[Elecraft] Fwd: AW: K3 KPA3 bias adjust

[Mike Harris]

This is interesting.

When I measure the current of my early K3 #00345 using the internal 
display I see only a small difference when in TX at 10W or 100W power 
setting.  Both are in the region of 2.25/2.35A TX (1.22A RX) with the 
internal measured voltage RX 14.1V TX 14.0V.

Question is does the KPA3 have bypass mode bias control?

No change if in TX test mode, ensuring no output. The bypass relay 
operates and the power display scales correctly with change over Hi/Lo 
power.

These numbers compare with the PSU current meter.

Anyone else seeing this? Has something gone missing with a firmware upgrade?

Regards,

Mike VP8NO


On 07/03/2019 16:03, Bob McGraw K4TAX wrote:
> I just looked at the current values of my K3s using the internal DISP 
> current and voltage values.
> 
> This is how it came from the factory after replacement of the KPA3A rev 
> E amp on 5/30/2018.
> 
> 
> In RX USB mode = 1.6A  Vcc = 13.8V  Audio volume at minimum.
> 
> In TX USB mode no audio,   10 watt PWR setting = 1.60A
> 
> In TX USB mode no audio, 100 watt PWR setting = 2.91A
> 
> The PWR delta is 1.31 amps
> 
> 
> In RX CW mode,  = 1.03A   Vcc 13.8V   Audio volume at minimum.
> 
> In TX CW mode PTT closed, key open, 10 watt PWR setting 1.54A Vcc  13.7V
> 
> In TX XW mode, PTT closed, key open, 100 watt PWR setting 2.85A Vcc 13.6V
> 
> The PWR delta is 1.31 amps
> 
> 
> Your values may be different if you have the 2nd receiver and can vary 
> depending on your Vcc.
> 
> 73
> 
> Bob, K4TAX