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Author Topic: Itech 8000 problem  (Read 7400 times)

Mario Roman

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Itech 8000 problem
« on: June 25, 2012, 09:54:36 pm »

Good day All,

After searching the web and several of these forums I'm not findiing a specific answer to my question so I thought I'd just post it. My apologies in advance if I haven't linked the right combination of words to get the desired results but I have tried searching for a while now.

I purchased a factory reconditioned itech 8000 a little over a year ago to run my 2 TH-118 subs and until this weekend it's performed flawlessly. Granted I'm never pushing it that hard, in fact at most clubs I'm only using 1 sub since it can easily outrun the 2 SM-96 tops I'm using in the system. This weekend while using both subs (Weird club layout calls for a top and sub in 2 separate rooms....don't ask..... ::)  ) the amp quit working about half way through our 1st set. I cycled power via the Blue A/C button in the rear to no avail. The symptom is no ready lights and the channel 2 clip light stays on even with nothing plugged into the unit except power.

I'm aware of the problems these amps had when they were 1st released and was comfortable with the fact that by 2011 Crown had identified those problems and had fixed them before reselling them as "factory reconditioned" with a 1 year warranty. But my luck being what it is, this is a few months out of warranty. I've read about ribbon cable problems and cracked circuit boards being a problem in the early days but can't seem to find anywhere this particular symptom and what the solution turned out to be.

I'm the service manager for a pro A/V integrator and have been a bench tech for 30+ years thus the amp will be hitting my bench 1st thing in the morning. Having never worked on an itech before and having no service manual (for the moment) I will be purusing through the unit looking for the obvious (ie. bad solder, cracks, loose connectors) but if anyone has seen this before and can keep me from reinventing the wheel I would greatly appreciate your sage advice. Thanks again for your help everyone.

Mario
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Mike Diack

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Re: Itech 8000 problem
« Reply #1 on: June 26, 2012, 04:23:13 am »

One clip light permanently on is a fair indicator of a blown channel. Chances are when you look under the hood you'll find little chips of broken 20N50 FETs floating around. You'll have to lift out the 8 big chokes to get a good look (easy as they are connected with QCs). Remember that these faults propagate back to the gate driver board so that will have to be replaced or repaired. The service manual is on the Crown website. One tricky thing is the necessity to replace the FET finger clips after a rebuild (I think the originals weren't springy enough or somethig).
M
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Mario Roman

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Re: Itech 8000 problem
« Reply #2 on: June 26, 2012, 11:14:55 am »

One clip light permanently on is a fair indicator of a blown channel. Chances are when you look under the hood you'll find little chips of broken 20N50 FETs floating around. You'll have to lift out the 8 big chokes to get a good look (easy as they are connected with QCs). Remember that these faults propagate back to the gate driver board so that will have to be replaced or repaired. The service manual is on the Crown website. One tricky thing is the necessity to replace the FET finger clips after a rebuild (I think the originals weren't springy enough or somethig).
M

Thanks for the info Mike. While I wasn't able to find the service manual at Crown's site I did manage to fix the amp. Thankfully it wasn't as bad as it could've been. I inspected the output board as you suggested and found none of the MOSFET's shorted. A good sign my problem wasn't there. I did find a multitude of potential bad solder connections which I repaired while I was in that section. Since Crown appears to have switched to lead-free solder, I suspect that the early connection problems these amps had was due to a poor manufacturing process for using this type of solder. I repaired countless connection problems from Sony, Panasonic, Sharp, JVC etc. when they switched to it around 07/08.

Upon leaving the amp on for a bit I found one of the heat sinks getting extremely hot on the board that has all the caps in the center of the unit. This heat sink would be on the right rear of this board with the amp upside down and the front towards you. Plugged into this board are two identical cards, one for each channel. I inspected both and found the channel 2 card to be very hot on it's lower right corner. I swapped the positions of the card and the clip light now stayed on on channel 1. Knowing I was onto something I did a closer inspection of the channel 2 card and found C628 to be shorted. This is a small surface mount capacitor. I measured the value of the good cap on the channel 1 card (out of circuit of course) and found a suitable replacement in our boneyard.

