ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 2 [All]   Go Down

Author Topic: QSC amp shutting down  (Read 10832 times)

David A. Parker

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1358
    • http://www.lostandfoundsoundco.com/
QSC amp shutting down
« on: February 26, 2011, 01:02:05 pm »

had a problem last night, 8 ohm monitor rated 225 watts rms, QSC PLX 2402 amp. One monitor on one side of amp, other side of amp open. Drummer's wedge. Drummer wanted kick in his wedge, so I obliged. Drummer was happy with it, but amp would red light and then shut down, cycle, come back on, everything's fine for a while, then it would redlight and shut down again, then back on. Normally I would think it was low voltage, but the other amps were on the same circuit, and none of them had a problem. I know when a voice coil heats up, it changes the impedence, so could this have in some way triggered the shutdowns?
Logged
David Parker
Lost and Found Sound
http://www.lostandfoundsoundco.com/

Ivan Beaver

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 9010
Re: QSC amp shutting down
« Reply #1 on: February 26, 2011, 01:37:13 pm »

David A. Parker wrote on Sat, 26 February 2011 13:02

had a problem last night, 8 ohm monitor rated 225 watts rms, QSC PLX 2402 amp. One monitor on one side of amp, other side of amp open. Drummer's wedge. Drummer wanted kick in his wedge, so I obliged. Drummer was happy with it, but amp would red light and then shut down, cycle, come back on, everything's fine for a while, then it would redlight and shut down again, then back on. Normally I would think it was low voltage, but the other amps were on the same circuit, and none of them had a problem. I know when a voice coil heats up, it changes the impedence, so could this have in some way triggered the shutdowns?

As the voice coil heats up, the impedance rises, and this puts "less" of a strain on the amp-so that would not be your problem.

A couple of thoughts.  Maybe the speaker cable has a problem-like an intermittant short.  That could cause the amp to shut down.

Is the fan working properly? Maybe it was getting hot and is shutting down due to thermal overheating.

Or the amp could have a problem-such as a cracked connection or an intermittant in a component.

Without more testing, it could be anything.
Logged
For every complicated question-there is a simple- easy to understand WRONG answer.

Can I have some more talent in the monitors--PLEASE?

Ivan Beaver
dB Audio & Video Inc.
Danley Sound Labs

David A. Parker

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1358
    • http://www.lostandfoundsoundco.com/
Re: QSC amp shutting down
« Reply #2 on: February 26, 2011, 03:54:19 pm »

yes, I realize it could be anything. Not an easy problem to duplicate in the shop. I don't know where to start. I have another spare amp, but if I just change it out, then I wont know if the amp in question is bad. I was hoping someone had a similar problem. Thanks for the one possibility you extinguished for me.
Logged
David Parker
Lost and Found Sound
http://www.lostandfoundsoundco.com/

John Watson

  • Jr. Member
  • **
  • Offline Offline
  • Posts: 56
Re: QSC amp shutting down
« Reply #3 on: February 26, 2011, 05:10:39 pm »

Did you try swapping channels, cables?
Logged

Scott Smith

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2722
Re: QSC amp shutting down
« Reply #4 on: February 27, 2011, 08:01:03 am »

I still go with voltage drop.  You added kick to the monitor which pushed the channel much harder.  A dynamic peak can cause an equally dynamic dip in voltage faster than you can see, but the amp still sees it.  

I run a bunch of PLX amps, and the only thing that shuts them off for me is voltage dips.  Often though, they do not all react the same, or at the same time.  One channel can go out, while the other remains... or the entire amp can shut down.  I have had amps that were idling shut down while sharing a circuit that was seeing voltage swings from a larger amp.  Give the amps solid voltage, and they perform flawlessly (assuming you don't have a wiring problem).
Logged
"Percussive Maintenance" - Bang on it until it works!
Scott Smith, South Florida - MIXING OLD SCHOOL WITH NEW

David A. Parker

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1358
    • http://www.lostandfoundsoundco.com/
Re: it's the amp
« Reply #5 on: February 27, 2011, 08:14:18 am »

ran the same band last night, I used a different wedge for the drummer, different cable, used the other side of the amp. It did the same thing, shut down after the band played about 45 minutes. I took that monitor, daisy chained it with one of the others on the identical amp right above it in the rack, with the same monitor mix, it ran fine all night. That amp had a 4 ohm load on one side and an 8 ohm load on the other. The one that was going down had an 8ohm load on one side. Even if it is going down due to low voltage, it's tripping too early. I have 3 extra identical amps that are spares.
Logged
David Parker
Lost and Found Sound
http://www.lostandfoundsoundco.com/

Chris Hindle

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1080
Re: it's the amp
« Reply #6 on: February 27, 2011, 09:29:42 am »

It sounds to me that the dust bunnies have taken over the heat sink...
Pull cover, vacuum amp,clean fan, rinse, repeat...
Logged
"Ya, whatever. Just stick a '57 on it, and get off the stage"
Chris.

David A. Parker

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1358
    • http://www.lostandfoundsoundco.com/
Re: it's the amp
« Reply #7 on: February 27, 2011, 09:33:45 am »

Chris Hindle wrote on Sun, 27 February 2011 08:29

It sounds to me that the dust bunnies have taken over the heat sink...
Pull cover, vacuum amp,clean fan, rinse, repeat...


sounds like a plan! I'm sure I need to do all of them.
Logged
David Parker
Lost and Found Sound
http://www.lostandfoundsoundco.com/

Dean Nishizaki

  • Newbie
  • *
  • Offline Offline
  • Posts: 1
Re: QSC amp shutting down
« Reply #8 on: February 27, 2011, 04:40:26 pm »

I had the same problem w/ a 3002 . Sent it in to QSC and they changed the Ribbon . Got it back and it did the same thing again on the 1st Gig . Sent it back and they couldn't find anything wrong w/ it . The Service Guy told me that he will change the Module as all the electronics go thru it . Said the amp will be like new . Not sure if you have a QSC repair shop in your area , but you can get a return form online .
Logged

David A. Parker

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1358
    • http://www.lostandfoundsoundco.com/
Re: QSC amp shutting down
« Reply #9 on: February 27, 2011, 04:55:15 pm »

Dean Nishizaki wrote on Sun, 27 February 2011 15:40

I had the same problem w/ a 3002 . Sent it in to QSC and they changed the Ribbon . Got it back and it did the same thing again on the 1st Gig . Sent it back and they couldn't find anything wrong w/ it . The Service Guy told me that he will change the Module as all the electronics go thru it . Said the amp will be like new . Not sure if you have a QSC repair shop in your area , but you can get a return form online .


ribbon cables are something I was thinking. I have one of the older ones that I had to send back for the mod. This one is newer, but that doesn't mean it couldn't be the ribbon cables still. Wish Bob Lee was still watching this forum.
Logged
David Parker
Lost and Found Sound
http://www.lostandfoundsoundco.com/

Chris Hindle

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1080
Re: it's the amp
« Reply #10 on: February 28, 2011, 08:30:03 am »

David A. Parker wrote on Sun, 27 February 2011 09:33

Chris Hindle wrote on Sun, 27 February 2011 08:29

It sounds to me that the dust bunnies have taken over the heat sink...
Pull cover, vacuum amp,clean fan, rinse, repeat...


sounds like a plan! I'm sure I need to do all of them.


I "do" mine at least once a year. Twice if there is a of of dusty outdoor stuff.
Logged
"Ya, whatever. Just stick a '57 on it, and get off the stage"
Chris.
Pages: 1 2 [All]   Go Up
 

Page created in 0.132 seconds with 16 queries.