{Collins} Re: 30L-1 "Tune" Meter



Donald,

Very good response.

Dave K4EWC
----- Original Message ----- 
From: "Donald Nesbitt" <drnesbitt@xxxxxxxxxxxxx>
To: <WEPackard@xxxxxxx>; <collins@xxxxxxxxxxxxx>
Sent: Wednesday, March 02, 2005 6:03 PM
Subject: {Collins} 30L-1 "Tune" Meter


Hi Bill.  I saw Sandy's post of your email on the reflector and hope that by
now you have had lots of responses including one from Sandy!

You are probably going to get a number of replies that encourage you to
forget about even trying to use the "Tune" meter on the 30L-1.  I'm sure you
will get lots of responses indicating how to tune for "maximum smoke" and
they will work! I'm assuming here that your interest is in seeing if it
actually does work and even trying to use it if it does.

When properly working and calibrated it makes tuning the 30L-1 up very quick
with almost no strain on the tubes and power supply or on the exciter for
that matter!

There have been a number of "Tune Meter" queries lately both here on the
reflector and on other sites.  Much of what I'll pass along you may already
know or are already doing.  If this is the case, please just disregard that
info.  My only intention is to "cover all the bases" just in case they need
to be covered!

NOTE:  All of what follows assumes that the 30L-1 does work and puts out
typical power (about 600-800 watts) under typical use.  Since you said that
you get 700 watts out of it, in all likelihood it does work!

First a couple of things to check.  Have you tried it into a DUMMY LOAD of
known quality?  If you are going into an antenna even one that appears to
have low swr, it might not be what you think and that will make a huge
difference in the tuning of the amp.  I'm picking up on one clue that this
might be the case as your email said that the LOADING CONTROL is all the way
CCW on 40 Meters when fully loaded to 700 watts or so output.  That just
should not be the case!  Yes, maybe a 3 + or - but not all the way CCW!  It
may be a clue that either your dummy load or antenna (if you are loading it
into one) is not as good as you thought!  Then again, there may simply be
something wrong with the output circuit of the 30L-1.  Another "clue" is
your reference to arcing.  That would indicate that the amplifier is "under
loaded" and the LOADING CONTROL should be advanced in the Clockwise
direction.

Check it on a good dummy load.

I am also assuming that you are using an external wattmeter as an indicator
of output and that you have indeed tuned it up for "Maximum Smoke" with 80
to 90+ watts of drive and are now interested in why, with the 30L-1 meter
switch in the "Tune" position, the meter does not indicate "Zero" on the
meter scale.

Now I'm going to run through my "standard" tuning procedure and advice with
respect to the 30L-1 and its "Tune" meter function.  This is the part where
you may get bored reading as you probably already know this - but - it might
be worth a look see.

What we are trying to accomplish here is to see if the "Tune" meter function
and associated circuitry in the 30L-1 are working and properly calibrated.
We are NOT trying to tune for MAXIMUM SMOKE under full drive in this test!

Here we go!

First:  Connect the dummy load, verify that your coax is good and make sure
that you have the 30L-1 set to the proper band!  If you don't, you will note
the same "problem" that you describe!  Of course, it is also likely that you
won't get any output at all and will simple destroy your nice new tubes!
Bet you have already checked the bandswitch  - but who knows, you might be
tuning it up for 40 on the 20 meter position.  Many have tried that!

Second: it is possible that there is simply something wrong with the
circuitry associated with the "Tune" meter position or that the variable
capacitor for the comparator circuit is simply mis-adjusted.  While this is
somewhat likely it's usually not out of whack to much unless someone has
been diddling with it!

Let's assume that the circuit is OK and that the capacitor is set
correctly - and - that you have it on the proper band.

Please keep in mind that my 30L-1's the circuit does work correctly (and it
is one of the items I deal with when I re-hab an amp) and that they are
properly set up using a two-tone test generator and pretty good scope.  In
short, they work!

Tune up the KWM-2 as usual.  If you have the 32S series xmtr, do the same
and if you have anything else, insure that it is properly tuned.