At this point I powered up the amp and while the clip light went away, I still didn't get my ready lights. Since I had already hooked up my laptop with System Architecht I decided to reload the firmware and after the amp rebooted everything started working again. Sorry for being a bit long winded but I want to provide enough detail to help someone else if they're searching for a solution to the same problem.

Thanks,

Mario
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ThomasKielhofner

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Re: Itech 8000 problem
« Reply #3 on: June 27, 2012, 12:47:43 am »

Thanks for the info Mike. While I wasn't able to find the service manual at Crown's site I did manage to fix the amp. Thankfully it wasn't as bad as it could've been. I inspected the output board as you suggested and found none of the MOSFET's shorted. A good sign my problem wasn't there. I did find a multitude of potential bad solder connections which I repaired while I was in that section. Since Crown appears to have switched to lead-free solder, I suspect that the early connection problems these amps had was due to a poor manufacturing process for using this type of solder. I repaired countless connection problems from Sony, Panasonic, Sharp, JVC etc. when they switched to it around 07/08.

Upon leaving the amp on for a bit I found one of the heat sinks getting extremely hot on the board that has all the caps in the center of the unit. This heat sink would be on the right rear of this board with the amp upside down and the front towards you. Plugged into this board are two identical cards, one for each channel. I inspected both and found the channel 2 card to be very hot on it's lower right corner. I swapped the positions of the card and the clip light now stayed on on channel 1. Knowing I was onto something I did a closer inspection of the channel 2 card and found C628 to be shorted. This is a small surface mount capacitor. I measured the value of the good cap on the channel 1 card (out of circuit of course) and found a suitable replacement in our boneyard.

At this point I powered up the amp and while the clip light went away, I still didn't get my ready lights. Since I had already hooked up my laptop with System Architecht I decided to reload the firmware and after the amp rebooted everything started working again. Sorry for being a bit long winded but I want to provide enough detail to help someone else if they're searching for a solution to the same problem.

Thanks,

Mario

Thanks for the great write up. Very useful information for all of us with reconditioned I-Techs.
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Conrad Muzoora

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Re: Itech 8000 problem
« Reply #4 on: June 27, 2012, 05:26:32 am »

I wouldn't touch a refurbished I-tech or MAi. Bought a nicely priced ma9000i and had to return it to crown twice in 2 years  for service with somewhat similar problems. The performance was great while it worked, but two mid-gig failures convinced me to put my money in my most trusted amps Q-S-C!. Sold the MAi and replaced it with heavy iron QSC RMX 5050, and a QSC RMX 4050 and have been happy since.
Conrad
www.kooleventug.com
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Mario Roman

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Re: Itech 8000 problem
« Reply #5 on: June 27, 2012, 08:07:13 am »

I wouldn't touch a refurbished I-tech or MAi. Bought a nicely priced ma9000i and had to return it to crown twice in 2 years  for service with somewhat similar problems. The performance was great while it worked, but two mid-gig failures convinced me to put my money in my most trusted amps Q-S-C!. Sold the MAi and replaced it with heavy iron QSC RMX 5050, and a QSC RMX 4050 and have been happy since.
Conrad
www.kooleventug.com

I agree, I much prefer QSC for their reliability. However at the time even at the dealer pricing i get, the Crown was considerably cheaper and had more power/channel. I was taking a gamble and hoping that if it went out it would do it during the 1st year while it was still under warranty and I could just send it to Crown and they would deal with it. But you know how the best laid plans go.  :-\

Mario
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ProSoundWeb Community

Re: Itech 8000 problem
« Reply #5 on: June 27, 2012, 08:07:13 am »


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