[Hammarlund] IF alignment on an HQ-180

[Roy Morgan]

At 09:36 PM 8/31/2005, Bob Young wrote:
>Does anyone here experience with this? I'm trying to use a Radio Shack 
>digital multimeter, while the manual says to use a VTVM, I have one but 
>don't trust it.


Bob,

Dave Faria comments that DMM's aren't any good for this but if that's all 
you have they can be used.  The most important caution is that if you are 
measuring a DC voltage at a grid that has RF at it, for instance at an 
oscillator, the straight copper test lead may disrupt the circuit 
operation. The solution is simple; put a 100 K or 1 meg resistor at the 
probe tip (and allow for the ten percent reduction indicated voltage if 
that is important.)

BUT.. you do have a VTVM, and I suggest you put a little time into fixing 
it up. There is nothing quite like the (justified) feeling that you've 
gotten the last little bit of peaking while adjusting a tuned circuit that 
comes from watching a moving needle instead of dancing digital figures.

If you ever get a chance to buy one of those VTVM's found in tv and radio 
shops in the 40's and 50's with the huge meter on the front, do it.  With 
just a little restoration, and likely new test leads, you'll have a meter 
that will let you be half asleep while doing alignments.  You can see the 
thing out of the corner of your eye as you tweak things on the chassis.

>I have the meter connected to the junction of L8 and C44, and the other on 
>ground like it says and I'm getting a straight -0.275 VDC no matter what I do.

My guess is that you either have the wrong test point, or there's something 
amiss with the circuit. (I recently aligned a very similar HQ-170 and got 
normal indications.)

>  I tried the 60 kHz. first, varied the generator signal and so on and the 
> multimeter reading never varies,

Did you have modulation on?  Did the audible signal or the S-meter vary up 
and down as you changed the signal generator output? If so, then you have 
the meter hooked up to some other spot.

>...it was a real son of a gun trying to get the probe on the the junction 
>of C28 and T5 and thought perhaps I wasn't getting a good connection,  it 
>took me about an hour to get it clipped on.

(Pause to download the manual from BAMA) ...

Note: this is the place to apply the SIGNAL from the signal generator, not 
measure the DC voltage.  The DC meter goes at the junction of L8 and C44 
near V9, the 12AU7.  The terminal on the T5 IF can should be reasonably 
accessible, but it may not be.  Some folks would solder a little short bit 
of wire with a loop on the end to that point to make future alignments easier.

  You can wrap a little wire around the tube pin (in this case Pin 7 of V5, 
6BE6) and re-insert the tube in the socket.  (a two-inch piece of solid #22 
wire found in phone wire works well.) Then clip the meter probe to 
that.  You  will need a blocking capacitor on the end of your signal 
generator lead to prevent disturbance to the DC voltage on that grid.

>  But the 3.035 mHz connection is a two second affair and I know I'm in 
> the right place, generator is ok and I have them on frequency counters

That all sounds good.

>The book says to put the calibration reset in the center, is that 
>something on an HQ-180A?

It says: "Make sure that the Band spread adjustable indicator is set at the 
center marker ... " This is a little mechanical thing that moves the line 
in the bandspread dial window to make the dial read correctly. Turn the 
front panel knob marked  "Calibration Set Control", item #2 in the picture 
in the manual, to see what happens.  In normal operation, it is used with 
the crystal calibrator to get the dial to read accurately. There is a 
little line on the fixed portion of the window - probably at the bottom of 
the window -  that indicates the center of the movement if the dial 
indicator line.  If your center marker is rubbed out or covered with dust 
and dirt, clean with Windex and a toothbrush* and apply a little bit of 
White-Out (or lacquer stick if you have one).   Set the line to center when 
you do the dial frequency calibrations as you adjust the local oscillator L 
and C adjustments.

*Keep ALL Windex, water, and other cleaners away from the frequency dials 
unless you are brave AND you know that what you are using will not take the 
dial markings off.  One wipe with the wrong stuff and the marks are GONE!

Good luck, and let us know how you make out.

Roy


- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828 Cell 301-928-7794
Work: Voice: 301-975-3254,  Fax: 301-948-6213
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