Tip & How-To about Televison & Video

Shorted Rectifier Diode (fuse keeps blowing)


This CRT tv is dead set, no reaction when the power button is pressed(no standby led light). I've open the back panel and check the faulty parts.


As you can see the fuse was badly burnt-out indication of excessive current due to short circuit.


I've checked the parts feeding the AC line to the power supply board (Power cord, VDR, Ceramic capacitor, Coil, Posistor, Degaussing coil) one by one and I've found out that one of the four rectifier diode has a leak which caused the glass fuse burnt-out.
Here's how to test the rectifier diode.

Good Diode
Note : Forward and reverse bias depend on what type of ohmmeter are you using, here I'm using a Japan Standard(Sanwa Brand).


Using an ohmmeter set it to X10 to see much easier the leak from the diode in reverse bias.

Forward Bias : test the diode by connecting the red test prod of the tester to anode and then the black test prod to cathode of diode. You will see the pointer will reads a faily low resistance(above picture).


Reverse Bias : test the diode by connecting the red test prod of the tester to cathode and then the black test prod to anode of diode. You will see at the picture(above) that the pointer didn't react (remains in infinity). This is a good diode.


Bad(leaky) Diode


Forward Bias will reads fairly low resistance.


Reverse bias unlike the good diode the pointer will also reads a fairly low resistance.

After confirming that the diode caused the fuse from blowing I've decided to replaced all four diodes since I have a lots in my stocks.


Remember that when you installing the new diode on the board, make sure that you will make it in the right polarity.



This steps is also applicable in the DVD Player,Flat panel, Projection, LCD TV, you have to disregard only the posistor and degaussing coil.

Have a nice day!
Thanks for using Fixya.

Jdvillanueva

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Power to TV won't come on. Check breakers and used new outlet... still no power


Hi ,

Here are steps that may help you fixing the problem. You should prepare tools and multimeter.

I'm assuming that your unit is dead set without an standby LED light and your outlet is live.1.Power cord - check the cord it might be opened (no continuity).This is due to frequent bending,pulling. 2. Power switch - check for dry joints, open contact. 3.Check the internal fuse- sometimes the fuse fail because of the power surge, replacing with new one will cure the problem, If this is the case I've advice you to use surge protector/AVR (Automatic Voltage Regulator). However if the fuse blew again this is an indication that you have a shorted parts on the power supply, you may visit the linkhttp://www.fixya.com/support/r8053361-fuse_keeps_blowing for more info. If no reaction and still the unit didn't power up then you have an open parts on the power supply.

4.If you see that the fuse is intact on the board, don't attempt to touch anything because there somefatal components stored electricity enough to hurt you with a simple mistake only.

The next steps should be done by an expert or qualified technician because isolating the problem on the power supply is technical and complicated.

Also check if your unit is under warranty before opening the back panel, it will void the warranty. Avail it because the manufacturer of your unit will fix it for free or a little charge only.

Hope it may help you.

Thanks for using fixya.

Feb 11, 2011 | Toshiba 32A33 32" TV

1 Answer

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Hi ,

Here are some DIY steps that may help you fixing the problem.

I'm assuming that your unit is dead set without an standby LED light and your outlet is live.1.Power cord - check the cord it might be opened (no continuity).This is due to frequent bending,pulling. 2. Power switch - check for dry joints, open contact. 3.Check the internal fuse- sometimes the fuse fail because of the power surge, replacing with new one will cure the problem, If this is the case I've advice you to use surge protector/AVR (Automatic Voltage Regulator). However if the fuse blew again this is an indication that you have a shorted parts on the power supply, you may visit the link http://www.fixya.com/support/r8053361-fuse_keeps_blowing for more info. If no reaction and still the unit didn't power up then you have an open parts on the power supply.

4.If you see that the fuse is intact on the board, don't attempt to touch anything because there somefatal components stored electricity enough to hurt you with a simple mistake only.

The next steps should be done by an expert or qualified technician because isolating the problem on the power supply is quite technical.

Also check if your unit is under warranty before opening the back panel, it will void the warranty. Avail it because the manufacturer of your unit will fix it for free or a little charge only.

Give a thumbs up if you find it useful.

Thanks for using fixya.

JDVillanueva

Feb 06, 2011 | Sony FD Trinitron WEGA KV-32FS120 32" TV

1 Answer

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Hi ,

Here are some DIY steps that may help you fixing the problem.

I'm assuming that your unit is dead set without an standby LED light and your outlet is live.1.Power cord - check the cord it might be opened (no continuity).This is due to frequent bending,pulling. 2. Power switch - check for dry joints, open contact, replaced if necessary. 3.Check the internal fuse- sometimes the fuse fail because of the power surge, replacing with new one will cure the problem, If this is the case I've advice you to use surge protector/AVR (Automatic Voltage Regulator). However if the fuse blew again this is an indication that you have a shorted parts on the power supply, you may visit the link http://www.fixya.com/support/r8053361-fuse_keeps_blowing for more info. If no reaction and still the unit didn't power up then you have an open parts on the power supply.

4.If you see that the fuse is intact on the board, don't attempt to touch anything because there somefatal components stored electricity enough to hurt you with a simple mistake only.

The next steps should be done by an expert or qualified technician because isolating the problem on the power supply is quite technical.

Also check if your unit is under warranty before opening the back panel, it will void the warranty. Avail it because the manufacturer of your unit will fix it for free or a little charge only.



Let me know if you need further assistance.

Hope it may help you.

Thanks for using fixya.

JDVillanueva

Feb 06, 2011 | JVC AV-27D302 27" TV

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