Channel 2 active eq not working.

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jdgebha
Bottle Rocket
Posts: 20
Joined: Mon Dec 09, 2013 1:55 pm

Channel 2 active eq not working.

Post by jdgebha » Sun Jul 15, 2018 1:20 pm

Channel 2 Active eq not working with either preset or sliders and neither fs or on mode. Channel 1 and 3 are fine. Diode or relay?

jdgebha
Bottle Rocket
Posts: 20
Joined: Mon Dec 09, 2013 1:55 pm

Re: Channel 2 active eq not working.

Post by jdgebha » Sun Jul 15, 2018 4:53 pm

I should also add that the panel and sound have been cutting out randomly. I did it like 5 times today and after that the active eq on channel 1 stopped working.

bandit2013
Triple Recto
Posts: 3105
Joined: Fri Feb 22, 2013 7:31 am
Location: North Carolina

Re: Channel 2 active eq not working.

Post by bandit2013 » Sun Aug 12, 2018 8:55 am

You can try a few things first, disconnect the footswitch cable and set the selector knob on the back to channel in question. See if the toggle switch on the front panel works or does not. It could be as easy as a cable issue with the footswitch control. However, with the footswitch disconnected and you still have issues, this would be the time to call Mesa Tech service.

The 5BGEQ is a complex circuit that involves relays, JFETS, and some additional control logic not found on the general schematic, and obviously the tuned circuits for the various frequency ranges. The Inductors are located on the Main board as are many of the parts except for the toggle switch controls and sliders, etc.... There is no hard bypass for the 5BGEQ circuit. So when it is turned off, the main differential amplifier is still in operation and uses a chain of resistor networks to feed the differential circuit. If you had the chassis out of the shell for what ever reason, you may have loosened up one of the ribbon cables, damaged a wire on the toggle switch, really hard to say what is the issue. Re-seating the cables may correct the issue. However this is not an invitation for you to open up the chassis if you never did this before or do not have experience working with high voltage circuits that will remain live after the mains is disconnected. Leave this diagnosis and or repair if needed to a certified Tech. Do not attempt to repair this amp on your own. If you want your warranty to remain intact, you mush have all work done by Mesa or through their certified repair locaitons.

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