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Title: QSC 3602 Reliabilty Issues-Anyone?
Post by: Chuck Simon on May 01, 2011, 01:41:30 pm
Last night I had a QSC 3602 go out on me and took the circuit with it.  I was running subs at 4 ohms and not really pushing it very hard.  It sounded great right up to failure.  It happens to be the newest of all my amps, less than one year old.  I have other QSC amps that are up to 10 years old and even a few Carvers doing monitor duty that are 17 years old without problems!

The good news is that QSC has a great warranty and I am sure they will take care of it.  Is mine just a fluke or has anyone else had issues with this model?  I read here of someone mentioning a failure of a 3602, so I was just wondering.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Matt Martin on May 01, 2011, 02:41:43 pm
I'm also using 3602s for subs. I have yet to have any issues, however, you said you didn't up until failure. I would also be interested to know if something is wrong with these for sub duty.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Bob Leonard on May 01, 2011, 02:51:43 pm
Last night I had a QSC 3602 go out on me and took the circuit with it.  I was running subs at 4 ohms and not really pushing it very hard.  It sounded great right up to failure.  It happens to be the newest of all my amps, less than one year old.  I have other QSC amps that are up to 10 years old and even a few Carvers doing monitor duty that are 17 years old without problems!

The good news is that QSC has a great warranty and I am sure they will take care of it.  Is mine just a fluke or has anyone else had issues with this model?  I read here of someone mentioning a failure of a 3602, so I was just wondering.

Chuck,
Years ago I posted my thoughts to this board pertaining to the 3602 and it's use with subs. I personally thought the amp was an amp that shouldn't be considered for that use. I felt the tone was fine, the power available fine, but the amp itself was far to succeptable to voltage variations and in particular low voltage conditions that would not otherwise effect other amps including those made by QSC.
 
To that point I removed ALL of my 3602s from sub duty and replaced them with heavy iron in the form of 4050HDs. I have never had a problem with these amps powering subs, regardless of conditions. I now use the 3602s to power my upper cabinets, SRX725s and have had no problems since.
 
If you balk at the use of heavy iron then the 4050HD is not for you. However, many members of this board have followed my lead since that time long ago and they are all very happy with the 4050HD. As for the 3602, it has no use for driving subs in my world.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Chuck Simon on May 01, 2011, 04:13:44 pm
Interesting comments, Bob, and I bet we'll see some interesting responses!

I usually use the QSC Powerlights in my bigger rack for serious sub duty, or my powered 618XLF's, but I like the flexability the PLX's powering a couple dual 15's for smaller jobs where space is a premium.  So, I am very much interested in as many opinions as possible.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Alan Sledzieski on May 01, 2011, 04:38:09 pm
Last night I had a QSC 3602 go out on me and took the circuit with it.  I was running subs at 4 ohms and not really pushing it very hard.  It sounded great right up to failure.  It happens to be the newest of all my amps, less than one year old.  I have other QSC amps that are up to 10 years old and even a few Carvers doing monitor duty that are 17 years old without problems!

The good news is that QSC has a great warranty and I am sure they will take care of it.  Is mine just a fluke or has anyone else had issues with this model?  I read here of someone mentioning a failure of a 3602, so I was just wondering.

Everything breaks. LOl
   Your going to get a bad amp from time to time. I think in this day of light wieght amps there are going to be many more failures.
  Im running crest pro series amps now, replacing the old heavy large ca series and v series crest amps I used. Never had a ca or v go down in 15 years, the pro series I'm not so lucky.
 A big sound company that I know started using crest pro amps as they are growing, there other amps are crown macrotech. 4 of there pro series amps went down in a year, the macros are fine.
 A buddy of mine went from a full crest ca rig to a qsc plx rig, no failures on the ca's, 2 plx's went down last year.
 A repair shop I know has seen a 4-1 increase in crown failures, comparing the macro the a I tech series lightweight amp, The Itechs are not as durable as the macro's.  But easyer to repair then a crest pro, as the crown is a modular design,  I have a pro9200 in the shop right now, and was told to dig a hole and bury it.  The shop preformed the hail Mary test on it right from crest, and blew up a bunch of outputs, as it happens sometimes.  lets not forget, crest is no longer crest, its peavy now.  Posibly looking for a ca 18 to replace it, but its heavy.
 My buddy went from crest v series to crown XTI series, same problem, a xti failed.

