[Heath] SB-104A VOX locks up

[Dale Putnam]

Hi Sandy,
  Mine has done that at times.. I found a loose ground, allowing rf back into the mic circuit.
Found it by dropping the pwr to qrp.. and also helped by dropping the mic gain.. 
lower power pointed to the rf feedback issue.. lower mic gain also pointed that way..
Good Luck!

Have a great day,
--... ...-- Dale - WC7S in Wy


________________________________________
From: Heath <heath-bounces at puck.nether.net> on behalf of JF <lhouseparker at livingston.net>
Sent: Tuesday, March 22, 2016 3:59 PM
To: Alexander N. Gerli; heath at puck.nether.net
Subject: Re: [Heath] SB-104A VOX locks up

On 3/21/2016 11:53 AM, Alexander N. Gerli wrote:
> Hi, folks!  Strange symptom this morning. The VOX is locking
> up, that is it won't release even if the Delay and AntiVOX are set
> minimum. Sensitivity is set just enough to trigger. Have to push
> the VOX button off to release it. PTT is normal.Was working
> correctly past few days.
> Anyone else have this symptom? The ICOD notes for the Transmit
> Audio Board aren't any help.
> 73,  Sandy AC1Y

Haven't heard of it before, could be a bunch of things, from
corroded/loose connectors to deteriorated components. Check to find
if it does this with the mic disconnected, and with a different mic.
If no change then I would first suspect the TX Audio/Regulator board
(board B). I don't recall if the ICs are socket mounted, but if they
are you could try re-seating them and/or substitution. Also try
re-seating all the boards, and verify the voltages on the various
power buses to board B.

If that doesn't help disconnect the RF from the drivers, put board B
on an extender board and verify its inputs from the various jacks and
controls:  mic jack, anti-vox, PTT/VOX button (being mechanical, it
is to be especially suspected), vox delay, patch in, key jack, vox
gain, mic gain, +RX line, all while monitoring the +TX and T/R relay
outputs.

73
John   KE5ZB


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