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Re: [Amps] AL-1200 - MO Power??

To: Tony Brock-Fisher <barockteer@aol.com>
Subject: Re: [Amps] AL-1200 - MO Power??
From: Scott McGrath <mcgrath@fas.harvard.edu>
Date: Tue, 20 May 2008 16:10:23 -0400
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Is it really worth stressing the amplifier for a <1Db gain in output 
power.   Also IMD will increase the warning is probably directed at 
preventing insulation breakdown in the secondary windings and/or eddy 
current problems with the laminations and hardware.

New Peter Dahl transformers are available so why not upgrade the 
transformer to one which has a 4KV secondary at rated input this would 
allow you to dial down the exciter and get a better sounding signal

- Scott

Tony Brock-Fisher wrote:
> I have had an AL-1200 for over a sunspot cycle. It has run well, but never 
> quite made the 'full boat' in terms of output. 1300 watts usually is what I 
> get. HV runs a tad low, around 3450 volts no load. I never drive it with more 
> the 100 watts (don't have a rig capable of more than that stock, and no, I 
> don't want to 'tweak' my Pro2 to make over 100 watts due to IMD concerns).
>
> I am tempted to rewire the transformer primary to boost the HV. If I wire it 
> for 220 instead of 240, it would boost the HV to 3763V. 9.1% boost in HV 
> would give me a 19% increase in Po for 1547 watts out (naturally I would dial 
> back the Pro2 for legality).
>
> Yes, of course I have read the warning in the manual that says not to rewire 
> the primary for more than 3700 volts.
>
> I'm assuming that this warning is because the voltage rating of the string of 
> HV caps is only 3600 volts (8 x 450V). (Which seems like a pretty marginal 
> design in the first place).
>
> Supposin' I was to add another cap to the string, with the proper bleeder 
> resistor. Now the HV rating of the cap string would be 9 x 450 or 4050 volts. 
> Total capacitance would go down from 210/8 (26.25 uFd) to 210/9 or 23.3 uFd - 
> not a huge deal.
>
> Does anyone see any problems with this idea? Any other concerns with boosting 
> the HV?
>
> -Tony, K1KP
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