Crown-IT4000-pwr-sm维修电路原理图.pdf

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1、Theory of Operation: I-Tech Power Supplies Eric Baker Last Edited 9/21/04 This work is intended to describe the operational theory behind the power supplies in the I-tech series of Crown amplifiers. Designers include: Eric Baker, Sergio Busquets-Monge, Ben Carroll, David Evans, and Gerald Stanley. T

2、opology: Phase-modulated, full-bridge, series-resonant converter Control strategy: Constant line current for improved power-factor Circuit Level Block Diagram The basic block diagram appears below as Fig. 1. The stages of power processing include the following: 1) EMI filter: Reduces power line cond

3、ucted noise from the power supply 2) Full-bridge rectifier: Rectifies the AC line providing a DC bulk supply for the full-bridge of switches 3) Impedance matching capacitor bank: Provides charge storage and a high-current low-impedance source 4) Full-bridge switch network: chops the DC bulk voltage

4、in to discrete pulses 5) Series-resonant tank: Works as a constant current source for the main power transformer 6) Step-up transformer: Steps up the voltage from approximately 60V on the primary to the secondary voltage 7) Full-bridge rectifiers: Creates pulsating DC from the high frequency AC coup

5、led through the transformer 8) Secondary energy storage: Serves as an energy storage reserve for the amplifier. Fig. 1. Block diagram of the power supplies EMI Filter SRT T 123 4, 5, 6 78 EMI Filter SRT T 123 4, 5, 6 78 RadioFans.CN 收音机爱 好者资料库 Phase Shift Modulation The core of the converter is made

6、 up of two half-bridges, shown above in 4, which are connected between a positive bulk voltage (Upper Buss) and a return (Lower Buss). The switches, in each half-bridge, alternate in turning on and off, at high frequency (40-41.7kHz), in order to obtain a 50% duty cycle square waveform at each of th

7、e respective center points. One center point (A or the leading leg made up of Q21,23,25,27,29, CH1; R1003=open,R1004=715K (R1006=pot) CH2; R1031=open,R1032=715K (R1034-pot) 4.1.5.2.3. Attach X10 probe (ground clip not needed) to respective channel on the buss bar the red LP/LN wire is, orienting the

8、 probe vertical and NOT leaning against the gate drive PWA. See Figure. 4.1.5.2.4. Power up from a cold start (i.e. 20-25 degrees C) ,and adjust associated OVER LAP / UNDER LAP pot from center. 4.1.5.2.5. Adjust the scope timebase for 50ns/div, 20V/div and tune scope offset and position until the ri

9、sing, upturn corner of the waveform is in center view. 4.1.5.2.6. While viewing the active wave on the scope, adjust the channel pot, watching this corner change from a more rounding feature to just starting to square off some. Stop tuning there, so the wave is more like the photo having a slight ro

10、und corner, not too square. The fans may come on which is ok but , since the unit is open thus heating is more rapid, it is recommended that the adjustment is done within 2 minutes from a room ambient temperature start. 4.1.5.2.7. Alternate, less accurate method: If an AC power meter is available, t

11、hen a power line draw check may be a measurement to ensure one of the two channels isnt consuming the majority of line power sum of the channels. 4.1.5.2.8. For example using an ITECH 6000: Using a line voltage of 120VAC 60Hz, connect an ITECH 6K thru a power meter. With the front panel switched off

12、 and turning on the back breaker, a typical power demand read on the meter might be around 5 watts (reduce readings by 50% for 240V measurements). Then, turning on the front panel power switch, and while waiting for the green “ready” lights to come on the power meter should respond up to about 50 to

13、 60 watts briefly. This is the internal high power supply coming on line before the two channels of the amplifier become awake. Then when the green “ready” lights come on the power meter should then go from the 60 watts to about 190 watt or very low 200 watt range. Here both channels are on line plu

14、s the power supply. 4.1.5.2.9. Turn off the back breaker and then pull out one of the channel Front End PWAs. Turn back on the back breaker and wait for the “green” ready lights to come back on. The power meter would then go from the 60 watts (power supply only) to about 120 watts or so approximate

15、(only one amplifier channel running). Turn off again, replace the first front end PWA and remove the other. If the power readings are within than 20 watts of each other then Over/Under Lap is set properly for each. Over-Lap/Under-Lap probe placement and scope reference of VP(red) node. Scope display

16、 showing proper adjustment of overlap/underlap Upper BCA Gate Drive is new (red) capacitors. Lower one is the original. 4.1.6. Firmware Upgrade / Version Check 4.1.6.1. There are several types of firmware files used in I-Tech amplifiers. Firmware is updated using TCP/IQ utility or System Architect.

17、Firmware versions may be verified using either software package, or via front panel LCD in the “Monitor” menu. Here are the firmware files used in I-Tech. 4.1.6.1.1. Loader: allows network to send new firmware to I-Techs. Filename - Italdr.bin. 4.1.6.1.2. LCD firmware: controls LCD and front panel.

