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sm124 monitor with noise

tonata

Experienced Member
Joined
Sep 11, 2019
Messages
186
Location
France
Hi,

I have a sm124 Atari hi-res monochrome monitor that produces an annoying buzz sound.
It does not matter if the Atari is working or not.
What can I do?
 

AnalogThinker

New Member
Joined
Feb 9, 2023
Messages
9
CRT troubleshooting is complex and requires a bit more information. A 60Hz buzz can be a grounding issue, or an issue in the Primary of your monitor's power supply section (a shorted Diode, a worn out Cap...).
However, as a CRT repairman, I worked on a bunch of SM124 that had a common failure around the largest variable inductor, where the ferrite core wasn't damped properly anymore and causing buzz and high pitch whine. The ferrite core is usually damped and by a thin piece of rubber band, preventing noise and the core to move.
You can open the monitor and locate the noise source by ear. If it turns out to be the coil, do NOT use a metal screwdriver while in operation. It will heat the screwdriver very fast by induction, and also impact the deflection coil settings momentarily, possibly causing too much stress and killing it.
As usual, please take all the precautions required when working in High Voltage environment, before opening it. It is recommended to bring it to a CRT Repair shop.
 

SiriusHardware

Veteran Member
Joined
Feb 15, 2014
Messages
805
Location
UK
I acknowledge AnalogThinker's experience in this area, but there is one small thing you can try before going inside the monitor - turn the volume control up and down - does that vary the loudness of the buzz? Can you tell whether the buzz sound is coming from the speaker or from something else inside the monitor?
 
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