HW-9 ?s

[mike bryce]

john...

what you did was not the best thing in the world, lucky the hw9 went kaput
instead of the drake.

you can check the audio coming into the audio driver by tapping into the
audio line just before the amp.

use a set of high (2000) ohm headphones and couple the phones to the rig
with a .1 cap. you should hear plenty of audio coming in though the phones.

if you do, then the lm338 is cooked.

if you don't, then move the phones down stream a bit and try the audio
predriver.

you can use a high gain amplifier inplace of the phones. I have one here
from ten tec called the utility amplifier. works great as a signal tracer!


--
Mike Bryce WB8VGE
SunLight Energy Systems
"Electricity at the speed of light"

> From: John Clifford <johnclif at ix.netcom.com>
> Reply-To: johnclif at ix.netcom.com
> Date: Wed, 18 Oct 2000 23:24:17 -0700
> To: HEATH at LISTSERV.TEMPE.GOV
> Subject: HW-9 ?s
>
> Greetings,
>
> Ran into a problem today with my HW-9, and am wondering if anyone out there
> can help me.
>
> I had the HW-9 and my Drake R8A connected to amplified speakers via patch
> cords, tying both headphone outputs together.  Evidently, too much
> voltage/current got back into the HW-9 as its audio stopped working.
> Separating everything shows that the HW-9 can barely be heard even with the
> volume cranked all of the way up.
>
> I pulled the schematic out, pulled the sheetmetal off, and started probing.
> The first candidate upstream was the LM338N audio amp IC.  Sure enough,
> testing for the expected voltages showed everything fine EXCEPT that the
> 'bootstrap' pin (#9) was putting out .5v instead of the schematic's
> suggested 7.0v.  The voltage didn't change even when I tuned the radio to a
> strong signal on 40m.
>
> I'm pretty sure the problem's not upstream in the RF stages, since the front
> panel meter jumps when tuning across a strong signal (verified on the R8A).
>
> I went searching for a new LM338N, figuring that for a few bucks I'd swap it
> out and see what happens.  Of course, this part is no longer made, but I've
> found a source on the Net and so should be up and running soon.
>
> My ?s:
>
> * If anyone with experience with the HW-9 or with electronics
> troubleshooting has any suggestions on what I should be checking out, I'd
> appreciate it.
>
> * If anyone knows of a pin-for-pin substitute for the LM338N, please let me
> know.
>
> Thanks, and please cc me a copy of your post since I may not yet be signed
> up on the Heathkit list.
>
> - 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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