Film-Tech Forum ARCHIVE: ''Load Fault'' light on DCM10D

my profile | my password | search | faq & rules | forum home

»	Film-Tech Forum ARCHIVE » Operations » Digital Cinema Forum » ''Load Fault'' light on DCM10D (Page 1)

This topic comprises 2 pages: 1 2

Author

Topic: ''Load Fault'' light on DCM10D

Anhtu Vu
Film Handler

Posts: 98
From: Montreal, Quebec, Canada
Registered: Jun 2013

posted 09-04-2013 08:38 PM

We just installed a new QSC system:

DCM10D
3 x SC423C
2 x SB5218
12 x SR8200
3 x DCA1622
1 x DCA3422
1 x DCA1824

So basically it's CP650/DMA8+ into DCM10D to amps and monitors.

Sometimes the ''Load Default'' light turns on for a split second before going off. It happens intermittently. Anyone knows what this means ??? Should i worry about it ???

On a side note, any QSC cinema experts in Montreal ??

Thx

| IP: Logged

Tony Bandiera Jr
Film God

Posts: 3067
From: Moreland Idaho
Registered: Apr 2004

posted 09-04-2013 11:22 PM

HI Anthu:

No, that "Load Fault" light is nothing to worry about...unless it stays on all the time. The software for that indicator is buggy..at low to moderate sound output levels it will frequently come on for no real reason.

If it DOES stay on for more than a few minutes, press and HOLD the "AMPS/PROC" button....the channel(s) with the fault will have a blinking yellow light in the AMPS row.

A fault can be anything from a short in the wiring to a blown speaker to a bad amplifier.

Another flaw with the monitor I found: If you shut down the amps you can still hear the sound through the monitor.....so be careful.

The DCM's are excellent monitors overall (and the DSP and crossovers are pretty good and versatile) but as a diagnostic tool for monitoring it gets a D- for the flaws I mentioned.

Sam from QSC pops in here every so often, and I have mentioned those issues to him..supposedly there was going to be an update to the firmware to address the Load fault and monitoring issues.

| IP: Logged

Anhtu Vu
Film Handler

Posts: 98
From: Montreal, Quebec, Canada
Registered: Jun 2013

posted 09-04-2013 11:47 PM

quote: Tony Bandiera Jr
No, that "Load Fault" light is nothing to worry about...unless it stays on all the time. The software for that indicator is buggy..at low to moderate sound output levels it will frequently come on for no real reason.

If it DOES stay on for more than a few minutes, press and HOLD the "AMPS/PROC" button....the channel(s) with the fault will have a blinking yellow light in the AMPS row.

A fault can be anything from a short in the wiring to a blown speaker to a bad amplifier.

Another flaw with the monitor I found: If you shut down the amps you can still hear the sound through the monitor.....so be careful.

The DCM's are excellent monitors overall (and the DSP and crossovers are pretty good and versatile) but as a diagnostic tool for monitoring it gets a D- for the flaws I mentioned.

Sam from QSC pops in here every so often, and I have mentioned those issues to him..supposedly there was going to be an update to the firmware to address the Load fault and monitoring issues.

Thanks a lot Tony. It's reassuring that i should not worry since, as you suggested, it's a bug. In my case the light does never stay on for more than 2-3 seconds.

How can you still hear sound through the monitors once the amps are shut down ?? This seems like a pretty serious bug!!!

Anyways, I just calibrated the system, using the QSC's software, and it sounds very good, still needs a bit more tweaking though.... in general, i find them a tad harsh in the high end.

Btw, while calibrating the levels in our room, i need to lower the output of the amps. Would you suggest doing it on the amps or leave all knobs at full and lower it in the software. I guess it should boil down to the same right ? My tech suggested the latter in case we need to swap out a bad amp, this way we don't need to remember where the knobs were set at.

Do you have Sam's (from QSC) last name and contact info ??

Thanks again

| IP: Logged

Clint Koch
Phenomenal Film Handler

Posts: 1435
From: San Luis Obispo, CA, USA
Registered: Feb 2002

posted 09-05-2013 12:31 PM

+1 (800) 854-4079
Sam Hynds

| IP: Logged

Carsten Kurz
Film God

Posts: 4340
From: Cologne, NRW, Germany
Registered: Aug 2009

posted 09-05-2013 03:13 PM

If you don't know the specifics of the output stage, I would usually not pull up the amps completely, but rather prefer to have the processor at around unity gain (or whatever applies) and not reduce level before the amps. Marking is no big thing.

