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Mains fuse blows immediatly on power up on trace elliot commando 100W bass amplifier

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Hi, The most common cause of this is blown output transistors, assuming this is not a valve amp. 
At any rate, this is something you will want to have looked at by a tech.

Posted on Sep 20, 2008

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Where can i buy a power transformer for Sansui 3900z ?


Let me guess...you took it somewhere for repair, and they told you it had a bad transformer and they couldn't fix it (after they took your money). Sansui began life as a transformer company, and unless something really silly was done (like replacing the stock fuse, which is probably 3 or 4A with a 15A fuse of something). I might mention that 'some' units sold for various locations have a thermal fuse installed internally to the transformer. I dunno if your model has this or not. I mention all of this because often times the phrase 'it has a bad transformer' is lame techspeak for 'I don't wanna fool with this thing'. If it blows the mains fuse on power up, then the most likely fault is that it has blown power transistors at the output of the amplifier. If it 'really' has an open primary winding in the power transformer, then it may well have a thermal fuse that has opened. Gary Brown in Orono, ME has fixed a few transformers for me with this issue. Google can help you find him.

Dec 24, 2014 | Sansui 3900z Stereo Receiver

1 Answer

Receiver blowing fuses


Problem is most likely shorted output transistors. These are the large transistors mounted on the heatsink. When these go short, they usually take out some the adjoining resistors in that channel.

Jul 08, 2013 | Denon AVR-1905 Receiver

1 Answer

My teac ag-680 fuse keep blowing everytime i replace it and plug the reciever up


are short in the audio output transistors may have been short since a channel 2 or maybe 4, also open resistance check carefully and change them after you put a 75w bulb in series 100w or where is the fuse clearly, you have to remove the fuse when you put the focus if all is well will turn on only a small incandescent and amplifier work well you put audio speakers and there will, if everything is well put the fuse back and ready.

Jan 14, 2013 | Teac AG-680 Receiver

1 Answer

Standby light is flashing on my marantz sr7001


hi,
First of all remove all the speaker connections from the amplifier. After that power the amplifier and check the Standby blinking (protect) show or not . if not, then any of the speaker is damaged also check the wire for any short circuit . If then also its goes to protection then it have some hardware truouble inside.

Amplifiers gose protect mode , when there is a hardware fault in side it. Its a warning that some thing is wrong.
Normally amplifiers show this when any of the output amplifier have some problem. there 6 amplifiers in this receiver . May occur when the output diver transistors of any of the amplifier become shorted. if the output transistor get shorted this will lead to flow of current through the speakers. To prevent this there is a protection circuit for each channels. One combined output of this protection circuit is connected to the system control. when the any of the output amplifier fails, the protection circuit detects it and switch of the speaker and sent data to the system control. when the system control get this data it will give a warning to the customer through display that PROTECT.
You have to check the amplifier.
For that you need digital multimeter,soledring iron screwdrivers etc
Open the amplifier , then power it on. Connect the negative terminal of the multimeter any where in the chase( metal body of the amplifer). Then connect the positive terminal to all the output transistors emitter pin one by one . The voltage should be bellow 0.5V. If any of the emitter of the transistor shows voltage more than +/- 0.5V., then that amplifier stage is faulty. Remove the transistors and check it. if it is shot then replace with a new one.
After replacing the transistors do not power up the amplifier directly from the main. You have to put a bulb of 60 watts in serial.
You can do this easily remove the mains fuse. Put the bulb in a holder. Now you have two wire from the holder. connect one of it to the one end of the fuse holder and the other wire to the other end of the fuse holder. Why using a bulb is, if there is any further problem in the amplifier stage on which the transistors replaced, there is a possibility of the new transistor get damage. if we use a bulb in serial with its mains supply ,when any overload in the amplifier occur the bulb will drop the current, by lighting itself.
After connecting the bulb in serious power on the amplifier. watch the bulb. It should light for one or two second and go dim ,then remove the power , remove the bulb insert fuse and connect the power and check.
(If the bulb shows bright light then there is some component also faulty in the same amplifier. after removing the power you have to check again the amplifier stage of which the transistor is replaced, for any other faulty components

OK

Aug 20, 2011 | Marantz SR7001

1 Answer

I need to know what amp fuse i need for my yamaha htr5840 receiver. i pulled out the blown one, but it only says 125 v. it does not tell me the amps.


