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K2 BFO test failed

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Mike Maiorana-2

K2 BFO test failed

Hello all. I have a K2, 6000+ serial number, that I'm trying to get working
correctly. Unknown history. A quick test showed the filters were not
properly adjusted (could hear both sidebands of carrier on some bands). I
thought it would be best to do a top-down alignment.

I adjusted the 4 MHz oscillator, verified the PLL reference oscillator
range (12.43 kHz), VCO test and VCO alignment. No problems up to that
point.

I'm having an issue at the BFO test. The BFO high frequency is 4916.04 kHz
and the low frequency is 4913.82 kHz. That's a difference of 2.19 kHz, well
below the 3.6 kHz stated minimum.

I verified the crystals at X3 and X4 were the correct type, along with the
values of D37, D38, C173 and C174. I didn't see any PCB trace damage in the
area. I reflowed the solder on those pins but didn't see a significant
change in the BFO frequency range. I checked the VBFO control voltage and
had 7.81 V at the high BFO frequency down to 0.00 V at the low BFO
frequency.

Any advice on how to move forward?

Thanks and 73,
Mike M.
KU4QO
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Don Wilhelm

Re: K2 BFO test failed

Mike,

The inadequate BFO range is usually a result of the L33 toroid leads not
being well soldered. The toroid wires are very fine and sometimes are
not visible to the naked eye, so use magnification to examine them.
When re-soldering, use a pointed tool to bring the fine toroid wires
down onto the solder pad instead of further up on the securing resistor
lead.

For adjusting the 4 MHz Reference Oscillator (that has nothing to do
with the BFO range), refer to the K2 Dial Calibration article on my
website www.w3fpr.com for the most accurate method of adjusting the
Reference Oscillator.

Be aware that the 4 MHz Reference oscillator can drift in normal
operation, so soon after adjusting it, run CAL PLL and CAL FIL while it
is still "on frequency". That oscillator is not used in operation for
the K2 frequency display. In other words, simply adjusting the 4 MHz
Reference does nothing for normal operation.

73,
Don W3FPR

On 9/30/2017 9:35 AM, Mike Maiorana wrote:

> Hello all. I have a K2, 6000+ serial number, that I'm trying to get working
> correctly. Unknown history. A quick test showed the filters were not
> properly adjusted (could hear both sidebands of carrier on some bands). I
> thought it would be best to do a top-down alignment.
>
> I adjusted the 4 MHz oscillator, verified the PLL reference oscillator
> range (12.43 kHz), VCO test and VCO alignment. No problems up to that
> point.
>
> I'm having an issue at the BFO test. The BFO high frequency is 4916.04 kHz
> and the low frequency is 4913.82 kHz. That's a difference of 2.19 kHz, well
> below the 3.6 kHz stated minimum.
>

______________________________________________________________
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]

Mike Maiorana-2

Re: K2 BFO test failed

Thanks Don.
I triple-checked the inductor wires and they are well soldered to the pads.
I also verified the value of the resistor across it, 5.1 Mohms. I reflowed
the solder anyway, but no change in the BFO frequency range.

If L33 wasn't connected would the oscillator even run?

If one of the two crystals was bad (or not soldered properly) would you
also see a reduction in BFO range?
What about if one of the varactors had failed?

Any further advice will be greatly appreciated.
Thanks and 73
Mike M.
KU4QO

On Sat, Sep 30, 2017 at 9:57 AM, Don Wilhelm <[hidden email]> wrote:

