Loudspeakers Amp in Protect Mode?

[MrsMcG]

Howdy! First post!
Drama teacher with a show in tech (100 middle schoolers!!!) on Monday, just found our QSC Powerlight 1.0 (1000W) amp in Protect Mode. No sound coming thru to speakers, board picking up fine...

Are we up a tree or a creek?

How would I figure out if another amp that is a 500W amp would work with our system? Where do I begin fixing this mess?

Thanks for any and all help.

 

[mbenonis]

Have you tried turning it on and off...that's the first thing I can think of. The manual's pretty useless, and unfortunately they charge for the service manual, so I'm not sure what to suggest other than that. You're sure that nothing changed (i.e., a speaker connection shorted out, etc?)

 

[Dionysus]

The amp in protect mode may indeed have nothing to do with the amp itself.
Try unhooking the speaker lines and starting it up again. Does it still go into protect?? If so has the power source changed? (Test it)...
This way you can narrow down the problem.

If it is the amp, and you are talking about using a 500w instead of a 1000w, that is literally half the potential power.
There is math that could be done to see if you really need the 1000w or if 500w would do, but I'd think whoever installed it in the first place would of installed the proper amp for the job.

 

[MrsMcG]

No knowledge of anything else shorting, or any power interruption/surge/whatever...
I found the manual online, and was very frustrated by how little actual info was there!

We turned it on and off... nada. I've been there ten years and this has never happened.

I am so frustrated I don't know what to do - I have no TD, and no time to handle the problem.

 

[MrsMcG]

I'm going to try what you've suggested in the AM.

I just happen to have access to the 500 - it's certainly not a long term solution - we're just hoping that whoever installed this overplanned, as it were, which wouldn't shock me.

We're also hoping that it was an overheating issue that might resolve itself after cooling down overnight it might magically be OK- there's a heating problem in the theatre, going on for months, and someone else left the amp on for days/ weeks, not sure which!

 

[lieperjp]

I've had this happen to one of my amps before. It turned out to be a bad power supply or something like that - we had to take it in to the shop to get it fixed. I don't remember if it was expensive or not. If you've done all you can do - don't open the amp if you don't know what you are doing. See if you can find someone to come in and test it, or take it in to your local, qualified repair shop.

 

[museav]

The usual caution here, but something caused the amp to go into protect mode and until you can verify that it is an internal problem specific to that amplifier then replacing it with another amp is potentially going to give the same result.

Can you tell us how the speakers are wired and the mode switch setting on the back of the amplifier? Have you verified that you do not have a bad speaker and that the amp is not trying to drive a short or an open?

 

[DLaudio]

I would suggest turning it off, then remove the speaker cables/jacks/speakons and repower the amp, did it go back into Protect or recover and start normally, If so you could have something as simple as a shorted speaker cable and you can buy a new one at most Music stores, Check for Obvoious broken jacks, loose or touching jacks...
Just because a speaker cable LOOKS good doesnt mean it is good, Buy a new one and try it. If that doesnt fix it Remove the XLR Cable from the amp and try switching channels from A to B to see if its both sides of the amp in protect mode, it could need cleaning, Is it full of dust, take a vacuum cleaner and clean the dust off the vents and the fan, Is the fan turning when you turn the amp on, it should run for a short time and then go off until its needed, AFTER all these things if its still not working I suggest trying the other amp, LABEL the wiring as to whats speakers etc....you might try and find a music store or Sound contractor who would be willing to come out and test it to see whats wrong

 

[rwhealey]

It could be a short circuit in the speaker cable. Could also be a overheating problem.

Give QSC a call. I hear they have really great support. Here's the contact info:

QSC Audio Products
Technical Services
1675 MacArthur Blvd
Costa Mesa, CA 92626 USA
Tel. 800-772-2834 (USA only)

The 500 watt will work temporarily -- you can't damage a speaker by underpowering it UNLESS you clip the smaller amp in an attempt to get the volume the bigger one provided. Just watch for clipping and you'll be fine.

 

[MrsMcG]

Hey all - we unhooked all cables and powered up the 1000W today - still in Protect mode.
The 550W worked like a charm - seems we had way more power than we needed for a 300 seat space with the 1000.

Going into tech week now, with the smaller amp - the 1000W is going in for service NEXT week!

Thank you all for your help - I'm so glad I found this resource!

 

[OTO1702]

Hi

I have the same issue with one of my QSC's amps. Well it can be amix of several issues.
One of the issues is permanent heat, After a while, the connection get loose and then you experience some partial discharges.

The other issue I found is a cracked potentiometer, 18K, with was Open circuit. no more resistance value.

Is the protect indication is on both channels ?

Oto