Wharfedale EVP X12P distorted o/p

[Nyqusit5]

Hi all,

I am currently trying to repair a Wharfedale EVP X12P power amp (schematic attached). The amp was blowing fuses with a load. I have changed the o/p transistors, the drivers and the ballast resistors. So far the output looks like the first picture (chopped off sine wave) without a load, and like the second picture with a load (only half of a sine wave). Even without a load and not taking the chopped part into account, the output is not very high (not as high as it should be).
I have checked all the diodes and transistors on the board and all seem fine.
Wharfedale EVP X15P.pdf

Anyone has any idea for what to look at next?

Thanks in adavnce!

[MarkusBass]

I have checked all the diodes and transistors on the board and all seem fine.

What about resistors? It looks like half of the amp is not working. Since you replaced output and driver transistors, I would look at Q9, Q10, Q12, Q13 and components in their neighbourhood - especially resistors (possibly open).

Mark

[Nyqusit5]

Ok, I'll check in components that area. Thanks!

[Nyqusit5]

the problem was located in the power supply. The rails were fine up to a certain power level, at which point the positive rail was collapsing.
Thanks for your help Mark.