[tspirer]

Hi JP,

So I finished building my 2nd EQ573II now that I got the replacement rotary knobs (thanks for the quick shipment!). 

All seems to work fine EQ-wise (haven't fully tested with preamp just yet), but I am having an annoying issue with lowband knob - when selecting thge 70 Hz filter specifically, it quiets down to extremely low-volume to no audio at all when source is not very loud. 
All other bands/off seem to work fine. 
Same for other knobs/selectors.

I doublechecked all solder joints, in looking at the schematic I was trying to figure out the signal flow when 70Hz is selected but I got a bit lost.

What would cause this? Which component(s) and traces that specifically are related to 70Hz selection, should I check?

Thank you.

Tal

[JPK]

You mean the high pass filter, I think.
You must check the solder joints of C17, C18 and L1. The pins on the inductors are sometimes oxidized and require some rubbing with the iron tip to make a good joint.
Also check J6 a&b and the rotary switch SW1.

[tspirer]

Yes the bottom most knob...
I am hoping it's not the rotary switch albeit it had to be desoldered once already slowly and carefully but still took a while, since I initially put it in the wrong place when not paying attention.
So it very well could have been damaged but it works fine except for 70Hz.

I'll check those other things you mentioned below later today.
Pls let me know if there is anything else I should look into.

thx
tal 

[tspirer]

Hi JP - that recommendation worked. 
I couldn't tell which joint was not soldered properly enough, but that's besides the point.
Followed your guidance and reapplied solder-gun/resoldered/flux/cleaned and I am getting signal on 70Hz lowcut! 

I think I saw this in another post here when originally looking for an answer re: my issue, but there is some sort of "clicky" lag when switching bands on that one, only to come in later just fine.

tested today extensively and I'm getting good and consistent sound through the EQ.

Thanks again!!