Question about NAD C320 2-Channel Amplifier

2 Answers

Amp : sansui au11000 blown transistors on driver board

I recently replaced my amps output transistors. i couldnt souce the originals so i used mj 15024 & mj 15025 .i checked for any shorts with 40 watt bulb in series with power input . checked dc offset ok!.i then took it to repair shop to have bias set (i dont own an occiloscope) the repair guy used a steel screw driver & subsequently burnt out 8 transistors on the side of the driver board he was adjusting.(all around the trimpot) here is my question! he sez that the amp shorted out because of a pre-existing condition i know its a stupid question to ask but what do you think happened? regards ross

Posted by on

  • redrooster Jan 16, 2009

    hey thats uncanny that is exactly what i ended up finding what was wrong! there was another transistor on board f-2568 tr06 that was a bit wonky that i replaced, it made it go into protection.

  • aircraften Mar 18, 2009

    denon pma630 neg.output tr.brakedown.i tried to repl.o/p tr.driver tr.but still valid

×

2 Answers

  • Level 1:

    An expert who has achieved level 1.

  • Contributor
  • 2 Answers

Sometimes just replacing the outputs that have shorted are not enough to complete the repair of a main amp...this is because sometimes there is an intermittant or full failure in the bias circuit. Typically the Bias POT is the culpret.....when these pots get dirty or fail, the bias current ramps up way too high and then the Output transistors blow.......always replace the POT as part of the repair.....also check the bias varistor (Diode Stack) as these can open up after the first failure. Always pay attention to the bias circuit as this is critical to completing the repair properly....bias current adjustments can be made by measuring the voltage accross the Emitter Resitors connected to the Power Transistors...should read about 10 millivolts. The MJ15024 and MJ15025 Outputs are perfect replacements for Your Power Amp...I use them as well. Your tech probably just touched the bias pot, and that was all it took to make it fail (Open up)..If he was savvy, he would have replaced that POT before Touching it.

Hope this info helps....

Eric

Posted on Jan 16, 2009

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points

    All-Star:

    An expert that got 10 achievements.

    MVP:

    An expert that got 5 achievements.

    Vice President:

    An expert whose answer got voted for 100 times.

  • Master
  • 682 Answers

May i ask you did you put silicone grease in your transistor and apply a good mica insulator in all of your transistor---------look for any burnt resistor or explosive capacitor -----check for scew tie your supply voltage to earth by wrong.

Posted on Aug 03, 2008

Add Your Answer

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

2 Answers

Crest audio cpx1500, one channel not working ,


The breaker is stuck because there's some internal circuit problem on the amp. Something is tripping it i.e. a wiring short or blown speaker driver if they're connected, or an output transistor has blown.

Fix the problem BEFORE trying to reset.

Switch all off. Disconnect your speakers from the power amp. Switch the amp back on. If it will reset now then you have a wiring or speaker issue. If it won't reset then the problem is something broke in the amp.

Transistors are part of the circuit board. They're soldered in and also bolted to heat sinks. Not a DIY fix unless you know what you're doing. Take the amp to a repair shop.

Sep 04, 2014 | Amplifiers & Preamps

1 Answer

Crest audio cpx 1500 , one channel stop working ,


The breaker is stuck because there's some internal circuit problem on the amp. Something is tripping it i.e. a wiring short or blown speaker driver if they're connected, or an output transistor has blown.

Fix the problem BEFORE trying to reset.

Switch all off. Disconnect your speakers from the power amp. Switch the amp back on. If it will reset now then you have a wiring or speaker issue. If it won't reset then the problem is something broke in the amp.

Transistors are part of the circuit board. They're soldered in and also bolted to heat sinks. Not a DIY fix unless you know what you're doing. Take the amp to a repair shop.

Sep 04, 2014 | Amplifiers & Preamps

1 Answer

I own a Aragon 4004 mkII. Recently the the banana plugs on the right speaker output touched bridging a contact. The amp had been turned on and left on for up to 10min with this short occuring. Now the...


Tough one. I repair these for a living. A number of possibilities exist. Likely output transistors are blown on the bad channel. Fuses are likely blown. If the fuses are BLACK inside, don't just put new fuses in, more damage WILL occur. This is a bit more than 'good with a soldering iron' will fix. You need to know how to test an output transistor. You need to look up the transistor type so you know what it is. A service manual will be a big help (I could not find one online.) If more than two outputs are gone on the one side, all should be changed, they are supposed to be MATCHED. Remove and replace all damaged outputs, or replace them all if two are blown. Find the driver transistors and check them for short circuits. After repair, start the amp on a dummy load of a 250watt light bulb to prevent destroying the amp if there is a problem. If you are unsure of any part of this, find an electronics technician to help.

