Posted 25 March 2014 - 01:06 PM
Posted 25 March 2014 - 11:44 PM
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.
Posted 26 March 2014 - 07:45 AM
Posted 26 March 2014 - 10:52 AM
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...
Posted 26 March 2014 - 11:51 AM
Posted 26 March 2014 - 12:19 PM
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!
Posted 26 March 2014 - 01:24 PM
Posted 26 March 2014 - 03:24 PM
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.
Posted 16 April 2014 - 04:06 PM
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.
Posted 16 April 2014 - 04:47 PM
Posted 16 April 2014 - 06:57 PM
Posted 17 April 2014 - 12:23 AM
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:
Any ways, I'm on a linux computer right now and can't open SA to check the EQ settings problem.
Will update later.
Posted 17 April 2014 - 12:09 PM
Posted 17 April 2014 - 03:55 PM
Look at the detailed calculation I did here for your speakers but a bit higher headroom:
What is it you want to accomplish with those limiters? Do you only want to protect against speaker damage?
Posted 17 April 2014 - 05:18 PM