[Dolbah]

High pass stopped working on my EQ573-II. I have two units, and switched the mainboard between them. The problem follows the mainboard.

When turning the knob the sound just flickers on each step, but no  noticable change in the frequency spectrum. 

Any idea where to start? I have reflowed all nearby joints and then some.

[JPK]

Maybe a bad solder joint on inductor L1.

[Dolbah]

Thanks! I actually misinterpreted the problem, by testing a tone with to little lowend. The actuall problem is that the unit that did not react as originaly described. actually is ok, but the other one is shaving off 3dB on all highs, when set to Hipass 360. It gradually lowers for each step on the high-pass.

[JPK]

Check the values and solder joints of R26, R27, R9, J6a, J6b, C13...C22, L1, RN1, RN2.

[Dolbah]

Check the values and solder joints of R26, R27, R9, J6a, J6b, C13...C22, L1, RN1, RN2.

thank you! it was somewhere on that route  All ok now