LG model RU-23LZ21 blowing inverter fuse

[NathanGJedi]

Re: LG model RU-23LZ21 blowing inverter fuse

I have the same inverter with the same problem. I tested the transistors and they all appeared to be good, but obviously, I missed one (nothing toned, though). So I shorted the fuse (just to test it, then I'd get a new one...), and one of the SI4532 chips belched forth fire. Of course, I pulled the plug. My questions are two-fold:

1. Will replacing the transistor fix the board, or did shorting the fuse do permanent damage to other chips? Opinions?

2. I have some SI4812 chips I use for laptop motherboards. Will they work in this?

Thanks!

[PlainBill]

Re: LG model RU-23LZ21 blowing inverter fuse

I have the same inverter with the same problem. I tested the transistors and they all appeared to be good, but obviously, I missed one (nothing toned, though). So I shorted the fuse (just to test it, then I'd get a new one...), and one of the SI4532 chips belched forth fire. Of course, I pulled the plug. My questions are two-fold:

1. Will replacing the transistor fix the board, or did shorting the fuse do permanent damage to other chips? Opinions?

2. I have some SI4812 chips I use for laptop motherboards. Will they work in this?

Thanks!

I like you. Repairing electronics for people like you paid for my oscilloscope, isolation transformer and a couple of TVs.

NEVER short across a fuse that has blown. If you best friend threatens to kill himself unless you short across a blown fuse - call his bluff. IF you have replaced all defective components and want to know if it is still drawing excessive current, either do it the right way and use a bench power supply with current limiting (expensive) or the frugal way - wire a 12V light bulb across the fuse position. My favorite is the 1157 automotive tail light.

1. You can only tell by tracing the signal line from the gate inputs to whatever drives them.

2. No. The SI4532 is N-channel and P-channel mosfets in a single package.
The datasheet has the information. The SI4812 is a single N-channel mosfet.

PlainBill

[retiredcaps]

Re: LG model RU-23LZ21 blowing inverter fuse

My questions are two-fold:

1. Will replacing the transistor fix the board, or did shorting the fuse do permanent damage to other chips? Opinions?

2. I have some SI4812 chips I use for laptop motherboards. Will they work in this?

1) You might have. Check some of the components that are directly connected to the chip.

2) No. Look at the two datasheets. It will be obvious once you look at them.

http://pdf1.alldatasheet.com/datashe.../SI4532DY.html

http://pdf1.alldatasheet.com/datashe.../SI4812DY.html

The original chip is available everywhere for less than $1. I suggest you get more than 1 just in case.

http://www.findchips.com/avail?part=SI4532

edit: PlainBill beat me again. Hmm, I must stop doing too much research on datasheets and findchips!

[tom66]

Re: LG model RU-23LZ21 blowing inverter fuse

Smoke testing electronics. I've done it before, but wouldn't recommend it. Melted MOSFETs are very difficult to remove; they can stick the board. I once decided to reverse the polarity of a DC-DC converter I built (reasons be unknown!); unfortunately, the little IC that once could (the MCP16301), could never again after melting into a blob of plastic.