Question about Amplifiers & Preamps

2 Answers

Nht subtwo blowing f1 fuse on ac input module. found shorted Q16 2SA1302 and Q15 2SC3281 transistors what was the reason for these parts failing and what else should i be checking.

Posted by on

  • e_norin Mar 07, 2009

    For the NHT SUBTWO with the Q14,15,16 and17 transistors removed measured the three pads on both Q15 and Q16 and the voltages are as follows E= 0.5, C= 126, B= 126. I had replaced all the 2SA1302,2SC3281 transistors and all six IRF 640's before i got your post, powered the unit up without input signal and got a green light. but when i hooked up input it then poped the F1 fuse on the ac input module again.if the problem is in the driver circut could u walk me thru this.thank you

  • Anonymous Apr 15, 2009

    the drivers transistor 2SC4793 or 2SA1837 are likely defective too, My has same problem. found Q13, 14, 15 shorted out. Also 1 large electrolytic capacitor 2200mf/200 open, I think the capacitor opened, cause the output transistors failure.

×

2 Answers

  • Level 1:

    An expert who has achieved level 1.

  • Contributor
  • 1 Answer

BE AWARE OF FAKE TOSHIBA 2SC3281 & 2SA1302 SOLD ON EBAY. THEY WILL KEEP ON SHORT OUT THE CIRCUIT. ANOTHER SOLUTION IS, REPLACE THEM WITH MOTOROLA MJL3281A & MJL1302A.ALSO CHECK THE POWER SUPPLY FILTER ELECTROLYTIC CAPACITORS 2200MF/200V, WHEN CHECK THESE LARGE CAPACITOR, MAKE SURE TO DRAINED OUT BY SHORTED 2 TERMINAL WITH 1K RESISTOR BEFORE TESTED.

Posted on May 19, 2009

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points

    Superstar:

    An expert that got 20 achievements.

    All-Star:

    An expert that got 10 achievements.

    MVP:

    An expert that got 5 achievements.

  • Master
  • 4,234 Answers

Try turning on the unit without the two transistors installed. Measure the DC voltages on the 3 pads to ground. These should read .6V,40V and 0, both +and -. If you read anything else, the driver circuit has a problem.

Dan

Posted on Mar 02, 2009

Add Your Answer

Uploading: 0%

my-video-file.mp4

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

×

Loading...
Loading...

Related Questions:

1 Answer

My AV-502A main amplifier fuse was blown,I checked the power transistors and found 2 shorted,C5198.I replaced it with new one, but the fuses still blown up, including the new transistors.


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!

Feb 02, 2016 | Amplifiers & Preamps

1 Answer

Additional detail about my AUREX STEREO AMP MODEL SB 130. I have change the rexridiwe / power diode but to no avail. This same result. The fuse rated 3.15 blown up 2 times. I wonder will is the cul


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.

Mar 07, 2014 | Amplifiers & Preamps

1 Answer

Amplifier no sound blowing fuses


When a fuse blows it means an overload in either the power supply or more likely the main amp section. The cause is a shorted transistor or IC. Chances are that the devices (one, more or all) attached to a big heat sink have failed.

Nov 21, 2013 | Amplifiers & Preamps

1 Answer

My SI-1230 was not working on channels 5-6 and 11-12. I opened the amp and replaced the fuses on those channels. Now the fuses blow immediately on channels 5-6 and the red protection light is on...


Chances are the main transistors or whatever powers channel 5 and 6 have shorted out. Fuses blow like this when there is an overload and these power types do that a lot. If it uses transistors, then a ohm meter will show them up quick. Because it will be just like you have touched the test probes together when you put them on the terminals, with the meter on the 1K setting. For the reason these parts are just acting like pieces of wire instead of doing their job.

Mar 12, 2011 | Niles SI-1230 12-Channel Amplifier

1 Answer

I have 3 Audiosource Amp-100 that have failed out


When the fuse keeps blowing you have an overload. The cause of which is either in the power supply or the main amp. It will almost for certain be a semi-conductor of some type acting like a piece of wire. A multi meter will show up a most faulty parts with this condition. On the Ohm setting applying the test probes to transistor terminals (E,C,B) you will get a responce like you had touch the probes together! The power transistors or whatever is on the heatsink are good at going short circuit, as people often short the speaker wires together.
Don't forget to check for burnt or damaged parts too.

As a rule of thumb with transistors when testing on a meter (1K setting) (best with moving coil scale meter than a digital) apply to base (B) and then to C & E you should get an ohms reading. If you don't get any reading (both ways) it's dead (open) and if the meter goes full scale - it's shorted.

Jul 31, 2010 | AudioSource AMP-100 2-Channel Amplifier

1 Answer

Roland KC-550 blows 500ma fuses in power supply for no appearent reason. Why does this happen and are fuses correct value?


