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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Wed Nov 30, 2011 12:51 am Post subject: This thing wont work! |
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Something looks funny but I just can't quite figure out what's wrong.......LOL.
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Nashou66
Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY
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tse
Joined: 03 May 2006
Posts: 1014
Location: Sweatbucket, Fl.
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| Posted: Wed Nov 30, 2011 1:03 am Post subject: |
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The smoke got out of some of the components.
Scott
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Wed Nov 30, 2011 1:15 am Post subject: |
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See folks, that's what happens when you replace a 1 amp fuse with a nail....
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Wed Nov 30, 2011 1:41 am Post subject: |
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And whats worse is the parts you see as bad are in the primary side of the P/S as circled in the print. And as you can see this is not a simple supply by any means and the potential for more damage is surely there. Even worse, I didn't some quick testing on a sensitive circuit fed from the secondary side and found damage. Which means the charge jumped ship and more investigating must be done. So now it's a matter of counting how many damaged mosfets along with other components.
Funny thing is the customer still wants it fixed. Looks like my irons will be burning hot for a few days....lol.
Any guesses as to what it is?
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Wed Nov 30, 2011 2:06 am Post subject: |
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Some kind of controller/ voltage regulator/inverter? The 'separate' circuit below the circled area confuses me...
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Wed Nov 30, 2011 2:11 am Post subject: |
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| Curt Palme wrote: | | Some kind of controller/ voltage regulator/inverter? The 'separate' circuit below the circled area confuses me... |
I figured you would be the first to guess right so I put mosfet in there to throw you off. No mosfets(well some) but lots of, lets say....switching transistors..... 
Last edited by macgyver655 on Wed Nov 30, 2011 2:17 am; edited 1 time in total
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Wed Nov 30, 2011 2:15 am Post subject: |
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Well, it looks like the MOSFETS are driving the DC supply line, so my assumption is that there's a load between the MOSFETS and the DC supply... it's that multitap coil going to the diodes that's throwing me off.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Wed Nov 30, 2011 2:23 am Post subject: |
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Those are actually IGBT's but I know it's hard to see in that print. I'll give you another hint and I'm sure you'll get it.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Wed Nov 30, 2011 2:27 am Post subject: |
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AnalogRocks
Forum Moderator
Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada
TV/Projector: Sony 1252Q, AMPRO 4000G
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| Posted: Wed Nov 30, 2011 2:27 am Post subject: |
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| Curt Palme wrote: | | See folks, that's what happens when you replace a 1 amp fuse with a nail.... |
ooO did the nail survive? 
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Wed Nov 30, 2011 2:34 am Post subject: |
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| AnalogRocks wrote: | | Curt Palme wrote: | | See folks, that's what happens when you replace a 1 amp fuse with a nail.... |
ooO did the nail survive? |
Whats funny is the fuse is still good.....
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Wed Nov 30, 2011 2:36 am Post subject: |
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Well that's a plain old power amp section...
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Wed Nov 30, 2011 2:39 am Post subject: |
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| Curt Palme wrote: | | Well that's a plain old power amp section... |
hehehe, yep. This is a QSC 2 channel Pro Power amp used by a local band.
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AnalogRocks
Forum Moderator
Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada
TV/Projector: Sony 1252Q, AMPRO 4000G
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| Posted: Wed Nov 30, 2011 2:40 am Post subject: |
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| macgyver655 wrote: | | AnalogRocks wrote: | | Curt Palme wrote: | | See folks, that's what happens when you replace a 1 amp fuse with a nail.... |
ooO did the nail survive? |
Whats funny is the fuse is still good..... |
Ya know, I hate that! 
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Wed Nov 30, 2011 2:40 am Post subject: |
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I think that multi tap coil thingy you saw is a transformer, if thats what you were looking at.
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Wed Nov 30, 2011 2:48 am Post subject: |
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With that kind of blowup, I'd call QSC on the cost of a replacement board. Tell them you'll post the pix of the blown board on every QSC and pro audio forum... heehee!
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Wed Nov 30, 2011 5:56 pm Post subject: |
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| Curt Palme wrote: | | With that kind of blowup, I'd call QSC on the cost of a replacement board. Tell them you'll post the pix of the blown board on every QSC and pro audio forum... heehee! |
Unfortunately that board is the entire power amp. I'll post a full pic later. Also, it's my understanding that water (more likely beer, lol) got splashed on it and that's why it fried.
The reason for the elaborate P/S is this is QSC's powerlite version which is probably at least half the weight of a regular power amp of this size. This was accomplished by eliminating that big transformer that creates most of that weight. Hence the elaborate supply.
This baby only weighs 21 lbs yet the power output is as follows:
Stereo:
550watts@8ohm
900watts@4ohms
1500watts@2ohm
Bridged mono:
1100watts@8ohm
2000watts@4ohm
3000watts@2ohm
All this and only drawing 10 amps..... That's why he's willing to shell out some bucks to get it going again.
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Wed Nov 30, 2011 6:03 pm Post subject: |
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| macgyver655 wrote: |
Stereo:
550watts@8ohm
900watts@4ohms
1500watts@2ohm
Bridged mono:
1100watts@8ohm
2000watts@4ohm
3000watts@2ohm
All this and only drawing 10 amps..... That's why he's willing to shell out some bucks to get it going again. |
OK, I'm calling you out, Mr! You of all people shouldn't believe the QSC specs. How do you get 3000 watts into a 2 ohm load from an amp that only draws 1200 watts from the AC line????? Shame on you! 
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Wed Nov 30, 2011 6:11 pm Post subject: |
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| Curt Palme wrote: | | macgyver655 wrote: |
Stereo:
550watts@8ohm
900watts@4ohms
1500watts@2ohm
Bridged mono:
1100watts@8ohm
2000watts@4ohm
3000watts@2ohm
All this and only drawing 10 amps..... That's why he's willing to shell out some bucks to get it going again. |
OK, I'm calling you out, Mr! You of all people shouldn't believe the QSC specs. How do you get 3000 watts into a 2 ohm load from an amp that only draws 1200 watts from the AC line????? Shame on you! |
LOL... Right here, disregard the circle:
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