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 Post subject: Drake L4B Amp Question
PostPosted: Feb Sun 18, 2018 9:06 pm 
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Joined: Feb Sat 28, 2015 8:37 pm
Posts: 553
Location: Walker, MI
Hey guys, been working on my L4B for a while and finally got it put back together and wired for 240V. When I got a year ago, the power supply caps where puking their guts out, and it was wired for 120V, so I didn’t want to run it and then life got in the way, so I just got the upgrades finished. I added the Harbach softstart board from Paul K0UYA, the Harbach PS upgrade, and replaced the glitch resistor with a proper one from Harbach.

During the refurb, I removed the front panel to clean it up, replace the blue gel for the lights, and change out one of the lamps on the meter. I am not 100% sure that I got the PLATE capacitor pointer back in the correct position, it is currently fully meshed at the 10 meter location. I can’t seem to find how the plate capacitor should be set for which band anywhere on the net. Anyone know how this should be set?

Thanks,
Eric
K8CCA


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 Post subject: Re: Drake L4B Amp Question
PostPosted: Feb Sun 18, 2018 9:11 pm 
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Joined: Jun Sun 19, 2011 2:31 pm
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Capacitor full mesh will occur at the low frequency extreme (bottom of line below the extreme low end of 80 meters).

This is pretty standard for most HF amplifier setups where the maximum capacitance will be needed at the lower frequency end of the range. The load cap is the same with the cap fully meshed for minimum loading and fully open for maximum loading and the loading cap will generally run at lower mesh as you increase frequency except in the case of very odd antenna loads (where a "tuner" should then be used).

Rodger WQ9E


Last edited by rsingl on Feb Sun 18, 2018 9:14 pm, edited 1 time in total.

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 Post subject: Re: Drake L4B Amp Question
PostPosted: Feb Sun 18, 2018 9:13 pm 
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Joined: Feb Sat 28, 2015 8:37 pm
Posts: 553
Location: Walker, MI
rsingl wrote:
Capacitor full mesh will occur at the low frequency extreme (bottom of line below the extreme low end of 80 meters).

Rodger WQ9E


Thanks Rodger, That was my issue, not sure what what I would do without your help! Putting out full power now.

Eric


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