[ICOM] FW: ALC error

[Adam Farson]

Following a discussion with my friend Matt KK5DR on a faulty amplifier which
applied positive ALC voltage to the exciter's ALC jack, I have added to my
website a page which cautions the Icom HF radio owner never to do this. The
page is general in nature, but gives the IC-756Pro3 as an example.
 
http://www.qsl.net/ab4oj/icom/ic756pro3/ealc.html

Cheers for now, 73,
Adam VA7OJ/AB4OJ

________________________________

From: matthew erickson [mailto:kk5dr at earthlink.net]
Sent: 06 March 2006 17:58
To: Adam Farson
Subject: ALC error


Hi Adam,
Thanks for researching and confirming what I suspected was the error in the
77 ALC system.
I plan to write about this in the article I'm doing on it now. 
This kind of defect is a bit alarming, it could actually cause serious
damage to an amp this has it, or even damage the exciter as well.
I think I'll replace all the parts in the ALC circuit, mainly due to the age
(30+ yrs), they may have changed value by a large margin, or have become
very leaky.
The DC power to the circuit is +55V, I'll change some resistors to bring
this down a good bit. 
After the circuit is finished I'll test it with the 4031 driving it, and the
Tek scope looking at the DC output, so I can see if there is any distortions
or + DC coming out. 
All going into the article as a tutorial for fixing the flaw.
 
Perhaps you might mention this defect and it's possible effect on one or
more of the groups. I think it would primarily pertain to tube type amps.
You would have to be careful not to re-enforce the "no ALC" guys, but site
it purely as a cause and effect flaw, and how it must be repaired to proper
operation.
I'm too busy doing  the "grunt work" to write a post of this nature. You can
use my name and call as reference for the post, and that I'm working on it
now. No rest for the wicked.
 
73 de Matt



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