Switch tripping when I turn on my Integrated Amplifier

[Sangeet]

I have an old Onkyo interga Integrated amplifier. This amplifier was was working fine till yesteday. I actually purchased a new Emotiva power amplifier few days back and was testing the sound quality of this integrated amplifier and the power amplifier by alternately connecting a speaker. I accidentely connetced the positive of both the amplifier to each other. The power amplifier had a good trip system so it tripped and is working fine. But this integaretd amplifier dropped dead. So I opened the top cover of amplifier and saw that the power fuse (7 A, 125 V) had been blowen. I got this fuse from a local electronic store and replaced it. But now when I turn on the amplifier, the trip switch of the room truns off. What do you think is the problem ? Can you please advice.

 

[Haoleb]

The problem is you damaged the output stage of the amplifier, if not other items and you need to have it repaired by a qualified tech for it to work again. You certainly do not want to plug it in or hook speakers up to it until it is fixed. If you open it up again and you see the 7A fuse is not blown but you are tripping the circuit breaker something else is also wrong. The 7A fuse in the amp should be blowing before the breaker trips. The replacement you got may not be the right type of fuse. Either way. It needs to be fixed.

Also, you never want to connect or disconnect anything on an amplifier while it is turned on- which it kind of sounds like what you were doing when this happened.

 

[Sangeet]

The problem is you damaged the output stage of the amplifier, if not other items and you need to have it repaired by a qualified tech for it to work again. You certainly do not want to plug it in or hook speakers up to it until it is fixed. If you open it up again and you see the 7A fuse is not blown but you are tripping the circuit breaker something else is also wrong. The 7A fuse in the amp should be blowing before the breaker trips. The replacement you got may not be the right type of fuse. Either way. It needs to be fixed.

Also, you never want to connect or disconnect anything on an amplifier while it is turned on- which it kind of sounds like what you were doing when this happened.

Thanks. Is there a way I can only use the preamp section ? I purchsed a new emotiva power amp and will be using that to drive the speakers but need a seperate preamp. Is there a way to isolate the output stage of the amplifier ?

 

[Sangeet]

The problem is you damaged the output stage of the amplifier, if not other items and you need to have it repaired by a qualified tech for it to work again. You certainly do not want to plug it in or hook speakers up to it until it is fixed. If you open it up again and you see the 7A fuse is not blown but you are tripping the circuit breaker something else is also wrong. The 7A fuse in the amp should be blowing before the breaker trips. The replacement you got may not be the right type of fuse. Either way. It needs to be fixed.

Also, you never want to connect or disconnect anything on an amplifier while it is turned on- which it kind of sounds like what you were doing when this happened.

Just to update: There are 3 sets of wires coming out of tranformer as below :-

a set of orange wire
a set of green wire

both the sets (total 4 wires) are going directly into the power amplifier section.

the 3rd set is a set of 3 wires (2 red and one black) and these 3 wires are going to the bridge network.

Now my question is that if I cut the connection to the power amp section i.e. cut both orange and green wires do you think I will be able to use the preamp section ?

 

[Sangeet]

The problem is you damaged the output stage of the amplifier, if not other items and you need to have it repaired by a qualified tech for it to work again. You certainly do not want to plug it in or hook speakers up to it until it is fixed. If you open it up again and you see the 7A fuse is not blown but you are tripping the circuit breaker something else is also wrong. The 7A fuse in the amp should be blowing before the breaker trips. The replacement you got may not be the right type of fuse. Either way. It needs to be fixed.

Also, you never want to connect or disconnect anything on an amplifier while it is turned on- which it kind of sounds like what you were doing when this happened.

Update :-

Please ignore above post regading different wires. I have now managed to turn on the amplifier by cutting the power supply to power amplifier section. Actually there are about 4 sets of wire coming out of the bridge network. 2 of these were going to the power amplifier section i.e. left and right channel. I have removed these 4 wires and the amplifier could turn on without any problem. All the lights etc are working but the problem is that there is no signal (output) from the preout.

 

[TLS Guy]

Update :-

Please ignore above post regading different wires. I have now managed to turn on the amplifier by cutting the power supply to power amplifier section. Actually there are about 4 sets of wire coming out of the bridge network. 2 of these were going to the power amplifier section i.e. left and right channel. I have removed these 4 wires and the amplifier could turn on without any problem. All the lights etc are working but the problem is that there is no signal (output) from the preout.

What you originally did is about the worst insult you can give any amp. Your are lucky you did not blow both of them.

As to your second problem, we don't know where the damage trail ended. Also without a circuit, I could not begin to tell you how to power the preamp section without the power amp section.

How many bridge rectifiers are there in the power supply? If only one then there will be voltage regulators for the power amp and preamp section and my be a few others. I suspect you have cut the power to the voltage regulator section of the power supply.

