[TenTec] VI+ Key Up Spike

[RICHARD ANDREN]

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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