studer 169 two channels sound weird

[lobit]

Ive had this mixer for a few years.. in the last month or so.. two of the channels develloped the exact same issue..  basically sounds a bit like a high frequency warble.. like the input is becoming frequency modulated.  i tried switching the position of the  bad modules around but no luck  tried to run the mixer on battery power  same problem.  when I cycle the power, there is a moment just as it powering up where the channels sound normal and then they get weird a second later.  thats what made me suspect power.

any ideas?

 

[hazel]

Are these channels correlative?

Try swapping a "bad channel" into a "good one". May be it's not channel strip but mixer.

Try also de-magnetize input transformers, run a 30Hz tone from min to max gain for 30 seconds through every channel...maybe i'm wrong so download 169 manuals from ftp://ftp.studer.ch/public/products/Mixing_Analog/169-269/

 

[lobit]

I tried swapping positions  good channel into bad channel..  its in the strips