I had the same problem with my souped up DX-100. I found some
CBS labs Volumax units, put one in line and problem solved. It seems
that some sort of audio peak limiting would allow you to keep using the
existing amp. You didn't say what you're using for a RF driver...and why
does it allow for excessive over modulation?
For the curious, my DX-100 uses a pair of 6DQ5's triode connected
in the modulator. The suggestion came from HLR to ground the control
grid and drive the screens with high level audio, push pull. This
effectively
turns them into zero bias high mu triodes. The driver uses a 70W Dyanaco
mono amp driving a backwards connected output transformer to step 8 ohms
up to about 2K for the screens. This lineup has unbelievable peak
capability.
Slight pops on the mic resulted in flashovers in the plate tank due to
overvoltage.
The Volumax fixed this and it sure did sound nice.
I wonder if this triode-connected tetrode trick would work for RF linears?
jeff
----- Original Message -----
From: "Ken Barber" <kbarber@monmouth.com>
To: "George Benko" <GBENKO@prodigy.net>
Cc: "AMPS" <amps@contesting.com>
Sent: Monday, October 09, 2000 10:58 AM
Subject: Re: [AMPS] 3CX1200
> George,
> Thanks for the information. The 3CX3000A7 looks like an excellent tube.
> Some have suggested using an 8877 which is a nice tube, however, I have
> both the AL-1200 and the AL-1500. When I drive the AL-1500 with 20 watts
> of carrier on 75 AM and setting it up with a single tone using a scope,
the amp
> puts out approximately 400 watts carrier, 1600 watts PEP tone. While
talking
> everything is fine, however, if I accidentally hit the mike stand (rare
occurrence),
> the audio spike kicks out the 8877 overload and I'm back to 20 watts. The
> AL-1200 (modded with 3800 volts under load) can put out the same power
> and is not as sensitive on overloads, perhaps because it has twice the
grid
> dissipation over the 8877. If I were strictly on SSB with low drive power,
--
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