KX1: Low output power

[Mike F.]

I'm finally getting back around to trying to finish my KX1, and now am finding that output power is a hair under 2w rather than the prescribed 3-4.

I'm connected to a regulated power supply at 13.8vdc, output is through a Byrd wattmeter to an MFJ 50 ohm dummy load.  R4 is fully clockwise.  I'm also using a reference receiver (a Yaesu 857D with a 3' wire as a receive antenna).  I clearly hear the tuning tone in the 857 at both 20m and 40m, and output power is identical on both bands.  Short keying bursts are nice and clear at the reference receiver.  An inline ammeter shows 0 amps both in receive and transmit (a bit odd, but I assume the current drawn is less than the minimum detectable by the meter).

Don will remember that I had some trouble with the toroids on the 3080 board, and rewound them.  That seemed to fix the first problem I had, a deaf receiver.  I've looked hard for a short on the LPF board but cannot find any, including the back side where L2-1 must clear the pad for L2-4.

Working through the troubleshooting tables, I seem to have eliminated all the easy things :-).  One item is to re-check the resistance on the relays, between pins 1 & 8.  I seem to remember seeing that resistance spec, but I can't find it now.  If someone knows it, please pass it along.

In looking at the relays, I noticed that the book calls for installing C56 across pins 2 & 3 of K1.  However, Figure 13 on page 34 appears to show C56 across pins 6 & 7?  Pin 1 has the tiny notch above it in the case, right?  I installed C56 just like is shown in Figure 13.  I also noticed my C56 is a disc, not the tantalum or whatever is shown in the Figure.  I didn't consider that an issue during assembly.

On the plus side, nothing seems to be getting hot :-).

--
73,
Mike, KC0KBC
Yaesu FT-857D, FT-8800R, VX-7RB
Elecraft KX1 #1819 (having its way with me), XG2
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[Mike F.]

On second thought (ok, I realized I was using the 100w slug in the Byrd and therefore reading the wrong scale), it seems to be running about 3w or just a hair more.  Within spec to be sure, and I know there's no real world difference between 3 & 4 watts.  I still wonder if there's any way to push it up just a hair more...

--
73,
Mike, KC0KBC
Yaesu FT-857D, FT-8800R, VX-7RB
Elecraft KX1 #1819 (in work), XG2

 -------------- Original message ----------------------
From: [hidden email] (Mike)

> I'm finally getting back around to trying to finish my KX1, and now am finding
> that output power is a hair under 2w rather than the prescribed 3-4.
>
> I'm connected to a regulated power supply at 13.8vdc, output is through a Byrd
> wattmeter to an MFJ 50 ohm dummy load.  R4 is fully clockwise.  I'm also using a
> reference receiver (a Yaesu 857D with a 3' wire as a receive antenna).  I
> clearly hear the tuning tone in the 857 at both 20m and 40m, and output power is
> identical on both bands.  Short keying bursts are nice and clear at the
> reference receiver.  An inline ammeter shows 0 amps both in receive and transmit
> (a bit odd, but I assume the current drawn is less than the minimum detectable
> by the meter).
>
> Don will remember that I had some trouble with the toroids on the 3080 board,
> and rewound them.  That seemed to fix the first problem I had, a deaf receiver.  
> I've looked hard for a short on the LPF board but cannot find any, including the
> back side where L2-1 must clear the pad for L2-4.
>
> Working through the troubleshooting tables, I seem to have eliminated all the
> easy things :-).  One item is to re-check the resistance on the relays, between
> pins 1 & 8.  I seem to remember seeing that resistance spec, but I can't find it
> now.  If someone knows it, please pass it along.
>
> In looking at the relays, I noticed that the book calls for installing C56
> across pins 2 & 3 of K1.  However, Figure 13 on page 34 appears to show C56
> across pins 6 & 7?  Pin 1 has the tiny notch above it in the case, right?  I
> installed C56 just like is shown in Figure 13.  I also noticed my C56 is a disc,
> not the tantalum or whatever is shown in the Figure.  I didn't consider that an
> issue during assembly.
>
> On the plus side, nothing seems to be getting hot :-).
>
> --
> 73,
> Mike, KC0KBC
> Yaesu FT-857D, FT-8800R, VX-7RB
> Elecraft KX1 #1819 (having its way with me), XG2
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft   
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com

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