[TowerTalk] HD-73 Rotator issues

[Dan Evans]

Greetings group,

Sorry for the long posts, if you are not interested please delete now!

Still fighting with the HD-73 control box.  I dug up a replacement 4.7V zener.  I replaced the zener, but, still no good.  So.... I figure the next step was to start pulling components off the board and testing each.

I noticed a ceramic cap and a pair of back to back diodes across two of the pot leads from the rotator so decided to start there.  (I'm no expert, but I'm guessing these are to keep RF out of the meter)    The cap looks pretty bullet proof, but the diodes are tiny so I pull them all to test.  One of the diodes was "open" and the other was shorted.   I have no idea what these were, but I had some 1N914's in the junk box so I put them in.

And, the meter is working!  Well, kind of, anyway...  The meter moves now, but it's no where near accurate.  The needle will cross a full 360* within about 1/4 turn of the rotator.   So, still more problems.

Did using the 1N914's change anything?  The exact diode type is not marked on the schematic, would this be critical?

I haven't started pulling resistors off the board yet, but that would seem to be the next step.  Only one of the resistors is a "high precision" type.  I'm guessing the meter uses this as a "reference".  Would the zapped diodes have took out the resistors?  They are not "open", but I haven't confirmed the values yet.  The resistor values are listed on the schematic, so they should be easy to replace.

Am I missing anything?  Yeah, I know it would likely be easier to buy a working controller, but it's become personal now!  :-)

As far as the contest goes, various other projects kept me busy all weekend anyway so I didn't get to play with the September VHF QSO Party.  However, I did get my newly refurbished, antique, 17B2 assembled and put up on the tower.  Yep, it's an antique.  It's one of the old ones with the 3 reflector elements.

73 all,
Dan
 
-- 
K9ZF
Amateur Radio Emergency Service, Clark County Indiana. EM78el
former K9ZF /R no budget Rover ***QRP-l #1269
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>________________________________
> From: Dan Evans <k9zf at yahoo.com>
>To: Richard Karlquist <richard at karlquist.com>; "towertalk at contesting.com" <towertalk at contesting.com> 
>Sent: Thursday, September 12, 2013 5:30 PM
>Subject: Re: [TowerTalk] HD-73 Rotator issues
> 
>
>
>Just an update on the HD-73 issue.
>
>
>The lamp is OK, and there was no voltage at the meter.  [an ohm meter across the meter measured a value, and the power from the DVM sent it to about half scale :-) ]
>
>
>So, I pulled the little circuit board and started checking voltages.  It looks like the tiny little 4.7V zener is bad.
>
>
>Good news:  Simple fix and a cheap part.
>
>
>Bad news:  I will have to order the zener, so no chance of repairing before the contest this weekend :-(
>
>
>73 all and thanks for the tips,
>Dan
> 
>-- 
>K9ZF
>
>
Talk'ians,

>
>Just picked up an Alliance HD-73 at a hamfest.  The previous owner sold it really cheap, because it has a problem...
>
>
>Anyway, the rotor turns fine but there is no direction indication on the control box. The needle just stays all the way to the left, it doesn't move when the rotor turns.  The box lights up, the rotor turns, but no direction indication.    I guessed it would be a simple fix, maybe even a problem with the wiring, but I haven't found the issue yet.
>
>
>What I did do was go through the trouble shooting section of the manual.  Basically, it walks you through the what the resistance values from pin to pin of the rotor.   All of the readings were normal, so I would rule out a problem with the rotor.  That leaves a problem with the control box.  I opened up the box and looked for obvious problems, but no such luck.  I am guessing it may be an issue on the circuit board near the meter, but I haven't pulled the board yet.  I see a few diodes and resistors on the board to check out.
>
>
>Before I completely dismantle the control box, has anyone run across this issue before?  Is there a common problem I should be looking for?  I'm not an electrical engineer, but I'm pretty good with a DVM and a soldering iron.  At least I think I am better with a soldering iron than whoever built this control box... (connections have big globs of solder...)
>
>
>Any tips appreciated.  I'm still hoping to get it put up before the VHF contest this weekend...
>
>
>73
>Dan
> 
>-- 
>K9ZF