The power consumpyion for yor amplifier is 350W / 440VA and the 2 switched AC outlets at the back panel can handle up to 100W, totally 450W. I suggest you to use a 5A / 110V fuse and in case burn down use an 6A / 110V fuse. DON'T INCREASE these values, you may damage the amplifier.

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Aug 13, 2011 | Yamaha HTR-5840 Receiver

1 Answer

My rx-v367 does not power on, i think the protective circuitry has been activated. How do I reset it?


hi,

AV receivers shows protect mode , when there is a hardware fault in side it. Its a warning that some thing is wrong. Is there is any standby light. If not check the AC fuse.
Normally AV receivers show this when any of the output amplifier get some problem. there are five amplifiers in this AV receiver. May occur when the output diver transistors of any of the amplifier become shorted. if the output transistor get shorted this will lead to flow of current through the speakers. To prevent this there is a protection circuit for each channels. One combined output of this protection circuit is connected to the system control. when the any of the output amplifier fails, the protection circuit detects it and switch of the speaker and sent data to the system control. when the system control get this data it will give a warning to the customer through display that PROTECT.

First of all remove all speaker connections from the amplifier and powerup the amplifier. If the amplifier turns ON then, then any of the speaker have some problem.
If not You have to check the amplifier.
for that you need digital multimeter,soledring iron screwdrivers etc
open the amplifier , then power it on. connect the negative terminal of the multimeter any where in the chase( metal body of the amplifer). then connect the positive terminal to all the output transistors emitter pin one by one . the voltage should be bellow 0.5V. If any of the emitter of the transistor shows voltage more than 0.5V., then that amplifier stage is faulty. Remove the transistors and check it. if it is shot then replace with a new one.
after replacing the transistors do not power up the amplifier directly from the main. You have to put a bulb of 60 watts in serial.
You can do this easily remove the mains fuse. put the bulb in a holder. now you have to wire from the holder. connect one of it to the one end of the fuse holder and the other wire to the other end of the fuse holder. Why using a bulb is, if there is any further problem in the amplifier stage on which the transistors replaced, there is a possibility of the new transistor get damage. if we use a bulb in serial with its mains supply ,when any overload in the amplifier occur the bulb will drop the current, by lighting itself.
After connecting the bulb in serious power on the amplifier. watch the bulb. It should light for one or two second and go dim . if so check the display, is there is protect mode is on or not . if not and come back to normal operation ,then remove the power , remove the bulb insert fuse and check
connect the power and check.
If the bulb shows bright light then there is some component also faulty in the same amplifier. after removing the power you have to check again the amplifier stage of which the transistor is replaced, for any other faulty components.
ok

Feb 17, 2011 | Yamaha RXV367 Receiver

1 Answer

The ic tda7293 is exploited, and I have no further information on the motherboard, I need to find the service manual, thanks


TDA7293 is a high-power high- voltage DMOS audio amplifier IC made by STMICROELECTRONICS. Its rated output power is 100W and maximum operating voltage is120V. And it is a monolithic integrated circuit in Multiwatt15 package which is intended for use as audio class AB amplifier in Hi-Fi field applications, such as home stereo, self powered loudspeakers and Topclass TV.

Feb 07, 2011 | Audio & Video Receivers

1 Answer

I have a Trace Elliot bass amplifier (gp7sm 130) and it makes a buzzing soound. Any ideas?


First check all of the ground connections both at the amp and bass. If the amp makes the buzzing with no input at all, the problem is most likely a bad cap in the front end of the amp. These are not the easiest to work on. I would suggest that you bring the amp to a servicer for repair. Anything that you can describe that indicates when the buzzing is more evident would be helpful in tracking down the problem.
Dan

May 05, 2008 | Audio & Video Receivers

1 Answer

Nad 218 thx power amp keeps blowing ac plug fuse


Hi there. From memory they had bridge rectifier problems with them going short circuit. Check them first. Sometimes the toroidal transformer can go a shorted turn, in turn blowing primary fuses. try to soft start it whilst it is blowing fuses, Best bet is to make up a special lead that has a 60w light bulb wired in series with the mains power supply(or across the fuse holdwer that is blowing:). Limits the power in the circuit to ... well you guessed it 60 watts.

check em out and let me know.

regards
Graeme

Apr 27, 2008 | Audio & Video Receivers

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