Thank you Dick and Paul. The circuit board issue looks promising from outside
the linear anyway.
My point is that this problem exists after repeated trips to Alpha repair. If
a board had a burn spot, it should have been fixed and a better method
installed to prevent reoccurance. Understand, I had TWO 87a at the same time
in Florida weather for whatever that may mean, and both gave me the same
trouble and repeatedly. Both went back to the factory.
My beef is that the PIN diodes system was a design fault in the line that was
very late addressed by Alpha and was never treated as a recall to fix this set
of problems. Further, Alpha did not install long term repairs to this faulty
design when the units were at service. Alpha knows of the problem, certainly,
and even offers parts to repair and partly prevent future incidents. In sum,
two units returned a total of five times should have alerted the system to a
better fix and my own units should have had more permanent fixes installed.
I know Alpha has new owners, all new since my returns, and I have good hope for
the future of the new owners. However, I think I have a legitimate complaint
about a design flaw set that has run up the expense of owning the units.
Thankfully, a good friend is looking over my unit now and is lots better help
than Alpha's past record.
Best of the New Year to all who helped me and very 73,
Charles Harpole k4vud@hotmail.com
> Date: Mon, 3 Jan 2011 14:02:52 -0500
> From: wc1m73@gmail.com
> To: w9ac@arrl.net; amps@contesting.com
> Subject: Re: [Amps] 87a Fault 9
>
> 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
> >
> >
> >
> >
> >
>
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