Friday, March 04, 2016

CROWN XTi Series AMPLIFIRES – firmware update – protection system – troubleshooting – Power amplifier Schematic diagram - audio system repair and service

Category: Audio system Repair and Service 

Contents of this article 

  • Firmware update
  • Protection system over view
  • Troubleshooting  


CROWN XTi Series

Updating Firmware RS-232 Method
If the microcontroller (U1, LPC2142) has NEVER been programmed before 
Connect the Serial 4-pin header to J2. IMPORTANT!! The header MUST be connected with the correct polarity or fatal damage can result. Pin 1 on the header should be connected to pin 1 of the connector. See figure below:

To program a new device connect the header to J2 and apply power. TP17 does NOT have to be pulled low because the micro does not have a valid program to run and will therefore automatically enter bootloader mode.
Open up the Philips Flash Utility Program (version 2.2.2)
Under Flash Programming, make sure the correct file is selected to download. S
elect the Device (LPC2142),
Select the XTAL Freq. (kHz): 16000
Select the Erase Entire Device button Select the correct file to load: (currently XTI_LPC_01_00_08b.hex)
Press the Read Device ID button. The Part ID and Bootloader ID will show up. If they do not and this operation times out, then most likely, the device is not in bootloader mode, there is something wrong in the configuration or setup or the cable is not correctly connected. If the device is not in bootloader mode proceed.
Select Upload to Flash and the programming will start.
After it is finished you may select Compare Flash. This will read back the flash memory and compare it to what was just programmed (Pass/Fail)
Cycle the Power to the amp and close the Flash Utility Program.
If the microcontroller (U1, LPC2142) has been previously programmed.
To reprogram a device, it is first necessary to put it in bootloader mode. This is done by shorting TP17 to ground during a power up. After the unit powers up, the ground can be removed or left connected, doesn’t matter. (Hint: Use a test lead connected to TP5(GND) on one end and TP17 on the other). The LCD should be blank.
Again follow the steps in Part 1 to connect the Serial interface board to J2 and open the Philips Flash Utility.
Press the Read Device ID button. The Part ID and Boot Loader ID should be displayed. Again follow the steps in Part 1 to send new firmware. If this does not work, there is most likely a hardware problem, check for shorts, correct power, bridges, other hardware problem.
To verify serial flash and check the current firmware version number
At any time hold down all three front panel buttons for at least 3 seconds. This puts the amplifier into a diagnostic mode. NOTE: While in this mode the front panel LED’s will NOT be updated. Also, the governor is disabled. Use the Next and Prev buttons to scroll thru the displays. They are outlined below:
Screen 1: Power Supply Temperature Sensor Read out in degrees C
Screen 2: Ch1 Temperature Sensor Read out in degrees C
Screen 3: Ch2 Temperature Sensor Read out in degrees C
Screen 4: Firmware version number read back from Serial Flash (eg. 1. 1. 0.15)
NOTE: The temperatures displayed are the raw unprocessed readings. They are updated approximately every 600ms and should be accurate.
LCD display looks to be corrupted.
If the text on the LCD looks to be bogus, it most likely is because the serial flash is blank or corrupt or is out of sync with the microcontroller program.
This problem can be resolved by updating the firmware via USB. This method ensures that both the serial flash and microcontroller are reprogrammed.
Programming the microcontroller (U1) and serial flash (U15) via USB
# Connect the amplifier to a PC via USB.
# Open up the CLoader Utility 2.10 or newer
# If fw is older than 1.0.22.0 send .hex file. Otherwise, send .s file
How to Use the CLoader Utility
Instructions: Simply run this utility with an amplifier connected to USB, it should show up in the dialog window. If it does not, unplug the USB cable, cycle power on the amp, plug in the USB cable again and try again.
If amplifier still does not show up, verify that the D+ USB data line is pulled high thru R19. With the USB cable unplugged, use a meter to measure R19, it should be pulled up to +3.3V thru Q23. Pulling this line high tells the USB host that the device is ready for communications.
After the amp shows up in the window, select "Load File" and select the firmware file to be downloaded. Wait for amp to reboot and download successful display.
To run from a command line
Simply type the name of the utility space and the name of the file to be loaded. When run from a command line, it creates a file named "LdrError.txt". There is a number inside this file as follows:
0 - Success
1 - Amplifier not found
