Finally I fix.

It seems that tr47 was damaged and from the swap proccess  from left channel  I accidentally put the same transistor..

I replacced it with bc161.

Now i must set the correct supply voltage.

The base voltage in right channel is 27.5 and left is 22.2

Thanks for your support

Glad you got it sorted out as I was out of suggestions. First try the bias adjustment.

How much the bias should be set?where exactly should I look?

The problem is that  the replacement transistor burned again after a few minutes..

The 250-ohm trimmer and TR45 governs how much no load bias is applied to each base. It is mounted on the heat sink to sense temperature and also adjust the bias. It’s possible that transister is bad or the adjustment is too high. The circuit calls for a BC311 and since the bias is not separately adjustable for its BC310 mate its possible that your BC161 is a poor match. Sorry, but its been too many years since I worked on one of these.

But Bc 161 specs are almost identical with bc 311.

Btw How many miliampere should I adjust?

The manual doesn't say anything for the adjustment.

In which transistor base should  I put the multimeter probes to take meausurement?

Thanks

 

The base of TR45 should be adjusted to 27.2 which should give you 26.6 at the collector of TR48. If the base of TR44 is 29.2V and you still are seeing a drop to 22V then the speaker output voltage before the output cap can’t be 28v. Note that the positive side has an 100 ohm resister to isolate it where the negative doesn’t. You need to further investigate after  TR47 for the current draw.

Stop swapping components. It will only up the risk of more trouble.
The idle current settings and measuring ponts are given in the service manual.
It's a voltage measured across the emitter resistors with no speakers attached and volume at zero (hence the term idle current).
7,5 mV if I remember correctly - see the manual.
But if a transistor burns, there is something else wrong - the burning transistor is not the reason.
And if you replace one or more semiconductors in an output stage, you MUST set the idle current again at first power up.
Bring the Beomaster up slowly on a variac while monitoring the idle current - power down immediately if something looks wrong.

Did you replace the electrolytic capacitors in the output stage? If you did, did you fit low-ESR types? You shouldn't, as that will often be asking for trouble.

Martin

Hello.

Which emmiter resistors are you referring?

No I didn't replace the output capacitors.

The manual aI read doesn't refer anything about bias procces setting.Not either any mv number set.I replaced tr47 bc311 with bc 161.But the base voltage would  come around 27 volt as I remember.

Don't get me wrong, it may sound harsh but I mean this in the best of ways when I say that
I have a feeling that you will not be the right person to do this repair.
Your methods will only bring more headache, and it appears your electronic education and experience is limited. Right?

Every educated electronic technician will know what the emitter resistors are and how to
measure idle currents.
The manual may state a mA figure, which is and refers to the actual current,
but a brief look at the emitter resistors value and a little bit of Ohms law will
allow you to measure the current through a resistor as a voltage across it, and
as an added bonus you can measure it without disturbing the circuit by lifting components.
You only need to take the top cover off to measure and adjust.

And I wasn't referring to the output series capacitors. I was referring to the capacitors
in the output stage itself, as that is where the problem is.
They must be replaced, and it's good advice to never fit low-ESR types in a circuit like this.

Output stages like this can give even trained tech people a good run for their money.

Martin