[AMPS] Problem with Ameritron AL-82

[Bert Barry]

Hi Mike,

You refer in this post to "leading character truncation".  The problems I have had either
resulted in a very slow build-up of output from the amp (of the order of seconds), or no
output at all.  In this case it was definitely a result of high and variable resistance in
the tx-gnd circuit.

I don't know anything about the switching characteristics of the AL-82, but I suppose it
could be a case of the FT-1000D relay not switching fast enough, although that is never a
problem with the Alpha 87.  Perhaps Rich Measures has a point and some amps require faster
switching than can be achieved by a mechanical relay.

It is conceivable, although unlikely, that both FT-1000's have the same problem. This seems
to be a known problem with this radio.  Before proceeding further I would suggest measuring
the resistance of the tx-gnd with key down (at the amplifier tx-gnd input, as Tom suggested)
while jiggling the plug on the back of the FT-1000.  It is a simple measurement, and will
eliminate this as a possible source of the problem.  The resistance should never be more
than an ohm or so.  It has to be at least 10 ohms for my problem to occur (with the Alpha
87).

Good luck.

Bert,  VE3QAA

Michael Tope wrote:

> Hi Gents:
>
> I finally got around to messing with this leading character truncation problem a little.
> Wednesday, I swapped out the problematic FT-1000D with another FT-1000D. This
> appeared to cure the problem until I noticed that the autotuner was activated on the
> FT-1000D. When I turned off the autotuner, the problem re-appeared on the second
> FT-1000D. This was despite a low VSWR reading between the AL-82 and the FT-1000D.
> When I reactivated the autotuner, the rise time appeared normal. I then start playing
> with the drive to the AL-82, and noticed that at some point (~1400W output and 250
> mA of grid current), the truncation problem re-occured (this time with the autotuner
> activated). When I backed down the drive a little (~200 mA grid current) everything
> seemed okay again. Curious, I swapped out the FT-1000's again, and was able to
> reproduce the exact same behavior on the first FT-1000D (e.g. no truncation with
> autotuner on, and moderate PA drive).
>
> Any thoughts guys?
>
> Thanks,
>
> 73 de Mike, W4EF..............................
>
> ----- Original Message -----
> From: "Bert Barry" <kimba@sprint.ca>
> To: <W8JI@contesting.com>
> Cc: "Michael Tope" <W4EF@dellroy.com>; "AMPS" <amps@contesting.com>
> Sent: Sunday, March 25, 2001 1:25 PM
> Subject: Re: [AMPS] Problem with Ameritron AL-82
>
> >
> > That's a good point Tom, but I suggest cleaning both the switch pins and the relay
> > pins as well as the swich contacts.   By a great coincidence, shortly after I posted
> > my note, my problem occurred again, after being OK for several months. (Last time I
> > simply reflowed the relay pins, and that worked, until now).  This time I measured
> > the resistance at the phono jack with key down and found it varied all over the
> > place, from a couple of ohms, up to 50 or 60, then back down to 15 to 20, as I
> > jiggled the phono plug.  I then took the bottom off and as soon as I touched the
> > relay (not the switch), the resistance dropped to less than an ohm.  I then sucked
> > the solder off the relay pins, resoldered, and resistance seems to be less than an
> > ohm, and doesn't vary while jiggling the phono plug.  But in view of your comments,
> > before putting the rig back together I'll clean and resolder the switch pins, and
> > spray contact cleaner on the switch contacts.  But my feeling is that it's the relay
> > pins that develop high resistance or open circuit from the vibration of relay
> > closures.
> >
> > The only problem with this approach is that I'll never be sure which was the
> > culprit!
> > Mike, let us know how you make out, and your opinion.
> >
> > Bert,  VE3QAA
> >
> > Tom Rauch wrote:
> >
> > > > I had exactly the same problem with my Alpha 87 driven by an FT-1000D.
> > > >  The problem was not the amplifier - it was a fault in the wiring to
> > > > the "tx-gnd" phono jack on the back of the FT-1000. Fortunately, at
> > > > least in my case, the problem was NOT in the FT-1000 tx-gnd relay,
> > > > which would have been a pig to replace.
> > >
> > > This makes me wonder.
> > >
> > > My FT1000D has dropped the switch lead a three times now, and
> > > while it was on the way out it did something similar to what Mike
> > > described except on many occasions it would NEVER close the
> > > amp relay.
> > >
> > > The first time I just barely touched the relay switch near the jack
> > > and it cured the problem. The second time (about a year later) I
> > > resoldered the connections on the switch, and it was OK for a
> > > week.
> > >
> > > The third time I cleaned the switch contacts, and it has been OK
> > > for almost a year now.
> > >
> > > I wonder if the switches aren't the problem, since mine would
> > > straighten out just by touching it or anything around it??
> > > 73, Tom W8JI
> > > W8JI@contesting.com
> >
> >
> >
> > --
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> > Submissions:              amps@contesting.com
> > Administrative requests:  amps-REQUEST@contesting.com
> > Problems:                 owner-amps@contesting.com
> >



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