Feb 20, 2012 | Amplifiers & Preamps

1 Answer

What is the power output in a power amp and is it expensive


the output transistors are 5 to 10 bucks each for most.there are 2 or 4 on each channel,depending on brand .some high end amps have 10 transistors on each channel.mosfets are a different story as they run 20 to 50 bucks each and there is 2 or 4 on each channel.some amps use a big IC instead of transistors.those have 16 to 24 pins and are easy to change. Those IC are 25 to 75 for a stereo one like stk4141 etc.since most yamaha amps are dc coupled,when the output transistors go,they take out the driver transistors as well.If you replace the outputs and the drive transistors are shorted,they will blow the outputs again.

Apr 14, 2010 | Yamaha P3500S Amplifier

1 Answer

I find n.2 power transistor type 2SC1116 (npn) and n.2 type 2SA747 (pnp) for SANSUI AU11000. tanks


Try Grandata Limited at www.grandata.co.uk
They had them both in a semiconductor catalogue they sent me!
£1.10 for the first and £4.25 for the other (prices 2005).

Jan 01, 2010 | NAD C320 2-Channel Amplifier

1 Answer

Marantz SR19 no sound?


When replacing output transistors on amplifiers it is generally a good practice to replace the output capacitors as well as the biasing resistors. Just because one transistor is bad does not mean that that is the whole problem. Look for what caused the problem. Bad speakers,bad wires,defective traces on circuit board,poor soldering. Also when mounting the transistor make sure it is insulated and grease it with a dab of silicone heat sink compound. Whenever I service a board I examine all components for tolerance as well. A resistor marked at 1% tolerance,example 1k ohm + or - 1% should read no less than 990 ohms and no more than 1010 ohms. Anything else your asking for trouble. Another point is that some amplifiers use matching pairs. Pairs complement each other in an output stage and must be replaced in pairs. I repaired a Sansui Amplifier a while back and it looked as if a power output resistor was burned. Comparing the two channels I figured the matching value from the other side and replaced all of them and the system has worked flawlessly for years now. I am a retired electrical engineer and have worked in a few areas of electronics for over 35 years. Hope this information helps you.   

May 06, 2009 | Teac A-1D 2-Channel Amplifier

4 Answers

ADCOM GFA 5802 POWER AMP NO SOUND, BUT POWERS UP.


Remove the output transistors and measure each of the sets of 3 pads and report the voltage readings here. I suspect that you have either a blown driver circuit or output transistors. The voltage readings will give me an idea on where to start looking for specifics.

Thanks,
Dan

Nov 11, 2008 | Adcom GFA-5802 2-Channel Amplifier

2 Answers

SANSUI AMP AU-D11-II


It is possible, but nlikely that the protection circuit is bad. More common are shorted output transistors or defective driver stage transistors. This should not be a difficult repair for anyone familiar with audio amps. Unsolder/remove Q22 and Q23 and measure the voltages at each of the 3 pads per transistor and post them here.

Thanks,
Dan

Nov 04, 2008 | Amplifiers & Preamps

1 Answer

Bose SA-3 Amp / Blown Fuse


The problem is not the transformer. You now have shorted output transistors at the very least. By corssing the wires you presented a zero(0) ohm impedence load to the output section. It quickly went into overload. Before the fuses had a chance to open up, the outputs fried. This unit will require new output transistors and perhaps the previous driver circuit will require parts as well. Figure on $20-$50 in parts plus hte local labor rate for the repair.

Dan

Sep 25, 2008 | Bose Lifestyle SA-3 2-Channel Amplifier

1 Answer

Channel short


Hi there, sounds like you may have a short to ground on the output transistors. Does it have transistors or an IC output. It is most likely that you have not replaced a mica washer or insulator. Check to ground with a meter from the case of the output devices.

Aug 24, 2007 | NAD S300 Amplifier

Not finding what you are looking for?
NAD C320 2-Channel Amplifier Logo

Related Topics:

1,970 people viewed this question

Ask a Question

Usually answered in minutes!

Top NAD Amplifiers & Preamps Experts

 Grubhead
Grubhead

Level 3 Expert

4576 Answers

The Knight
The Knight

Level 3 Expert

68172 Answers

Larry Stiles
Larry Stiles

Level 2 Expert

286 Answers

Are you a NAD Amplifier and Preamp Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...