[Amps] 87 a query re align motors?

[Dick Green WC1M]

Replacement of the PIN diodes, by itself, would not have cleared the segment
memories. 

I guess RF Concepts could have accidentally wiped the memories when doing
diagnostics before or after the replacement, but that seems unlikely.

The only other way to lose your default segment memories that I know of is
to replace the CPU. In that case, you're starting with blank segment
memories. In fact, there a bunch of critical parameters that are blank as
well, such as the correct position for the band switch on each band, various
voltage thresholds, etc. Each amp is custom-programmed at the factory when
built or when the CPU is replaced. I know this because I had to have the CPU
replaced after a lightning hit. I was able to take advantage of a rare trip
by Brad to the East Coast, during which he replaced my CPU and programmed
the critical parameters. But he didn't have time to tune the default
memories and gave me the procedure to do it (for various reasons I still
haven't gotten around to it -- I just programmed the user memories for my
antennas.) I assume this is the procedure RF Concepts had you do. However,
it doesn't seem likely that they would have replaced the CPU without telling
you and without fully programming it.

I'm speculating, but it's possible that something is wrong with one or both
of the PIN diodes they replaced, or they're not soldered in right. Another
possibility is that something in the output path was jarred loose in
transit. In these cases, the amp would see different output impedance and
all of the default and user segment memories would have to be retuned. Note
that I replaced both of my transmit PIN diodes and did not have this
problem. The segment memories I had previously programmed worked, though
since I use AlphaMax that just means that they're close enough for AlphaMax
to do what it needs to do.

I can think of one more possibility: there was some flaw in your amp when it
was built, such as an off-spec PIN diode, a loose connection, something
wrong in the output path, etc., but it wasn't severe enough to prevent
tuning of the default segments. Maybe RF Concepts fixed the flaw in the
process of replacing your PIN diodes, which is why the tuning needed to be
redone.

73, Dick WC1M

-----Original Message-----
From: Gary E. Jones [mailto:garyejones at cmaaccess.com] 
Sent: Saturday, March 26, 2011 8:40 AM
To: amps at contesting.com
Subject: Re: [Amps] 87 a query re align motors?

Charles:

Since you didn't mention any of this in your post, I assume that it did not
happen, but just in case, let me share a similar experience. 

I had to return my amp (87A) to Alpha to replace pin diodes, which gave out
after about 12 years of use. When I got the amp back "fixed", the factory
had done something that cleared all the segment tuning on 4 or 5 of the
bands, meaning that although it worked fine on all bands before, three or
four of the bands were badly out of tune when I got the amp back. It would
kick to error on those bands regardless of how much power I was putting into
the amp (even a few watts immediately kicked the amp into fail mode). What I
had to do was manually re-program those bands by hand, because as I said, I
would kick the amp into fault mode even with 5 or 10 watts of drive. 

So I had to tune everything into a dummy load at 50 ohms, and even sometimes
try various segments within a band at the lowest drive I could get out of
the transmitter before I could find a sweet spot to begin the tuning of that
band, and finally with much playing around, I could get a band to come back
into reasonable tune. I literally had to manually tune and save each band
segment back into the computer memory. The manual tune and save process are
described in the manual. 

It took a lot of work, but now I have it working on all bands 160 to 10. RF
Concepts and Molly were very helpful in giving me some advice on this but
never gave me a clear idea of what happened at the factory because there are
supposed to be stored factory defaults for each band that you can retrieve
easily following the procedure. But my guess is that these defaults got
erased while on the bench and the amp got totally out of tune, and I had to
find the correct settings from scratch. I bought a good dummy load that
could take a reasonable amount of 1500 watts and worked on it slowly over
several days, and got my problem under control. 

       Hope any of that helps....

                     Gary      W5FI 






-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
Behalf Of Charles Harpole
Sent: Friday, March 25, 2011 1:29 AM
To: amps at contesting.com
Subject: [Amps] 87 a query re align motors?


I need advice re the Alpha 87a .... all the auto tuning via AlphaMax or by
hand run the motors/caps all the way to one end or the other and give me a
not-so-good load with the TUNE indicator 7 to 9 LED bars to the RIGHT of
center.  Either this is a bad SWR load (shows ok on other rigs/tests) or
maybe the tuning stepper motors and caps are misaligned.
 
Anyone have advice about problem or a fix??????????
73,

Charles Harpole k4vud at hotmail.com 
 		 	   		  
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