Audio Players & Recorders Logo

Related Topics:

John Tlusty Posted on Jan 18, 2019

I have a wonderful old Yamaha M-40 Stereo Power Amp. It has a thump-prevention speaker protection circuit that does NOT kick off and engage the speakers...

I do have the schematics for this amp. The problem started after a power surge attack. I have 4 Yamaha M-series power amps, the other 3 survived, this particular one - the protection circuit stays engaged. I know a little about electronics, but don't really know where to start with this guy. Is it a bad relay, or something in the amp circuitry that keeps the protection circuit engaged?? TIA for the help! *** So, I researched this issue, and figure I need to test the Output Transistors. I ordered a transistor tester to do this with. I figure I need to remove the transistors to check them...?? Am I barking up the right tree?

1 Answer

Phone Doctor

Level 1:

An expert who has achieved level 1.

Corporal:

An expert that hasĀ over 10 points.

Problem Solver:

An expert who has answered 5 questions.

  • Contributor 11 Answers
  • Posted on Feb 24, 2019
 Phone Doctor
Contributor
Level 1:

An expert who has achieved level 1.

Corporal:

An expert that hasĀ over 10 points.

Problem Solver:

An expert who has answered 5 questions.

Joined: Nov 17, 2007
Answers
11
Questions
0
Helped
2644
Points
29

Hi there. More than likely the power output stage has a problem (possible if the amp was on at the time of the surge). It would be best to have a proper component tester to check the stage components but component testers are expensive. But the good thing is that you have an other working amp. Since you don't have the knowledge or proper equipment I would suggest to open up both amps and compare the readings of the same points of each amp. A shorted or cut-off power semiconductor would show even on a multi-tester set at the diode scale. Check also ALL the fuses and fuse resistors related to the output stage (resistors under 1? (brown black black 1? or gold brown black 0.1?) .

5 Related Answers

Anonymous

  • 631 Answers
  • Posted on Nov 02, 2008

SOURCE: Amp Power light will not go on. Protection light is lit- Thump sound in speakers

It probably has shorted output transistors. To eliminate other possible causes, read through the following page.

Amplifier in Protect Mode - Troubleshooting

Let me know if you have any other questions.

Ad

Anonymous

  • 363 Answers
  • Posted on Sep 22, 2007

SOURCE: Hooking up speakers to amp

YES ! This is usually ok, the speaker cabinet should contain a high pass filter or crossover on the tweeter to decouple it from the low frequency signals. My Linn Index speakers are wired like this.

Michael Borelli

  • 979 Answers
  • Posted on Oct 25, 2007

SOURCE: Power on problem

Time for a little repair here. It seems that one or more channels have developed an excessive drain on the supply, and has caused the threshold to trip and shut you down. It's more than likely shop time at this point....accordianman

Anonymous

  • 1512 Answers
  • Posted on Jan 11, 2008

SOURCE: Onkyo A-RV401 amp is not sending any sound to the speakers.

The protection circuit is self resetting, it operates only when there is a fault condition in the amp. there is most probably a failure in the output stages of the amp causing a dc offset condition in the speaker output. The protection cct operates to prevent damage to your speakers. It may be difficult to offer a solution to you for this, it gets a bit complex to fix from here...you may have dry solder joint problems in the output stages, or more likely, failed output components. if you have a transistor checker(ohms meter), then you may be able to determine if any output transistors have failed, I recommend taking the amp to a good HiFi guy for repair. Many (including myself) often replace the all transistors to the last 2 stages when outputs fail. assures reliability in the future to repair this way, but the cost goes up a bit also. expect at least $120 to repair is it is a failed output stage.

Anonymous

  • 236 Answers
  • Posted on Mar 19, 2008

SOURCE: yamaha dsp-/e300 wont switch on

no display at all in your front panel?

you said power supply is ok... all voltages...
i remember DSPE300, small power amp only IC. can you check your +/- main power supply if ok it should be around +/- 35V. If it's there then place your meter neg to speaker ground, the + to red and try to run on the unit. see if you'lll get a pulse in AC meter mode. Or a DC voltage in DC mode.
then check also your secondary supply that's about +/- 15volts. Your standby voltage for the CPU to work is 5V. please check that as well



If the trouble is main amp, you should still have a display screen. Unless it is a total breakdown and main out totally shorted, it really wont turn on but you said you seem to find voltage.

reden

Ad

Add Your Answer

×

Uploading: 0%

my-video-file.mp4

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

×

Loading...
Loading...

Related Questions:

0helpful
2answers

My yamaha rxv595a keeps on shutting itself off when im watching movies as soon that it gets loud it shuts off but its not even that loud how do i fix this problem i tried the ohms switch in the back and it...

That is a safety switch in most receivers. When something gets too loud it cannot give the load off to the speakers and shuts off to protect itself. This can mean that the receivers getting old, or that you might need to split the job. You might need an stereo amplifier to split the job. Check the cables and speakers. Recievers can only give so much to so many speakers at so much sound. That is what the whatts are for. The more whatts the better, the lesser whatts, the lesser speakers its going to be able to handle at high volumes.
0helpful
2answers

Htr 5630 shut off in 2 sec.