NOW HERE IS WHERE THINGS GET TO BE FUN - YOU WILL KEEP THE 30L-1 METER IN
THE "TUNE" POSITION THROUGHOUT THE PROCEDURE.  This will be hard - you will
want to switch over to the "D.C. Amps" position - resist that urge!

Keep the 30L-1 meter in the "Tune" position.  With the 30L-1 Power Switch in
the OFF position, the 30L-1 meter should read at the "Zero" on the scale and
when turning it ON it should still read zero with the meter in the "Tune"
position.  If this is not the case, use the mechanical adjustment on the
meter to correctly set it to the "zero."

Turn on the 30L-1.  KEEP the 30L-1 meter in the "Tune" position.

Make sure that the "Mic Gain" control on your M-2 or 32S is in the fully
counterclockwise position (turned down).  If you are using something else,
just make sure that the "carrier" or "power" control is set to minimum.

Put your M-2 or 32S Emission switch in the "Tune" position.  Begin to rotate
the "Mic Gain" control clockwise (slowly) while observing the 30L-1 "Tune"
meter.  As you do this, it will swing either above or below the "Zero" on
the meter scale.

KEEP THE 30L-1 METER SWITCH IN THE "TUNE" POSITION!

Use the plate "Tuning" control on the 30L-1 to "dip" the 30L-1 meter - STILL
KEEPING THE 30L-1 METER SWITCH IN THE "TUNE" POSITION.  If  the dip occurs
on the meter ABOVE zero, turn the 30L-1 "Loading" control counterclockwise
to bring the "dip" to zero - if the dip occurs on the meter BELOW the zero,
turn the 30L-1 "Loading" control clockwise to bring the needle to the zero
mark.  Continue to do this "dance" as you increase the Mic Gain control (or
exciter power) with the exciter Emission switch in the "Tune" position.
RESIST the urge to move the exciter Emission switch to the "Lock" position.
This will be hard.  Don't do it!  KEEP the EXCITER EMISSION SWITCH in the
TUNE position.  You only need 20 watts or so of drive for this tune up test!

KEEP THE 30L-1 METER SWITCH IN THE "TUNE" POSITION!

NOTE:  Using the M-2 or the 32S series, the maximum amount of drive that you
will put into the 30L-1 in this position will be about 20 watts and that is
ALL that is necessary to properly tune the 30L-1 up using a properly
calibrated and functioning "Tune" meter position on the 30L-1 !

The idea here is to have the 30L-1 meter show zero when the 30L-1 plate
tuning control shows it dipped (AGAIN WITH THE 30L-1 METER IN THE "TUNE"
POSITION) all the while only putting about 20 watts into it.  Once this is
accomplished - you're done!  Well, you're done if it is working correctly!

When you drive it with 70 to 100 watts you will notice some slight wiggle on
the 30L-1 meter with the meter switch in the "Tune" position.  That is
because the circuit, again assuming it is operating correctly,  is not
"perfect."

NOTICE  that in this procedure, the 30L-1 meter switch was NEVER placed in
the "D.C. Amps" position - ONLY in the "Tune" position!

Once your have accomplished this "tune" you might want to check to see how
it did!  * * * Go easy when you do in case it really is not working
correctly or is mis-calibrated.  If you have a peak reading wattmeter, it
should show a reading about the same as you get when you tune for maximum
smoke - actually, it will likely indicate a bit over that number because of
the dynamic nature of your SSB or CW signal as compared to the "all out -
flat out" sort of steady state conditions when using the "tune for maximum
smoke" procedure.

If this does not work then you either have the bandswitch on the 30L-1 set
to the wrong band (or the knob is not on the shaft correctly or the shaft
has turned) or there is indeed something wrong with the circuitry or it is
mis-adjusted.

Now in all candor I must tell you that most guys and gals really don't do it
this way.  They just tune the amp for maximum output with maximum drive and
go with it!

In all fairness to them, the "Tune" position of the 30L-1 metering circuit
will only be useful if the circuit is not flawed and it has been properly
adjusted by using a two-tone audio signal and a good scope.

Have fun es 73 -- Don N4HH



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Sponsored by the Collins Collectors Association http://www.collinsradio.org
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