It would help to know what you mean by " Blew the
main tuning cap" Air variable caps, even though they
have arced, are still fine. Even if a carbon path has
developed, it can be cleaned out. And the cap remains
good. My guess is high circulating current is the problem.
As to the spike - I've watched mine carefully and there
is NO Leading Edge Spike, and I would doubt seriously
that any do. The threads on actual spikes have been
referencing the FT-1000 series of transceivers.
The OMNI-6 has a very steep leading edge, causing
what most people would call hard or harsh keying, but
I don't think any I have heard of had a spike, which indicates
a rise above normal level and decay back to a normal
level.
If your amp's tuning capacitor arced, there are a lot of
causes, such as a load changing under voltage, etc, and if
you're using afsk, it could be the audio output from the generator,
but certainly not from a keying spike which would not be
present under rtty conditions anyway.
Give us some more info on what happened.
73 de KL7HF
-----Original Message-----
From: RICHARD ANDREN <andrenr@ul.com>
To: tentec@contesting.com <tentec@contesting.com>
To: <tentec@contesting.com>
Date: Friday, December 11, 1998 4:39 AM
Subject: [TenTec] VI+ Key Up Spike
>
>There was a discussion here a while back regarding the key up spike
>produced from the Omni VI+. Here's a little background to my problem. I
>have no fancy test equipment, just a basic scope, meter, etc, so I can't
>measure this stuff. I'm thinking about this now as I blew the main tuning
>cap in my MLA-2500 in the last rtty contest. Bringing the input to the amp
>up slowly while keyed down or with ssb, no problem. I attempted to run the
>rtty contest at 700w output, well below what the amp can handle, but after
>1-1/2 hours, the main tuning cap melted, not a good thing! Could the key
>up spike, or whatever you choose to call it, contributed to the breakdown?
>The MLA will keydown at 1000w, but maybe this spike that's been talked
>about could have contributed? I agree the MLA design isn't exactly what I
>would call a beefy/built up unit, but this is what I've got to work with.
>This was the first rtty contest I've used the amp for.
>
>At this time, I can limp the MLA up to 1500w, but if I key it with a little
>juice, like 400w out, ZZZAP!!! I think a key up spike is initiating the
>breakdown. Am I wrong?
>
>I haven't fixed the amp yet because I may need to modify it with a vacuum
>cap instead of the air variable. Maybe it has nothing to do with the Omni,
>and it was just time for the cap to blow? I won't be able to read
>responses until Monday morning. What do you think?
>
>Hope to catch everyone in the contest this weekend on 10m!
>
>73, Rick N9THC
>
>
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>
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