First, I¹d like to echo Paul¹s comments about the 87A. Like all equipment,
it needs maintenance from time to time. But I¹ve been able to keep mine
running for over 15 years. Alpha has always been extremely helpful and
effective at diagnosing and resolving problems.
Second, I recently had a bout with faults 8, 9 and 11. I think I posted a
writeup on this reflector about it not long ago. You can search for it on
the website.
My problem was a little different than yours in that it caused a sudden
failure of the amp on transmit, after which it wouldn¹t transmit without
producing one of the above fault codes. Eventually the amp wouldn¹t even
warm up without faulting. With Alpha¹s assistance, I found that one of the
transmit PIN diodes was blown. After replacing it, the amp worked OK until
it got to about 1500W, then it would fault again. I think it was fault 11 or
9, but I don¹t remember. Anyway, Alpha once again helped me troubleshoot,
which led to discovery that the insulator pad under L1 on the T/R board had
partly disintegrated over the years, allowing the inductor to arc to the
ground plane of the circuit board underneath. The repeated arcs had dug a
nice hole in the board. The arcs were undoubtedly responsible for the faults
related to PIN diode current, and ultimately killed one of the transmit PIN
diodes. Luckily, I found the root cause of the problem before blowing
another very expensive transmit PIN diode.
If you¹re know how to work inside amps, and are comfortable doing so, UNPLUG
THE AMP, remove the cover, and remove the small perforated cover over the
T/R compartment. Look for burned or charred areas on the T/R board,
especially near and under L1. Remember to replace both covers before you
plug the amp in again.
I repaired L1 myself by removing it, cleaning off the old insulating pad,
cleaning up the PCB, installing a new insulating pad (a piece of rubber
sound insulation mat), rewinding with the correct gauge magnet wire, and
reinstalling L1 with a layer of silicone between it and the insulating pad
for mechanical stability and more insulation. I was able to do all this
without removing the T/R board, which is a bit of a chore.
Of course, your problem might not be caused by L1. It could be caused by a
problem with the LV supply. Alpha has some troubleshooting steps you can
follow to try to isolate the cause, but since it sounds like it happens
intermittently, I would check for evidence of arcs at L1 first.
Hope this helps.
73, Dick WC1M
On 1/3/11 9:07 AM, "Paul Christensen" <w9ac@arrl.net> wrote:
>> > I have been plagued for years with my 87a giving Fault 9. Been back to
>> > the clowns at Alpha several times for same problem. The 87a may be
>> > Alpha's big mistake in their line. Piece of junk.
>
> I think that's a bit harsh, Chuck. There are many 20 year-old, problem-free
> 87As performing very well on the bands every day. There's a reason why it's
> faulting and it's a matter of uncovering the root problem. It's easy to
> say that there's a design flaw when it's you that has the burden of
> isolating a persistent problem.
>
> By now, you know the fault is relates to "transmit PIN diode forward current
> below minimum." But, the problem may be indirectly related to something
> like the LV power supply or arcing on a wiring harness, for example.
>
> I know that Alpha has the means to isolate these types of faults, including
> quick component and/or board substitutions. Since it's been back to them
> several times, is it an intermittent fault, occurring only occasionally?
>
> Paul, W9AC
>
>
>
>
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|