Too much noise between stations!
Posts: 668
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Joined: Jun 2011
City: Elko,MN.
Hello fellow radio friends
Have a Zenith 9S367 that I have been working on restoring and have an issue with too much noise between stations. Seems like reception could be better if I compare it to my other radios which are located in the same room.
I have rec-capped it, replaced a few resistors, and tried twerking the alignment.
Alignment was pretty much right on just adjusting to the loudest position by ear.
Tubes are tested and any weak tubes were replaced.
Anyone have an idea what could be causing this?
murf
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City: Lexington, KY
Noisy tubes will often not fail on a tester Try swapping the tubes out one-by-one with known good tubes, preferably from one of your other Zenith sets that don't have this issue. Also try cleaning the tube pins and sockets.... often I'll use some of these small brushes moistened with contact cleaner for the sockets:
https://www.harborfreight.com/airbrush-c...68155.html
John KK4ZLF
Lexington, KY
"illegitimis non carborundum"
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Yup, John, that's why many of the top level tube testers in the old days had an earphone jack to plug in a headset to test for microphonic tubes. You are right about the tube sockets being a potential cause, I have had it happen. A cold (bad) solder joint can also cause microphonic problems. This is why it is important to be sure of each solder joint we make as we repair these old radios.
Posts: 668
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City: Elko,MN.
Thanks, but been down that road many times now hoping I will find the problem.
Did find a bad tube socket on one of my 10 tube zenith that I am having issues with static on warm up.
Replaced the 6V6 socket and it helped a lot, but still have some static on warm up.
So I know cleaning the pin holes helps, if they thru holes. My 10 tube sockets are blind, so very hard to clean.
When the radio in question is on station, the noise goes away. Just between stations.
Hope this helps!
Murf
Posts: 668
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Joined: Jun 2011
City: Elko,MN.
Tried many different tubes with no change.
Can try cleaning pin holes if they are thru holes. Not sure on this one.
Works great when its on a station that is stronger.
Murf
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City: Menlo Park
State, Province, Country: CA
Is it just more sensitive? With a good AGC and a lot of dynamic range, plus RF amplification, it might just be bringing the interstation noise up higher?
What antenna are you using?
I don't hold with furniture that talks.
Posts: 668
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City: Elko,MN.
Using a single wire about 20 ft long.
(This post was last modified: 08-26-2021, 08:32 AM by murf.
Edit Reason: Wrong answer
)
Posts: 1,824
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City: Sneedville, TN
What is the situation with other AM radios being used in the same area? Try this with both a battery powered transistor and another plug in tube radio. Use the same outlet. Do they exhibit similar interference? If the plug in radio shows it, but the transistor one does not, the noise is on your home's power lines. If it is on both, the interference is in the air. If so, you are just another victim of the modern RF pollution. Welcome to the club.
Posts: 668
Threads: 144
Joined: Jun 2011
City: Elko,MN.
The others are in my display room and plugged into the same power strip.
Definitely something with the radio.
Can try moving it to another room?
Murf
Posts: 668
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Joined: Jun 2011
City: Elko,MN.
The others are in my display room and plugged into the same power strip.
Definitely something with the radio.
Can try moving it to another room?
Murf
P.s. have a single wire antenna wire on the radio. About 20 ft and attached to the back of the cabinet.
Posts: 668
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City: Elko,MN.
Correction!
Not using the wave magnet on this one as it does not use one.
My other 10 tube radios use that antenna.
Posts: 813
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City: Shenandoah,
State, Province, Country: Pennsylvania
Murf just a thought here. I sometimes hear background noise on my sets and have discovered it’s coming from my electric company’s meter, the type that sends my usage back to them electronically. Found it by accident while sitting on my deck with a portable. I noticed it depends on how I orient the radio. I finally walked up to the meter with the radio and it gets worse the closer I get to the point where if I have the set right next to the meter the noise totally drowns out all but the strongest station!
Ron
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I'm thinking that the AGC is not working correctly. When you tune a strong station the AGC is supposed to cut the gain of the RF/IF stages so it won't be so loud but also bump the gain on weaker stations. Maybe because the wavemagnet antenna is not in the circuit the first RF stage isn't getting AGC.
Posts: 668
Threads: 144
Joined: Jun 2011
City: Elko,MN.
I did correct my previous message about the antenna.
It has a single 20 ft wire that I just attached to the back of the cabinet.
So, could this also cause this problem?
I have another of this model in the same room that works great with the same antenna wire setup.
Posts: 668
Threads: 144
Joined: Jun 2011
City: Elko,MN.
Good news guys!
Moved the radio into another room today, and the noise between stations is gone.
Go figure.
Seems that every radio has its own personality I guess.
Put a different radio where the 9 tube was and it works fine.
Problem solved!
Thanks for all the help guys!
murf
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