 Long winded and may have went off in a tangent, but don't expect any of the light wieght switching amps to hold up like a old linear supply with a 30 lb transformer.

 Good luck
Al
   
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Chuck Simon on May 01, 2011, 05:13:24 pm
Carver was the first of the light weight switching amps, and as I said, I have some I have been using 17 years without problems.  However - monitor duty - not subs. 
I have a friend that's been running a pair of 4 ohm SRX718's out of each side of a PLX3402 for years now, and he pushes them in the red on a regular basis, extracting every volt possible out of that amp!  I would hope that the 3602 would be even better.  Maybe I got the one rotten apple in barrel.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: David Parker on May 01, 2011, 05:36:15 pm
I've been running my subs on PLX3402's for many years, 4ohms stereo operation. 3 of them. One went down during the whole run, and it turned out to be a weak component, just an expected bad apple now and then. Didn't cost much too fix. I'm sure I could get better performance from heavier amps, but then I'd have to haul the heavier amps in and out every night, and most of the time I'm alone.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Jeff Bankston on May 01, 2011, 06:49:19 pm
yeah the old haevy 75 pound QSC 3800 and 50 pound QSC 3500 with seperate power transformers and metal case toshiba transistors are bullet proof. ohhhh my back !!!
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Robert Weston on May 01, 2011, 08:19:16 pm
I use the PLX-3602's for subs (4ohm - bridged).  Never had a problem with them, except they need a good steady amount of current (i.e. they really need to be on their own circuit).  The can run a bit hotter than the 3402's, (as has been mentioned before in this forum), but I've never had one fail.  Though, with the amount of current they need to run, I've tripped many breakers.

About a year ago, had a 3402 power supply fail during a sound check (amp was running FOH mid/high).  QSC was superb in managing the repair and getting the amp back to me.  The largest amount of time spent getting it repaired was the shipping time to and from QSC.

Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Bob Leonard on May 01, 2011, 08:51:49 pm
I use the PLX-3602's for subs (4ohm - bridged).  Never had a problem with them, except they need a good steady amount of current (i.e. they really need to be on their own circuit).  The can run a bit hotter than the 3402's, (as has been mentioned before in this forum), but I've never had one fail.  Though, with the amount of current they need to run, I've tripped many breakers.

About a year ago, had a 3402 power supply fail during a sound check (amp was running FOH mid/high).  QSC was superb in managing the repair and getting the amp back to me.  The largest amount of time spent getting it repaired was the shipping time to and from QSC.

Hot is not the word for it. I push my systems hard, as hard as anyone, and the only component I've had problems with are 3602s when used for subs. My first bad experience years ago was an outdoor concert. I had good voltage to the amps and every 3602 I owned shut down at one point or another. Every one of them was hot enough out front to burn your hand on. Since replacing them I have had NO problems, even at the same venue, and under the same conditions the 4050HDs run ICE COLD. OK for tops, not OK for subs. Weight is not a factor when 500-1000 people are standing out front wondering why the system JUST WENT FUCKING DEAD.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Robert Weston on May 01, 2011, 08:59:59 pm

Hot is not the word for it. I push my systems hard, as hard as anyone, and the only component I've had problems with are 3602s when used for subs. My first bad experience years ago was an outdoor concert. I had good voltage to the amps and every 3602 I owned shut down at one point or another. Every one of them was hot enough out front to burn your hand on. Since replacing them I have had NO problems, even at the same venue, and under the same conditions the 4050HDs run ICE COLD. OK for tops, not OK for subs. Weight is not a factor when 500-100 people are standing out front wondering why the system JUST WENT FUCKING DEAD.