> Mike,
>
> The inadequate BFO range is usually a result of the L33 toroid leads not
> being well soldered. The toroid wires are very fine and sometimes are not
> visible to the naked eye, so use magnification to examine them. When
> re-soldering, use a pointed tool to bring the fine toroid wires down onto
> the solder pad instead of further up on the securing resistor lead.
>
> For adjusting the 4 MHz Reference Oscillator (that has nothing to do with
> the BFO range), refer to the K2 Dial Calibration article on my website
> www.w3fpr.com for the most accurate method of adjusting the Reference
> Oscillator.
>
> Be aware that the 4 MHz Reference oscillator can drift in normal
> operation, so soon after adjusting it, run CAL PLL and CAL FIL while it is
> still "on frequency". That oscillator is not used in operation for the K2
> frequency display. In other words, simply adjusting the 4 MHz Reference
> does nothing for normal operation.
>
> 73,
> Don W3FPR
>
>
> On 9/30/2017 9:35 AM, Mike Maiorana wrote:
>
>> Hello all. I have a K2, 6000+ serial number, that I'm trying to get
>> working
>> correctly. Unknown history. A quick test showed the filters were not
>> properly adjusted (could hear both sidebands of carrier on some bands). I
>> thought it would be best to do a top-down alignment.
>>
>> I adjusted the 4 MHz oscillator, verified the PLL reference oscillator
>> range (12.43 kHz), VCO test and VCO alignment. No problems up to that
>> point.
>>
>> I'm having an issue at the BFO test. The BFO high frequency is 4916.04 kHz
>> and the low frequency is 4913.82 kHz. That's a difference of 2.19 kHz,
>> well
>> below the 3.6 kHz stated minimum.
>>
>>

Don Wilhelm

Re: K2 BFO test failed

Mike,

How did you check the value of the resistor. If you used your DMM while
it was in-circuit, then you have an open L33. The BFO would oscillate,
but the range would be restricted as yours is or more narrow.

First thing, check capacitors C173 and C174 to be certain you have the
correct values installed. Those blue capacitors with the yellow
printing on them are difficult to read, so use a magnifier and lots of
light.

Then check D37 and D38 to be certain they are oriented correctly - the
slightly angled side is the "rounded" side.

Make certain RP6 is well soldered - reflow with a hot iron (750 degF)
and apply a bit of extra solder - you really one need the flux. The
iron dwell time should be about 3 seconds, but watch for the solder to
flow out onto both the solder pad and the component lead to assure good
soldering - up to 5 seconds dwell will not hurt anything.

Then when doing the BFO Hi and BFO LO frequency checks make sure RP6 pin
7 goes to quite near 5 volts and also quite near zero volts.

The above are the easiest items to check.
Keep in mind that the resistor which holds L33 is really an insulator,
it serves no electrical function.

You are correct that a bad BFO crystal could cause the problem, but to
change them (change them as a matched pair), you have to lift L33. Not
too bad is you are careful, leave the leads connected to the resistor
leads, heat the solder pad and pull the resistor lead out - repeat for
the other side and lift L33 and the resistor off as an assembly.

So try the easy stuff first, and if that does not cure it, contact
Elecraft Support and request a pair of BFO crystals and a new L33 and
5.1 meg resistor to replace them.

73,
Don W3FPR

On 9/30/2017 5:40 PM, Mike Maiorana wrote:

> Thanks Don.
> I triple-checked the inductor wires and they are well soldered to the
> pads. I also verified the value of the resistor across it, 5.1 Mohms.
> I reflowed the solder anyway, but no change in the BFO frequency range.
>
> If L33 wasn't connected would the oscillator even run?
>
> If one of the two crystals was bad (or not soldered properly) would
> you also see a reduction in BFO range?
> What about if one of the varactors had failed?
>
> Any further advice will be greatly appreciated.
> Thanks and 73
> Mike M.
> KU4QO
>
> On Sat, Sep 30, 2017 at 9:57 AM, Don Wilhelm <[hidden email]
> <mailto:[hidden email]>> wrote:
>
> Mike,
>
> The inadequate BFO range is usually a result of the L33 toroid
> leads not being well soldered. The toroid wires are very fine and
> sometimes are not visible to the naked eye, so use magnification
> to examine them. When re-soldering, use a pointed tool to bring
> the fine toroid wires down onto the solder pad instead of further
> up on the securing resistor lead.
>
> For adjusting the 4 MHz Reference Oscillator (that has nothing to
> do with the BFO range), refer to the K2 Dial Calibration article
> on my website www.w3fpr.com <http://www.w3fpr.com> for the most
> accurate method of adjusting the Reference Oscillator.
>
> Be aware that the 4 MHz Reference oscillator can drift in normal
> operation, so soon after adjusting it, run CAL PLL and CAL FIL
> while it is still "on frequency". That oscillator is not used in
> operation for the K2 frequency display. In other words, simply
> adjusting the 4 MHz Reference does nothing for normal operation.
>
> 73,
> Don W3FPR
>
>
> On 9/30/2017 9:35 AM, Mike Maiorana wrote:
>
> Hello all. I have a K2, 6000+ serial number, that I'm trying
> to get working
> correctly. Unknown history. A quick test showed the filters
> were not
> properly adjusted (could hear both sidebands of carrier on
> some bands). I
> thought it would be best to do a top-down alignment.
>
> I adjusted the 4 MHz oscillator, verified the PLL reference
> oscillator
> range (12.43 kHz), VCO test and VCO alignment. No problems up
> to that
> point.
>
> I'm having an issue at the BFO test. The BFO high frequency is
> 4916.04 kHz
> and the low frequency is 4913.82 kHz. That's a difference of
> 2.19 kHz, well
> below the 3.6 kHz stated minimum.
>
>

