[Amps] alpha 87a and Pro II question

[Floyd Sense]

Louie: While John is correct when he says proper improper operating 
procedures can result in these problems, the 781 is known to have had 
internal ALC circuitry problems that caused a leading spike to be generated. 
Some 781s were produced with an electrolytic capacitor installed in the 
wrong polarity, and some had component values installed that did not match 
the original schematic.  There was also a problem with a resistor value on 
the power supply board being incorrect, resulting in a voltage used in the 
ALC circuitry being too low.  After I made the recommended changes, the 
leading spike was no longer a problem.  Those who had contacted Icom over 
the years regarding these problems received similar responses - "that's the 
way things work and nothing can be done to fix it".  In fact, when all 
components were installed to match the schematic and the supply voltages 
were correct, the problem was fixed.  This problem also existed in earlier 
775s, and I've never seen any documentation indicating a solution had been 
found there.  On the other hand, other Icom rigs I've owned, including the 
765 and 746 did not exhibit the leading spike problem.

I suspect that John is referring to the setting of the Drive and Power 
controls possibly being the cause of a similar problem.  If one sets these 
too high, depending upon the ALC to limit the power from the transceiver, it 
makes sense that a spike could occur owing to the response times of the ALC 
circuitry in the amp and transceiver.

73, Floyd - K8AC

----- Original Message ----- 
From: <Gudguyham at aol.com>
To: <shr at swtexas.net>; <desk at nwlink.com>; <amps at contesting.com>
Sent: Tuesday, October 11, 2005 9:13 AM
Subject: Re: [Amps] alpha 87a and Pro II question


> Jon, I believe that is was in fact a 781 that my buddies were having
> problems with in this regard.  PLEASE....You mention about reading the 
> manual and
> fixing the problem,  Since I don't own an ICOM radio or  manual and the 
> poster
> with the problem may not have one either....can you  tell us what in the 
> manual
> tune up procedure makes this problem go away.  I  am curious to know what
> resolves this problem.   Louie
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>