I've heard others say the same thing about the 3602's.  Though, I don't push my system too hard (hard enough though).  The clip lights will occasionally come on -- this is about where I'll run it.  If I need to push it any harder, I feel like I may be approaching the "not enough rig for the gig" situation.  However, my issues are usually related to onsite electrical current being sub-par to even run the 3602's where I like to.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: David Parker on May 01, 2011, 09:01:27 pm
I use the PLX-3602's for subs (4ohm - bridged).  Never had a problem with them, except they need a good steady amount of current (i.e. they really need to be on their own circuit).  The can run a bit hotter than the 3402's, (as has been mentioned before in this forum), but I've never had one fail.  Though, with the amount of current they need to run, I've tripped many breakers.

About a year ago, had a 3402 power supply fail during a sound check (amp was running FOH mid/high).  QSC was superb in managing the repair and getting the amp back to me.  The largest amount of time spent getting it repaired was the shipping time to and from QSC.

Hot is not the word for it. I push my systems hard, as hard as anyone, and the only component I've had problems with are 3602s when used for subs. My first bad experience years ago was an outdoor concert. I had good voltage to the amps and every 3602 I owned shut down at one point or another. Every one of them was hot enough out front to burn your hand on. Since replacing them I have had NO problems, even at the same venue, and under the same conditions the 4050HDs run ICE COLD. OK for tops, not OK for subs. Weight is not a factor when 500-100 people are standing out front wondering why the system JUST WENT FUCKING DEAD.
must be a difference between the 3402 and 3602. My 3402's don't run very hot, even when they are sitting out in the sun all day long and it's 100 degrees. Like I said, I'm sure the 4050's would be better, and I'd love to have them, but I've got a good, lightweight horse, and I'm gonna ride him.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Robert Weston on May 01, 2011, 10:31:15 pm

Hot is not the word for it. I push my systems hard, as hard as anyone, and the only component I've had problems with are 3602s when used for subs. My first bad experience years ago was an outdoor concert. I had good voltage to the amps and every 3602 I owned shut down at one point or another. Every one of them was hot enough out front to burn your hand on. Since replacing them I have had NO problems, even at the same venue, and under the same conditions the 4050HDs run ICE COLD. OK for tops, not OK for subs. Weight is not a factor when 500-100 people are standing out front wondering why the system JUST WENT FUCKING DEAD.

must be a difference between the 3402 and 3602. My 3402's don't run very hot, even when they are sitting out in the sun all day long and it's 100 degrees. Like I said, I'm sure the 4050's would be better, and I'd love to have them, but I've got a good, lightweight horse, and I'm gonna ride him.

Exactly -- the weight is a big issue.  My amp rack used to weigh ~400 lbs (filled with Crown/Crest); and when you are the only one loading out/in, it gets old really quick.  Replaced all the "big iron" with QSC's.  Now the rack weighs ~200 lbs and has about 3 times the amount of power.  The older amps performed well under various voltage loads, but the weight was becoming a major issue - I bought a 1000 lb portable winch to pull the amp rack in the cargo van; then I thought, "what the hell I am doing, just get more efficient amps".



Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Phil Strickland on May 01, 2011, 11:45:25 pm
I run 3602's on subs, and they get a little hot, but no real problems. Of course, now that I've read this thread I'll be keeping an eye on them a little more.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Bob Leonard on May 02, 2011, 07:00:50 pm
Exactly -- the weight is a big issue.  My amp rack used to weigh ~400 lbs (filled with Crown/Crest); and when you are the only one loading out/in, it gets old really quick.  Replaced all the "big iron" with QSC's.  Now the rack weighs ~200 lbs and has about 3 times the amount of power.  The older amps performed well under various voltage loads, but the weight was becoming a major issue - I bought a 1000 lb portable winch to pull the amp rack in the cargo van; then I thought, "what the hell I am doing, just get more efficient amps".