18、Filename - ITDAPP-vx_xxx.bin. 4.1.6.1.3. DSP firmware: handles all audio processing and network communications. Filename - ITAxxxx.bin. 4.1.6.2. What version firmware should I be using? 4.1.6.2.1. Version 1.202 or higher. Older versions do not contain important feature and performance enhancements,

19、such as quieter fan operation, optimized thermal compression, etc. 4.1.6.2.2. As a general rule, if the amplifier is running 1.202 or higher, there is no reason to upgrade unless you require specific features contained in the new version. 4.1.6.3. If you have problems loading new firmware 4.1.6.3.1.

20、 Turn the amplifier off. Hold both encoders down and turn the amplifier on. This will force the amplifier into “bootloader” mode and allow you to re-send firmware. 4.1.6.4. Important notes about updating firmware 4.1.6.4.1. You should always update DSP and Display firmware at the same time, to the s

21、ame version level. Other combinations of Display and DSP firmware have not been tested together. 4.1.6.4.2. Updating the loader is not always required. When updating the loader, do NOT interrupt the AC mains or stop the process. 5. Troubleshooting and repair tips 5.1. All troubleshooting should begi

22、n with a careful assessment of the amplifier assembly. On all amplifiers, check and verify the following items: 5.1.1. Correct PWAs: All PWA numbers and versions are correct for the model amplifier you are repairing 5.1.1.1. Example: Check for IT8000 parts in an IT6000 or IT4000 5.1.1.2. Example: Ch

23、eck Lp/Ln coils for correct part number. IT4000 and IT6000 use the same coils, IT8000 uses different coils. 5.1.2. Firmware: 5.1.2.1. Verify firmware versions are V1.202 or higher. See Section 4.1.6. 5.1.2.2. Using front panel monitor menu or network connection, verify that amplifier model, serial n

24、umber, and date code match the product labeling and PWAs. 5.1.3. Cables: Visually and physically check that all cables and connectors are properly inserted and locked, not damaged. In addition, pay special attention to the following: 5.1.3.1. Check all ribbon cables for proper attachment of clamped-

25、on connectors (insulation displacement connectors). 5.1.3.2. Check thin white sensor wires from main power supply inductor. Ensure they are not pinched or damaged in other power supply parts. 5.1.3.3. Check Lp/Ln coil wires to ensure they are securely fastened to the buss bars 5.1.4. Hardware: Visua

26、lly and physically check that all fasteners are in place and securely installed. 5.2. Amp fails to meet published specifications 5.2.1. 2 Ohm Bench Power/THD 5.2.1.1. IT8000 only: Check for correct Lp/Ln coils, part number 136862-1 5.2.1.2. Check Underlap/Overlap adjustment 5.2.1.3. Check IMON (curr

27、ent monitor) adjustment 5.2.1.4. Verify sense resistors on output filter are well soldered 5.2.1.5. Check (12) screws (103436-10610) that attach output filter PWA to main amp PWA for proper installation and torque. See sheet 1 of assembly drawings. 5.2.1.6. Verify correct PWA number on power supply

28、controller 5.2.1.7. Missing capacitors on power supply control PWA 5.2.1.8. Check cable J3 from EMI PWA for solder bridges, defective cable, loose connector 5.2.2. 4 Ohm Bench Power/THD 5.2.2.1. Verify correct PWA number on power supply controller 5.2.2.2. Missing capacitors on power supply control

29、PWA 5.2.2.3. Check cable J3 from EMI PWA for solder bridges, defective cable, loose connector 5.2.3. 8 Ohm Bench Power/THD 5.2.3.1. Check for correct part number on input PWA 5.2.3.2. Check for correct model number on LCD “Monitor”menu 5.2.3.3. Verify correct PWA number on power supply controller 5.

30、2.3.4. Missing capacitors on power supply control PWA 5.2.3.5. Check cable J3 from EMI PWA for solder bridges, defective cable, loose connector 5.2.4. Output Noise 5.2.4.1.Verify that all PWA mounting screws to chassis are present and properly torqued. See assembly drawings. 5.2.4.2. If serial numbe

31、r is 001500, replace USP3T PWA. Vendor-supplied defective capacitors caused noise problems on many amps in this serial number range. The problem is intermittent and may not be observed on the bench. The problem gets progressively worse over time. 5.2.4.2.1. Note: This problem is often described as c

32、licking, popping, percolating sounds coming from the amplifier, even when no input signal is present, or when fully attenuated. If the customer presents this complaint, replace the USP3T. 5.2.4.2.2. When replacing USP3T, the replacement board must have serial number and model number information prog

33、rammed. This can be done by Crown Factory Service, or International Distributors can obtain the necessary software utility from Crown Service. 5.2.5. Output DC offset 5.2.5.1. Defective input PWA 5.2.6. IMD (Intermodulation Distortion) 5.2.6.1. Check Underlap/Overlap adjustment 5.2.7. Frequency resp

34、onse 5.2.7.1. Check for correct Lp/Ln coils 5.3. Indicator lights illuminated 5.3.1. Thermal 5.3.1.1. Verify both fans are present, properly connected, and running 5.3.1.2. Verify both fans are the correct part number. IT8000 uses different fans than IT6000 or IT4000. See assembly drawings. 5.3.1.3.

