Newton eMate backlight hum

[jonschwenn]

I had a mostly working eMate that needed a hinge repair and was not recognizing touch events. I rebuilt the hinges and replaced the screen cable. Everything is back to working order -- except that I hear a hum when I turn on the backlight. I don't recall hearing it before.

Does anyone have an idea of what it may be? I think the re-soldering was good but maybe it's something I did?

 

[splorp]

The hum is always present in backlit Newton devices. It’s caused by the switching power circuit and affects the high voltage transformer associated with the EL backlight. I’m wondering if pulling things apart and reassembling the eMate moved a few things slightly to cause the hum to be more noticeable?

Further reading:

AppleCare Knowledge Archive: MessagePad and eMate: Noise Emission Levels