Checking KPA relays

classic Classic list List threaded Threaded
5 messages Options
Reply | Threaded
Open this post in threaded view
|

Checking KPA relays

n0jrn
Gang:           I'm finally off for the weekend.   Just curious, what is the
easiest way to check the low pass filter relays to see if they are
working?????

I've already checked U2 and pins 13 -18 are going low as they should.  I'm
just not sure what I should be looking for to determine if the relays are
working.

Thanks and 73

Jerry          N0JRN

______________________________________________________________
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
Reply | Threaded
Open this post in threaded view
|

Re: Checking KPA relays

Don Wilhelm-4
Jerry,

I assume you are working on a KPA100 - if not, please ignore.
The easiest way to check the relays and the LPF of the KPA100 is with an
antenna analyzer.
Put the KPA100 to the right of the K2 (upside down on a book or other
support) with the ribbon cable connected to the K2.  Power only the base
K2 through the coaxial jack.
Put the leads of a 50 (ok, 51 will do fine) ohm resistor into the
connector that normally connects to the AUX RF header.
Power the K2 on and select each band in turn.  For each band, scan
through the frequency range of the antenna analyzer to determine the
cutoff frequency for the LPF - it should be higher than the band edge,
but lower than the 2nd harmonic.
If all bands meet that criteria, the relays and LPF are correct -
assemble the KPA100 to the base K2 and go.

73,
Don W3FPR

n0jrn wrote:

> Gang:           I'm finally off for the weekend.   Just curious, what is the
> easiest way to check the low pass filter relays to see if they are
> working?????
>
> I've already checked U2 and pins 13 -18 are going low as they should.  I'm
> just not sure what I should be looking for to determine if the relays are
> working.
>
> Thanks and 73
>
> Jerry          N0JRN
>
> ______________________________________________________________
> 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
> ------------------------------------------------------------------------
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 9.0.717 / Virus Database: 270.14.114/2575 - Release Date: 12/19/09 03:33:00
>
>  
______________________________________________________________
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
Reply | Threaded
Open this post in threaded view
|

Re: Checking KPA relays

n0jrn
In reply to this post by n0jrn
Thanks Don:

Easy enough !           I appreciate that very much.

Yes I am working with my KPA100.  I'm looking for why the K2 drops out of TX
when I try to adjust output above 35 watts.

A couple of the bands are also showing excessive current draw and high
reflected.

Just wanted to check the relays and make sure everything in the LPF first.

I've spent a good part of the evening reading the archives for similar
issues.   Your comments in most cases take folks back to the SWR bridge and
related components.

BUT         first things first !

Have a great evening

Jerry

> I assume you are working on a KPA100 - if not, please ignore.
> The easiest way to check the relays and the LPF of the KPA100 is with an
> antenna analyzer.
> Put the KPA100 to the right of the K2 (upside down on a book or other
> support) with the ribbon cable connected to the K2.  Power only the base
> K2 through the coaxial jack.
> Put the leads of a 50 (ok, 51 will do fine) ohm resistor into the
> connector that normally connects to the AUX RF header.
> Power the K2 on and select each band in turn.  For each band, scan
> through the frequency range of the antenna analyzer to determine the
> cutoff frequency for the LPF - it should be higher than the band edge,
> but lower than the 2nd harmonic.
> If all bands meet that criteria, the relays and LPF are correct -
> assemble the KPA100 to the base K2 and go.

______________________________________________________________
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
Reply | Threaded
Open this post in threaded view
|

Re: Checking KPA relays

Don Wilhelm-4
Jerry,

Yes, do check the LPF and relays first just as a 'confidence builder'.
If that is all working fine, then I would first direct you to the
wattmeter section.  Check with an external wattmeter in-line.  If the
output power is in excess of 100 watts no matter what the requested
power setting, then the KPA100 wattmeter is not working (D16 and D17
usually is the problem).  Once you obtain proper power level control,
then other problems can be addressed if necessary.

