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Re: SR-150 PWR Supply

 

Thanks,

I can make the power supply the common point ground or run a ground from both radio?and power supply to the operating table ground buss. I don't expect to have 60hz AC and if so I'll rework the mic audio circuit, not the chassis earth ground.? The breaker panel is less than 4ft away and the operating position ground buss bar is tied to the breaker panel ground whose ground rod is less than 6ft away.? In the SR-2000 the mic audio is a straight run to the audio tube. Not sure if the shielded mic line is grounded at the mic jack or not but hum is easy enough to remedy if it pops up... Lots of fun in 2025.

73
dave
wa3gin

On Wed, Jan 1, 2025 at 11:30?AM Jack Brabham - KZ5A via <kz5a.jack=[email protected]> wrote:
I just finished a complete rebuild on my? PS 150-120.? I choose to stay with a 2 prong polarized power cord mostly due to Walter Cates recommendation to avoid 60hz hum on the TX.? ?Didn't see why at first but I think I've codgertated it out.? ?The TRX? and PS were designed together and? the TX is intended to be the common signal ground point for both.? With? a 2? prong polarized plug and cord this works fine but will not support a GFI.? ?
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If you add? a? 3 prong? cord to? the PS the 60hz current passed? by C201 and C202 appears on the electrical Ground and can be passed to the electrical Common via the main AC breaker box? where the 2 are terminated to the same buss.? ?This can appear as a 60hz potential between a station RF ground and the electrical Common which apparently can find it's way into the TX audio.
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This is no doubt highly situational depending? on house and station wiring.? ?If you use a 3 prong AC cord and encounter the hum, deleting C201 and C202 might fix it.? Also the 60hz current passed onto the electrical Ground by the capacitors? could? trip a GFI considering that is the current they are intended to sense.??
?
A ferrite on the power cord can functionally? replace? the caps.
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73 Jack KZ5A
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