Hi,

I have a Beomaster 7000 which started to behave like that: once I turn it on, it sends a humming sound to one loudspeaker and immediately turns itself off.

If I disconect the loudspeaker, it works- display and etc.

So, finnaly only one channel is working !

It was used before with Beolab Penta and I had no clue that one of the channel is not working because the system is working fine when connected on Powerlink ! Now Penta are gone and I'll use passive speakers with the system...

 In case I use the headphones, the system it does not turn off - one channel is OK, the other has a humming...

 

Any help will be highly appreciated,

thanks

Sounds like a component failure - either a transistor or a capacitor has blown and could well have gone open circuit. The protection circuit is switching the Beomaster off to prevent damage. Needs servicing but I am sure it will be fixable. Sounds as if it is in the power amplifier from the symptoms. Just check that there is not a dodgy connection in the DIN plug of the loudspeaker though!

Peter :

Just check that there is not a dodgy connection in the DIN plug of the loudspeaker though!

i had a very similar situation w/ a bm6000. it, in fact, turned out to be the wiring in the din plug! certainly worth a look!

thanks for your fast answer...

 

 

It is not the plug. I switched the speakers and I have the same behavior!

 

Because I have a channel that is in working condition, I could try to open the <box< and see if the final transistor are the problem!

 

However, taking into consideration that I have  a humming sound ( which seems to be amplified), I doubt that the final power transistors are the problem!

 Any ideea?

 regards,

 

 

Yes...

There is a 3-pin cable between amplifier and the preamp... green, yellow and some other colour, maybe brown. Disconnect it from the preamp.

If the humming continues, it's the amp. If not, then its the preamp.

You could also connect a signal source to this cable, but use only a very low level or you blow the speakers. If both channels work, then its a defect preamp.

Martin

Die_Bogener:

Yes...

There is a 3-pin cable between amplifier and the preamp... green, yellow and some other colour, maybe brown. Disconnect it from the preamp.

If the humming continues, it's the amp. If not, then its the preamp.

You could also connect a signal source to this cable, but use only a very low level or you blow the speakers. If both channels work, then its a defect preamp.

Martin

 

 

 

I'll try this tonight...

 

However, I removed the cover of the Beomaster and look what I found inside...

 

 It seems that something happened with the final transistors and some resistors...

 

I'll use the multimeter and verify the voltage by comparation with the good channel ...

 

Any ideea what else could be guys?

 

and this is actually the module that swittch from headphones to the speakers...

 

look at the black part!

Wow, that looks really bad, amp and preamp are gone...

Overvoltage, maybe somebody hooked the amp output directly to 220 volt line...

No fun, last month i had a pair of BL5000 amps here for repair. The owner had connected the output of the amp directly to the 220V power line (instead to a second speaker set...) and switched on the light... wow, that was a firecracker  

hm......

 

the preamp is OK!

 

It seems that the final transistors are gone!

Question for electronists? In this case, what is the way to do to be sure that no other components are gone? Power UP the Beomaster with the final transistors removed?

Anyone has an ideea what voltage to check?

What kind of final transistors I have to order?

 

 

Please bear in mind that one channel is OK......only one is not working!

thanks!

The relais unit is part of the preamp... but probably this part can be repaired, there are not too much components on it. Probably some wires are gone...

The amp is powered by the transistors BDV64 and BDV65. Replace them. Replace also the damaged resistors. Then try it again ;)

guys,

 

I replaced the final transistors and 2 resistors- one that is 2.2k and 390ohm.

Then I verified all the components and compared with a multimeter  everything with the good channel.

Disconected the cable thats go to the headphones switch......

 Then PowerUp and in few seconds BUMMMM

 Now, the 2 final transistors are gone, with one of the Power resistors that is few ohms if I<m not wrong...

 

any ideea what had happened?

Yes...

 the "no load current" was a little bit to high... both transistors opened at the same time, to much current.

Do you have a service manual at all? Just replacing some exploded parts is not enough. Both boards are burnt, the black colour means a lot of heat, overvoltage and burnt wires, cables and connections. Have you reworked this already?

Have you ever repaired a power amp? Plug and Pray does not work with these parts. At least you need a special power supply for servicing at a lower voltage with a power limiting funktion, some safety/fuse resistors in the power supply of the amp and only then i would power up the amp.

Martin