AustralianMonitor-DCM250-pwr-sm维修电路原理图.pdf

Australian Monitor 1 Clyde Street, Silverwater NSW 2128 Australia +61 2 9647 1411 .au SERVICE INFORMATION DCM250 POWER AMPLIFIER CONTENTS: OPERATION MANUAL CIRCUIT DESCRIPTION SET-UP / TEST PROCEDURE SCHEMATIC DIAGRAMS PCB OVERLAYS COMPONENT LISTS RadioFans.CN 收音机爱 好者资料库DCM250250w Power AmplifierOperating ManualTEM PFAILON 24211815129630+3HIMAINSD C M 2 5 0RadioFans.CN 收音机爱 好者资料库Product DescriptionThe DCM250 is a 250 watt power amplifier designed for commercial installations. It can be used for either low impedance(4 ohm) or 100v line speaker systems. The amplifier can be mounted in a standard 19” equipment rack or it can be usedon a shelf or table. The DCM250 features a line level input (with parallel output) and is normally used with mixers, mixeramplifiers or other power amplifiers. The DCM250 will operate from 230/240 VAC 50 Hz (115 VAC 60 Hzwith factory modification) or 24 VDC and will meet its full performance specification on either voltage supply. TheDCM250 also features a DC battery trickle charge facility, auto-sensing fan cooling, plus overload, short circuit andover temperature protection.DCM250, 250 Watt Power AmplifierFront Panel FeaturesPower SwitchThe rocker switch located in the front centre of the panel turns AC power on to the DCM250. Rocking the power switchto the right to turns the AC power on. When the AC power is on, a blue LED will glow. Please note that this switchdoes not switch DC voltage. If a DC voltage supply is connected to the DCM250, the amplifier will operate as soonas the connection is made, regardless of the position of the AC power switch. If both an AC and DC voltage supply areconnected and you rock the AC power switch to the off position, the DCM250 will automatically continue tooperate normally from the DC supply (and the mains failure LED will also glow under these conditions).Level ControlThe output level control is located in the centre of the front panel, just to the left of the mains rocker switch (re-cessed screwdriver adjustable pot). Turning the control clockwise will increase the output of the DCM250 towardsits maximum output level while turning the control counter-clockwise will decrease the output level. Adjust thiscontrol for the desired output level depending on the level of the input signal (from a mixer or other signal source).The factory default setting for this control is such that a 1 volt input will give a 100 volt output.Amplifier Status DisplayThe amplifier status display highlights the operating condition of the DCM250.The status display indicates:High Temperature: This red LED glows if one of the fans has failed and the amplifier has been shut down by itstemperature control circuitry. If this LED is glowing and the fans have not failed, it means that the amplifier is operatingin an ambient environment that is too hot for fan cooling to make any difference to the temperature of the amplifier.Power: This LED glows blue if AC power is switched on to the DCM250. Note that this LED does not indicate thepresence of a DC supply voltage.TEM PFAILON 24211815129630+3HIMAINSD C M 2 5 0Rear Panel FeaturesAC Power InletThe 3 pin IEC power inlet is located on the bottom left of the rear panel and accepts a standard mains power lead fittedwith an IEC connector. Before plugging in a power lead, please check the rear panel of the amplifier to ensure that thevoltage label shows the correct AC operating voltage for your part of the world.The inlet is equipped with an in-built AC fuse holder fitted with a 6 Amp slow blow fuse plus a spare fuse. Please ensurethat the mains power cord is disconnected before attempting to check or replace this fuse. Power consumption is 400VA (max).Speaker Output Terminal StripLocated on the top left of the rear panel is the speaker output terminal strip. Reading from left to right, the connectionsare:COMCommon or “-” for low impedance speaker loads (4 ohms).4The “+” for 4 ohm speaker loads (use with common)COMCommon or “-” for 100v speaker loads (maximum load of 40 ohms at 100v)100The “+” for 100v line speaker loads (use with common)Please ensure that the correct “Common” is used. Low impedance and 100v loads can be used simultaneously but pleasepay careful attention to the overall speaker load. When used individually, the low impedance load should be 4 ohms orhigher while the 100v line load should not fall below 40 ohms. When both outputs are used simultanously, ensure thatneither output is loaded to maximum.24 Volt PowerLocated on the rear panel are the red and black connection posts for 24v power. This feature can be used as either a back-up facility (if mains power fails) or for applications where AC power is not available. The left side red post is the +(positive) terminal while the right side black post is the - (negative) terminal. The DC current drain is 15 Amps maximumat full power. This socket also provides trickle charge to a DC battery supply (if connected) when the DCM250 isoperated from AC mains power. The level of trickle charge is 300 mA, maximum.Mains Failure: The LED glows red if there is a failure in the AC mains power supply. However, this LED will only glowif there is a DC supply voltage present. If no DC supply voltage is present then this LED will not glow.Output Level VU Meter: A 10 segment LED VU meter is provided to give an indication of the output signal level of theamplifier from -25 to +3 dB. During normal operation, the LEDs will oscillate with changes in the program signal. Careshould be taken to avoid more than occasional illumination of the red LEDs. If the LEDs in the red zone are litcontinually, then the output level control (or the level of the input signal to the DCM250) should be adjusted to