Question about NAD C350 2-Channel Amplifier

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NAD C350 replaced blown fuses but new ones blow on power up. Thanks for the info but how do I check the transistors?

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Take a ohm meter and measure resistance from emiter to collector should have a few kilo ohm on output transistor.
If no ohm meter available , remove output transistors from circuit.
note position of transistor . you have a NPN and a PNP for each channel.
Replace fuse and power up. If fuse blows check bridge in the power supply.

80% of the time output transistor burn and blow the fuse.
before replacing output transistors check driver transistors they probably burnt also

Posted on May 04, 2008

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2 Answers

After I put a fuse in the player, and plug into wall, the fuse immediately blows.


Hi,
Your fuse blown again because you have a short on the circuit. You may visit my link http://www.fixya.com/support/r8053361-fuse_keeps_blowing for more info.
I've suspect that you have short on rectifier diode/main filter capacitor/regulator IC/transistor. This is quite fixable.
Hope it may help you.
Thanks for using fixya.
JDVillanueva

Feb 03, 2011 | Samsung DVD-V3650 DVD Player/VCR

1 Answer

The mains input fuse (4amp) and a (1amp) fuse on the main power out board were blown. Replaced fuses and switched on, blown again, disconnected output from transformer to main board (4amp) fuse did not...


The cheapest option is to replace the transistors (a quick check on google will tell you how much they are). If they are common transistors you will be able to find them and get them quicker then searching for a board that could be no longer being made.

Sep 02, 2010 | Mackie SWA1501 Subwoofer

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

Our TV suddenly stopped working and will not come back on


Hello,

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 died, It can be dead at anytimes.Tries websites Shopjimmy.com,Ebay.com to buy a refurbish power supply board for the replacement.
Good luck....

Jun 05, 2010 | iLO 3200 32 in. LCD Television

2 Answers

Mackie 1200/1400 blows all 4 10 amp fuses


missmatched impedance, insufficient ground, blown transistor.

Jul 20, 2009 | Bob Mackie Mackie M-1400i Power Amplifier...

1 Answer

Blows fuse when turned on


this is a normal behavior if one of the power supply transistors have blown. take the unit to an enlectronics repair. they can either change the transistors affected (usually more than one) or replace the power supply board.

May 29, 2009 | Sansui DTV3200 32" TV

1 Answer

INFINITY BASSLINK X BLOWS FUSES


What probably happened was both of the final audio output transistors shorted. This caused a higher than normal drain on the switching transistors on the primary side of the torrid power transformer causing one to short and then blowing the fuse. I replaced both switching transistors and ramped up the current to about 5 amps. I could see the power supply was not working but there was still a short. I traced the short to both audio output transistors. Replaced them and unit is like new. After I found a service manual on this item it was a breeze to find the problem.

Sep 19, 2008 | Infinity BASSLINK Car Subwoofer

2 Answers

Main fuse blown on CT-32G11 32" Panasonic TV, Replacement fuses continue to blow.


If the main fuse keeps blowing, check the horizontal output transistor for a shorted condition and diodes in that section as well.

Jan 12, 2008 | Panasonic CT-32G11 32" TV

1 Answer

Car Amp keeps blowing fuses


The reason why fuses blow is that the current is too much. Is the fuse rating according to the specs ? If yes then ... One or more output power transistor (or audio power IC) may be shorted. have it checked before replacing another fuse as this might cause more damage.

May 22, 2007 | Profile CL1200 Car Audio Amplifier

1 Answer

Subwoofer not working


if u are a technician then its easy to check, problems are, blown fuse, power amp IC output transistor may be blown, check for burnt componenets. changing and blowing a fuse means ur output IC or transistors are shorted.

May 15, 2007 | KEF Audio KHT 2005.2 System

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