Chopper transister blown fuse blown

There are several reasons. If you find one shorted transistor in a push-pull stage you should always replace both. One might be faulty but not shorted, but when in operation it does the other one in. You might have also missed another shorted part such as a diode or voltage regulator. Hunt around looking at the circuit of the confirmed shorted parts and test or replace anything off that circuit.
Finally check your speakers and wiring to them. Shorted output transistors have generally two ways of going like that. Wires touching each other or bad speakers, or having it too loud!

You could be having a shorted rectifier or shorted chopper transistor . Either way it calls for the work of a experienced service engg:

Hello,
first you have to open the back cover of the television to check for blown fuses.

A blown fuse is a very common type of fault due to poor design very often triggered by power surges due to outages. However, the most likely parts to short are easily tested, usually in-circuit, with an ohmmeter and then easily removed to confirm.

Note that it *may be* useful to replace a fuse the *first* time it blows (though it would be better to do some basic checks for shorted components first as there is a small chance that having a fuse blow the second time could result in additional damage which would further complicate the troubleshooting process). However, if the new one blows, there is a real problem and the only use in feeding the TV fuses will be to keep the fuse manufacturer in business!

Sometimes, a fuse will just die of old age or be zapped by a power surge that caused no damage to the rest of the TV. However, it must be an EXACT replacement (including slo-blow if that is what was there originally). Else, there could be safety issues (e.g., fire hazard or equipment damage from too large a current rating) or you could be chasing a non-existent problem (e.g., if the new fuse is not slo-blow and is blown by the degauss circuit inrush current but nothing is actually wrong).

If the fuse really blows absolutely instantly with no indication that the circuits are functioning (no high pitched horizontal deflection whine (if your dog hides under the couch whenever the TV is turned on, deflection is probably working).) then this points to a short somewhere quite near the AC power input. The most common places would be:

Degauss Posistor - very likely.
Horizontal output transistor.
Power supply regulator if there is one.
Power supply chopper (switchmode) transistor if there is one.
Diode(s) in main bridge
Main filter capacitor(s).

You should be able to eliminate these one by one.



Test the rectifiers individually or remove and retest the resistance.


If these test good, use an ohmmeter with the set unplugged to measure the horizontal output transistor. Even better to remove it and measure it.

C-E should be high in at least one direction.
B-E may be high or around 50 ohms but should not be near 0.

If any readings are under 5 ohms, the transistor is bad. The parts sources listed at the end of this document will have suitable replacements.

If the HOT tests bad, try powering the set first with your light bulb and if it just flashes once when the capacitor is charging, then put a fuse in and try it. The fuse should not blow with the transistor removed.

Of course, not much else will work either.

If it tests good, power the set without the transistor and see what happens. If the fuse does not blow, then with the good transistor (assuming it is not failing under load), it would mean that there is some problem with the driving circuits possibly or with the feedback from the voltages derived from the horizontal not regulating properly.

Look inside the TV and see if you can locate any other large power transistors in metal (TO3) cans or plastic (TOP3) cases. There may be a separate transistor that does the low voltage regulation or a separate regulator IC. Some TVs have a switchmode power supply that runs off a different transistor than the HOT. There is a chance that one of these may be bad. If it is a simple transistor, the same ohmmeter check should be performed.

If none of this proves fruitful, it may be time to try to locate a schematic.

A blown fuse is a very common type of fault due to poor design very often triggered by power surges due to outages or lightning storms. However, the most likely parts to short are easily tested, usually in-circuit, with an ohmmeter and then easily removed to confirm.
But if otherwise your power supply board is dead, It can be dead at anytimes.Tries websites Shopjimmy.com,Ebay.com to buy a refurbish power supply board for the replacement.
Hope this helps....

.

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).

Hope you can find out what it is...

regards

Triarcuate

I'm not too familar with this model, but to give you some pointers, you will find when you have this problem the fuse will go straight away as there will be some of the semi-conductors short circuited. Check your bridge rectifier diodes & also the chopper transistor in the power supply. As a general check, test most of the diodes & power transistors & replace any that read short circuit on your meter. Hope this may help you as a guide line.

This could be a problem with the power supply. Yes there is a fuse on the power supply & if you have a multi-meter & are competent with electrical safety, you could test it. However, if it has blown then almost certainly something else will have caused it. You might have a short circuit bridge rectifier or faulty chopper transistor. If the fuse is ok, then you will need to check voltages from the power supply to find out what feeds you have. There may be a start resistor open circuit for example. If most of the start up voltages are ok, then you need to look at the line output stage & check if this circuit is getting any voltage supply.

IT SOUNDS LIKE YOU MAY HAVE A BLOWN FUSE, AND HAVE TO CALL PHILLIPS.

hi.^.^
most of all. don't change the fuse if it was blown cause maybe the high voltage transistor is shorted, capacitors are blown, burnt resistor, or a grounding is bad.
And all of these may affect your TV's performance so much.
sometimes it causes fire. you don't want that ofcourse.

There are many different ways that an amp can fail but the two most common failures are shorted output transistors and blown power supply transistors (< those are not blown). There are several types of protection circuits in amplifiers. The most common are over-current and thermal. The over-current protection is supposed to protect the output transistors. Sometimes it doesn't work well enough to prevent the failure of the output transistors but it will work well enough to shut the supply down before the power supply FETs are destroyed. If the amp remains in protect mode, goes into protect mode or blows the fuse as soon as the remote voltage is applied, shorted output transistors are almost certainly the cause. If the fuse protecting the amp is too large, if the protection circuit doesn't respond quickly enough or if the power supply is poorly designed, the power supply transistors may fail. If you see a lot of black soot on the power supply transistors (near the power transformer), the power supply transistors have failed. Soot on the board doesn't necessarily mean the transistors have failed. Sometimes, technicians don't clean up the mess from a previous failure.
In general, when a transistor fails, it will either short (common for output AND power supply transistors) or open (common for power supply transistors). Transistors act like valves. They control the current flowing through a circuit. A shorted transistor acts like a valve that's stuck open (passing too much current). In the case of an output transistor, the shorted transistors tries to deliver the full rail voltage to the speaker output terminal. If you've ever seen a damaged amp that pushed or pulled the speaker cone to its limits when the amp powered up (common on some Rockford amplifiers), that was almost certainly due to a shorted output transistor. When checking transistors, you most commonly look for shorted connections inside the transistor. You do this by using a multimeter to look for low resistance connections between the transistor's terminals.
Note:
I used the terms short and open on the previous paragraph. A short (short circuit) is a path through which current flows that should not be there. An open (open circuit) is a break in the circuit.

There are no internal fuses on any car audio Amplifier. Servicing will be required.

If the power supply transistors blew out, it's possible that the output transistors have failed (shorted).

If you're going to try to repair it, there are likely 2 blown driver transistors near the driver IC (TL494). You must check them. If they're blown, the new 3205s will blow out again.