- Carsten

| IP: Logged

Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 09-06-2013 01:18 AM

The QSC DCM products depend on all amps at full. A nasty design trait of the dataport input of the amplifiers is that they put series resistors in line to force one to turn the signal up on the crossover. I've seen numerous DCMs clip out before the amplifiers...it can be quite frustrating. I can't express enough how much I HATE the design. I've never had an issue in the Basis stuff working with the Dataports...just the DCMs.

So, if you are using a DCM...turn the amps up all of the way. If you have any odd channels on an amp without any speakers...say Center on channel 1 but nothing on channel 2...then be sure to turn channel 2 DOWN all of the way or you'll get a load fault there.

On the surrounds...pay attention the series/parallel thing in the set up of the monitor. You always start with 1 of each. So...if you have two surrounds that are paralleled together...that would be 1-series and 2-parallel. If you don't get that right...you could get a load fault.

Make sure all of the impedances for your designated speakers are correct too. When in doubt...measure them yourself.

| IP: Logged

Marco Giustini
Film God

Posts: 2713
From: Reading, UK
Registered: Nov 2007

posted 09-06-2013 11:44 AM

Steve,

I've noticed that problem numerous times. Why QSC would design such a feature on purpose?

| IP: Logged

Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 09-06-2013 05:21 PM

I don't know but I've been VERY vocal to them about my displeasure about the dataport design. One thing I've noted with QSC...their gain structure is all over the place and they don't do much to manage it. When you combine that with the lack of tools to be able to set it up yourself, you get one piece clipping before another.

| IP: Logged

Marco Giustini
Film God

Posts: 2713
From: Reading, UK
Registered: Nov 2007

posted 09-06-2013 05:23 PM

I've struggled in the past to avoid clipping at the DCM. I thought they'd have solved the issue with the new DCM 10/20/30 but it does not look so and the DCP series also seems to follow the same criteria.

| IP: Logged

Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 09-07-2013 08:23 AM

I've put in a handful of DCP300s now. Thus far, while there are gain structure issues I've yet to have it clip out before the amps. One has to really watch themselves on the input side to get everything right. QSC gets so many things right in their upper-end DCP stuff like the Basis and now Q-Sys...but on the cinema DCP solutions...it just makes me scratch my head on how some of it makes it to production the way it is.

One thing I have also done is just skip the Data port crap and wire straight to the Phoenix connector. You can run the monitor lines to the Dataport if you want the load sensing or possibly the "Amps On" feature but if you skip the dataport, you'll not have gain structure issues anymore. Set your inputs right and you'll have plenty of gain...then use the amps inputs (as one should) to get the gain structure on the output right...you'll never clip the DSP that way.

I might just make a board that allows one to use the data port cables but breaks out the audio lines to feed the amps via the Phoenix connectors. It wouldn't be too hard and it would eliminate this annoyance.

| IP: Logged

Marco Giustini
Film God

Posts: 2713
From: Reading, UK
Registered: Nov 2007

posted 09-07-2013 01:52 PM

That's a great idea, thanks.

So you're saying that the resistors are on the dataport inputs of the amps?

DCA and ISA amps do have gains on the back or protected on the front, it is easy and safe to adjust the levels on the amps themselves. Amps are also quite reliable, the replacement issue is so rare that I'd rather have the proper gain structure.

Thanks again
Marco

| IP: Logged

Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 09-07-2013 02:43 PM

Yes, the resistors are on the amplifiers.

| IP: Logged

Marco Giustini
Film God

Posts: 2713
From: Reading, UK
Registered: Nov 2007

posted 09-07-2013 06:23 PM

Thanks. That helps quite a lot.

| IP: Logged

Anhtu Vu
Film Handler

Posts: 98
From: Montreal, Quebec, Canada
Registered: Jun 2013

posted 09-10-2013 07:43 PM

I finally got a chance to talk to Sam @ QSC. Hopefully, he can drop by to answer some of your questions.

Basically, he suggested to wire all surrounds in parallel, no need for series-parallel. He also explained the reason why the data port was design that way.

Anyways, I rechecked my set up and everything was done up to specs for the exception of one loose wire on one of the surround. Hopefully the load fault was caused by that.

So far, aside from the ''load fault'' coming on once in a while, i've never experienced clipping from the DCM and the system sounds great after further adjustment.

| IP: Logged

Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 09-11-2013 06:24 AM

With respect to the dataport wiring (series resistors)...he is just putting lipstick on a pig...it was a bad design, period. The number of clipping systems (easily proven) goes to prove it. It, without a doubt, raises the noise level of the system too.

| IP: Logged

All times are Central (GMT -6:00)

This topic comprises 2 pages: 1 2

Printer-friendly view of this topic

The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion and agrees to release the authors from any and all liability.