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Pete, Electronic Engineer
Category: TV
Satisfied Customers: 15449
Experience:  Over 16 years of experience installing and repairing electronics.
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Hello, I have a Samsung model sp43q5hl1x projector wont

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I have a Samsung model sp43q5hl1x projector wont come on I Checked power up to the ic regulator voltages are 160 , pin 3 of ic is up and down between 10 volts and17.9 unstable ,any help would be appreciated

Hello Chris,
Welcome to JustAnswer!
I am Pete, and I'll be happy to assist with your question today.

It seems that the voltage regulator IC is malfunctioning since the output is fluctuating.
Check that there are no dry solder joints on the device.
If it appears to be soldered ok, it may be defective and will need to be replaced.
Customer: replied 3 years ago.
Hello Pete,
I want to be more clear on this, The circuit in question is a smps circuit the regulator pin 3 is the controlling voltage input from an optoisolator connected to a transistor who,s emitter feeds pin 3 the turn on and turn off voltages, the voltages are from 1.2 to 17.9 Now the circuit wont oscillate and the secondary side of the transformer wont produce any dc voltages mymy

Without a physical board to test or detailed schematics and datasheets it is impossible for me to work out how the circuit should perform.
Your voltage fluctuation symptoms will most likely be due to a defective regulator and it will have to be replaced.
Customer: replied 3 years ago.
Ok Pete,

You might be right! When power is turned on in the circuit I get a noisy whining fromr the transformer which means a component has failed before or after the transformer and it just might be the regulator

Good deductions and analysis, Chris...
replace the regulator and let me know if the replacement device emits a more stable voltage.
Pete and 2 other TV Specialists are ready to help you
Customer: replied 3 years ago.
Ok Pete will let you know by weekend


Customer: replied 3 years ago.
Hello Pete
The reason for the tv not staying on after being powered up was due to a shorted flyback transformer ,this caused the smps transformer to have a high whinning pitch and not the ic regulator that was suggested to be the culprit earlier.

This case is now closed, and how do you rate me ?


Hi Chris,
I would rate that as an excellent job well done!