Electronics > Repair

Please Help - Alesis MEQ230 graphic eq


Greetings everyone! Im a total newbie here my first post ;D
Id really appreciate some help as i have tried everything i know (very little)..

http://www.alesis.com/meq230 (mines form 1989 i think!)

i have no idea what happened to it, it doesnt turn on. didint get a charger with it.
i takes 9v AC so i modded an ac/dc adapter, made sure i got 9vAC out of it and tried that..no response.

opened it up and took everything apart, no damaged/blackened parts or pads. the caps look OK - completely fresh (looking), flat tops. (

Fed it 9vAC when disassembled and tested the power jack, Its OK and powering the board and components etc.
not sure what to do next! any idead what might need fixing??
i dont own an oscilloscope, just a crappy multimeter but might get access to one.


first thing I would check is the output of the two voltage regulators. The 7912 should output -12v and the 7812 should output +12v. The output pin on both of them is pin 3. Next I would check the relay. Do you hear a click when you turn it on?

Ive fixed loads of Alesis gear over the years and normally when it wont turn on its because the previous owner lost the PSU and tried one that was so incorrect it took out the voltage regulators. Some Alesis is very fussy about the voltage and as such can be a paint to find a universal PSU to work as well as it being run from AC. Also check the diodes as these tend to go as well.

The reasoning a Alesis tech gave me for the AC was based on common mode rejection due to everything in a rack normally being balanced. That being said most things in a outboard rack normally take the 240 or 120 from the wall and deal with dropping and isolation inside the unit. A more feasible reason would of been the need for a positive and negative supply like that used for mixers.

Other things that Ive seen but this is normally on the Quadaverb Miniverb units and off the top of my head cant remember the MEQ230 is that there is normally two big dropper resistors that tend to get hot and go open.

Ill have a better look at the pics and see if anything jumps out at me.


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