[Elecraft] Fwd: AW: K3 KPA3 bias adjust

[Don Wilhelm]

Chuck,

True, but make sure that current is being distributed equally between 
the 2 devices.  Set both pots to full CCW and then adjust one for a 
400-500ma rise, then adjust the other for another 400-500ma rise.
You should then have a 1 amp rise total, but you will be assured that 
each device is drawing the proper amount of idle current.

73,
Don W3FPR

On 3/7/2019 1:34 PM, hawley, charles j jr wrote:
> Could you be mistaken on my procedure? The 1 amp plus or minus is 
> typical with three K3s es that I know of. There are two devices and 
> two trim pots.
>
> This instruction is only for one device since he says "the BIAS pot" I 
> believe...
>
> "If there is much more current than this, set the BIAS pot to minimum
>  (fully counter clockwise). Then tap XMIT (not TUNE) and note what the
> current is in VFO B's readout. Slowly turn up the BIAS pot until you see
> 400-500mA more current that was seen with the BIAS pot at minimum."
>
> I am looking at the total current accessible from DISP and read out on 
> the front panel. First I go to the LPA only, read the total current 
> drawn by the rig under XMIT SSB(no modulation) and then engage the KPA 
> by turning up the power knob and I subtract the first reading from the 
> second. I get about 1.05 amps.
> Am I close to knowing the total current into the KPA this way?
>
> I feel that this important knowledge about how to set up the amp is 
> fuzzy or not well known...the why I asked the question.
>
> Thanks for the replies!!
>
> Chuck Hawley
>  c-hawley at illinois.edu
>
>  Amateur Radio, KE9UW
>  aka Jack, BMW Motorcycles
>
> ------------------------------------------------------------------------
> *From:* Don Wilhelm <donwilh at embarqmail.com>
> *Sent:* Thursday, March 7, 2019 12:10 PM
> *To:* hawley, charles j jr; elecraft at mailman.qth.net; Mike Harris
> *Subject:* Re: [Elecraft] Fwd: AW: K3 KPA3 bias adjust
> Chuck,
>
> The instruction cited was for a 400-500 ma rise TOTAL (not per device).
> So I conclude your bias is set too high or there is a problem in the
> bias circuit.
>
> 73,
> Don W3FPR
>
> On 3/7/2019 9:31 AM, hawley, charles j jr wrote:
> > Thanks for the info. Using xmit for the low power amp and then going 
> to the high power amp shows a difference of 1.05A. So my devices are 
> showing about 500+ ma each. In the ball park.
> > Thanks so much for the reply.
> >
> > Chuck Hawley
> >   c-hawley at illinois.edu
> >
> >   Amateur Radio, KE9UW
> >   aka Jack, BMW Motorcycles
> >
> > ________________________________
> > From: elecraft-bounces at mailman.qth.net 
> <elecraft-bounces at mailman.qth.net> on behalf of Mike Harris via 
> Elecraft <elecraft at mailman.qth.net>
> > Sent: Thursday, March 7, 2019 5:43 AM
> > To: elecraft at mailman.qth.net
> > Subject: [Elecraft] Fwd: AW: K3 KPA3 bias adjust
> >
> > Hi,
> >
> > Forwarded a 2009 email exchange for your info. I have NOT tried this so
> > use with care and at your own risk.
> >
> > Regards,
> >
> > Mike VP8NO
> >
> >
> > -------- Forwarded Message --------
> > Subject: AW: [Elecraft] K3 KPA3 bias adjust
> > Date: Sat, 3 Jan 2009 19:46:55 +0100
> > From: Koppendorfer Klaus <KK at ccf.net>
> > To: Jan Erik Holm <sm2ekm at telia.com>
> > CC: Elecraft at mailman.qth.net <Elecraft at mailman.qth.net>
> >
> > Locate the BIAS pot at the front of the KPA3, between the heat sink and
> > the KPA3 shield. Note what the display current is in the VFO B readout
> > when you tap the Display button and turn the VFO B knob to the current
> > readout. In RX, it should be 1.0A or so.   In XMIT (not TUNE), it should
> > be about 1.90 to 2.0A when the Power knob is set to 12w or above so the
> > KPA3 is made active (but there is no RF output since XMIT is used). Or
> > you can press the PTT button but do not speak.
> >
> > If there is much more current than this, set the BIAS pot to minimum
> > (fully counter clockwise). Then tap XMIT (not TUNE) and note what the
> > current is in VFO B's readout. Slowly turn up the BIAS pot until you see
> > 400-500mA more current that was seen with the BIAS pot at minimum.
> >