Robert,
Have you given any thought to putting fewer amps in smaller racks. ::)
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Robert Weston on May 02, 2011, 07:38:14 pm

Robert,
Have you given any thought to putting fewer amps in smaller racks. ::)

Actually, I had....  :D But the added expense and management of more cases and extra work to setup stage L &R with cables, etc... It become more efficient to use one 16 space rack.  I know this all sounds trivial, but it takes 3 of us about 5 hours to setup for a show (FOH and stage, including sound check).  And sometimes it's been just me setting up for the shows (for the first couple of hours or so). 

Having said all this, I've been reconsidering using smaller cases; though, transportation space is becoming a premium.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Mac Kerr on May 02, 2011, 07:46:55 pm
Actually, I had....  :D But the added expense and management of more cases and extra work to setup stage L &R with cables, etc... It become more efficient to use one 16 space rack.  I know this all sounds trivial, but it takes 3 of us about 5 hours to setup for a show (FOH and stage, including sound check).  And sometimes it's been just me setting up for the shows (for the first couple of hours or so). 

Having said all this, I've been reconsidering using smaller cases; though, transportation space is becoming a premium.

It is jut one more case. Two 8RU instead of one 16RU, each weighs half as much. Both go on one side of the stage, stacked on top of each other so they take up no more room and cable the same as your current method. They are just easier to load in and out, and more flexible to find room for in the truck and in the warehouse.

Mac
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Tim McCulloch on May 02, 2011, 08:27:22 pm
Everything breaks. LOl
   Your going to get a bad amp from time to time. I think in this day of light wieght amps there are going to be many more failures.

I disagree.  We've moved into Crown I-Techs in a big way, liquidating our Macro Techs and never looking back.  We have almost twice as many I-T as we had M-T but send out the same number per year for service. 

Hands down, the most reliable amp we've used are the Crest 8001.  The issue for them is parts support, and we've got access to a good-sized stash of critical pieces... but when we sell off or scrap the pSeudo4 rig, the Crests will be sold off.  Probably will take the proceeds and use for partial payment on I-TechHD for the VerTec rig, and use the original I-Techs for the conventional rig that replaces the 4s.

It's good to have a plan :D

Tim Mc
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Steve Hurt on May 02, 2011, 08:57:34 pm
It is jut one more case. Two 8RU instead of one 16RU, each weighs half as much. Both go on one side of the stage, stacked on top of each other so they take up no more room and cable the same as your current method. They are just easier to load in and out, and more flexible to find room for in the truck and in the warehouse.

Mac

Modularity is good, but it does come with a price
2 racks instead of 1 = Twice as much work. Two trips in, instead of one.  Two trips out, instead of one. 
Have to stack the rack once you're in and unstack to load out.  (assuming you are physically able to hoist that rack by yourself
Twice as many rack covers to pull & store on the in, twice as many to find, sort, and put back on on the out.
Every strategy has it's benefits and negatives.  Pick what works for you.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Alan Sledzieski on May 02, 2011, 09:09:40 pm
I disagree.  We've moved into Crown I-Techs in a big way, liquidating our Macro Techs and never looking back.  We have almost twice as many I-T as we had M-T but send out the same number per year for service. 

Hands down, the most reliable amp we've used are the Crest 8001.  The issue for them is parts support, and we've got access to a good-sized stash of critical pieces... but when we sell off or scrap the pSeudo4 rig, the Crests will be sold off.  Probably will take the proceeds and use for partial payment on I-TechHD for the VerTec rig, and use the original I-Techs for the conventional rig that replaces the 4s.

It's good to have a plan :D

Tim Mc

  See what happens after the I T's have as many years of service as the old macro's?  Just guessing here.....   : )
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: luis Markson on May 02, 2011, 10:15:47 pm

but when we sell off or scrap the pSeudo4 rig, the Crests will be sold off. 


