Electrical Transistor question???

sbisdabomb · 6th April 2005, 06:16 PM

I'm from the DIY projector fourms on this site and have a question I thought you guys might beable to help me with.

I have an LCD monitor that I bought broken, backlight doesn't work. I found a surface mounted transistor on the inverter board of the LCD that was humming, looks to be arcing internally. I can't find the actual transistor anywhere (jameco, mouser, digikey, and some others) as expected. The transistor outputs somewhere between 500-2800 volts, and my multimeter can only measure up to 500v. There is an identical transistor on the board and I was wondering if I could put a resistor accross the one that was working - so it ouput less current and voltage, and then calculate what it acutally ouput so I could attempt to find a replacement transistor.

If I'm totally off base here, or in way over my head just let me know.

Thanks in advance guys,
Eric

sbisdabomb · 6th April 2005, 06:52 PM

It's a transformer not a transistor.

thomas997 · 6th April 2005, 11:54 PM

Is the cold cathode bulb good?

Chances are the transformer will be the same as the ones found in cold cathode computer light inverters.

You can try applying a smaller ac voltage to it and measuring the output to find the ratio.

sbisdabomb · 7th April 2005, 05:51 AM

yeah the cold cathode is in good shape, it's the transformer that's shot. My buddy is an EE major and has access to all sorts of tools, I think I'm gonna take it to the lab with him and see exacty what it outputs. but any help is still welcom and appreciated.

6th April 2005, 06:16 PM	#1
sbisdabomb diyAudio Member Join Date: Dec 2004 Location: fort collins, co	Electrical Transistor question??? I'm from the DIY projector fourms on this site and have a question I thought you guys might beable to help me with. I have an LCD monitor that I bought broken, backlight doesn't work. I found a surface mounted transistor on the inverter board of the LCD that was humming, looks to be arcing internally. I can't find the actual transistor anywhere (jameco, mouser, digikey, and some others) as expected. The transistor outputs somewhere between 500-2800 volts, and my multimeter can only measure up to 500v. There is an identical transistor on the board and I was wondering if I could put a resistor accross the one that was working - so it ouput less current and voltage, and then calculate what it acutally ouput so I could attempt to find a replacement transistor. If I'm totally off base here, or in way over my head just let me know. Thanks in advance guys, Eric

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6th April 2005, 06:52 PM	#2
sbisdabomb diyAudio Member Join Date: Dec 2004 Location: fort collins, co	It's a transformer not a transistor.

6th April 2005, 11:54 PM	#3
thomas997 diyAudio Member Join Date: Feb 2004 Location: Vancouver	Is the cold cathode bulb good? Chances are the transformer will be the same as the ones found in cold cathode computer light inverters. You can try applying a smaller ac voltage to it and measuring the output to find the ratio.

7th April 2005, 05:51 AM	#4
sbisdabomb diyAudio Member Join Date: Dec 2004 Location: fort collins, co	yeah the cold cathode is in good shape, it's the transformer that's shot. My buddy is an EE major and has access to all sorts of tools, I think I'm gonna take it to the lab with him and see exacty what it outputs. but any help is still welcom and appreciated.

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