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possible qsc rmx amp problem

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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=107027
Printed Date: 28 March 2024 at 11:03pm
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Topic: possible qsc rmx amp problem
Posted By: zigzagwanderer
Subject: possible qsc rmx amp problem
Date Posted: 19 April 2022 at 8:34pm
just bought 2x QSC RMX 4050 amps - the clip light on one channel of one of the amps doesn't illuminate on switch on, nor does it illuminate when i try to drive it into clip. the channel's audio appears to be fine, 

we switched the channel connectors over to test the clip LEDs and both have worked so its not the LED itself.
anyone know what this could be?



Replies:
Posted By: Conanski
Date Posted: 19 April 2022 at 10:10pm
Did you check and then cycle the dip switches on the back even if they looked like they were set correctly?


Posted By: zigzagwanderer
Date Posted: 20 April 2022 at 12:16am
Ok... 3 hours later, figured it out...
Was a faulty connector cable between the main boards and the pcb with the pots and LEDs.



Posted By: Line Array
Date Posted: 20 April 2022 at 8:38am
Originally posted by zigzagwanderer zigzagwanderer wrote:

Ok... 3 hours later, figured it out...
Was a faulty connector cable between the main boards and the pcb with the pots and LEDs.


ironic because QSC amps don't use a lot of ribbon cables, connectors etc.

seems prudent to look for amps that only use the bare minimum number of internal cables, connectors etc.

my old QSC PLX is failing at the volume knob pots which sound kind of rusty with sound occasionally dropping out until you fiddle with them a little - those are something i would avoid too if possible.  if it's possible to have volume control entirely in the digital domain or at least without any kind of physical contacts that can go bad.

basically eliminate as many contacts as possible.

what are the most failure prone components in an amp ?

it's probably contacts followed by capacitors and power devices only when overdriven or under-cooled.

does that sound about right ?  

what makes an amp reliable ?


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https://dissidentsound.discoursehosting.net


Posted By: RoadRunnersDust
Date Posted: 21 April 2022 at 3:21pm
Originally posted by Line Array Line Array wrote:

QSC amps don't use a lot of ribbon cables, connectors etc.


But when they do they are utter poo (reference the 1st generation PLX series)

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www.guildfordcablecompany.co.uk" rel="nofollow - www.guildfordcablecompany.co.uk


Posted By: zigzagwanderer
Date Posted: 23 April 2022 at 12:49pm
ok , further to my previous post 
I botched the faulty cable to check it worked ok and I now need a replacement cable 
I think I need a 6 pin female to female JST cable approx 100mm long , the pins are 2.5mm centres.
I've looked everywhere I can think of and can't find a suitable cable available in the UK anywhere 
If possible I'd prefer not to have to make it up and have to buy a crimping tool etc  
Anyone know where I can source one , the proper QSC one would be nice but I'm not overly fussed as long as its ok quality  


Posted By: RoadRunnersDust
Date Posted: 23 April 2022 at 1:13pm
Could you just solder wires onto the pins? (You can usually pull the plastic housing off the PCB leaving the pins like solder turrets)

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www.guildfordcablecompany.co.uk" rel="nofollow - www.guildfordcablecompany.co.uk


Posted By: zigzagwanderer
Date Posted: 23 April 2022 at 1:28pm
Originally posted by RoadRunnersDust RoadRunnersDust wrote:

Could you just solder wires onto the pins? (You can usually pull the plastic housing off the PCB leaving the pins like solder turrets)

Fare point but that would make servicing the pots etc at a later date more difficult as Id have to unsolder the wires to be able to remove the the pcb with the pots on 




Posted By: simonp1100
Date Posted: 23 April 2022 at 1:58pm
Originally posted by zigzagwanderer zigzagwanderer wrote:

ok , further to my previous post 
I botched the faulty cable to check it worked ok and I now need a replacement cable 
I think I need a 6 pin female to female JST cable approx 100mm long , the pins are 2.5mm centres.
I've looked everywhere I can think of and can't find a suitable cable available in the UK anywhere 
If possible I'd prefer not to have to make it up and have to buy a crimping tool etc  
Anyone know where I can source one , the proper QSC one would be nice but I'm not overly fussed as long as its ok quality  

Found this within 5 minute search:

http://https://www.ebay.co.uk/itm/183273982429?hash=item2aabfb09dd:g:M5MAAOSwujBZx6Ds" rel="nofollow - https://www.ebay.co.uk/itm/183273982429?hash=item2aabfb09dd:g:M5MAAOSwujBZx6Ds

WinkWinkLOL


Posted By: RoadRunnersDust
Date Posted: 23 April 2022 at 2:04pm
Pots on an RMX? You mean there’s something else to do with them other than short the wiper to the input? LOL

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www.guildfordcablecompany.co.uk" rel="nofollow - www.guildfordcablecompany.co.uk


