Panasonic RC-6030BA Radio Buzz

[Dialupdude]

Hi all, I’m new to the wonderful world of flip clocks and have recently acquired a National Panasonic RC-6030BA at a good price from a local seller. The clock itself as well as the alarm worked perfectly after being lubricated but the radio only plays a strange humming/buzzing noise whenever it is turned on and no matter how it is tuned or adjusted. Sometimes the buzzing will seem to pop in and out, like the radio will be playing fine and then the buzzing will appear for a few seconds and then disappear. Only to come back less than a minute later and not go away. Additionally, whenever the radio is buzzing the clock’s light goes dimmer, this does not happen when the radio is working normally. Any help with diagnosing this issue would be much appreciated! Thanks.

[Guest]

Welcome!

You say this is a National Panasonic so is this an international (European/Asian) version of the clock? US versions were usually just labeled Panasonic.

There's an obvious electrical fault inside, possibly. Is the humming coming directly out of the speaker or elsewhere from the cabinet, in general? Have any of the switches been cleaned? Noise can be introduced if the switches and potentiometers (volume control) are dirty.\

Otherwise...there is something else at play here and you'll need to have it looked at. Could also be a short circuit or failing component.

[Dialupdude]

This is an Australian version of the clock, yes the humming is coming from the speaker, and yes I have cleaned the switches and potentiometers. Could it be a bad capacitor maybe? The sound almost sounds like the alarm, just quieter, so maybe there could be a short somewhere? But then again the sound does come and go if you leave the radio on for a while.

[Guest]

Yes, possibly a bad capacitor and most likely the filter capacitor, usually the largest cap on these radios.

[Dialupdude]

Thanks for the help, I’ll replace some caps this weekend and report back.

[Dialupdude]

Sorry I didn’t respond. I replaced three capacitors and the buzz still hasn’t gone. It seems to occur completely randomly.

[Dialupdude]

Here is a video of the clock in action. This is after all the capacitors were replaced.

https://youtu.be/ZHyUbvbMDOg

[gschmidt958]

Sounds like it could be power line frequency hum. It could be picking up something else in the room. Does it still happen if you move it to another location? I would check connections to any grounding conductors. Also, consider reflowing any solder joints that aren't smooth and shiny.

Greg

[Dialupdude]

Same results all over the house. I’ve noticed if I touch the speaker while it’s buzzing it seems to go away until I stop. I’ll check the solder joints this weekend but it seems like it might just be gremlins.

[gschmidt958]

I wonder if the connection to the antenna is marginal. Some units have internal antennas, some actually use the power cord as the antenna. You might consider touching up any solder joints related to the antenna connection. Of course, always make sure the unit is not powered when working on it. It could also be something in the tuning section.

Also, you can easily check capacitors for internal shorts simply by checking for continuity across their leads on the PCB. You should read 0v (and/or hear a beep, if your multimeter has that feature). Once again, only do this when there is no power to the unit.