[Elecraft] KPA100 bringup problem: only 1-W of output

Fri Dec 27 09:27:06 2002

Hi

The first thing I would check is the RF cable and connector. The connector
in the K2 should have the ground pin on the outside next to the case. Check
the cable to make sure the pins are in the right holes. I assume the 150
volt supply is ok if not you need to get it running so the T/R switch will
work. The most likely problem with the 150 V supply is T3 miss-wound or bad
solder joint.

The KPA100 has a current sense circuit that takes over and indicates the PA
current on the K2 display. It is normal for the current display to indicate
the KPA100 current above 10 watts.

Don Brown
KD5NDB

----- Original Message -----
From: "Brian Machesney" <[email protected]>
To: "'elecraft'" <[email protected]>
Sent: Thursday, December 26, 2002 4:13 PM
Subject: [Elecraft] KPA100 bringup problem: only 1-W of output

> Everything went smoothly through build and test until p. 47, "Transmit
> Tests." I'm now going through the forest of DC checks, but I'm hoping
> that someone among the august group of reflector-watchers can help me
> understand what's happening, particularly since the "factory gurus" are
> enjoying a well-deserved rest.
>
> When I connect the KPA100 to a dummy load and enter TUNE mode at
> 0.1-10-W, everything looks good. When I increase the power to 11-W or
> above, the output power indicated by the K2 is only 1-W (SWR=1.0). I
> don't have an external wattmeter, but when I connect the rig to an
> antenna the S-meter indication in a second receiver is consistent with
> this behavior.
>
> I'm using an Astron SS-25 supply. A digital multimeter placed in series
> with the high-current supply leads indicates 520-mA in receive with PA
> ON. In transmit it shows 1.75-A at 10-W power setting and 5.7-A at any
> power setting of 11-W or higher. The K2's internal ammeter also shows
> 1.75-A at 10-W, but only 4.8-A at 11-W or above. From my reading of the
> KPA100 manual, I thought the K2's internal ammeter reflected the current
> into the 10-W amplifier stage; I didn't expect the K2's ammeter to show
> more current after the KPA100 was engaged. Is this significant?
>
> Can anyone more familiar with the KPA100 suggest where I should focus my
> troubleshooting efforts? Thankfully, the base K2 still works the same as
> before the KPA100 was installed, so I'm not totally QRT.
>
> Brian K1LI
> K2 #3070, K1 #252
>
>
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