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QSC RMX1850HD Channel 1 Low

Printed From: Speakerplans.com
Category: General
Forum Name: Amp Forum
Forum Description: The 'Stopping Jake Fielder moaning constantly' forum description...
URL: https://forum.speakerplans.com/forum_posts.asp?TID=108998
Printed Date: 27 March 2026 at 7:52am
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Topic: QSC RMX1850HD Channel 1 Low
Posted By: richard stringer
Subject: QSC RMX1850HD Channel 1 Low
Date 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.



Replies:
Posted By: njw
Date Posted: 24 March 2025 at 8:47pm
 It could be something simple like a dodgy gain pot, not unknown on the rmx amps.


Posted By: kedwardsleisure
Date 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

North Staffordshire



Posted By: richard stringer
Date 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. 


Posted By: Conanski
Date 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.


Posted By: Randy Bohannon
Date 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? 



Posted By: simonp1100
Date 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 ?.

Thumbs Up




Posted By: richard stringer
Date 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. 


Posted By: richard stringer
Date 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 ?.

Thumbs Up



Channel 2 works fine so at present I have both speaker cabs connected to channel 2.


Posted By: richard stringer
Date 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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