Mike Maiorana-2

Re: K2 BFO test failed

Don,
Thank you again for your very detailed response. I think I've found the
problem.
After doing the visual checks you suggested I wanted to try and isolate the
crystals to see if the problem was there.
I left L33 alone and carefully removed the BFO crystal that was accessible
without removing the inductor. Now CAL FCTR showed the BFO frequency as
00000. Interesting.

I then removed L33 and the second BFO crystal. Using a simple crystal
tester/oscillator I have showed the second crystal (the one under L33) did
not oscillate. The other crystal seemed to oscillate fine. So, it looks
like an order for a pair of BFO crystals should get me back in business, or
at least let me continue the alignment. Hopefully this was the only problem.

Thanks again Don for your expert advice. I'll follow up when I get the
replacement parts.
Best regards and 73
Mike M.
KU4QO

On Sat, Sep 30, 2017 at 6:12 PM, Don Wilhelm <[hidden email]> wrote:

> Mike,
>
> How did you check the value of the resistor. If you used your DMM while
> it was in-circuit, then you have an open L33. The BFO would oscillate, but
> the range would be restricted as yours is or more narrow.
>
> First thing, check capacitors C173 and C174 to be certain you have the
> correct values installed. Those blue capacitors with the yellow printing
> on them are difficult to read, so use a magnifier and lots of light.
>
> Then check D37 and D38 to be certain they are oriented correctly - the
> slightly angled side is the "rounded" side.
>
> Make certain RP6 is well soldered - reflow with a hot iron (750 degF) and
> apply a bit of extra solder - you really one need the flux. The iron dwell
> time should be about 3 seconds, but watch for the solder to flow out onto
> both the solder pad and the component lead to assure good soldering - up to
> 5 seconds dwell will not hurt anything.
>
> Then when doing the BFO Hi and BFO LO frequency checks make sure RP6 pin 7
> goes to quite near 5 volts and also quite near zero volts.
>
> The above are the easiest items to check.
> Keep in mind that the resistor which holds L33 is really an insulator, it
> serves no electrical function.
>
> You are correct that a bad BFO crystal could cause the problem, but to
> change them (change them as a matched pair), you have to lift L33. Not too
> bad is you are careful, leave the leads connected to the resistor leads,
> heat the solder pad and pull the resistor lead out - repeat for the other
> side and lift L33 and the resistor off as an assembly.
>
> So try the easy stuff first, and if that does not cure it, contact
> Elecraft Support and request a pair of BFO crystals and a new L33 and 5.1
> meg resistor to replace them.
>
> 73,
> Don W3FPR
>
> On 9/30/2017 5:40 PM, Mike Maiorana wrote:
>
>> Thanks Don.
>> I triple-checked the inductor wires and they are well soldered to the
>> pads. I also verified the value of the resistor across it, 5.1 Mohms. I
>> reflowed the solder anyway, but no change in the BFO frequency range.
>>
>> If L33 wasn't connected would the oscillator even run?
>>
>> If one of the two crystals was bad (or not soldered properly) would you
>> also see a reduction in BFO range?
>> What about if one of the varactors had failed?
>>
>> Any further advice will be greatly appreciated.
>> Thanks and 73
>> Mike M.
>> KU4QO
>>
>> On Sat, Sep 30, 2017 at 9:57 AM, Don Wilhelm <[hidden email]
>> <mailto:[hidden email]>> wrote:
>>
>> Mike,
>>
>> The inadequate BFO range is usually a result of the L33 toroid
>> leads not being well soldered. The toroid wires are very fine and
>> sometimes are not visible to the naked eye, so use magnification
>> to examine them. When re-soldering, use a pointed tool to bring
>> the fine toroid wires down onto the solder pad instead of further
>> up on the securing resistor lead.
>>
>> For adjusting the 4 MHz Reference Oscillator (that has nothing to
>> do with the BFO range), refer to the K2 Dial Calibration article
>> on my website www.w3fpr.com <http://www.w3fpr.com> for the most
>>
>> accurate method of adjusting the Reference Oscillator.
>>
>> Be aware that the 4 MHz Reference oscillator can drift in normal
>> operation, so soon after adjusting it, run CAL PLL and CAL FIL
>> while it is still "on frequency". That oscillator is not used in
>> operation for the K2 frequency display. In other words, simply
>> adjusting the 4 MHz Reference does nothing for normal operation.
>>
>> 73,
>> Don W3FPR
>>
>>
>> On 9/30/2017 9:35 AM, Mike Maiorana wrote:
>>
>> Hello all. I have a K2, 6000+ serial number, that I'm trying
>> to get working
>> correctly. Unknown history. A quick test showed the filters
>> were not
>> properly adjusted (could hear both sidebands of carrier on
>> some bands). I
>> thought it would be best to do a top-down alignment.
>>
>> I adjusted the 4 MHz oscillator, verified the PLL reference
>> oscillator
>> range (12.43 kHz), VCO test and VCO alignment. No problems up
>> to that
>> point.
>>
>> I'm having an issue at the BFO test. The BFO high frequency is
>> 4916.04 kHz
>> and the low frequency is 4913.82 kHz. That's a difference of
>> 2.19 kHz, well
>> below the 3.6 kHz stated minimum.
>>
>>
>>
>