What you are about sounds dangerous and likely to extend the damage. I suspect that unit is most likely at the end of the road.

 

[Sangeet]

What you originally did is about the worst insult you can give any amp. Your are lucky you did not blow both of them.

As to your second problem, we don't know where the damage trail ended. Also without a circuit, I could not begin to tell you how to power the preamp section without the power amp section. .

Thanks for working with me on this. Today is Sunday and I worked on this whole day and the progress is really good. I have managed to turn-on the preamp section (both channels).

Since I knew that when i was doing the experiment, only one channel of this amplifier was connected, I was sure that the problem will be with just one channel. So I alternately connected the power supply wires from the bridge network to both the channel and the good news is that the right channel is working fine and there is a problem with left chanel power amp section. So if power is suppied to just the right channel power amplifer section. This channel works fine and so does both channels of the the preamp section. This is because there is an electronic switch that gets activated if there is power supply to the power amp section.

So now the preamp section is just working fine and I have connected a seperate power amp (external) to my system.

Right channel of the integrated amplifier is also working fine.

But if I give power supply to the left channel of power amp section the fuse blows.

NOW what do you think is the problem with left channel power amplifier section ? Is the transistor burnt ?

How many bridge rectifiers are there in the power supply? If only one then there will be voltage regulators for the power amp and preamp section and my be a few others. I suspect you have cut the power to the voltage regulator section of the power supply.

There are 2 transistor per channel on the power amplifier section i.e. 1 each 2SA1494 and 2SC3858. I will try to send picture of the power amp section.

 

[TLS Guy]

Thanks for working with me on this. Today is Sunday and I worked on this whole day and the progress is really good. I have managed to turn-on the preamp section (both channels).

Since I knew that when i was doing the experiment, only one channel of this amplifier was connected, I was sure that the problem will be with just one channel. So I alternately connected the power supply wires from the bridge network to both the channel and the good news is that the right channel is working fine and there is a problem with left chanel power amp section. So if power is suppied to just the right channel power amplifer section. This channel works fine and so does both channels of the the preamp section. This is because there is an electronic switch that gets activated if there is power supply to the power amp section.

So now the preamp section is just working fine and I have connected a seperate power amp (external) to my system.

Right channel of the integrated amplifier is also working fine.

But if I give power supply to the left channel of power amp section the fuse blows.

NOW what do you think is the problem with left channel power amplifier section ? Is the transistor burnt ?



There are 2 transistor per channel on the power amplifier section i.e. 1 each 2SA1494 and 2SC3858. I will try to send picture of the power amp section.

For certain the output power transistors are shorted out and need replacing.

The question is do the drivers and some of the diodes in the phase splitter section ahead of the output transistors need replacing also?

 

[Sangeet]

There are 2 transistor per channel on the power amplifier section i.e. 1 each 2SA1494 and 2SC3858. I will try to send picture of the power amp section.

I'm new in this forum so not sure on how to send image.

 

[TLS Guy]

I'm new in this forum so not sure on how to send image.

An image will not help me much.

You need to load your images to a photo sharing site. Then copy the URL of the jpg images and paste them in the URL box of the yellow envelope in the website tool bar. When you rest your mouse over it is will say "insert image," so you know you have the correct icon.

 

[Sangeet]

An image will not help me much.

You need to load your images to a photo sharing site. Then copy the URL of the jpg images and paste them in the URL box of the yellow envelope in the website tool bar. When you rest your mouse over it is will say "insert image," so you know you have the correct icon.

Now sure on whether this will help but can you help me identify whay the problem could be.

 

[Sangeet]

For certain the output power transistors are shorted out and need replacing.

The question is do the drivers and some of the diodes in the phase splitter section ahead of the output transistors need replacing also?

By power transistor you mean either or both 2SA 1494 and/or 2SC3858. I'm sorry for asking but I'm a mech engineer and not sure on how to check if these transistors are shorted. I do have a multimeter, solder iron etc at home.

 

[TLS Guy]

Now sure on whether this will help but can you help me identify whay the problem could be.

There is no image. There is no link directing to a picture URL.

Your problem is blown and shorted output transistors for sure, and possibly problems in the phase splitter/driver section.

 

[TLS Guy]

There is no image. There is no link directing to a picture URL.

Your problem is blown and shorted output transistors for sure, and possibly problems in the phase splitter/driver section.

The devices you have listed are matched complimentary power transistors.

This is the NPN.

This is the PNP.

They are both from Sanken.

I can see the driver transistors, and associated diodes. I have no idea if they are damaged or not.

I know that both those matched Sanken devices need replacing for sure, because the fuse is blowing.