Posted By: zigzagwanderer
Date Posted: 23 April 2022 at 2:35pm
Originally posted by simonp1100 simonp1100 wrote:

Originally posted by zigzagwanderer zigzagwanderer wrote:

ok , further to my previous post 
I botched the faulty cable to check it worked ok and I now need a replacement cable 
I think I need a 6 pin female to female JST cable approx 100mm long , the pins are 2.5mm centres.
I've looked everywhere I can think of and can't find a suitable cable available in the UK anywhere 
If possible I'd prefer not to have to make it up and have to buy a crimping tool etc  
Anyone know where I can source one , the proper QSC one would be nice but I'm not overly fussed as long as its ok quality  

Found this within 5 minute search:

http://https://www.ebay.co.uk/itm/183273982429?hash=item2aabfb09dd:g:M5MAAOSwujBZx6Ds" rel="nofollow - https://www.ebay.co.uk/itm/183273982429?hash=item2aabfb09dd:g:M5MAAOSwujBZx6Ds

WinkWinkLOL

Now why couldn't I find that Confused
Thank you 


Posted By: Line Array
Date Posted: 23 April 2022 at 7:23pm
my PLX pots are not doing too well ...

could you put in an on/off switch in place of them rather than shorting ?

to act as a mute button ?

or would the transient be too loud ?

also do all pots suffer this fate or not ?

the pot on my Benchmark DAC ( a home / studio product ) is only faring slightly better than the QSC one - they're both about 15 years old ... Benchmark is considered very high quality yet still has this problem

i wonder if there are some known ways to adjust volume that aren't so problematic.  i don't mean to revive my PLX but for future purchases.

for example if you control the volume digitally - will you lose bits of resolution ?  or is it irrelevant with 24 bits having more resolution than amp has noise floor ?


-------------
best place on the internet >>>

https://dissidentsound.discoursehosting.net


Posted By: RoadRunnersDust
Date Posted: 23 April 2022 at 8:36pm
If you short the wiper to the input leg then the pot still acts like a soft mute switch if you wind it all the way off

Conductive plastic pots don’t suffer this age related fate (unless they literally get worn out from use) as the issue is the carbon tracks of the pots corroding, I always replace carbon track for conductive plastic whenever I’m repairing kit, guitars, etc.


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www.guildfordcablecompany.co.uk" rel="nofollow - www.guildfordcablecompany.co.uk


Posted By: Line Array
Date Posted: 24 April 2022 at 9:43am
that's really interesting !

-------------
best place on the internet >>>

https://dissidentsound.discoursehosting.net


Posted By: kedwardsleisure
Date Posted: 24 April 2022 at 6:52pm
just stick new pots in and away you go. You can buy them anywhere.

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Kevin

North Staffordshire



Posted By: mitchiemasha
Date Posted: 18 July 2022 at 11:53am
Where can we get the right pots at a good price? Upgraded quality for QSC. Who and what do people recommend?

Thank you


Posted By: Earplug
Date Posted: 18 July 2022 at 12:49pm
Originally posted by mitchiemasha mitchiemasha wrote:

Where can we get the right pots at a good price? Upgraded quality for QSC. Who and what do people recommend?s

Thank you


What size & value are they? I have some very nice "vintage" pots here surplus from a Soundtracs desk refurbishment!   LOL LOL LOL

Otherwise - I wouldn't worry too much about it. 99% of the pots on the market now come from Shenzhen!  Embarrassed




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Earplugs Are For Wimps!


Posted By: RoadRunnersDust
Date Posted: 18 July 2022 at 1:21pm
https://cpc.farnell.com/w/c/electronic-electrical-components/resistors/potentiometers-trimmers-accessories/rotary-potentiometers?product-range=p160%20" rel="nofollow - https://cpc.farnell.com/w/c/electronic-electrical-components/resistors/potentiometers-trimmers-accessories/rotary-potentiometers?product-range=p160

you just need to choose the right value and taper

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www.guildfordcablecompany.co.uk" rel="nofollow - www.guildfordcablecompany.co.uk


Posted By: APW
Date Posted: 18 July 2022 at 4:13pm

The correct pot for the plx2 range is a 4 pin pcb mounted 5k pot, QSC part number PT-250002-00

 

…. For older models it’s a 10k pot part number PT-310000-CR



Posted By: mitchiemasha
Date Posted: 19 July 2022 at 12:30am
Delete please


Posted By: mitchiemasha
Date Posted: 19 July 2022 at 12:31am
Originally posted by APW APW wrote:

The correct pot for the plx2 range is a 4 pin pcb mounted 5k pot, QSC part number PT-250002-00


How about QSC RMX? 

Thank you


Posted By: APW
Date Posted: 19 July 2022 at 8:49am
https://parts.qsc.com/amplifiers" rel="nofollow - https://parts.qsc.com/amplifiers

select the exact model from the dropdowns and it'll give you the part number.



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