Is that a quadraphonic system?
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Tim McCulloch on May 03, 2011, 12:27:00 am
  See what happens after the I T's have as many years of service as the old macro's?  Just guessing here.....   : )

So far I'd say it will be no different.  Of the Macros, we had a few that were more than 10 years old, a couple of them were still under warranty.

You can hide behind "see what happens in the future" but right now I have the empirical evidence that the I-Techs are no more problematic than our Macros, and currently have fewer problems needing factory service than the Macros.

We have I-Techs that are nearly new and others that are 5 years old.  There seems to be no difference in service needs based of date of production.  You don't have to believe me, but I encourage you to post based on your personal experiences rather than anecdotal hearsay and your "beliefs" regarding power supply topology and longevity.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Alan Sledzieski on May 03, 2011, 05:48:22 am
So far I'd say it will be no different.  Of the Macros, we had a few that were more than 10 years old, a couple of them were still under warranty.

You can hide behind "see what happens in the future" but right now I have the empirical evidence that the I-Techs are no more problematic than our Macros, and currently have fewer problems needing factory service than the Macros.

We have I-Techs that are nearly new and others that are 5 years old.  There seems to be no difference in service needs based of date of production.  You don't have to believe me, but I encourage you to post based on your personal experiences rather than anecdotal hearsay and your "beliefs" regarding power supply topology and longevity.

Tim,

Its not beliefs, reread my first post, everyone I know that went from the heavy wieght iron to new light wieght stuff is having problems. Crest at the top of the list, plx, then I T .  Went to the shop yesterday to see how my 9200 is coming along, not so good......  Funny, a xti and a I T came in for repair also.  Basic words out of the repairmans mouth, buy a old macro, as he knows I'm looking for something in the 2 kw range, 4 ohm stereo.  He did comment that the I T's are easy to work on, modular, and crown actually stands behind there product.
 He showed me the test procedure, right from crest, on how to do some trouble shooting on my 9200.  the most unprofessionall, obvious that even crest ( PEAVY ) doesn't know whats going on.  One line said, Hail Mary test, say a Hail Mary, do this and that, if smoke doesn't appear, move onto step 2,,,,,,, After reading the test, my quest for a 9200 is over, as for any more of the new crest 9200's.  I'm looking for a older ca 18 now.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Bob Leonard on May 03, 2011, 09:04:55 am
So far I'd say it will be no different.  Of the Macros, we had a few that were more than 10 years old, a couple of them were still under warranty.

You can hide behind "see what happens in the future" but right now I have the empirical evidence that the I-Techs are no more problematic than our Macros, and currently have fewer problems needing factory service than the Macros.

We have I-Techs that are nearly new and others that are 5 years old.  There seems to be no difference in service needs based of date of production.  You don't have to believe me, but I encourage you to post based on your personal experiences rather than anecdotal hearsay and your "beliefs" regarding power supply topology and longevity.

Tim,

Its not beliefs, reread my first post, everyone I know that went from the heavy wieght iron to new light wieght stuff is having problems. Crest at the top of the list, plx, then I T .  Went to the shop yesterday to see how my 9200 is coming along, not so good......  Funny, a xti and a I T came in for repair also.  Basic words out of the repairmans mouth, buy a old macro, as he knows I'm looking for something in the 2 kw range, 4 ohm stereo.  He did comment that the I T's are easy to work on, modular, and crown actually stands behind there product.
 He showed me the test procedure, right from crest, on how to do some trouble shooting on my 9200.  the most unprofessionall, obvious that even crest ( PEAVY ) doesn't know whats going on.  One line said, Hail Mary test, say a Hail Mary, do this and that, if smoke doesn't appear, move onto step 2,,,,,,, After reading the test, my quest for a 9200 is over, as for any more of the new crest 9200's.  I'm looking for a older ca 18 now.