73,
Don W3FPR

n0jrn wrote:

> Thanks Don:
>
> Easy enough !           I appreciate that very much.
>
> Yes I am working with my KPA100.  I'm looking for why the K2 drops out of TX
> when I try to adjust output above 35 watts.
>
> A couple of the bands are also showing excessive current draw and high
> reflected.
>
> Just wanted to check the relays and make sure everything in the LPF first.
>
> I've spent a good part of the evening reading the archives for similar
> issues.   Your comments in most cases take folks back to the SWR bridge and
> related components.
>
> BUT         first things first !
>
> Have a great evening
>
> Jerry
>
>  
>> I assume you are working on a KPA100 - if not, please ignore.
>> The easiest way to check the relays and the LPF of the KPA100 is with an
>> antenna analyzer.
>> Put the KPA100 to the right of the K2 (upside down on a book or other
>> support) with the ribbon cable connected to the K2.  Power only the base
>> K2 through the coaxial jack.
>> Put the leads of a 50 (ok, 51 will do fine) ohm resistor into the
>> connector that normally connects to the AUX RF header.
>> Power the K2 on and select each band in turn.  For each band, scan
>> through the frequency range of the antenna analyzer to determine the
>> cutoff frequency for the LPF - it should be higher than the band edge,
>> but lower than the 2nd harmonic.
>> If all bands meet that criteria, the relays and LPF are correct -
>> assemble the KPA100 to the base K2 and go.
>>    
>
> ______________________________________________________________
> 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
> ------------------------------------------------------------------------
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 9.0.717 / Virus Database: 270.14.114/2575 - Release Date: 12/19/09 03:33:00
>
>  
______________________________________________________________
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
Reply | Threaded
Open this post in threaded view
|

Re: Checking KPA relays

n0jrn
In reply to this post by n0jrn
 OK,            Back in the shack and checking the LPF of my KPA100.    Per
Don's direction,   I disconnected the amps RF line from the main board of
the K2 and installed a 50 ohm resistor in the plug end of the RF line.

( resistor measure 50.5 ohms per my DMM )

Hooked my MFJ 259B  to the PL259 on the KPA100 and checked results of the
low pass filter set up on each band.

Results as follows:

160 Mtr           1.8         1.2-1          45 ohms
                        2.0         1.2-1          49 ohms

80 Mtr             3.5         1.3-1          53 ohms
                        4.0         1.3-1          49 ohms

40 Mtr             7.0         1.2-1          41 ohms
                        7.4         1.2-1          41 ohms

30 Mtr             10.1        1.4-1         50 ohms
                       10.150     1.4-1         50 ohms

20 Mtr            14.0         1.2-1         40 ohms
                       14.4         1.1-1         40 ohms

17 Mtr            18.065      1.2-1        37 ohms
                       18.2          1.2-1        37 ohms

15 Mtr             21.100     1.3-1        35 ohms
                        21.4         1.3-1        34 ohms

12 Mtr             24.890     1.2-1        35 ohms
                        24.990     1.2-1        35 ohms

10 Mtr             28.0          1.3-1        33 ohms
                        28.3          1.3-1        33 ohms
                        28.9          1.3-1        33 ohms

Becomes obvious that K3 - K12 are switching and the filters are intact.

Just a quick recap on the problem I have with my KPA100,   while trying to
do the Transmit tests on page 50 of the KPA manual,  something is causing
the KPA100 and / or the K2 to drop out of TX around the 35 watt level on all
bands.

I've read as much as can be found in the archives on this and similar
issues.  I know I've got to go back and reset the bias of the amp to insure
it is correct.

I'll retest the output from there and see if I've gained anything.

FWIW,     I am using a quality watt meter in line with my dummy load.  The
watt meter agrees with the K2's displayed results relative to the amount of
output and reflected power.

I have reset C1 a couple of times and I've been working with R26 to see if I
can gain any improvement with it's adjustment.   ( I can get to around 50
watts on the lower bands by working with R26 but my requested power and
actual output are off quite a bit when I do that )

SO,    for tonight's activity !

I'll recheck the bias settings,   check voltages at D11 through D14 and
recheck T4.

Any other suggestions would be great.

I'll let you know what I come up with.

73         Jerry             N0JRN




______________________________________________________________
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