Bridge Rectifier - Lionel 445 Switch Tower

Turn the supply voltage down to a level that it just operates satisfactorily - as low as possible.

I believe the mechanism applies the voltage to a spring-loaded solenoid that moves the figures.  The buzzing is from the AC voltage collapsing to zero as it alternates polarity...plus, minus, plus, minus....  So the force on the spring is essentially pulsing off and on 120 times per second and the mechanism vibrates at that frequency.

If you insert a bridge rectifier the alternating voltage does not change polarity so it is always "plus" so to speak, but it still collapses to zero just as often as before so it is a pulsing voltage and the mechanism still vibrates.

You can smooth the pulsing using a capacitor.   Choosing a capacitor value involves knowing how much current the solenoid requires; I don't have this accessory or I'd "do the math" for you.  Maybe somebody else will step in.  What's your preferred component source (mail-order, Radio Shack, eBay, whatever)?  A reasonable starting point might be 1000 uF, 35 Volt capacitor which is about $1-2. 

Also, if you want to pursue the capacitor method, tell us what power source you're using or have available to drive this accessory.

I feel your pain, I installed a 6 amp rectifier to operate my water tower and it is still noisy, just like it is on AC..

Marty

Thanks for the advice.  I found an acceptable solution for me.  The fixed voltage around 16 volts was too high.  I changed the power source to use track power (no bridge rectifier) and it is considerably quieter.

That is your issue - 16 volts AC comes out about 22 volts DC from the rectifier.

Martin Derouin posted:

I feel your pain, I installed a 6 amp rectifier to operate my water tower and it is still noisy, just like it is on AC.

A #30 water tower?

Yes, it is not the one with the pumper mech...

Marty

Martin Derouin posted:

I feel your pain, I installed a 6 amp rectifier to operate my water tower and it is still noisy, just like it is on AC..

Did you try Rob's suggestion of lowering the AC voltage? 

A rectifier alone does not create "smooth" DC.  You need a capacitor to do that.  Otherwise you still have rapidly changing voltage that induces vibration/buzzing in the solenoid-spring mechanism.   Was it a 6 Amp rectifier (2 terminals) or a 6 Amp bridge-rectifier (4 terminals) like Richbar initially tried?  It's easier (smaller/less expensive capacitor) to smooth a bridge rectifier's output.

If the noise is new, perhaps something came loose, separated, whatever on the mechanism and needs tightening.