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#1 makis

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Posted 25 March 2014 - 01:06 PM

Hello. I own an itech 6000 which I use for my 728 subs. But I wonder for how long is he going to live. What is the lifetime of an amp like that (in operating hours I mean)? Thanks in advance.

#2 dakos

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Posted 25 March 2014 - 11:44 PM

Dear Makis,
I have seen itechs that were installed in churches, turned on from the very first day of install and sold with as much as 40000 hours on them, in great condition. I've also seen amps that had much less hours on them (500) in the worst condition you can imagine. I think such an amp doesn't break by the number hours it has (unless it's super high) but rather by it's condition and the way it was treated over the years.
Avi

#3 makis

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Posted 26 March 2014 - 07:45 AM

Thanks Avi. Is there any way to figure out the condition of an amp or it just has to malfunction first? Mine has about 15000 hours and since I bought it used I don't know how it was treated. What do you think? Also thinking of buying an 8000 for the subs and use the 6000 on the mids of my 725. Is this going to be a relief for the 6000?

#4 dakos

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Posted 26 March 2014 - 10:52 AM

15,000 hours is allot, especially on a touring amp, obviously you don't have a lemon. But, as far as I know there's no way to know if an amp is close to it's end of life, you would need to open up the amp and look for puffy caps, dust accumulation (easily fixable), any burn smelling parts on the board, noise from fans or any irregular operation. These are general maintenance rules not itch specific. All these things should be done every time the amp is serviced, have you ever had it serviced?

The 8000 fits the 728 (one per channel) better then the 6000 but the difference wouldn't be audible, it would just give you a bit more headroom.

Maybe my friend Alain can shed some light on the subject...
Avi

#5 makis

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Posted 26 March 2014 - 11:51 AM

I 've opened him yesterday to see for dust. Not much dust at all, even at corners or somewhere else that cannot be cleaned easily, no puffy caps, just a tiny irritating noise from the fans. In general the interior seems pretty new comparing with an XTI for example I bought new(and now has about 300 hours)

#6 joust

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Posted 26 March 2014 - 12:19 PM

My dear Dakos, thank you for your trust and confidence!

You are correct to state that the lifetime of a product is not necessarily determined by its age! Just look at me! :)

When I receive older equipment, and not necessarily an ITech,  the first thing to do is to effect a visual inspection of the unit; It will let you know if certain components are at the end of their life cycle and may need to be replaced. Next, inspect the output module for heat strains, dirt, corrosion or contamination, mounting, etc.

In the case of an ITech, I will disassemble and remove the output module completely. I would then inspect and clean the fans and remove dirt and debris accumulated by the ventilation of the fans. Then I will inspect and clean the output module and heatsinks of dirt and debris.
Remove the output filter board and inspect the mounting rings for wear and tear;
Remove and inspect the BCA coils; Unsolder the coils and inpect the coil leads to make sure that you have 3 to 5 mm to apply solder;
Remove and inpect the BCA clamps on top of the o/p devices; Some clamps will need to be reformed to apply pressure on the o/p devices.and heatsink; Replace the clamps if necessary;
Remove the heatsinks and clean off the thermal compound. Note : two different heatsink are available; (I recommend the heatsink with the recessed ceramic isolator (for the flyback diodes) 'set' in the heatsink and not the heatsink with the ceramic on top. The recessed isolator assures that the transistors and diodes are all level on the heatsink compared to the initial release of the heatsinks;)
Clean both heatsinks and output devices; Add a small amount of thermal compound to heatsink and devices; Remount the clamps and the t-sens foam over the o/p devices. Inspect the mounted devices so that they move as little as possible. (Note : If the devices are not clamped down enough, the device will heat up quicky and destroy itself!)

Notice that on the hi-side half of each output channel, the furthest transistor has a thermal sensor placed under a foamy strip. This needs to be replaced, in most cases, if the foam is rock hard; If there was little pressure on the thermal device the cicrcuit will run hot. Add a drop a thermal compound in the tab hole, where you will locate and set the thermal sensor.