Alan,
What Tim is saying is based on numbers, so before anyone can speculate a sample has to be compared to the total, not just what a particular dealer or tech has to say.
 
I'll use an example based on my day job. On Thursdays I work with a medical company who supplies two (2ea.) servers to hospitals for a single purpose. These servers are one active and the second a cold spare. If one fails then the cold spare is placed on line and the failed server sent back to me for overhaul, reload and failure analysis. Field engineers are not allowed to work on these systems. The manufacturer of these servers is well known with an immaculate reputation.
 
Last Thursday I had twelve (12) systems on the bench. I was approached by a company engineer who stated. "Why do we buy this junk." I asked what he based that statement on and he pointed to the 12 systems on the bench. My reply was simple. I asked him if he knew that his company had over 5000 of these systems in the field, and that the majority of these systems would only need a hard disk and OS rebuild. He replied "I didn't know that."
 
That's far less than a 1% failure rate.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Tim McCulloch on May 03, 2011, 10:10:31 am
Tim,

Its not beliefs, reread my first post, everyone I know that went from the heavy wieght iron to new light wieght stuff is having problems. Crest at the top of the list, plx, then I T .  Went to the shop yesterday to see how my 9200 is coming along, not so good......  Funny, a xti and a I T came in for repair also.  Basic words out of the repairmans mouth, buy a old macro, as he knows I'm looking for something in the 2 kw range, 4 ohm stereo.  He did comment that the I T's are easy to work on, modular, and crown actually stands behind there product.
 He showed me the test procedure, right from crest, on how to do some trouble shooting on my 9200.  the most unprofessionall, obvious that even crest ( PEAVY ) doesn't know whats going on.  One line said, Hail Mary test, say a Hail Mary, do this and that, if smoke doesn't appear, move onto step 2,,,,,,, After reading the test, my quest for a 9200 is over, as for any more of the new crest 9200's.  I'm looking for a older ca 18 now.

Repair techs see 100% failure rates on every model.  Users should not.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Chuck Simon on May 03, 2011, 10:51:36 am
If the theory that "Heavy Weight Iron" is the only thing acceptable for subs is true, that would make just about every powered sub(class D amps) useless!
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Alan Sledzieski on May 03, 2011, 07:24:13 pm
Repair techs see 100% failure rates on every model.  Users should not.

Not sure I understand this.  100% failure rate means every amp will blow.

Tim,
Simple, around here, from what I see, lightwieght amps fail more, and are more a throw away item.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Steve Hurt on May 03, 2011, 10:07:16 pm
Not sure I understand this.  100% failure rate means every amp will blow.

Tim,
Simple, around here, from what I see, lightwieght amps fail more, and are more a throw away item.

If a repair tech sees an amp, it's broken.  So, 100% of the amps the repair tech sees are broken. 
100% failure rate (in his eyes)  He doesn't see the the ones that are working.

If the company sells 10 times as many of a new amp than the old one and the repair tech sees 5 times as many of that amp,
The tech may think they suck because he's seeing 5 times as many, but reality would be that the new ones are twice as reliable as the old ones.

Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Bob Leonard on May 04, 2011, 01:14:53 am
If the theory that "Heavy Weight Iron" is the only thing acceptable for subs is true, that would make just about every powered sub(class D amps) useless!

I think you're confused. I never said you needed heavy iron for subs. I've said I don't like the 3602 for sub duty, and I've said that for years. There are plenty of lighter amps out there that can run high powered subs just fine, and from any number of manufacturers including QSC. The 3602 just isn't one of them in my opinion based on my, and others, experiences. Powered systems designed specifically for a single task should never have an issue if used properly regardless of driver type or size.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Chuck Simon on May 04, 2011, 09:48:29 am
Quote
I think you're confused. I never said you needed heavy iron for subs.

I think you're confused. I never said you said anything. 
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Bob Lee on May 06, 2011, 01:27:34 pm
like a old linear supply with a 30 lb transformer.