Sounds like you have a bad amp IC or transistors.
When these go bad they almost always put roughly 40 volts dc from the amp power supply to the speaker terminals. The protection circuit senses this dangerous (to your speakers) dc voltage and disconnects the speaker terminals from the amp via internal relays (the ones you hear click) and puts it into protect mode. If it didn't the dc voltage would quickly toast the voice coils of the connected speaker.

0helpful
1answer

I have blown the protection circuit on my yamaha rx 600d amp anyone with a clue whats needed to fix?

Hi friend,when something goes wrong in the output of the amplifier the protection circuit take place to prevent further damage could cause by DC power such as speakers or other related circuits...I think in your situation either one or both output amp stage have blown,then the protection cct turned on (not blown protection circuit!?). If so you have to check all the output transistors for short cct, if shorted you must also check all the DC bias cct nearby such as small transistors,resistors...If you are not familar with amplifier it better to find a tech as all amplifiers need a very precide repair technic , If the DC BIAS were wrong , when you turn on the power it will blow straight away! All times and cost will be waisted!
GOOD LUCK!
Tan Ta
0helpful
1answer

My jbl stereo wont turn on. when i turn my truck on it just lights up and then goes straight back off

Hi there Willieulin.
I wonder if the speakerwires are shorting the amp in the JBL stereo!
One or more speakers could be blown......
The protection circuit is most likely doing its job, protecting your stereosystem from damage.
If you have a extra amp connected to the stereo, check if it is wired right.
Try to turn the ignition key "only" so the lights on the stereo turn on. If you turn it further so you start the engine it most likely turns the stereo off.
If that happens the powerwires to the stereo are wrongly connected.
Luck with the problem.
Iceman.

2helpful
1answer

When push the power button, I can hear a relay click but the unit will not power up. I took the cover off and fuses are good. Can't find anything in the trouble shooting section of the manual. What do you...

When the unit functions correctly, you should hear 2 clicks. The first is the power relay that "starts" the unit. The second is the speaker protection relay that will kick in the speaker connection. If you do not hear the second click, the unit is in protect mode. This means that a problem was detected in the amp section and the unit is prevented from connecting the speakers. This is done to prevent further damage. Typically the output transistors fail and cause this. Expect a parts cost in the $25-$50 range for this repair.

Dan
2helpful
1answer

No sound from htr-5840 when switched on. I hear

These units have protection circuits that will prevent the speaker relay from engaging if there is a problem detected. There is also a circuit that causes a delay in the engaging of the relay to allow the amp to "settle in". This prevents the old "thump" that was common in older models when the set was first turned on. In your case, either the RC circuit is faulty causing excessive time to pass before turning on the relay, or there is excessive voltage floating around that the protection circuits are detecting and thus preventing the relay from turning on.

In any case, this will require additional diagnosis using some test equipment. This is not a problem that will be easily resolved remotely. Please bring this unit to a repair shop for an estimate. Once you have that info, we can assist with the actual repair.

Dan
0helpful
2answers

My Stereo Is Always On Protect Can It Be Easily Fixed

Protet mode is a special diagnostic mode that starts when a fault is detected.

When in protection mode the unit is prevented from starting by protection circuit, so to prevent further damage.

Check the speakers and speakers wiring, a contact in speaker wires, or faulty speakers can send the unit in protection.

Try unplugging power cable for one hour or so. then connect cable back and see if you get rid of protect state. Sometimes accumulation of electrostatic charges inside circuit capacitors can kick in protect mode. In that case unplugging the unit from main for some times can get rid of electrostatic charges, and reset circuits by draining power completely.
If that was the problem, you will not get Protect when plugging back power cable.

If you do all the above and still get Protect, then there is a real fault.

In that case the unit may be disassembled and tested to find the fault.

If that is the case I suggest contacting the manufacturer at the number listed on the owners manual, or asking a quote on repair to a local technician.
0helpful
1answer

Thumping speakers - no power light is on - wired correctly

the amp is going into protect mode due to something wrong in the amp or some thing in the wiring to it ooh yea if you are getting 18v power to the amp that is way to high it should not be higher then 15v if the amp is in protect mode it will not play at all.
0helpful
1answer

Amp Power light will not go on. Protection light is lit- Thump sound in speakers

It probably has shorted output transistors. To eliminate other possible causes, read through the following page.

Amplifier in Protect Mode - Troubleshooting

Let me know if you have any other questions.
Not finding what you are looking for?

393 views

Ask a Question

Usually answered in minutes!

Top Yamaha Audio Players & Recorders Experts

 Grubhead
Grubhead

Level 3 Expert

5755 Answers

Brad Brown

Level 3 Expert

19187 Answers

Paul Bade

Level 3 Expert

1818 Answers

Are you a Yamaha Audio Player and Recorder Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...