Fuses blow when there is an overload. This is caused by a faulty part in either the power supply (such as transformer or any semi-conductor -diodes, rectifier, IC, transistors etc) or in the main amp stage - anything on the heat sink. The most common cause is a semi-conductor acting like it was just a piece of wire. A cause of an overload alsot is a speaker wire shorting, which blows out the transistors on the heat sink or whatever is on there, they in turn blow the fuse!
Whatever value fuses is put in will blow! The higher the rating however could cause something to get hot thus causing a fire, before they do go!
If the 500ma fuses where the originals marked on the end cap, then stick with them. Often it is writtten on the PC board too.

May 20, 2010 | Amplifiers & Preamps

1 Answer

Pioneer djm800 keeps blowing fuse J on main processing board. Fitted an anti surge plau to try and stop fault but fuse went again after 10mins use.


Replacing the fuse to a different rating or type is very dangerous! The fuse is blowing because something has failed and is causing an overload. The fuse is there to protect and stop whatever is causing the problem from overheating the Amp and causing a fire.

Now to what might be causing it to blow. In most cases it's either something in the power supply for instance the transformer or any semi-conductor such as diodes, voltage regulator or what converts the supply from AC to DC.
The other area that will cause the fuse to blow is the main amp section, the transistors etc of which will be found on the heatsink.
If you have an Ohm Meter you can test transistors with it and diodes. In this case it will show up well, for when you put the test probes to the terminals it will be just like you have touched the probes together.

May 09, 2010 | Amplifiers & Preamps

1 Answer

Pyle Pro PZR 3000 Watt


I think you will find that something has failed and is causing a short circuit, that's the reason the fuses are blowing and not because you are fitting the wrong type.
I should look at the main devices (anything on a heat sink) first. If they are transistors, you can test them with a Ohm meter. If it gives a reading as if the transitors was acting like a piece of wire, it's gone.
Sometimes you might see evidence of burning or even a hole in something.

Sep 09, 2009 | Amplifiers & Preamps

1 Answer

Peavey TNT 160 has no response from both inputs, only preamp in


In my experience fuses rarely blow due to age! I suspect that whatever the guy said the problem was it was really a faulty transistors or IC in the power amp board.
You can check transistors with an Ohm meter in circuit to some extent. (the ones with a scale and needle are best for this) Look for a short between the terminals of each power transistor on the heat sink first. If any transistor sends the meter full across (both ways) you have found the fault.

Apr 24, 2009 | Peavey VTB1 1-Channel Amplifier

1 Answer

NHT SA-3


Appreciate the direct "Ask Me". With reference to your post here;

Voltage checks are done with the power on whereas resistance/continuity check are performed with the power off and preferably the component out of circuit. The VOM would do.

You posted that the fuses have not blown and therefore you are assuming that the output transistors are not defective. Pls confirm this by performing a check on the base to collector to emitter of the output transistors. This page would illustrate how to check a transistor using a VOM. The output transistor once removed from the circuit (pls mark which goes to where), laying flat with the pins/feet pointing towards you would be base, collector and emitter. Although the real outputs if 2SA1302/2SC3281 would be larger.
c05c37f.jpg
Most NHT sub amps are standard design amplifiers. To my knowledge, NHT amps (but not all) uses a unique design to supply power to the output transistors. The fuses does not tie directly to the output transistors from the +/- of the power supply. Instead the fuse goes to several power MOSFETS (IRF640) that regulate/control/monitor the current/voltage supplied to the output transistors. If any of the IRF640 is blown, the output would have no voltage even if the fuses are good.

To be more specific and to confirm the above, would appreciate if you could post/share the schematic diagram.

May I also inform you that there are posts made by other members of the community (our co-experts, I am aware that you have provided solutions yourself in some other posts) that would be of additional help. ginko has posted the method/manner by which you could test the transistors and other components, while bunnydawg addressed the fuse not blowing. welcomejee has posted with an amp schematics of an NHT Subtwoi.There were however and I would expect more posts that are too general/generic to be of any real use to you. I would leave it to your discretion to filter through the flood of information.

As a site policy, once you rejected a solution or give it a "Thanks for Trying", that particular post/expert would no longer be viewable. For your benefit, may I suggest that you copy and paste the "workable solutions" to a document that you would have a record of previous or no longer viewable postings.


Jan 04, 2009 | Amplifiers & Preamps

Not finding what you are looking for?
Amplifiers & Preamps Logo

Related Topics:

441 people viewed this question

Ask a Question

Usually answered in minutes!

Top Amplifiers & Preamps Experts

 Grubhead
Grubhead

Level 3 Expert

4590 Answers

Donald DCruz
Donald DCruz

Level 3 Expert

17129 Answers

The Knight
The Knight

Level 3 Expert

68301 Answers

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

Answer questions

Manuals & User Guides

Loading...