Calrec PQ1549 rev.4 from the Gyraf

Hello Guys
For some time I have a problem with the 1549 EQ.
When you start it turned out that only work Low-Mid and Hi-Mid Sections.
The high does not work ... potentiometers rotate as nothing changes.
and the lower section shall be instituted and began working as a generator.
Maybe there is a problem with feedback somewhere, but I can not find it.
for the record. I complied with all the polarities of the scheme and I measured voltages. examined several times for installation errors. IC sockets are not covered directly soldered to the board.

Sorry for Bad English...
Thank you for Help...

Please use the dedicated help thread - that way any solution can be re-used later by someone with related problems:

calrec PQ1549 help thread: http://www.groupdiy.com/index.php?topic=5957.0

Similar problems has been seen before, I think - often in higher frequency bands

Jakob E.