Question about Amplifiers & Preamps

1 Answer

NHT SA-3 Ben- Please explain how to do the checking you mentioned. I have (if I can find them) schematics for the SA-3. Let me know how to do the testing you mentioned. I have a multimeter to check V/A/ohns. Do I need something to check resistance (ESR?) as well? Thanks. Jeff

Posted by on

  • Jscopus Jan 04, 2009

    The schematic is helpful. I have the 5 page schematic somewhere and am trying to track it down. Those are the correct transistors. You have to take the transistors out to test them? I was hoping I could just test them on the board as it will be a pain to pull everything out. Is it possible to do a board test, and if okay check other things before I start pulling things apart? As Mentioned I already replaced the two paired 10K and 6800uf electrolytics that had leaked all over. I cleaned up the board as well.

    Thank you for your well thought out input.

    Jeff


×

1 Answer

  • 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.

    Brigadier General:

    An expert that has over 10,000 points.

  • Master
  • 6,966 Answers

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.
NHT SA-3 - 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.


Posted on Jan 04, 2009

  • Louie  Role
    Louie Role Jan 04, 2009

    Testing them while still on the board would not be conclusive. You would also be testing the other components connected to the 3 pins.

    Why not try this first. Power it up, Set the VOM to 100VDC or thereabouts, test the voltage across each of the capacitors that you have replaced with respect to ground. One would be +, the other would be -. Do the same to the 2 fuses. Again, one would be +, the other would be - with respect to the ground. Do the same to the collector/center leg of the transistors, similarly one would be +, the other would be - with respect to the ground.

    pls post back results.


×

Add Your Answer

Uploading: 0%

my-video-file.mp4

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

×

Loading...
Loading...

Related Questions:

1 Answer

Somebody have a schematic of SHARP SA 103?


no doubt you already have this- http://elektrotanya.com/sharp_ad-018_sa101_sa103_tech_bulletin.pdf/download.html [its the service bulletin] Were I you I would get with Sharp USA and ask them for it.

Aug 21, 2014 | Amplifiers & Preamps

1 Answer

I need the schematic of SHARP SA 103


What is a amplifier receptor? I've been repairing for nearly 40 years, and never heard of one. You may have to describe it's use.

Aug 21, 2014 | Amplifiers & Preamps

1 Answer

Where is fuse in Bose SA-3 Amp


If there is not an external round push and turn style fuse port then it is in the unit itself. You will have to take it apart.

Jan 27, 2013 | Bose Lifestyle SA-3 2-Channel Amplifier

1 Answer

How to equalize extra speakers?


The only thing you can do to equalize those speakers. Make sure that you have them in faze. + to + and - to - and left to left and right to right. Make sure that your speaker can handle the ohms. (the same ohms) for example If your amp is rated to handle 8 ohms then your speakers should have 8 ohms. The speaker wattage should also be abit more than what your amp can produce. Distortion is your worst killer of speakers.

Mar 26, 2012 | Bose Lifestyle SA-3 2-Channel Amplifier

1 Answer

Bypass Triggerrelay Sharp SM-7700H.


usually this triggered input would require a 5volt d.c.
signal to turn the unit on.

Mar 20, 2010 | Amplifiers & Preamps

2 Answers

Bose SA-3 amp and a non bose sub.. I keep blowing the amp..


How many ohms is your sub? The SA 3 Amp can only handle speaker(s) 6 ohms and greater. A lot of subs, as I understand, are 2 and 4 ohms typically. If yours is 2 or 4 ohms, then that explains it. The speaker would be "straining" your amplifier and blowing it.

Oct 02, 2009 | Bose Lifestyle SA-2 2-Channel Amplifier

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.


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

Mar 01, 2009 | Amplifiers & Preamps

1 Answer

I have a NHT SA-2 Amplifier 1996 model year. Once unit warms up I get load poping noises from the subwoofer. Please advise what may be causing this to happen.


sounds like speaker is clipping (overdriving) put a meter onthe disconnected speaker and see what the resistance is,4 ohms ,8 ohms ,if the meter wont stay in one place (numbers changing constantly) you have a burnt or damaged coil in your sub, if that is not the problem change your RCA's cables to make sure it not a bad wire including speaker wires! GOOD LUCK

Dec 15, 2008 | Now Hear This SA-2 Amplifier

1 Answer

Schematics for the Onkyo


Benimur,

I don't have the info on the initial question/posting, but Onkyo systems I have worked on often have open driver transistors as well as shorted outputs. With one of the driver transistors open, the voltages tend to float to one side. The 18V you mention sounds like that is what is happening. have the initial asker replace the driver transistors (as a pair) just like the outputs.

Keep me posted.
Dan

Oct 06, 2008 | Amplifiers & Preamps

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

Related Topics:

406 people viewed this question

Ask a Question

Usually answered in minutes!

Top Amplifiers & Preamps Experts

 Grubhead
Grubhead

Level 3 Expert

4576 Answers

Donald DCruz
Donald DCruz

Level 3 Expert

17129 Answers

The Knight
The Knight

Level 3 Expert

68157 Answers

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

Answer questions

Manuals & User Guides

Loading...