Help with Linn Majik IP output Bias setting

[K3YHL]

Hi all, I'm hoping someone can help me with a problem.

I have just repaired a Linn Majik -IP Amplifier that had all output transistors blown along with numerous other components in the supply line.

It was that bad I think the previous owner had connected the Pre-amp pins the wrong way around and the thing went bang.

Any way the problem that I have is that I need to set up the new output transistors bias which is normally an easy job following the service manual instructions.

Unfortunately I cannot find any info anywhere on the net and my pleading with Linn and numerous other service centres came to a dead end as no one would provide me with the info.

I have attached a PDF with the Mainboard schematics but this does not mention the process.

Is there any way to set up this amp without the correct procedure?

Thanks in advance
Key

 

[blek stena]

Hi,

From the schematic posted i can se that there are no output transistors beacuse power section is made with TDA1514A ICs. Were you aware od that?

Regards,

 

[blek stena]

There are 2 ICs for each channel working in parallel. The BIAS is set by the IC itself. There is also servo circuit in for each IC. Did you check the offset at output terminals?

 

[K3YHL]

Hi, thanks for getting back. I presumed that i had to set the bias as there are VR pots for both channels. In my limited previous experience these are use to set the output bias for the amp.
I have never come across a servo circuit before.

I haven't actually powered up the amp yet since i replaced all the blown components as I wanted to make sure any adjustments were correct.

Do you know what the VR's are for and do I need to do anything with them?

Key

 

[blek stena]

There is VR only at output of one of the two parellel ICs. VR is placed in negative feedback loop. I would say that it is there as option to equalize the voltage gain of the both ICs.

Regards,

 

[PRR]

The trimmer adjusts resistor tolerance. Changing the chip makes almost no difference. Leave the trimmer alone.

 

[K3YHL]

Ok thanks for your advice, I will go ahead and power her up with fingers crossed.