Other questions was RE: [Elecraft] K2 Alignment and Test, Part III: High current

[K.Kishimoto]

Hi Don and everyone else who responded,

The current readings @ 5W and 10W are now at the upper end of normal levels. 
T4 was reversed and needed to be turned around. The power wire is also on 
the thin side, 16g or 18g. I'll find a replacement tomorrow.

Two new interesting problems have cropped up as well:
a) 20m band, tuned Zepp: The S-meter is pegged on +40dB when the preamp is 
on. With the preamp off,  the meter settles down to around S5 (S5-S9 when 
copying a signal). On 40m, antenna tuned, the LED reads +40dB with preamp 
and +20dB without. Tried following the S-meter setup instructions in the 
manual, including those on the XG1 mini-kit, but nothing seems to prevent 
the LED from locking into the upper limit when the preamp is on. Is this 
normal? The AGC can be switched on and off as well as set fast or slow. With 
AGC off, the S-meter drops to zero.

b) The gain drops intermittently from an S-meter reading of +40dB to S2 with 
preamp on. The audio also diminishes in intensity at the same time. The last 
time it did this, I tapped the left side of the radio a couple of times and 
it stopped dropping out. This sounds like a loose component, bad connection 
or bad solder joint. Where should I begin my search? The IF stage? Could it 
be a toroid with a bad solder joint?

Thanks,
Kathy


> ------------------------------
>
> Message: 43
> Date: Sun, 25 Dec 2005 01:44:48 -0500
> From: "Don Wilhelm" <w3fpr at earthlink.net>
> Subject: RE: [Elecraft] K2 Alignment and Test, Part III: High current
> To: "K.Kishimoto" <mobileuser at shaw.ca>, <elecraft at mailman.qth.net>
> Message-ID: <NGEDLJLDCGJIHEGPMIJPCEEADPAA.w3fpr at earthlink.net>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Kathy,
>
> I suggest that you tackle the voltage drop problem before investigating 
> the
> current draw.  What size wire are you using for the power wiring? - it
> should be 16 guage or larger.  Next check all the connections from the 
> power
> supply to the K2 - they should be tight or well soldered.  If no problem 
> is
> discovered in the power supply wiring itself, measure the voltage at the
> power supply output terminals under the load in transmit - compare to the 
> K2
> display.  The K2 display should show about 0.3 volts less than the power
> supply output due to the protective series diode.
>
> Lastly, check the soldering in the K2 12 volt path to be certain there are
> no high resistance solder joints.
>
> Once you get the voltage drop under control, the current should fall in 
> line
> with what is expected.  You receive current draw is about normal.
>
> 73,
> Don W3FPR
>
>> -----Original Message-----
>>
>> Power supply: SEC 1223 (23A)
>> Unit type: K2, no options installed
>> Passed Alignment and test, Part II
>> Passed all resistant checks
>>
>> Baseline voltage and current (backlight on)
>> 13.5v, 0.24A
>>
>> Transmit voltage and current into Elecraft 20W Dummy load (Using TUNE
>> function)
>> At 5W: 12.7v, 1.84A
>> At 10W: 12.1v, 2.98A
>>
>> The current draw seems far too excessive given the suggested range in the
>> manual. What components could potential cause this problem? The
>> voltage drop
>> seems high as well given the capacity of the PSU.
>>
>> Thanks,
>> Kathy
>> *Merry Christmas!*
>>