AVR Left channel not working

[Sylar]

I got a new pair of cables with bananas and connected them. The cable has self locking bananas. But the cable being a bit heavy, and curved one way, came loose from the terminals & it ended up shorting. The AVR i think went into protection mode.
Since then, the left channel (the one which shorted), is not working right. Test tone emits a very low volume, static sound, just like one from tuning a radio. It plays music, but at a very low volume. I have tried resetting the processor. Swapped speakers from L to R. Speakers are just fine.

Not sure what to do to fix it. Is this a serious issue? Any suggestions on what's wrong & how I could fix this?

 

[lsiberian]

I got a new pair of cables with bananas and connected them. The cable has self locking bananas. But the cable being a bit heavy, and curved one way, came loose from the terminals & it ended up shorting. The AVR i think went into protection mode.
Since then, the left channel (the one which shorted), is not working right. Test tone emits a very low volume, static sound, just like one from tuning a radio. It plays music, but at a very low volume. I have tried resetting the processor. Swapped speakers from L to R. Speakers are just fine.

Not sure what to do to fix it. Is this a serious issue? Any suggestions on what's wrong & how I could fix this?

Is it under warranty?

 

[AcuDefTechGuy]

Do you have a choice of using "A" speakers and "B" speakers?

If so, try switching over to the "B" speakers terminals.

 

[Sylar]

Is it under warranty?

Yes.

Do you have a choice of using "A" speakers and "B" speakers?

If so, try switching over to the "B" speakers terminals.

I have the Marantz 7005. It has 'Front B/Height' outputs. I switched to the B terminals, and the left channel has the same issue.

I also noticed that, when switched to B terminals, and with Front A set as output, the Front Wide Left is fine. Checked using test tone.

 

[lsiberian]

Yes.


I have the Marantz 7005. It has 'Front B/Height' outputs. I switched to the B terminals, and the left channel has the same issue.

I also noticed that, when switched to B terminals, and with Front A set as output, the Front Wide Left is fine. Checked using test tone.

Go into your settings and check to see if it got turned off somehow. If you continue having issues contact Marantz.

 

[Sylar]

I was under the impression the amp's built in protection would kick in when the wires shorted...am i wrong?
If not, any specific reason why the protection didnt kick in? ...or did it?

...any calculated guesses on what could be wrong? Should i be worried

 

[TLS Guy]

I was under the impression the amp's built in protection would kick in when the wires shorted...am i wrong?
If not, any specific reason why the protection didnt kick in? ...or did it?

...any calculated guesses on what could be wrong? Should i be worried

You can never rely on protection circuits to prevent serious damage if you short the output of an amp at the speaker terminals.

Output stages can, and often do blow, if you short the speaker terminals, especially if the short occurs when the amp is producing appreciable power.

Unfortunately output transistors are inclined to blow before protection circuits can activate.

You have blown the output stage of the amp on that channel.

The best protection is NEVER shorting the output stage of an amp.

I suspect Marantz will repair this receiver under warranty, although they do not have to under the circumstances.

I would get rid of those cables before your receiver comes back from repair.

 

[Sylar]

The problem occured bcos one banana sprung loose from the terminal although they have a self locking mechanism. Would these bananas serve as a reliable replacement?

I was using this

 

[Sylar]

You have blown the output stage of the amp on that channel.
...
I suspect Marantz will repair this receiver under warranty, although they do not have to under the circumstances.

What would this typically cost to repair? I mean replacement parts cost, service excluded. (Output stage transistor...opamp?)
Is there something that I can do to.. not be bounced off warranty.

 

[GranteedEV]

Doing anything yourself would instantly void the warranty. I would see what marantz does for you first.

 

[TLS Guy]

The problem occured bcos one banana sprung loose from the terminal although they have a self locking mechanism. Would these bananas serve as a reliable replacement?

I was using this

I prefer this type.

I find they are less likely to come out. Also it is unlikely two reds will short. This is worse than shorting a black and a red. It will blow two channels and protection will be of no use at all.

 

[Sylar]

3 power transistors & a few resistors in the output section were toasted...hopefully will get mine fixed & working in another couple of weeks

 

[TLS Guy]

3 power transistors & a few resistors in the output section were toasted...hopefully will get mine fixed & working in another couple of weeks

Thanks for the follow up!

 

[Sylar]

I double checked the terminals with the cables. The problem is at the speaker terminal of PSB. The bananas do not really fit in well.
It fits in solid & tight into the marantz, and dosent come out easy as one really needs to pull it out, so shorting at receiver end is highly unlikely unless I screw up. Also 2 reds shorting is not an issue...no intend to Bi Amp the speakers.

Will maybe use some kind of transparent scotch tape or something to insulate the conductive part of the bananas which is exposed.

I was searching for dual bananas with soldering or ones where the wires go in through the end and sits inside unlike the one above. Dosent fit in like this, but like this. Any idea where these are available.