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Beomaster 4400 Fuse blown after switching to loudspeaker "2"

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flipper62
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flipper62 posted on Wed, Jul 27 2016 1:59 AM

Dear members,

My main fuse T 2.5 A is blown after I turned on the swich for the second pair of loudspeakers, although there was no set of loudspeakers attached to the second port. The overload signal was burning for a short while and after 2 seconds there was a complete shutdown. One of the main fuses was blown.

Before I replace the fuse, can any of you bright members tell me what can be done to repair this. I know I have little information at the moment.

I replaced the fuse OF 2, but as soon I powered it up, it blew again, without switching the BM on. Could it be the 2 large capacitors OC8 & OC9 of each 10.000 uF ?

 

 

 

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Menahem Yachad
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Firstly, rig up a Dim Bulb Tester - google.

Then replace your fuses.

Connect the machine via the DBT, and as long as there is a fault, the bulb will illuminate, and the fuses will NOT blow.

Saves you a lot of aggro this way.

Then start measuring voltages around the big power transistors on the rear panel,a nd compare them to the Schematics.

You'll figure out quickly where the problem is.

I doubt that those big caps are responsible - you can measure for 35V across each one.

You can also follow my recent BM4400 Power Amp Faults thread - but that does NOT mean that my problems are also your problems. It's still in progress at this time.

Menahem

Dillen
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Dillen replied on Tue, Aug 16 2016 7:29 AM

Did the fuse blow BEFORE you powered on the Beomaster ?

Martin

flipper62
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Hello Martin,

 

Yes, they blow before.

flipper62
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Hello Menahem,

 

Thank you for your advise. I follow it up.

Dillen
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Dillen replied on Tue, Aug 16 2016 11:02 AM

That's strange because the power switch comes first - then the fuses and transformer.
Could be that the power switch is at fault, not switching off. I've seen that before.
But there will still be another reason for the blowing fuse.

Is it a type 2317 or a US version (round mains voltage setting switch at the back or not)?
Are the fuses correct type and rating?

Martin

flipper62
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Hello Martin,

 

It's the  European version with voltage setting. I have to correct myself, the fuse blows when the power in switched on, but I only get  68 volts (70 volts normal ?) over the rectifier at 240VAC Is this correct?

Dillen
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Dillen replied on Tue, Aug 16 2016 12:06 PM

Are you measuring on the input or output side of the rectifier (is that 68-70V AC or DC) ?

Martin

flipper62
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Hello Martin,

 

It's the output ( input 240 VAC, output 68VDC)

flipper62
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Hello Martin,

 

Sorry, Input 52 V

Dillen
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Dillen replied on Tue, Aug 16 2016 3:29 PM

Doesn't sound all wrong.
Does the fuse still blow when you switch speaker set 2 on? Anything connected to those sockets?

Martin

flipper62
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Hello Martin,

OK that sounds good.Smile

Yes the fuse stiill blows. I think I found the problem a transistor shows some black smoke residu around the pins on the board. This transistor is connected with the power transistor(s) for the right channel.

 

 

 

 

flipper62
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It's TR219 (connected to signal transformer 0TR200)

Dillen
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Dillen replied on Wed, Aug 17 2016 5:08 AM

Sounds like oxidation, thats quite common and usually not a problem unless the components pins are eaten away.

Check whatever is connected to the speaker set 2 sockets. Disconnect it and try running the Beomaster without it.

Check the socket wiring and solder tags for shorts.

Martin

flipper62
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Hello Martin,

 

Thank you. I'm a couple of days away.

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