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QSC RMX 5050 Failure

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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=75263
Printed Date: 29 March 2024 at 8:30am
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Topic: QSC RMX 5050 Failure
Posted By: taurusty
Subject: QSC RMX 5050 Failure
Date Posted: 15 January 2013 at 12:01am
See pics attached.
Appears a Channel 2 output stage cap (63V 12000uf) burst & being on the underside pushed the pcb up to the metal divider. Resultant short/fire took out 20 devices
6x 2SA1987
6x 2SC5359
4x IRF 1407
4x MUR 1540
 
Can't seem to locate that last on the island so may have to buy the board w all devices.
Reading up on the net has now revealed myriad cap issues w various RMX models.
 
Ah well, if it comes to the worst can always use it for parts!
 



Replies:
Posted By: luton_soundman
Date Posted: 15 January 2013 at 1:42am
just out of interest what was the amp playing and driving before it happend?


Posted By: levyte357-
Date Posted: 15 January 2013 at 1:56am
Smoothing caps always need monitoring/regular service on older big iron amps.

Especially CA18/JBL MPX1200.


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Global Depopulation - Alive and Killing.


Posted By: taurusty
Date Posted: 15 January 2013 at 2:07pm
Luton: 7 5050's. 4 ea with 1 JBL SRX 725F on each channel crossed at 100Hz.
The other 3 ea have an SRX 728S on a channel plaing 40 - 100hz.
This one was on a 725 & took the 2 15's in the box with it when it went. Strangely the horn was unaffected which I attribute to to DC blocking caps in the internal xover.
 
Lev: Frankly don't see what servicing you can give a cap. It either works or not.  If you're lucky to catch it as it starts to bulge, well....
 
Now have a decision to make re the remaining siz: Do I change out 6x24 caps proactively?


Posted By: levyte357-
Date Posted: 15 January 2013 at 2:13pm
Originally posted by taurusty taurusty wrote:

 
Lev: Frankly don't see what servicing you can give a cap. It either works or not.  If you're lucky to catch it as it starts to bulge, well....
 
Now have a decision to make re the remaining siz: Do I change out 6x24 caps proactively?


Basically when you buy the amp, and every few gigs, you pass amp to engineer to service and check smoothing caps, for bulging/leaking.


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Global Depopulation - Alive and Killing.


Posted By: mattd
Date Posted: 15 January 2013 at 9:40pm
Originally posted by levyte357- levyte357- wrote:

Originally posted by taurusty taurusty wrote:

 
Lev: Frankly don't see what servicing you can give a cap. It either works or not.  If you're lucky to catch it as it starts to bulge, well....
 
Now have a decision to make re the remaining siz: Do I change out 6x24 caps proactively?


Basically when you buy the amp, and every few gigs, you pass amp to engineer to service and check smoothing caps, for bulging/leaking.

Every few gigs? you must be joking! just replace them when they go and have a yearly service surely??


Posted By: levyte357-
Date Posted: 15 January 2013 at 10:03pm
Originally posted by mattd mattd wrote:

Originally posted by levyte357- levyte357- wrote:

Originally posted by taurusty taurusty wrote:

 
Lev: Frankly don't see what servicing you can give a cap. It either works or not.  If you're lucky to catch it as it starts to bulge, well....
 
Now have a decision to make re the remaining siz: Do I change out 6x24 caps proactively?


Basically when you buy the amp, and every few gigs, you pass amp to engineer to service and check smoothing caps, for bulging/leaking.

Every few gigs? you must be joking! just replace them when they go and have a yearly service surely??


Might not be convenient for the 500 ppl at gig, if you wait for them to go. LOL


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Global Depopulation - Alive and Killing.


Posted By: odc04r
Date Posted: 15 January 2013 at 11:17pm
Bulging caps are not that much of a problem in reality unless you are using 2 decade old amps or designs with cheap components.

I'd say a service every few years depending on how hard the life of the kit is and how full of dust it gets is perfectly adequate. And I wouldn't expect to have to replace the smoothing caps more than every decade or so.


Posted By: Elliot Thompson
Date Posted: 16 January 2013 at 11:29am

Originally posted by taurusty taurusty wrote:


Can't seem to locate that last on the island so may have to buy the board w all devices.


You should contact QSC and order the parts. There may even be an authorised repair centre in Jamaica in which you can purchase the part from. The amplifier may be still under warranty from QSC pending on when you purchased the amplifier.

Best Regards,

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Elliot Thompson


Posted By: taurusty
Date Posted: 16 January 2013 at 4:02pm
No auth dealer here.
Plus w what I have read about QSC &  Chinese manufacture/components definitely sourcing quality devices elsewhere. I got everything except the MUR devices.
This amp is less than 3 years old BTW...


Posted By: APW
Date Posted: 16 January 2013 at 4:34pm
Originally posted by taurusty taurusty wrote:

No auth dealer here.
.
.
.
This amp is less than 3 years old BTW...


You're amp is still under warranty,

The official QSC distributor for Jamaica is: -
AV Technology Panama Corp.
Edificio Met 1 piso 8
Calle 74 San Francisco
Panama City
Bahamas

sales@avtechnologypa.com


Posted By: Elliot Thompson
Date Posted: 16 January 2013 at 8:07pm
Whether your QSC is made in China or the United States, QSC will honour a valid warranty. So it would be a matter of sending the amplifier to the authorised service centre and your RMX 5050 would be fixed free of charge.

