Author Topic: EQ573-II - High band bypass issue

April 06, 2021, 09:34:33 PM
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Dolbah

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I did some final testing today, and realized i have a issue with the bypass on the high-band on one of my modules. There is a big wide bell increase in the 4-5k area.
As soon as i turn the high-band on, it behaves normally. I took some screenshots of the spectrum while running a pink noise through them, to visualize it:


First picture is of the unit that works, all bands are bypassed (XLR is switched on):



Second picture is of the other unit with the issue. All bands are bypassed (XLR is switched on):



Thirs picture is also from the unit with the issue, in this one the high-band volume knob is dead center, but the frequency knob is on "10"


So you see, when the high band is on, it sound correctly, seems to be something with the bypass circuit itself, or the switch?





Also a seperate minor issue: The SW5 Low-pass switch on the one of the modules are a bit flakey. If i turn on the Low-pass and gently press the switch up or down, the sound of the module dissapears.
I have gone over the soldering of the switch and reflowed it, but the issue is still there. Not a big problem, but could the be the switch itself?




April 07, 2021, 09:51:42 AM
Reply #1

JPK

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Quote
There is a big wide bell increase in the 4-5k area.
Check that you didn't rverse one of the resistor networks on the back of the switch PCB.

In such a case, do not try to unsolder it, there is a risk of breaking a via. Cut the pins and replace by a new one.
Look for solder bridges on this PCB. Check the solder joints on R15, R16 and SW3.


Quote
The SW5 Low-pass switch on the one of the modules are a bit flakey.
You could simply replace it. Same remark as above, do not try to unsolder it. Split it into pieces with cutting pliers until you can extract the pins one by one.

JPK

April 07, 2021, 12:59:13 PM
Reply #2

Dolbah

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All components are placed correctly, but i did a full reflow of the switch and R15+16  and scrubbed everything with a toothbrush and some cleaner, and now its all fine =) Thanks!



By some weird reason, SW5 is not cauing dropouts either anymore. Can't see the connection, but all well now