEK 422 scope with 10 x probe. I see nothing at pin 19 or at pin 3 of Z2 the 50 mhz clock. At pin 3 of Z2, clock output, I measure gnd (with power off, of course). I also measure gnd at pin 4 of Z2, but also see 2.7 vdc when the unit is powered up. No VFO or MCLK signals are visible. This is confusing(!)
>
>I’m kinda stymied at this point, and any suggestions are welcome!
>Should I be able to hear the VFO signal on an outboard receiver?
>Should I be able to see the VFO signal at some point, and where is the best measurement point?
>Another note: I am using the directions from Don Wilhelm’s letter of 4 May, 2011 regarding replacement of components for KXB3080 option prior to installing the option. This includes C27,C26,C1,T2. He will know what I am referring to.
>Sorry to run on for so long.
>
>Any help or suggestions, please?
>
>Thanks for the bandwidth.
>
>73
>Ron Dickerson WA7BME
>______________________________________________________________
>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
>Message delivered to [hidden email]

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Don Wilhelm-4

Re: no DDS VFO output/KX1

In reply to this post by wa7bme

Ron,

Welcome to the Elecraft reflector.

If your 'scope is capable of seeing a 50 MHz signal of 100 mV peak to
peak amplitude, yes you should see a good 50 MHz signal from the
oscillator Z2.
If you have no oscillator there, and you measure 2.7 volts in Z2 pin 4,
you may have a bad oscillator - no oscillator, the DDS will not work.

If you put a short antenna on the oscillator (Z2 pin 3) you should be
able to hear it in a receiver with its "antenna" located a short
distance from the added antenna wire.

If you indeed do not have an oscillator signal, it is likely a warranty
repair and you should contact [hidden email] to request an RSA.
But make sure the leads of the components mounted in the vicinity do not
have solder bridges that is shorting something to ground or another
signal line. Such builder errors are not warranty repairs.

There is nothing in the "KXB3080 'shortcut' instructions that would
interfere with the DDS signal.

If you doubt the capability of your scope, use an RF probe to look for
the oscillator and/or DDS signal. Measured on an RF Probe you should
have at least 70 mV signal at U2 pin 19.
Check for a signal at pin 20 too - if you have a signal at pin 20, check
your work for solder bridges and other errors - like wrong value
components at L4, L5, C39, C51, and C52 - check especially C52 to be
sure it is 22pF (220) and not the 220pF (221) capacitor, those marking
are difficult to see.

73,
Don W3FPR

On 8/23/2014 6:50 PM, [hidden email] wrote:

> Hello All:
> My first time to post to this list.
> I am building KX1 S/N 2825 and have progressed to page 43 Alignment and Test Part 2 with no problems. I have completed tests through page 44-keyer.
> I have not been able to proceed to the Receiver Alignment section, page 45, because I can not discern any signal from the DDS VFO, so not able to hear any
> signals, on either 20m or 40m.
> My question is this: should I be able to see the VFO signal at pin 19 of U2? I am using an old TEK 422 scope with 10 x probe. I see nothing at pin 19 or at pin 3 of Z2 the 50 mhz clock. At pin 3 of Z2, clock output, I measure gnd (with power off, of course). I also measure gnd at pin 4 of Z2, but also see 2.7 vdc when the unit is powered up. No VFO or MCLK signals are visible. This is confusing(!)
>
> I’m kinda stymied at this point, and any suggestions are welcome!
> Should I be able to hear the VFO signal on an outboard receiver?
> Should I be able to see the VFO signal at some point, and where is the best measurement point?
> Another note: I am using the directions from Don Wilhelm’s letter of 4 May, 2011 regarding replacement of components for KXB3080 option prior to installing the option. This includes C27,C26,C1,T2. He will know what I am referring to.
> Sorry to run on for so long.
>
> Any help or suggestions, please?
>
>

Don Wilhelm-4

Re: no DDS VFO output/KX1

In reply to this post by Fred Townsend-2

Fred,

What that means is that at 30 MHz, the amplitude is reduced by 3 dB.
Usually, such a 'scope is useful for determining if there is a signal
(assuming the 'scope has adequate vertical sensitivity), but should not
be used to measure signal voltage with accuracy above about 10 MHz.

73,
Don W3FPR

On 8/23/2014 7:47 PM, Fred Townsend wrote:
> Ron I have no comments about the KX1. However I do seem to recall the Tek 422 has a 30 MHz bandwidth with a P6006 probe.
>
> 73
> Fred, AE6QL
>
>

______________________________________________________________
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Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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