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Sony TV KV-XR29M31 with supply blow-up. Fet Q608 and Q607 short circuit taking horizontal output Q and R642 .1 ohm. Is it caused by dried-out caps and does it take IC 602? Appreciate any help. Thanks.

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Replace the FETs with ones from Sony distributor. Do not substitute. Replace all of the small blue disc caps in the area. These can short causing the power supply to fry. In your case, the HOT probably was the initial problem, not the supply.
Dan

Posted on May 01, 2008

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HOW TO FIXS HITACHI TV WONT COME ON RED LIGHT FLASHING PROJECTION TVI


model number?little more info...first thing check for short in power and
horizontal output transistor-common problem.also bad connection
cap in horizontal output circuit can cause blown fuse

May 28, 2014 | Hitachi Projection Televisions

1 Answer

My 1998 hitatci tv keeps blowing fuse whats wroung


The TV has two power supplies, low and high voltage. Most likely the high voltage transistor (called a Horizontal Output Transistor or HOT) is shorted due to a malfunctioning high voltage transformer (the biggest piece on the board with the large red wire coming from it. If the low voltage is bad most likely the diode pack (full wave rectifier) or the voltage regulator chip.
Remember fuses are to keep the unit from catching fire by opening up when a short circuit draws too much current. If you cannot replace the cause of the current draw, it's time to buy a new TV.

Feb 27, 2014 | Projection Televisions

1 Answer

Tv wont turn on?


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....

.

Jun 05, 2010 | Zenith R57W46 57" Rear Projection...

1 Answer

No power


hello,
First check if the TV plug is connected to the mains socket.
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.

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.

Unplug the degauss coil as this will show up as a low resistance.

First, measure across the input to the main power rectifiers - it should not be that low. A reading of only a few ohms may mean a shorted rectifier or two or a shorted Posistor.

Test the rectifiers individually or remove and retest the resistance.

Some sets use a Posistor for degauss control. This is a little cubical (about 1/2" x 3/4" x 1") component with 3 legs. It includes a line operated heater disk (which often shorts out) and a PTC thermister to control current to the degauss coil. Remove the posistor and try power. If the monitor now works, obtain a replacement but in the meantime you just won't have the automatic degauss.

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.
Good luck

May 21, 2010 | Samsung HCN4226W 42" Rear Projection...

1 Answer

SONY KP-61V90 tv will not power on, red light in front,


Its 2 times blink error code that shows +B volt supply (+135 volts) is shorted, most probably horizontal output transistor is shorted, replace it.
If you are good in soldering parts in circuit board then take out horizontal transistor, check it, found shorted then replace it with same number.

Horizontal output Transistor Q502 number is 2SD2578 and available in Part Store for $10
Let me know for further query, if any.
Thanks.

Nov 18, 2009 | Sony Projection Televisions

3 Answers

HORIZONTAL OUTPUT TRNSISTOR SHORTS WHEN POWER ON TV


ALL the next is with the tv unplugged (NO NO power)
  • resold the jungle (video processor) all around
  • following the horizontal drive pulse path and arriving to the horizontal area just after the horizontal transformer and in the base of the horizontal DRIVER there is a electrolytic capacitor (if this chassis uses this one,) Change it (maybe is dry)
  • solder all components i just told you in the last step. horizontal driver, transformer, etc
  • remember:
  • if a transistor is blowing with no reason (there is a reason: the collector receives 130 volts but cannot hold it forever, It has to be in some place. if the switching pulse doesn't arrive to it the transistor throws this 130 volts and burning itself. i hope it is help full.

Apr 15, 2009 | Projection Televisions

1 Answer

Chirping Problem


Hello,
I posted this earlier but it applies in this case so here goes,

The chirping sound is either a shorted Horizontal Output Transistor (HOT) / Power FET (whichever one is used in this case) or the IHVT (Flyback Transformer) has developed a short in its windings. In ether case both components will have to be replaced. I would suggest you have a qualified TV technician come over and troubleshoot the problem and give you an estimate on the repair.
However, if you are doing this repair yourself take into mind that the HOT and the IHVT (flyback) are in a series circuit configuration and if the Flyback is bad I would change out the HOT also, and vice verse.

I hope this helps,

Thank you,

Shuttle83

http://www.electron-age-technologies-llc.com

Nov 30, 2008 | Philips 50P8341 50" Rear Projection...

1 Answer

Horizontal output transistor failure


check b+ comming from p/s. also check for blue flat caps in line with h-output circuit. if blown out the side. remove them from circuit. also might have a HVT goin bad. I believe this is also the model that might have a mod for h-out running too hott that requires adding a resister in the h-drive circuit. also try a heavier duty h-output.

Apr 09, 2008 | Toshiba 51H93 51" Rear Projection HDTV

1 Answer

TV - worth fixing or pitch?


Horizontal output and regulator transistor often short out on this model causing a dead condition. Also the resistor right next to the regulators goes open as well. Electronix.com has a sony repair kit to fix the power supply. You just have to check the numbers on your Horizontal output transistor to make sure you get the right kit for your model.

Feb 03, 2008 | Projection Televisions

1 Answer

Sony Big Screen TV Not Powering On


This looks like a problem with the High Voltage or switching power supply section of the TV set. What you need to do is to measure the voltage from the HV transformer to the Anodes of the CRTs with a high voltage probe, and check the voltage output of the switching power supply. What may have happened is a component may have shorted out causing an over-current condition with is triggering the shutdown circuit (These are the relays you are hearing). I would check the Horizontal Output transistor, and the components in that section of the TV.

In addition check the voltage test points on the HV / Horizontal and switching power supply board. This will determine if the section is working or not (most likely not). Make sure you have a schematic, and multimeter and a high voltage probe.
I hope this helps,
Thank you,
Shuttle83

Aug 15, 2007 | Sony KP-46WT500 46" Rear Projection...

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