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T-4XB CW Key Up Hum

Tim Randa
 

As the title suggests my T-4XB has a hum when keyed up in cw mode. At first I thought it was sidetone and tried a couple of replacement 6EV7 tubes hoping that was an easy fix but it was not. The more I listen it really sounds like a loud hum. The sidetone still sounds fine and is louder than the hum. This does not happen when keyed up in ssb mode. I would appreciate some suggestions from the boards gurus as to where to look. Many years ago I was thinking I tackled this problem before with the hayseed capacitor can but my memory is far past its prime.

Thanks in advance for your time in responding

Tim? K?FL
 

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Dear Tim

Interesting problem. Where do you hear this hum? ?In the R-4B speaker? Assuming you are operating the T-4XB as Twins? ?Have you decoupled the connecting cables on by one and monitored any change? Is earthing connected properly?

73 Rob PA9Z


Op 2 jan 2024 om 04:27 heeft Tim Randa <randaranch@...> het volgende geschreven:

?As the title suggests my T-4XB has a hum when keyed up in cw mode. At first I thought it was sidetone and tried a couple of replacement 6EV7 tubes hoping that was an easy fix but it was not. The more I listen it really sounds like a loud hum. The sidetone still sounds fine and is louder than the hum. This does not happen when keyed up in ssb mode. I would appreciate some suggestions from the boards gurus as to where to look. Many years ago I was thinking I tackled this problem before with the hayseed capacitor can but my memory is far past its prime.

Thanks in advance for your time in responding

Tim? K?FL

Tim Randa
 

Hi Rob and thanks for the response. Yes the T-4XB is connected to a R-4B receiver. The hum is present with the receiver turned on or off. I tried as you suggested unplugging each cable one at a time with no difference in the problem. Any other suggestions are appreciated.

Tim
 

Hi Tim
So the humming comes from the speaker?? Is it a 60 Hz AC hum, you recon??
KR Rob
Tim Randa
 

I guess I should have avoided confusion on my original?post. The memory of possibly?fixing the issue before with a hayseed capacitor?can was on a different set of twins. I honestly don't remember for sure what the?symptom?was that?led me to install the capacitor?can but it might have been?the issue I now?have with the hum.Thanks for the emails wondering what I meant. So any other thoughts on hum in the cw mode before it takes a trip to the Drake repair guru??

I'd appreciate?some advice

Tim

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