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KR8MR
09-07-2016, 08:26 PM
I have an LG minisplit. The main controller board in the outside unit has MOSFETs (2SC2333) TO-220 that are going bad. The unit has been in service for about 7 years and now this is a regular problem. Apparently in my opinion the 310V DC bus is getting hammered.

It is a mini split with 2 indoor units above doors.

I have a manual from LG (PDF)

Multi Type Air Conditioner
SERVICE MANUAL
Outdoor Unit: A2UH243FA0(LMU240HE)

There is another small PC board that has the mains fuse which blows and what looks like chokes and MOVs for power conditioning. I suspect that one of the MOVs has failed but cannot see a VISIBLE failure on that board. The LG schematics are helpful but DO NOT layout whats on the power supply (filtering?) PC Board.

My first fix replaced one of (2) MOSFETS (2SC2333) lasted 2 weeks then replaced the other one and it lasted just 12 hours and died during a nearby T-Storm.

Obviously I can keep stuffing 2SC2333's but its a real hassle. I haven't found the CAUSE of the problem. Anyone else have this problem?

Steve Kramer
Taylors, SC 29687

KR8MR
13-07-2016, 03:49 PM
I have an LG minisplit. The main controller board in the outside unit has MOSFETs (2SC2333) TO-220 that are going bad. The unit has been in service for about 7 years and now this is a regular problem. Apparently in my opinion the 310V DC bus is getting hammered.

It is a mini split with 2 indoor units above doors.

I have a manual from LG (PDF)

Multi Type Air Conditioner
SERVICE MANUAL
Outdoor Unit: A2UH243FA0(LMU240HE)

There is another small PC board that has the mains fuse which blows and what looks like chokes and MOVs for power conditioning. I suspect that one of the MOVs has failed but cannot see a VISIBLE failure on that board. The LG schematics are helpful but DO NOT layout whats on the power supply (filtering?) PC Board.

My first fix replaced one of (2) MOSFETS (2SC2333) lasted 2 weeks then replaced the other one and it lasted just 12 hours and died during a nearby T-Storm.

Obviously I can keep stuffing 2SC2333's but its a real hassle. I haven't found the CAUSE of the problem. Anyone else have this problem?

Steve Kramer
Taylors, SC 29687

Actually I am using 2SK2333 MOSFET sorry for confusion...if anyone is reading anyway I wonder. This website doesn't seem to get much traffic.

monkey spanners
13-07-2016, 09:01 PM
I read the original post, no idea on the answer to your question, i'd never mess about swapping components on a customers circuit board, and an LG at 7 years old is probably due for replacement tbh.

Greek_engineer
14-07-2016, 03:10 PM
Can you send me the manual so as to help you?
bozionelos@yahoo.gr

KR8MR
16-07-2016, 06:13 PM
Can you send me the manual so as to help you?
bozionelos@yahoo.gr

Thank you for your kind offer.

I was able to get a new 'power board' from MCM Electronics Centerville Ohio USA. ($38) Kind of a shot gun approach when the line to line 14mm MOV is likely the cause and all that needs replacement. The schematic in the manual shows a modified power suppression circuit with 2 additional common mode MOVs going to ground thru a single reverse biased 1N302. And the passive filter has larger capacitors.

I will replace both 2SK2333 MOSFETs this time regardless of which one has failed and the large DC filter cap on the mother board as well. This should hold me for a few more years. The date codes show this thing was assembled in 2006. If it lasts more than a month I will install a large whole house 220V rated surge suppressor like the one Eaton makes at the outdoor unit. This will help protect the electronics before I have something fail on an indoor unit.

This ductless split system came with my house. I will likely never buy an LG product. HH Gregg stopped supporting them. LG tech support admits that their manuals are often incorrect and they do not provide the component level details that I need. The instructions have poor translations to English. The power board was omitted from the manual. This is what you get when you buy foreign. I think it is ludicrous to have such a complex micro-controller board located out of doors. typically this sort of electronics is protected in a NEMA4X enclosure with anti condensation heaters.