HW-9 ?s

[John Clifford]

Greetings,

I am glad to report that my HW-9 survived the LM388 transplant and is now
happily growling, whistling, and beeping away.  As a respondent noted, the
chip is/was an LM388, not an LM338.  For those of you with HW-9s who might
be interested, the replacement chip is available from NTE as the NTE828 (a
direct pin-for-pin replacement).

I dug out an old 4-channel Radio Shack mixer I used to use with
synthesizers, and that should protect both my R8 and my HW-9 from ever
having this problem again.

Re the testing tips I received, one respondent noted that I could use a
high-gain amplified speaker as an AF probe.  I neglected to mention that my
particular HW-9 (purchased used on eBay) had an amplified speaker installed
(circuit board mounted to the underside of the cabinet top, speaker also
mounted, holes drilled in cabinet top to let sound through).  This speaker
was able to pick up the faintest bit of audio.  That, combined with the fact
that while every incoming pin into the LM388 had the correct voltage the
outgoing 'bootstrap' pin #9 didn't, is what led me to believe it had to be
the problem.

I have to admit that the Heathkit-supplied schematic with voltages was a big
help in troubleshooting.  I wish that every manufacturer of electrical items
that supplied schematics also provided expected voltages at major components
to facilitate troubleshooting.  I'm sure there is a way to use a calculator
and the correct formulas to compute these values... but I don't know how to
do it.  Any pointers to websites, books, etc., that explain this would be
appreciated.

Thanks again for the help I received.  Now... on to troubleshooting my HW-7
(transmitter works, low audio w/static but no signals on receive).

 - jgc
John Clifford
Weapons Safety, Inc.
13215 SE 30th St.
Bellevue WA  98005

  vox: 425-649-8623
  fax: 425-644-5302
email: johnclif at weaponssafety.com
 http: www.weaponssafety.com

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