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Beomaster 3000-2: Left Channel Dead

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junius
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junius posted on Thu, May 24 2012 7:10 PM

Hi, this is my first B&o product and my first post on this forum.

I should mention that I don't have much experience tweaking with audio equipment but have repaired some computer components in the past.

I bought this receiver purely for its aesthetics - I just couldn't help myself. When I turned it on the other day, I had the right channel working through headphones. The left channel is completely dead. All pots and switches seem to work on the right channel, and I get good audio through both tape input and tuner (didn't try the phono inputs). All lights seem to work as well.

Other than the left channel, I can't seem to get any response from the lit dial in the bottom right of the face (I'm assuming it's tuner signal strength), and there was an audible hum coming from the power supply.

When I opened up the unit, I noticed that one fuse (further from the rear edge of the receiver) was blown. There is also a blown resistor visible from the top of the unit (see image). Finally, there is a crack in what seems to be a spliced on circuit board directly behind the tuner dial. When I replaced the fuse the hum seemed to go away but the left channel remained dead. There is a burning smell from the blown resistor but I couldn't notice any other unsettling odors from anywhere else in the unit. The resistor is so fried I can't make out the color bands to buy a replacement.

I hope some of you can lend a hand with the diagnostics. I'm wondering if the blown resistor could be the reason that my left channel is dead. Should I do some more poking around before I take on this project? Thanks in advance.

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Step1
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Step1 replied on Thu, May 24 2012 8:36 PM

You picked a fun first project there! You will not find a lot in common with computer diagnostics though. Amplifiers are particularly difficult to fault find if you don't have the necessary experience as it is very easy for one faulty component to start off a chain reaction. Also a fault that seems to be in the latter stages can actually stem from just about anywhere within the amplifier, and vice-versa! That resistor has failed secondarily to something else, so just replacing it will not help you, and could cause more issues!

Olly

Dillen
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Dillen replied on Fri, May 25 2012 8:59 AM

Burned output stage, burned driver stage, burned idle current circuit and probably a little more.
Replace all components in the affected output channel - or replace the circuit board and
the three related transistors on the cooling fin.

Martin

chartz
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chartz replied on Fri, May 25 2012 11:07 AM

Plus the thin green PCB appears to be broken.

Jacques

Dillen
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Dillen replied on Fri, May 25 2012 12:11 PM

chartz:

Plus the thin green PCB appears to be broken.

Yes, that will be for the FM presets. It can be bridged with a couple of thin leads.

Martin

junius
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junius replied on Fri, May 25 2012 3:32 PM

Thanks everyone - your responses made the decision to take the unit to a decent vintae audio shop for repars that much easier. I'll post once I get it back in case anyone's interested to know how it all turned out.

Cheers

Dillen
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Dillen replied on Fri, May 25 2012 4:04 PM

junius:

... in case anyone's interested to know how it all turned out.

We are, so please do !

Martin

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