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QSC RMX1850HD Channel 1 Low
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richard stringer View Drop Down
Young Croc
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Points: 830 		Post Options Post Options   Thanks (0) Thanks(0)   Quote richard stringer Quote  Post ReplyReply Direct Link To This Post Topic: QSC RMX1850HD Channel 1 Low
    Posted: 24 March 2025 at 8:29pm
I have a QSC RMX1850HD and channel 1 is so low it's barely audible while channel 2 works normally, is it worth getting the amp repaired or throwing it away and buying a new amp? My speaker cabs are Wharfedale Delta 12 cabs they're 400 watts continuous average power rated I was thinking maybe getting a QSC RMX2450 off Ebay.
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njw View Drop Down
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Points: 2700 		Post Options Post Options   Thanks (0) Thanks(0)   Quote njw Quote  Post ReplyReply Direct Link To This Post Posted: 24 March 2025 at 8:47pm
 It could be something simple like a dodgy gain pot, not unknown on the rmx amps.
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kedwardsleisure View Drop Down
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Points: 5157 		Post Options Post Options   Thanks (0) Thanks(0)   Quote kedwardsleisure Quote  Post ReplyReply Direct Link To This Post Posted: 24 March 2025 at 9:56pm
carefully, and while it's playing, prod around the ribbon cable that connects the pcb to the rear board, they're known to go intermittent. Use an insulated tool, pencil or bit of plastic.
Kevin

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richard stringer View Drop Down
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Points: 830 		Post Options Post Options   Thanks (0) Thanks(0)   Quote richard stringer Quote  Post ReplyReply Direct Link To This Post Posted: 24 March 2025 at 10:27pm
The gain pot does work it does adjust the sound level it's just it's barely audible but it is audible, plus the sound isn't intermnittent it's on all the time it's just very, very low in level. 
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Conanski View Drop Down
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Points: 2757 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 25 March 2025 at 11:34pm
Exercise all the dip switches on the rear panel and make sure they are set correctly for the way you are using the amp... which I'm guessing is normal stereo.
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Randy Bohannon View Drop Down
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Points: 121 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Randy Bohannon Quote  Post ReplyReply Direct Link To This Post Posted: 26 March 2025 at 7:11am
these amps are effector cap coupled so it is just possible that If the outputs have blown the drivers are left effectively powering the load and so the amp produces audio but very quietly. 

Just a theory, based on experience fixing old vintage cap-coupled amplifiers. 

With it off and the caps discharged, can you test the outputs on that channel with a multimeter? 
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simonp1100 View Drop Down
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Points: 1150 		Post Options Post Options   Thanks (0) Thanks(0)   Quote simonp1100 Quote  Post ReplyReply Direct Link To This Post Posted: 26 March 2025 at 7:42am
Have you tried swapping the inputs to the amplifiers ?.
Are you using balanced or unbalance signals for the inputs ?.
The gain pot could also have gone high resistance ?.

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Edited by simonp1100 - 26 March 2025 at 7:44am
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richard stringer View Drop Down
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Points: 830 		Post Options Post Options   Thanks (0) Thanks(0)   Quote richard stringer Quote  Post ReplyReply Direct Link To This Post Posted: 26 March 2025 at 9:58am
Yeah there is audio but very, very quiet on channel one. Do you guys know anyone technically qualified to repair it based in Lincolnshire where I live? I don't have a car so can't take it anywhere far away to get it repaired. 
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richard stringer View Drop Down
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Points: 830 		Post Options Post Options   Thanks (0) Thanks(0)   Quote richard stringer Quote  Post ReplyReply Direct Link To This Post Posted: 26 March 2025 at 9:59am
Originally posted by simonp1100 simonp1100 wrote:

Have you tried swapping the inputs to the amplifiers ?.
Are you using balanced or unbalance signals for the inputs ?.
The gain pot could also have gone high resistance ?.

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Channel 2 works fine so at present I have both speaker cabs connected to channel 2.
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richard stringer View Drop Down
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Points: 830 		Post Options Post Options   Thanks (0) Thanks(0)   Quote richard stringer Quote  Post ReplyReply Direct Link To This Post Posted: 26 March 2025 at 9:59am
Originally posted by Conanski Conanski wrote:

Exercise all the dip switches on the rear panel and make sure they are set correctly for the way you are using the amp... which I'm guessing is normal stereo.

All the dip switches are in their correct positions.
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