[TenTec] Herc II idling collector current adjustment

[Phil Chambley, Sr.]

Ken...

I agree completely.  While you've got it opened, though, you might consider
changing out U5 on the distrib board.

73
Phil
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----- Original Message ----- 
From: "Ken Brown" <ken.d.brown at verizon.net>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Monday, February 21, 2005 5:13 PM
Subject: Re: [TenTec] Herc II idling collector current adjustment


> Thanks again Phil.
>
> The PA module idling currents were not high. With the amp not keyed they
> were all zero. And keyed with no drive, they were all around 0.4 to 0.5
> Amp. I now have them adjusted to as close to 0.50 Amp as I can get.
>
> The Ic meter on the Hercules reads 12 Amps as soon as it is powered on.
> The increase when keyed with no drive looks like 2A, but of course on a
> 100 A scale, with divisions only every 25 A, that is difficult to tell.
> When putting out 500 watts it reads 75 A and maybe 80 A at 550 watts.
> The 12 Amperes being indicated at power on, with no keying or drive,
> must not be an accurate indication. I suspect a DC offset in the LM358s
> that are being used in the Ic monitoring circuitry. There is definitly
> not 12 A going to the PA modules with no drive to the amp.
>
> I have also measured the individual PA module currents with enough drive
> to indicate 50 A on the Ic meter. This produces about 200 watts output,
> and the currents to each PA module are all very close to 10 A each. So
> the modules are all working nearly equally hard, and there is a 10 to 12
> A offset in the Ic meter indication.
>
> Measuring full drive current draw of the PA modules would be a little
> more difficult. Most of the difficulty would be in finding the
> appropriate instrument, or making a shunt. From what I can see so far,
> there is not really any excessive current draw. I'm thinking about a fan
> for the 9420 again.
>
> Ken  N6KB
>
> >With the amp turned on its side, and with the front panel at the left,
> >looking at the amplifier boards:
> >
> >Bias board pots
> >R14 controls upper left amp
> >R10  controls upper right
> >R2  for lower left
> >R6 for lower right
> >
> >
> >
> >
> >
>
>
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