HW100 nightmare

[David Goncalves]

DMM will give some measurements outside of 20-50% of manual values. Just as
note on that.

David Goncalves
W1EUJ

On Fri, Mar 19, 2010 at 5:37 PM, Herman N4Ch <N4ch at aol.com> wrote:

> Something that's very quick and easy to do (and  safe........you do it with
> the radio powered down and unplugged) regarding  finding the cause of
> problems such as low drive, poor sensitivity, an oscillator  that won't
> start,
> inability to get PA idling current to where it should be,  etc., is to use
> a
> simple auto-ranging digital multimeter, and simply go thru a  quick
> exercise
> of "ohming out" all those old resistors in your  transceiver.   Keep a roll
> of masking tape handy, and whenever you  find a bad resistor, mark it with
> a
> piece of tape, and then replace the bad  resistors once you are done going
> thru the rig with the DMM.   It's  amazing how many out of tolerance old
> resistors (that look just  fine......no sign of ever overheating, etc.)
> I've
> found in old Heathkits, Swans,  Drakes, and many others.   Often they will
> be
> 2-3 times the resistance  value they should be, with the higher-wattage
> ones
> (1 and 2 watt versus 1/2  watt) being the biggest offenders.   The larger
> wire-wound types  seldom have this problem........usually when they go bad,
> they are  open.    The old carbon composition resistors can climb in value
> significantly even if they are never used..........I hate to think about
>  how
> many virgin, never soldered to, straight-leaded NOS resistors I've  pulled
> out of the parts bins to use, only to find they had twice the number  of
> ohms they should have had.   When you replace resistors, consider  the
> newer
> film types.........my experience is they don't "drift" upward in value
>  like
> the old composition types do.   Just last week, I went thru an  old Swan
> 350
> that had poor receive sensitivity and low output.........and I  found 10-12
> resistors that were at least 50% high in resistance, and over half  of
> those
> were 1 and 2 watt ones.   Replacing them fixed all the rig's  issues.
> Resistors are simple to check and cheap to replace, and I  bet you will
> find
> several in that old HW-100 that have climbed high in  value.   Good luck.
>
> 73, Herman, N4CH.
>
>
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-- 
David Goncalves

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Products bought, sold or traded here is the responsibility of the
parties involved.  This list and the City of Tempe are not responsible
for losses or misrepresentations of any kind.  Buyer beware!

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