Varistor is a problem for all your electronics

Home Model Engine Machinist Forum

Help Support Home Model Engine Machinist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.


Well-Known Member
Staff member
Global Moderator
Feb 12, 2009
Reaction score
Clovis Ca
The varistor is surge protection is a lot electronics. It is a one shot protection like fuse. Can be real pain to replace. They are solder in to board.

They are use whole house surge protection in some parts of USA.

It will not protect electronics on same side as the varistor.


It comes in different colors to just keep on your toes.

Now you know why sometimes your electronics just die a $0.15 part died of from some supplies $15.00

I use a surge power strip on my electronics. If blow the varistor then throw it was and grab one off shell and keep going.

Think this part when you DRO or DC board dies


{A varistor (a.k.a. voltage-dependent resistor (VDR)) is a surge protecting electronic component with an electrical resistance that varies with the applied voltage.[2] It has a nonlinear, non-ohmic current–voltage characteristic that is similar to that of a diode. Unlike a diode however, it has the same characteristic for both directions of traversing current. Traditionally, varistors were indeed constructed by connecting two rectifiers, such as the copper-oxide or germanium-oxide rectifier in antiparallel configuration. At low voltage the varistor has a high electrical resistance which decreases as the voltage is raised. Modern varistors are primarily based on sintered ceramic metal-oxide materials which exhibit directional behavior only on a microscopic scale. This type is commonly known as the metal-oxide varistor (MOV). }