2 - File invalid or not found
3 - USB communications error
4 - Abort Button pressed
The loader terminates upon encountering an error, or when successfully programming the amplifier. The error file is blown away if found when the loader starts, and is written just before it terminates.
It helps to have the utility and firmware file in the same directory and with no spaces in the folder names. If there are spaces, use " " around the path name.
Protection Features
Thermal Limiter 
The thermal limiter should have the following profile. The limiter threshold should be ramped down very smooth and slow to -24dB (0.25 dB/sec). The release from -24dB to 0 should also be very smooth and slow (0.125 dB/sec). The jump to -36dB and -42dB will be quick and fast, however, the output should be squashed down so much at this point, I don’t think it will be a problem.
= 80C Turn the front panel red thermal LED ON
= 81C Slowly ramp down -3dB
= 82C Slowly ramp down -6dB
= 83C Slowly ramp down -9dB
= 84C Slowly ramp down -12dB
= 85C Slowly ramp down -15dB
= 86C Slowly ramp down -18dB
= 87C Slowly ramp down -21dB
= 88C Slowly ramp down -24dB
> 90C Flash the LCD message “OVR TMP”
= 92C Set limiter to -36dB
= 98C Set limiter to -42dB
= 99C Flash the LCD message “TMP MUTE” and mute that amp ch
= 110C Fire the Crowbar and shut the amp down (last chance protect)
Cool Down
= 96C Unmute amp channel, Limiter set to -42dB – Flash “OVR TMP”
= 92C Set limiter back to -36dB
= 90C Set limiter back to -24dB
< 90C Stop Flashing “OVR TMP”
= 86C Very Slowly ramp up to -21dB
= 85C Very Slowly ramp up to -18dB
= 84C Very Slowly ramp up to -151dB
= 83C Very Slowly ramp up to -12dB
= 82C Very Slowly ramp up to -9dB
= 81C Very Slowly ramp up to -6dB
= 80C Very Slowly ramp up to -3dB
= 79C Very Slowly ramp up to 0dB Turn the front panel red Thermal LED OFF
Shorted Output Protection (2000/4000 models only)
This is really an extension of the clip limiter. It is based on the number of clip events. If the clip eliminator routine has counted 243 clip events and run the limiter all the way down to -24dB, it continues to count clip events. If the clip count gets up to 5243 (approximately 500ms after full attenuation), then a “SHORT” routine is entered. The channel is muted, the ready LED turned off and a message is displayed on the LCD “SHORT 1”; 1 for ch1 or a 2 for ch2. If the amp is in bridge mode, both channels should mute and the display message will be for ch1.
The amp channels are held in mute for one second. After that, they are unmuted, if the short condition persists, they are muted again. The amp should be capable of enduring this condition indefinitely. Because during a short condition, there is no output voltage, the tracker will keep the rails at the minimum 30V, so amplifier is not in a highly stressful state.
Troubleshooting
1. After power up an audible tone may be heard in the speakers.
Part Description: R809: C.P.N.: A11368-49910 4.99K 1% 0603 SMT Resistor R810: C.P.N.: A11368-10020 10K 1% 0603 SMT Resistor R814: C.P.N.: A11368-40220 40.2K 1% 0603 SMT Resistor
Procedure:
1) Place amplifier on bench and remove the top cover using a Torx 15 bit.
2) Locate and replace resistors R809, R810, and R814 with the values listed above.
2. Capacitor C925 goes out of tolerance causing the Crystal Y901 to make the DSP and or Codec chip to become unstable, i.e. Loud Static or Pink type noises, “Short” appear on the display, random level changes in output, audio output to drop out on one or both channels, severely distorted audio on one or both channels.
Part Description: C925: C.P.N.: A11369-100J1 10pF Capacitor 50V 0603 SMT
Procedure:
1) Place amplifier on bench and remove the top cover using a Torx 15 bit.
2) Locate and replace capacitor C925 with the value listed above. See Figure 1 below
3. Electrolytic Fluid leaking from caps causing board damage.
Part Description: 133323-1; Cap, 3800UF 125V Alum Elect.
Procedure: Some of the electrolytic capacitors used in XTi, CDi, and DSi amplifiers have been found to have a defect that allows them to leak fluid onto the board. The fluid could eventually cause the high voltage traces on the printed circuit board to short and the amplifier to fail.
Inspect the area around C47 and C48. If fluid is observed in this area the main board must be replaced.
4. Erratic volume, no audio or intermittent audio on the output. The Signal LED may stay lit even without audio output.
Part Description: 138911-4; XTi Display board “New”
138912-4; CDi/DSi Display board “New”
Procedure: When an XTI, CDI, or DSi amplifier is returned with a complaint of changing volume level or intermittent output audio, replace the display board with a 13891X-4 or greater revision.
POWER AMPLIFIER CIRCUIT DIAGRAM  
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