However, if you opened up the amplifier and began unsoldering parts, while the amplifier was still under warranty, chances are, you voided the warranty.

Best Regards,

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Elliot Thompson


Posted By: djkeet
Date Posted: 16 January 2013 at 11:23pm
This is sounding like a design flaw in the power supply stage under powered/inferior caps and like anything in life this puts pressure on other things give it a couple more years we might hear more cases like this
NB.my simplistic analysis

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Soundbite


Posted By: levyte357-
Date Posted: 17 January 2013 at 2:22am
May also have been a case of cheap, bodged repair by previous owner.

This is why I say, if buying used amp to keep, get it checked and serviced the day you buy it.

Numerous 4050HDs have passed thru my hands, and none have ever developed that problem.




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Global Depopulation - Alive and Killing.


Posted By: taurusty
Date Posted: 17 January 2013 at 5:40am
Ahhm, this is one of six amps bought brand new. 
I added the seventh (also brand new) on the 29th of December last.
 
Yes Elliott, I suppose the warranty is voided.
Have lost faith in the brand neways...!


Posted By: levyte357-
Date Posted: 17 January 2013 at 10:06am
Originally posted by taurusty taurusty wrote:

Have lost faith in the brand neways...!


To be honest, I know 5050s & 4050s are used as 4 ohm stereo sub amps in JA a lot, never understood this.

IMHO, neither suitable for this, unless using 400Wrms drivers.

IIRC, aren't the transformers rated at something silly like 800VA each or something?




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Global Depopulation - Alive and Killing.


Posted By: taurusty
Date Posted: 17 January 2013 at 1:36pm
Agreed.
Most use it 2 ohm stereo. they recognise that it sounds way different from an MXa but i guess it's the cheapest brand amp available here.
 
There's a thread on here where I even saw  one culprit using it on dual T18 hybrids 1 ohm one side for 3 years w/o a problem!
 
Dunno the xformer rating, cking the scematics...


Posted By: kedwardsleisure
Date Posted: 22 January 2013 at 10:57pm
I am always changing caps in QSC amps. It doesn't matter whether it is a chinese RMX with chinese capacitors or an american MX with american capacitors, they eventually bulge and sometimes leak & flash over. Electrolytics have a limited lifespan and some amps run them harder than others.


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Kevin

North Staffordshire



Posted By: levyte357-
Date Posted: 22 January 2013 at 11:11pm
Originally posted by kedwardsleisure kedwardsleisure wrote:

I am always changing caps in QSC amps. It doesn't matter whether it is a chinese RMX with chinese capacitors or an american MX with american capacitors, they eventually bulge and sometimes leak & flash over. Electrolytics have a limited lifespan and some amps run them harder than others.


Would lower rated transformers, place extra strain on the smoothing ?

Sure the transformers in 4050HD, are not same spec as those in Macrotech MA2400.


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Global Depopulation - Alive and Killing.


Posted By: Muckerbarnes1
Date Posted: 23 January 2013 at 1:35am
Lev, the rating of the TX and caps in PSU are very relevant. Some VERY old amps with bolt on high ripple caps are still working fine.
 
If the TX is lower VA rated and the TX o/p voltage falls the ripple current across the cap may increase. Caps work harder and fail.
 
If the TX is the same voltage and insufficient VA the same may apply as the TX saturates and voltage falls. Caps fail again.
 
Big TX. Big caps. Job done.  It's all relevant with 50Hz psu. Different with SMPS, but still not cured or perfect.
 
I have amps here near 30 years old with perfect caps that have been thrashed for years, so there you have it. Caps are very important, as is TX.
 
Yes smaller VA rated TX would put extra strain on smoothing caps, less strain on high capacity Hi ripple caps. i.e. expensive ones, which are more capable.
 
Much the same scenario really.  You pay for what you get.. Smile


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Billy Dawg.


Posted By: Dub Specialist
Date Posted: 23 January 2013 at 1:54am
thats explains it then mucker that why thay use these beasts then.




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treat all creation with respect. For music is sound...sound is vibration...vibration is energy... and energy begets life. Therein lies my passion! MUSIC IS LIFE


Posted By: Muckerbarnes1
Date Posted: 23 January 2013 at 2:17am
Oooo.. Class sub busters... no probs with caps there, even when a zillion years old prototype.
 
Enjoy that Jayson. One come back last month from 1992 for the first time....
 
Billy dawg likes this baby 1500 VA one.
 
 
 


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Billy Dawg.


Posted By: service dept Steve
Date Posted: 23 January 2013 at 9:28am
In the interest of fairness to QSC I should point out that there are certain failure modes on class H and G amps that reverse bias the capacitors, there are also failure modes which double the supply voltage to them, in both cases it simply involves failure of the cascode diode and/or one or more switching fets, reverse bias any capacitor and it will pass into history, so it may have been the end result of a chain reaction that damaged the cap, add to that the fact that simply shorting a cap to the ironwork or even missing it out of circuit shouldn't cause that kind of damage.


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We are not "They", We are "The others" http://www.servicedept.co.uk" rel="nofollow - http://www.servicedept.co.uk -



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