I'm aware that a blown fuse is the result of some other problem, i.e., the transformer, diodes in the rectifier curcuit ect. What I'm wondering is, if there could be a problem with maybe the horizontal output transistor, or even the convergence module. I don't have a schematic for this chassis and was hoping that someone could help me out with a copy. Any help would be greatly appreciated.
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Re: No power, blown fuse in power supply
This TV has a few fuses and it not easy to troubleshoot it without the schematics, and is very unlikely that the convergence fuses will cause a complete no power on this TV.
What is the location of the blown fuse?
Where do I send you a copy of the service manual?
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Check the rectifier diodes in the power supply for shorts and look at all the filter capacitors in the power supply. Look for puffy discolored and domed tops. All filter capacitors must have flat tops. Check the windings of the transformer for darkened or burnt spots and test for shorts in both the primary and secondary windings
A module or an amp is doing a short cicuit. It's time to check if all transistors are valid. Be careful, bipolar and FET transistors behave differently. It can help to compare one by one each transistor from the RIGHT and LEFT amps. Good luck.
Fuse blowing is due to excessive current drain and the the first clue is the blown fuse itself. If the fuse blows with a flash a bang and splatters copper across the inside of the glass you have a hard blow caused by a dead short on the power supply, check for power switch flashing over internaly. Short circuit main filter capacitors. Shorted turns in power transformer primary winding. If fuse just separates check for short on output transistors C to E. Try isolating fault by disconnecting LT pos/neg supplies to output stage. Also check for partial shorts on speakers and speaker wires using an analog ohm meter on low ohms setting.
Why did you replace the fuse? If it was blown then you need to take the amp in for servicing. Iffthe fuse is glass and it was silvery on the inside, that is a hard short and is likely a power supply problem. Probably a rectifier diode or filter cap. Pray that it isn't the power transformer. Diodes are cheap... few pennies... caps a few bucks at most. Power transformer... you DO NOT want to know.
When the fuse blows suspect an overload in either the power supply or Main Amp section.
Check for burnt/damage parts first!
Power Supply faults that will blow the fuse are: Transformer, Rectifier, Voltage Regulator, Large Electrolytic Capictors, Diodes & any other semiconductor connected with it.
Main Power Amp faults are: any semiconductor device on the heatsink.
Check the power supply transformer primary driver transistor and the associated components (some diodes and capacitors, resistors, an optocoupler maybe) and the rectifier diodes (or a bridge) and capacitors at the transformer secondary, what you are looking for is a short circuit, however, the short may as well be in another section of the circuit board (a shorted component may sometimes have signs of damage caused by heat, but this is not a rule).
There is a small glass fuse there as well. These units have aswitch mode power supply and the transistor that is attached to the heatsink sometimes gets shorted. This is the most likely problem. If you feel comfortable working on these and can solder, let me know and I'll provide more detailed information.
1. Make sure the AC power source is ok.
2. Make sure the AC power cord is good with no damage.
3. Look to see if there is a reset button on the rear of the set. If not, then look for a blown AC fuse inside the set.
Since the set works fine on +12VDC, the majority of the TV set is ok. You have a problem in the AC power supply. It could be a blown fuse, bad rectifier / regulator, bad step-down transformer.
The TV typically runs from +12VDC. The AC supply steps-down the 120VAC and rectifies it into +12VDC to power the TV. At some point in the TV, there is junction point where the +12VDC from the sets internal AC supply meets the external +12VDC power source. Usually they are electrically isolated from each other with a switch or with diodes.
Please let me know if I can be of further assistance to you.