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XV144 shutdown

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MW0RSS

XV144 shutdown

Hi all

I have a used XV144 that loses power after a short time. I have tried it
with my K2 (using the KIO2) and also a couple of different QRP rigs, driving
it directly with a few watts. I have arranged jumpers accordingly, depending
on how the XV144 is being driven.

It completely loses power after a random amount of time. The power loss
seems unrelated to how much power the unit is delivering (the XV144 loses
power just the same, whether it’s giving 5W or 20W output).

It doesn’t seem to be a heat problem.

Any suggestions would be welcome.

Pete MW0RSS

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Don Wilhelm

Re: XV144 shutdown

Pete,

The most probable cause is that the power module is at fault. Re-check
the XV series construction manual to be certain the PA module is mounted
correctly with the right mounting hardware (in the right order) along
with the heat spreader and thermal pad. The back side of the module
must be in contact with the heat spreader, or it will throttle back power.

If all that is correct, then the PA module may be damaged.
If you can follow the schematic, then you can trace the problem at
several points while measuring the RF voltage with an oscilloscope.
There are some checks on the RF board that you can check to see if the
Local Oscillator is dropping in RF voltage (you can check that at a test
point with a DMM).

With an oscilloscope you can tell if the 28Mhz drive to the mixer is
dropping.
With great caution, you can also check the RF output of U6 (if your
oscilloscope and 10X probe is rated for 200MHz), but be careful not to
let your 'scope probe couple to the other circuits giving rise to
oscillation and erroneous conclusions.

73,
Don W3FPR

On 3/19/2018 6:41 PM, MW0RSS wrote:

> Hi all
>
> I have a used XV144 that loses power after a short time. I have tried it
> with my K2 (using the KIO2) and also a couple of different QRP rigs, driving
> it directly with a few watts. I have arranged jumpers accordingly, depending
> on how the XV144 is being driven.
>
> It completely loses power after a random amount of time. The power loss
> seems unrelated to how much power the unit is delivering (the XV144 loses
> power just the same, whether it’s giving 5W or 20W output).
>

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wayne burdick

Re: XV144 shutdown

Administrator

In reply to this post by MW0RSS

Pete,

After establishing the desired power output level, try turning off ALC (see owner’s manual; CONFIG:TX ALC).

If turning the ALC off eliminates power fade, then it’s a firmware problem. If this doesn’t help, then something is heating up, possibly a cold solder joint or component.

Wayne
N6KR

> On Mar 19, 2018, at 3:41 PM, MW0RSS <[hidden email]> wrote:
>
> Hi all
>
> I have a used XV144 that loses power after a short time. I have tried it
> with my K2 (using the KIO2) and also a couple of different QRP rigs, driving
> it directly with a few watts. I have arranged jumpers accordingly, depending
> on how the XV144 is being driven.
>
> It completely loses power after a random amount of time. The power loss
> seems unrelated to how much power the unit is delivering (the XV144 loses
> power just the same, whether it’s giving 5W or 20W output).
>
> It doesn’t seem to be a heat problem.
>
> Any suggestions would be welcome.
>
> Pete MW0RSS
>
>
>
> --
> Sent from: http://elecraft.365791.n2.nabble.com/
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

Don Wilhelm

Re: XV144 shutdown

Pete,

What Wayne indicated applies only to the K3 and the K144XV transverter.
It is not applicable to the XV144 being driven by the K2.
The K2 has no provision to turn off the TX ALC.

But I would add that you might monitor the K2 output with a QRP
wattmeter to determine if the K2 is reducing power or the XV144.
A measurement of the RF voltage from the K2 will determine that. For
that measurement, you must use an oscilloscope with a 10X probe.
Alternately, an oscilloscope at the XV144 28MHz input to the mixer will
tell you whether the 28MHz energy is steady or sagging over your
transmit time.

73,
Don w3FPR

On 3/19/2018 8:11 PM, Wayne Burdick wrote:
> Pete,
>
> After establishing the desired power output level, try turning off ALC (see owner’s manual; CONFIG:TX ALC).
>
> If turning the ALC off eliminates power fade, then it’s a firmware problem. If this doesn’t help, then something is heating up, possibly a cold solder joint or component.
>
> Wayne
> N6KR
>
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MW0RSS

Re: XV144 shutdown

Thanks guys. The K2 is OK; it is currently driving my XV50 with no problems.
It used to also drive the XV144 when I first got it, so my cables are wired
OK and the KIO2 is working properly.

The XV144 behaves the same whether driven by the K2 or any other QRP rig. It
now seems to develop no output. Rx is OK, but there's no power output at
all. I have got through the alignment procedure up the the part that says
that TP5 should have volts on it when the unit is put into Tx and power
applied. It doesn't seem to have any significant volts on TP5.

Adjusting R22 while driving it no longer produces any output. It seems to
have been a gradual deterioration.

Pete

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