Mike Maiorana-2

Re: K2 BFO test failed

Don,
My replacement BFO crystals arrived today and I installed them. My BFO
range is now 5.66 kHz. FIXED! Thank you!

I have to add a note about what I call "Elecraft Mojo". The crystals were
back ordered so there was a delay before they could be shipped. The package
was sent Friday from California on its way to Florida. USPS web page said
that the package would deliver on Monday. I checked the tracking info this
morning (Sunday) and it said that the package was at the local sorting
facility. So, on track for a Monday delivery. I went out to the mailbox to
drop off an outgoing letter this afternoon and I was surprised to see a
Priority Mail box inside. Sure enough, it was my Elecraft parts order,
delivered by the USPS ON SUNDAY!!! To make sure I wasn't losing my mind I
checked the tracking info again and sure enough, it was sorted and
delivered today. I have NEVER received regular mail on a Sunday. Just more
of that Elecraft Mojo.

And, of course, my tiny little order was treated with the same urgency and
respect as when I bought the radio new. What a great company.

Now, off to finish the alignment!
Thanks again and 73
Mike M.
KU4QO

On Sat, Sep 30, 2017 at 10:53 PM, Mike Maiorana <[hidden email]> wrote:

> Don,
> Thank you again for your very detailed response. I think I've found the
> problem.
> After doing the visual checks you suggested I wanted to try and isolate
> the crystals to see if the problem was there.
> I left L33 alone and carefully removed the BFO crystal that was accessible
> without removing the inductor. Now CAL FCTR showed the BFO frequency as
> 00000. Interesting.
>
> I then removed L33 and the second BFO crystal. Using a simple crystal
> tester/oscillator I have showed the second crystal (the one under L33) did
> not oscillate. The other crystal seemed to oscillate fine. So, it looks
> like an order for a pair of BFO crystals should get me back in business, or
> at least let me continue the alignment. Hopefully this was the only problem.
>
> Thanks again Don for your expert advice. I'll follow up when I get the
> replacement parts.
> Best regards and 73
> Mike M.
> KU4QO
>
>>
>>> I'm having an issue at the BFO test. The BFO high frequency is
>>> 4916.04 kHz
>>> and the low frequency is 4913.82 kHz. That's a difference of
>>> 2.19 kHz, well
>>> below the 3.6 kHz stated minimum.
>>>
>>>
>>>
>>
>