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Re: [Amps] Alpha 87A fault 33 when pressing TUNE DOWN

To: "'Dave'" <>, <>
Subject: Re: [Amps] Alpha 87A fault 33 when pressing TUNE DOWN
From: <>
Date: Thu, 1 Aug 2019 14:01:45 -0400
List-post: <>
You should call or email Glenn at Alpha to see what the message indicates
and if he's seen it before. I'm puzzled by "failed to initialize". If it's
completing warmup you'd think it initialized both caps, but perhaps the Tune
Down LED not flashing indicates that initialization failed. But you'd think
that's when fault 33 would occur, not when you press Tune Down.

I'm pretty sure each tuning cap shaft has a disk with markings and a light
sensor. The amp can't detect the position from that, so at the end of warmup
it moves them to an end position and then counts the markings to arrive at
the position for the current tuning segment. From then on, it knows where
the cap is positioned. Or something like that. At least, that's how my Acom
2000a works. Once had a problem with it "forgetting" tuning which I traced
to the plate shaft on one of the caps being loose, causing the plates to
overshoot the target position. Probably not an issue here, but worth

It's possible (but unlikely) that the Tune cap isn't actually moving during
warmup, but the firmware isn't reporting that until you try to move it. I've
seen fault 34 a few times with a tune cap or motor that got a little sticky
when the amp hadn't been used for a long while, and the fix was to exercise
the Tune or Load motors back and forth by pressing segment buttons that are
widely separated (e.g., go back and forth between 160 and 10.) Maybe Tune
Down not flashing during power on is an indication of that?

Another possibility is that there's something wrong with the Tune button.
Have you tried changing the tuning with the segment buttons? If you can do
that, exercise the motors as described above, then try Tune Down again.

Doesn't seem likely that it could be a problem with the segment tuning
memory, but just in case I'd reinitialize it by setting the amp to use
Default tuning.

On the fault 8, if you didn't do it before, you should go back into the T/R
box and carefully check L1 and the area around it for signs of arcing
(carbon traces.) A known problem with older 87As is disintegration of the
rubber insulator under L1, causing arcing with the PCB and possibly the
nearby screw head. This can cause faults 1, 8 or 9, and can destroy one or
both TX PIN diodes (not sure if it can destroy any of the RX PIN diodes. The
fix is to remove L1 and the insulating pad, replace the pad with something
less likely to disintegrate (I think I used a piece of Dynamat), and rewind
or replace the choke. To avoid having to remove the T/R board, which
requires some desoldering, I clipped L1's leads high, leaving two short
leads still soldered to the PCB, to which I soldered the rewound choke.

You might want to check with Glenn to see if there are any AlphaMax upgrades
left. It's a very worthwhile upgrade and could incorporate a few firmware
fixes the amp may not have. The only one I'm aware of is replacement of the
Zener diode string on the HVPS board. Alpha used to sell the new chain as an
upgrade, and it's easy to install.

73. Dick WC1M

-----Original Message-----
From: Dave <> 
Sent: Tuesday, July 30, 2019 11:37 AM
Subject: [Amps] Alpha 87A fault 33 when pressing TUNE DOWN

Hi all

Looking at an old 87A for a friend. 
This is a 91xxx s/n without AlphaMax and NO updates done to amp. 

Originally faulting with fault 8. Replaced bad RX PIN diodes with 1N4007
diodes and TX PIN with pair of UM4006D. No more fault 8. 

Now whenever you press TUNE DOWN it immediately faults with fault 33. (Tune
motor failed to initialize).

Another clue is on power up both Load 
LEDs flash but only the TINE UP LED flashes twice. (Tune down does not
flash). But Tune Down LED does light when pressing Tune Down. 

Any ideas appreciated   

Dave wo2x

Sent from my waxed string and tin cans. 

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