No such thing as a "linear" supply, except for maybe a battery.  ;)
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Mike Diack on May 06, 2011, 04:55:02 pm
Repair techs see 100% failure rates on every model.  Users should not.

Ha ha - but repair techs also do work for distributors, so they also get a good idea of the ratio of failures to total number of units sold (close to 100% in the case of iTechs in the first year...the situation has latterly improved) and they also get to know all the local sound reinforcement companies (so get an idea of how things fare in the field). They also get to know how the manufacturers handle the inevitable infant mortalities (unimpeachable in the case of QSC). ***ALL*** amp manufacturers have some failures - it's how these things are handled that really counts.
M
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Bob Leonard on May 07, 2011, 01:42:02 am
like a old linear supply with a 30 lb transformer.

No such thing as a "linear" supply, except for maybe a battery.  ;)

I've built linear amplifiers for HF that use 3600 volt power supplies. Does that count?  ;D
 
Good to see you post Bob. Hope my dislike of the 3602 isn't upsetting you. And, as a matter of fact the world should also know that all of my ampliers are QSC and that I have used QSC since the product line was conceived. Failures in the past 16 years? ONE.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Alan Sledzieski on May 07, 2011, 08:05:19 am
No such thing as a "linear" supply, except for maybe a battery.  ;)

Thanks, I don't know how power supplies work, but I was reffering to the amps with big old transformers.
Just picked up a ca18 yesterday I'm happy.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Todd Rasmussen on May 07, 2011, 08:39:01 am
If a repair tech sees an amp, it's broken.  So, 100% of the amps the repair tech sees are broken. 
100% failure rate (in his eyes)  He doesn't see the the ones that are working.

If the company sells 10 times as many of a new amp than the old one and the repair tech sees 5 times as many of that amp,
The tech may think they suck because he's seeing 5 times as many, but reality would be that the new ones are twice as reliable as the old ones.


If one considers the reliability of an amplifier with MTBF of "X" hours, adding just one new part that is less than 100% reliable decreases the MTBF of the amp.

I think the point Alan is making, and I tend to agree, is that newer amps tend to be more complex with the switching designs and the DSP stuff. So, merely by the (likely) addition of more parts and more complexity, the reliability inherently decreases if these additional parts/systems are anything other than 100% reliable. The only way to maintain (or grow) reliability then is to make reliability improvements in other areas to offset the new content's failure rate.

That said, I don't know what the numbers are but I do know that individual reports of failure don't necessarily imply the overall reliability experience of the entire population. MTBF of 10,000 hours doesn't mean every amp will last 10,000 hours, it means only that it is the average of the population. On a population of two, amp A fails after 1 hour use and the other fails after 19,999 hours means MTBF = 10,000 hours. Of course, such a small population is merely for example.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Alan Sledzieski on May 07, 2011, 10:27:27 am

If one has an amplifier with MTBF of (for example) 10,000 hours, adding just one part that is less than 100% reliable decreases the MTBF of the amp.

I think the point Alan is making, and I tend to agree, is that newer amps tend to be more complex with the switching designs and the DSP stuff. So, merely by the (likely) addition of more parts and more complexity, the reliability inherently decreases if these additional parts/systems are anything other than 100% reliable. The only way to maintain (or grow) reliability then is to make reliability improvements in other areas to offset the new content's failure rate.

That said, I don't know what the numbers are but I do know that individual reports of failure don't necessarily imply the overall reliability experience of the entire population. MTBF of 10,000 hours doesn't mean every amp will last 10,000 hours, it means only that it is the average of the population. On a population of two, amp A fails after 1 hour use and the other fails after 19,999 hours means MTBF = 10,000 hours. Of course, such a small population is merely for example.