Once the output module has been reassembled mount it back into the amplifier. Power up and adjust underlap/overlap adjustments.

Of course, firmware update is mandatory!

Hope this helps!

Alain

#7 makis

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Posted 26 March 2014 - 01:24 PM

Thank you very much. You were more than helpful. Your answer was excellent, this is what I was looking for. I'll disassemble the unit and let you know if anything occurs. Thanks again!

#8 joust

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Posted 26 March 2014 - 03:24 PM

Hello Peter,
It shouldn't be too difficult. The best way I found was to remove the DSP/input combo cards and then the main board can be removed easily. Note : The carrier screws are located on the top of the amplifier and also need to be removed. Just make sure that the isolator is set back when reinserting the main board. Aslo, before reinserting the DSP/input cards, make sure the display cable is hooked up to the DSP card!
Also, it is advisable to discharge the rails power supply (there's up to 300V between the positive and negative rails!). The main rails connector from the SMPS module is a good place to discharge the psu. Please, do not use a screwdriver to discharge these voltages! :) I constructed my discharge-meter using an old hand held analog meter (to simply view the voltage as it discharges) and a few PTC (positive temperature coefficient resistor) devices in parallel with the meter probes. These PTC devices are around 6 ohms and will increase resistance with temperature. You could use similar devices, like those blue round components used in the crowbar circuit that is located on the SMPS module.

#9 makis

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Posted 16 April 2014 - 04:06 PM

Hello once again my friends.
I would like to have your opinion on an other matter if that's OK with you..
I use an XTI 1002 for the high frequency drivers of my 725s, can you please suggest the right settings of limiter and EQ, because it's a bit tricky since the DSP on the XTI is not sufficient.

#10 dakos

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Posted 16 April 2014 - 04:47 PM

You can download all the tuning files for the SRX725 from the JBLPRO web site under Support->Download then you mark "Tuning tech notes" and scroll down to "SRX700 Tunings", Download and extract its contents. Open the created folder and there will be many subfolders and one .pdf file, open the .pdf file. Scroll down to page four, you will have a column called "SRX725 BI AMP" - HIGH. That's the data you need.
Avi

#11 makis

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Posted 16 April 2014 - 06:57 PM

As I said before I need limiter values which are not provided in this PDF and also XTIs EQ is not very compatible with the PDF's tunings.

#12 dakos

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Posted 17 April 2014 - 12:23 AM

Oops, didn't see that :)

The limiter calculation is just one line long:
10 X Log(P1/P2)=10XLog(75/275)= −5.6427143 dBfs.
That's the number you input the limiter.
Use long attack and release times, 4 seconds attack and 8 seconds release to start with.
Never clip this amp!!

Did you also try the files here:
http://www.crownaudi...SRX_Presets.zip

Any ways, I'm on a linux computer right now and can't open SA to check the EQ settings problem.
Will update later.
Avi

#13 makis

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Posted 17 April 2014 - 12:09 PM

Thanx man. You are the best.. I didn't try the presets cause I didn't know what to expect,  but it's my next move. What do yo think about itech's limiters? I have mine set at 145V 1200W for the 725 mids  and 160 V 1600W for the 728 plus the peak limiter enabled on both 6000 and 8000. No need for extra headroom besides that 6db of the speakers. What I want is the system to limit just before distortion if none in the signal chain of course..

#14 dakos

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Posted 17 April 2014 - 03:55 PM

The voltages you wrote are too high, how did you reach those numbers?

Look at the detailed calculation I did here for your speakers but a bit higher headroom:
http://www.crownaudi...?showtopic=4431

What is it you want to accomplish with those limiters? Do you only want to protect against speaker damage?
Avi

#15 makis

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Posted 17 April 2014 - 05:18 PM

Exactly. I have read that topic but this numbers don't work for me.