LG Side by Side

[AJ]

I had a big long explanation for how and why a fuse should not blow, even in voltage spike situations, but when I hit "Post" ApplianceJunk took too long to respond and I lost it all!

Sorry about that. We have been having some issues with our new host/server that I have been trying to get resolved today.


Thanks for posting.

[PARTech]

With two LG boards (and one GE) that I am looking at the line in goes straight to the (soldered in place) fuse not to a varactor.  Seems that would indicate a problem more with the logic on the board or a power supply problem.

[ApplianceGuru]

You are right.  I stand corrected.

On the LG board, the replaceable fuse is not protected by the varactor.  The line voltage goes through the fuse, and then straight to the varactor.  So if the varactor draws a lot of current from a spike, it will blow.  Of course, if the varactor drew that much current, it has most likely been weakened, although I don't know of any way to see how much the varactor has been ruined.

The fuse is rated in amps, and the varactor is rated in power.  A higher voltage at a fixed amperage will result in more power being dissipated by the varactor.  ( Voltage x Current = Power )  A 1 amp fuse blowing at a 1,000 voltage spike would put 1,000 watts across the varactor for split second.

I suppose by designing the circuit this way, when a severe voltage spike happens, you might get a blown fuse, which tells you the varactor has been weakened, and is no longer dependable.

[ApplianceGuru]

Basically, if it's your fridge, and you are a DIY'er, put in a fuse, and see what happens.  Of course, now that the voltage spike protection circuit has been weakened, the next spike might not get dissipated, and it could damage board components the second time around.

If you are a professional, replace the board, because you have no real way of knowing what damage has happened, and paying customers really hate dealing with the hassle of call-backs.

American power line voltages are so well regulated, most of us only experience one or two serious household voltage spikes in or lifetime.  The fact you don't get call-backs within your warranty time has a lot do do with reliable American power.

If this appliance was in Mexico, it wouldn't last a year!  (yes, I have seen this happen many times)  Down there people put UPS power supplies, and surge protectors on expensive electronics.

[tgoods]

I installed a fuse holder and fuse on an LG in Sept 2010,  http://appliancejunk.com/forums/index.php?topic=6741.msg30366#msg30366. It's still working.  The service manual even says to replace the fuse if blown even though is not meant to be replaceable.  Fuses and circuit breakers trip for no reason all the time.  It's called nuisance tripping.  I do agree that if want to ensure no callbacks, replace the board.