XV144 L16 Adjustment

[Joe Barger]

Hi All,

I'm having trouble getting 20W out of an XV144.  I get around 7W out with 5W
drive (with the jumpers set for 5W drive), and more drive doesn't produce
more output.  The drive attenuation resistors show a little "burned" color,
but a check with an ohm meter says they are OK.  The voltages in the
troubleshooting chart look fine.  Receiving seems to be OK as well.  It's
part of a club station, so it's possible it's been overdriven at one point
or another.  I replaced the MAR-3 (in case it was damaged), but no
difference.  While adjusting the 28MHz IF strip I noticed that L16 peaks
when the slug is removed from the top of the can.  The instructions say this
is normal for L17, but is it also normal for L16?  The voltage at TP5 was
still going up quickly when the slug came out, so it seems the inductance
needs to be even lower to reach resonance.

When I first build the unit it tuned right up and worked fine.
Unfortunately I didn't make any notes on where L16 was then.

Any sage advice before I drag a 'scope out of a lab to the shack to continue
troubleshooting?

Thanks

joe n6kk


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[Joe Barger]

Just to close off the issue (if anyone else has this problem and wonders
what happened ...)

It turned out to be a shorted overdrive protection LED (D10, D11).
Apparently it was overdriven at some point and the LED sacrificed itself.
Replaced the LED and everything is working well again.  The L16 slug is
approximately a couple turns from the top of the can, which is where the
instructions say it should be.

73

joe n6kk

----- Original Message -----
From: "Joe Barger" <[hidden email]>
To: <[hidden email]>
Sent: Tuesday, September 04, 2007 10:20 PM
Subject: [Elecraft] XV144 L16 Adjustment

> Hi All,
>
> I'm having trouble getting 20W out of an XV144.  I get around 7W out with
> 5W drive (with the jumpers set for 5W drive), and more drive doesn't
> produce more output.  The drive attenuation resistors show a little
> "burned" color, but a check with an ohm meter says they are OK.  The
> voltages in the troubleshooting chart look fine.  Receiving seems to be OK
> as well.  It's part of a club station, so it's possible it's been
> overdriven at one point or another.  I replaced the MAR-3 (in case it was
> damaged), but no difference.  While adjusting the 28MHz IF strip I noticed
> that L16 peaks when the slug is removed from the top of the can.  The
> instructions say this is normal for L17, but is it also normal for L16?
> The voltage at TP5 was still going up quickly when the slug came out, so
> it seems the inductance needs to be even lower to reach resonance.
>
> When I first build the unit it tuned right up and worked fine.
> Unfortunately I didn't make any notes on where L16 was then.
>
> Any sage advice before I drag a 'scope out of a lab to the shack to
> continue troubleshooting?
>
> Thanks
>
> joe n6kk
>
> _______________________________________________
> 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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