QSC Amplifier RMX 2450 - Gain Problem

[Laurens_Hendrickx]

Today I bought 2 second hand QSC amplifiers.
When I tested them at home, they both have kind of the same problem: the gain is full open, no mather how I put the button.
By one amp if i set the gain at zero, the low frequenties are less, but mid and high are at max volume
The other amp gives always all he has, no mather what I do with the gain knob...

Anyone who can help me with this?
(Sorry for my english, but I think you'll understand the problem)

 

[americanaudiophile]

Check that all the dip switches on the rear are set correctly. Here is a link to the manual
http/www.qsc.com/resource-files/productresources/amp/discontinued/rmx/q_amp_rmx_series2ru_usermanual.pdf
If that doens't help it sounds like the amps may have been modified at some point. Since they are not working the same way if you open them up you should see some difference in the way they have been wired. A tech or repairman should be able to put them back to normal. Here is the service manual
http/bmamps.com/Schematics/QSC/QSC_RMX_Service_Manual.pdf