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Author Topic: 120 cycle per minute rfi from Henry 2KD  (Read 550 times)
W4IJ
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Posts: 14




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« on: November 09, 2017, 02:31:42 PM »

My Henry 2KD just started generating what appears to be a 120 cycle per MINUTE, 20 cycle per second, wide frequency "hash".    I haven't experienced this with any of my other amps, and I suspect that perhaps the original cooling fan has brushes that are worn down, if in fact it even has brushes.

If it were a capacitor breaking down, I would suspect a much higher frequency hash.

Has anyone had a similar experience or has a suspicion as to where I should look?

Many thanks.
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AC7CW
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Posts: 965




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« Reply #1 on: November 09, 2017, 05:28:31 PM »

Did you directly observe the minutes freq or secs freq?
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Novice 1958, 20WPM Extra now... (and get off my lawn)
W4IJ
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Posts: 14




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« Reply #2 on: November 09, 2017, 09:11:37 PM »

Yes I did.  I heard it on the speaker, saw the pulses on the screen of my IC7300, and counted it as best as I could while watching the second hand on my watch.

I know the rpms of the fan far exceed 120 cpm.
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N2EY
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Posts: 4436




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« Reply #3 on: November 10, 2017, 04:00:08 AM »

My Henry 2KD just started generating what appears to be a 120 cycle per MINUTE, 20 cycle per second, wide frequency "hash". 

but.....that doesn't add up.

120 cycles per minute is 2 cycles per second.

20 cycles per second is 1200 cycles per minute.
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W4IJ
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« Reply #4 on: November 10, 2017, 07:19:06 AM »

Oops..................it is indeed 2 cycles per second!!!!  120 cycles per minute.   Duh.  Thanks for letting me know.

This morning it is gone.  The amp has been on for about five minutes.  I'll leave it running and see if the hash returns. 

Any ideas now that I have corrected the post?
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N2EY
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« Reply #5 on: November 11, 2017, 06:13:28 AM »

Oops..................it is indeed 2 cycles per second!!!!  120 cycles per minute.   Duh.  Thanks for letting me know.

This morning it is gone.  The amp has been on for about five minutes.  I'll leave it running and see if the hash returns. 

Any ideas now that I have corrected the post?

Some kind of RC circuit involved. Capacitor charges up through a resistance, then there's an arc of some kind, voltage drops, charges back up again, etc.

73 de Jim, N2EY
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