does anyone know what it takes to make the sensor alarm on the helix hx4635 work properly.? any help appreciated.

so this sensor functions even if the main power is off?   I will try your tip  to see what happens.   do u happen to know how to and were to get parts to repair the cassette decks? 

also one last thing my box is super clean with the exeption of the battery holder one sping coil has damage corrosion.  from a battery that was left in there. I went to radio shack and bought a universal batt holder so could clip the wire spring, as a last result to repair. have any tips or a place that carries better quality parts? thanx so much for your help .............

Depending how bad the corrosion in the battery contact springs, you can try and use car battery anti-corrosion gel with a brush or q-tip to restore it, protect it and get better contact as well with batteries....it has helped me a few times 

Can you pl. suggest some brands available easily that works well. Also, I am wondering whether it can be used to restore the RCA sockets? Does the anti-corrosion gel affect plastic?

Your expertise would be helpful. Thanks...

good point,....but i wouldn't let it touch plastic to be safe....if its possible to remove the metal parts to clean it....any brand should help....it may or may not work in some cases some may be tougher to work on....ive just used in some cases where ive seen green corrosion on it...and has helped remove it...sometimes you have to work at it allot to do so.....