[R-390] Resistance Measurements and Trouble Shooting

[Cecil Acuff]

Greetings Group,

        I would look at what the predominant resistor tolerance is in the
circuitry.  For the Halli's 20% might be pretty standard.  For a piece of
Mil equipment I would expect no greater than 10%.  I would use that as my
reference while going through the checks.  I think a circuit analysis would
also be in order....you need to know what you are measuring in there and try
to get under the bottom and break it down to more individual components when
you find a resistance measurement that is out of whack from what the book
says to expect.  I have found that many of the high value resistors are
effected the most by their age.  Also if there are still all the old BBOD
type caps in the circuit the resistance measurements will most likely be
effected.  (ugly red tiny chief caps in the old Halli's)

Cecil...
----- Original Message ----- 
From: "David Hallam" <dhallam@RapidSys.com>
To: "R-390 List" <r-390@mailman.qth.net>
Sent: Saturday, January 31, 2004 5:18 PM
Subject: [R-390] Resistance Measurements and Trouble Shooting


> Here is a question from someone who is trying to learn this trouble
shooting
> business.
>
> After circuit resistance measurements have been made, at what point do you
> say that there is a problem and start checking individual components?  Is
it
> ( 5%, ( 10%, (20% of the value stated in the manual, or ?  I realize that
> the circuit under consideration makes a difference; some obviously have to
> have closer tolerances than others.
>
> The item under consideration is a Hallicrafters HT-32B transmitter.  I
don't
> think resistances in say the audio circuit would have to be as tight as
the
> balanced modulator, for instance.  Or am I wrong?
>
> What is a good place to start?
>
> David C. Hallam
> KC2JD
>
>
>
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