35、 Verify power supply main resonant inductor is correct part number 5.3.1.4. Check power supply thermal sensor. If shorted to heatsink, controller PWA likely damaged also. 5.3.2. Fault 5.3.2.1. Amp Gate Drive PWAs: check C526, C527, C629 for physical damage 5.3.2.1.1. NOTE: When replacing amp gate dr

36、ive PWA, set Overlap/Underlap pots to their middle position before powering on the amplifier. 5.3.2.2. Blown FET in main amplifier stage. 5.3.2.3. Check (12) screws (103436-10610) that attach output filter PWA to main amp PWA for proper installation and torque. See sheet 1 of assembly drawings. 5.3.

37、2.4. If both fault LEDs illuminate immediately after power-on (1 second), and LCD is dark, and power LED is lit, and serial number is in the range below, then check main power supply PWA version. If 6 or lower, move SCR on main power supply PWA. Contact Crown technical support for instructions. Seri

38、al numbers affected: IT4k: 006702 thru 8419 IT6k: 006908 thru 8219 IT8k: 006684 thru 8569 5.3.3. Ready 5.3.3.1. Check C1047 for physical damage or soldering problems 5.3.3.2. If amp operates normally but ready lights randomly flash on and off, ensure that display ribbon cable is routed away from Lp/

39、Ln coils at front corner of amplifier. 5.3.4. Signal 5.3.4.1. Check U400 for proper placement and soldering 5.3.5. Clip 5.3.5.1. If serial number is in the range 005730 010000: Check Lp/Ln wires for secure connection to buss bars on main amp PWA. Some “wiggle” is normal, but the connector should req

40、uire some force to remove from the buss bar. 5.3.5.1.1. If connector is loose, carefully tighten with pliers and re-install. Check again for secure connection after installation. 5.3.5.2. If main PWB version is 6 or lower: Check W2B on output filter PWB near speakon connector. Ensure that W2B is not

41、 shorted to trace on PWB. 5.3.5.3. Check current sense transformer on output filter PWA 5.3.6. All indicators are off, including LCD backlight 5.3.6.1. Amp blown, see section 5.4.4 5.3.6.2. Main PS blown, see section 5.4.5 5.3.6.3. If date code is = 220V, then replace EMI PWA 5.3.6.4.1. Serial numbe

42、rs affected: IT4k: 006702 thru 8419 IT6k: 006908 thru 8219 IT8k: 006684 thru 8569 Note: In early 2005, EMI PWAs were shipped directly to all Crown distributors affected by this problem for advance replacement in the S/N ranges above. 5.3.7. LCD Problems 5.3.7.1. LCD is illuminated, but contrast is w

43、rong or appears dark purple 5.3.7.1.1. Replace D401 on display board with part manufactured by On Semiconductor. 5.3.7.2. LCD attenuation settings read “-100” on both channels, front panel knobs do not control attenutation 5.3.7.2.1. The front panel is not communicating with the USP3T. Check R485 an

44、d U402 on display PWA for proper soldering. 5.3.7.2.2. When replacing USP3T, the replacement board must have serial number and model number information programmed. This can be done by Crown Factory Service, or International Distributors can obtain the necessary software utility from Crown Service. 5

45、.3.7.3. LCD is not illuminated at all 5.3.7.3.1. Verify display ribbon cable fully seated 5.3.7.3.2. Check for solder bridges or cold solder on J400 and Q401. 5.3.7.3.3. If both fault LEDs are on, see section 5.3.2 5.3.7.4. LCD partially illuminated, portions of display missing 5.3.7.4.1. The LCD co

46、nnector may contact vias on the display board. Remove LCD and re-install. If problem persists, replace with new display PWA. 5.4. Other Failures 5.4.1. Fans do not run 5.4.1.1. Check display PWA R459, R488, R489 for proper soldering 5.4.1.2. Verify model number of amplifier using front panel LCD “mo

47、nitor” menu. 5.4.1.3. Verify fans properly installed and connected 5.4.1.4. Check placement of transistors in fan drive circuit, ensure they are not shorting to the heatsink clip. 5.4.2. Network communications do not function 5.4.2.1. Check RJ45 network connector for proper soldering. Re-touch if ne

48、cessary. 5.4.2.2. Check RJ45 network connector locking mechanism. Insert a network cable and pull gently. If the cable comes out, replace the connector. 5.4.3. “Power Draw” “Light Zap” 5.4.3.1. Amplifier draws large currents at power-on, blows breakers. 5.4.3.1.1. Power Supply heatsink insulator: Ch

49、eck for presence and proper location. See section 5.4.5.1. 5.4.3.1.2. Main amp PWA: verify proper polarity on all large electrolytic caps 5.4.3.1.3. Main amp heatsinks: verify presence and proper location of insulator/shield between heatsinks and chassis. See sheet 4 of assembly drawings, section A8. 5.4.4. Amp section blown 5.4.4.1. Check thermal sensors on amp heat sinks. If these are pinched under the FET clip, this failure will occur. 5.4.4.2. If serial