The gentleman I bought the ca18 from tried 2 pro 9200's, they both went down in the first year, or second. his friend bought 6 9200's, 3 or 4 of them went down in the first 2 years.  I'm the not so proud owner of 4 8200's, I use 1 bridged on a double 18, I run 4 double 18's.  If I loose 1 double 18 do to a amp going down, no big deal, the show goes on.  If I put a 9200 on my 4733's and it goes down, its a big deal.  That's why I bought the ca 18.
 Whatever the case is, between crest, qsc, and crown, the new light weight amps fail much more often then the old big transformer amps, I can count and do the math, lol.  Problem is, there heavy.  Imagine lifting 5 ca 18's and 2 ca9's into the back of a pickup.  I'm to old for that.
 Wish crest was still crest.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Chuck Simon on May 07, 2011, 11:44:45 am
So, did anyone happen to see the title of this thread?  Man, it's hard to get a straight answer around here!
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Bob Leonard on May 07, 2011, 11:21:00 pm
So, did anyone happen to see the title of this thread?  Man, it's hard to get a straight answer around here!

I read the post, and I think I gave you more than one answer. I have some more if you like.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Jeff Bankston on May 08, 2011, 12:16:07 am
So, did anyone happen to see the title of this thread?  Man, it's hard to get a straight answer around here!
Mongos straight !
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Doug Maye on May 08, 2011, 10:30:55 am
So, did anyone happen to see the title of this thread?  Man, it's hard to get a straight answer around here!
There are probably better than 20 of them in this area being used on sub duty. To the best of my knowledge none have had problems due to the amp itself. Power in the venues yes, amps no.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Bob Leonard on May 08, 2011, 11:07:56 am
So, did anyone happen to see the title of this thread?  Man, it's hard to get a straight answer around here!
There are probably better than 20 of them in this area being used on sub duty. To the best of my knowledge none have had problems due to the amp itself. Power in the venues yes, amps no.

Define "power in the venue". If you mean the amp shuts down with a 5 volt fluctuation in line voltage that equates to poor design IMO.
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Alan Sledzieski on May 16, 2011, 05:42:07 pm
No such thing as a "linear" supply, except for maybe a battery.  ;)

So scroll down to where it says power supply, it says linear, so I'm confused,, as usual.  Is this the input, like 120v?

http://www.crestaudio.com/assets/literature/specs/116972_11560.pdf
Title: Re: QSC 3602 Reliabilty Issues-Anyone?
Post by: Bob Leonard on May 16, 2011, 09:07:20 pm
No such thing as a "linear" supply, except for maybe a battery.  ;)

So scroll down to where it says power supply, it says linear, so I'm confused,, as usual.  Is this the input, like 120v?

http://www.crestaudio.com/assets/literature/specs/116972_11560.pdf (http://www.crestaudio.com/assets/literature/specs/116972_11560.pdf)

Bob Lee is of course sorrect. The linear in power supply refers to the voltage regulator used, not to the power supply.
 
"
A linear regulator (http://forums.prosoundweb.com/wiki/Linear_regulator) provides the desired output voltage (http://forums.prosoundweb.com/wiki/Voltage) by dissipating excess power in ohmic losses (http://forums.prosoundweb.com/wiki/Ohm%27s_law) (e.g., in a resistor or in the collector–emitter region of a pass transistor in its active mode). A linear regulator regulates either output voltage or current by dissipating the excess electric power in the form of heat (http://forums.prosoundweb.com/wiki/Heat), and hence its maximum power efficiency is voltage-out/voltage-in since the volt difference is wasted. In contrast, a switched-mode power supply regulates either output voltage or current by switching ideal storage elements, like inductors (http://forums.prosoundweb.com/wiki/Inductor) and capacitors (http://forums.prosoundweb.com/wiki/Capacitor), into and out of different electrical configurations.
 
Ideal switching elements (e.g., transistors operated outside of their active mode) have no resistance when "closed" and carry no current when "open", and so the converters can theoretically operate with 100% efficiency (i.e., all input power is delivered to the load; no power is wasted as dissipated heat)."