reducethe output level. Too much output level can cause distortion, activate the internal limiter or possibly damage theconnected speaker system.230 VCC4100NCOHMAC FUSE 6A S/BDC FUSE2 X 10A S/B24 VDCINPUTENGINEERED BY AUDIO TELEX COMMUNICATIONS PTY LTD SYDNEY AUSTRALIAVOLTNC240 VTwin DC Fuse ReceptaclesLocated on the rear panel are two DC fuse receptacles. Access each DC fuse by turning the cap counter-clockwisewith a screwdriver. The value of the fuse is 10 Amps slow blow. Please ensure that the AC power switch is in theoff position and that the mains power cord is disconnected before attempting to check or replace this fuseCooling Fan (Air Intake)The cooling fans are temperature sensitive and will only switch on when the temperature of the DCM250 had reached apre-determined range. The fan will stay on and only switch off again once the temperature of the DCM250 has fallenbelow a pre-determined level. If the DCM250 is operating continually at conservative levels and proper load conditions,it is possible that the cooling fan will not switch on at any time during normal operation. When operating, the fan workswith air flow from the front to the rear of the DCM250.Fuse SizesMains, 240 VAC : 6 Amperes Slow Blow.XLR Audio Input and Parallel OutputThe input to the DCM250 is transformer balanced 10K ohms. When signal is connected to one XLR, the otherXLR becomes a line level output allowing the input signal to be distributed (split) to other amplifiers. In someprojects, the same input may be looped through to multiple amplifiers using this method. Up to 6 amplifiers can belooped together without any noticeable loss in level. A distribution amplifier should be used when more than 6amplifiers need to be looped.The XLRs are wired as follows: Pin 1: Shield. Pin 2: Hot, +, Positive. Pin 3: Cold, -, Negative1. Save the carton and packing material even if the equip-ment has arrived in good condition. Should you everneed to ship the unit, use only the original factory pack-ing.2. Read all documentation before operating your equip-ment. Retain all documentation for future reference.3. Follow all instructions printed on unit chassis forproper operation.4. Do not spill water or other liquids into or on the unit,or operate the unit while standing in liquid.5. Make sure power outlets conform to the power re-quirements listed on the back of the unit.6. Do not use the unit if the electrical power cord isfrayed or broken. The power supply cords should berouted so that they are not likely to be walked on orpinched by items placed upon or against them, payingparticular attention to cords and plugs, convenience re-ceptacles, and the point where they exit from theappliance.7. Always operate the unit with the AC ground wireconnected to the electrical system ground. Precautionsshould be taken so that the means of grounding of apiece of equipment is not defeated.8. Mains voltage must be correct and the same as thatprinted on the rear of the unit. Damage caused byconnection to improper AC voltage is not covered byany warranty.9. Have gain controls on amplifiers turned down duringpower-up to prevent speaker damage if there are highsignal levels at the inputs.10. Power down & disconnect units from mains voltagebefore making connections.11. Never hold a power switch in the “ON” position if itwont stay there itself!12. Do not use the unit near stoves, heat registers, ra-diators, or other heat producing devices.13. Do not block fan intake or exhaust ports. Do notoperate equipment on a surface or in an environmentwhich may impede the normal flow of air around theunit, such as a bed, rug, weathersheet, carpet, or com-pletely enclosed rack. If the unit is used in an extremelydusty or smoky environment, the unit should be peri-odically “blown free” of foreign matter.14. Do not remove the cover. Removing the cover willexpose you to potentially dangerous voltages. Thereare no user serviceable parts inside.15. Do not drive the inputs with a signal level greaterthan that required to drive equipment to full output.16. Do not connect the inputs / outputs of amplifiersor consoles to any other voltage source, such as abattery, mains source, or power supply, regardless ofwhether the amplifier or console is turned on or off.17. Do not run the output of any amplifier channelback into another channels input. Do not parallel- orseries-connect an amplifier output with any otheramplifier output.Audio Telex Communications Pty Ltd is not respon-sible for damage to loudspeakers for any reason.18. Do not ground any red (“hot”) terminal. Neverconnect a “hot” (red) output to ground or to another“hot” (red) output!19. Non-use periods. The power cord of equipmentshould be unplugged from the outlet when left un-used for a long period of time.20. Service Information Equipment should be servicedby qualified service personnel when:A. The power supply cord or the plug has beendamaged.B. Objects have fallen, or liquid has been spilled intothe equipmentC. The equipment has been exposed to rainD. The equipment does not appear to operate normally,or exhibits a marked change in performanceE. The equipment has been dropped, or the enclosuredamaged.Important Safety InformationDCM Series Circuit Description The DCM series are power amplifiers designed for commercial installations. They can be used for either low impedance (4 ohm/8 ohm) or constant voltage line speakers (100v/70v). These amplifiers can be mounted in a standard 19” equipment rack or they can be used on a shelf or table. The DCM series feature line level input (with parallel output) and are normally used with mixers, mixer amplifiers or other power amplifiers. The DCM series will operate from mains voltage or 24VDC. The DCM series also feature a DC battery trickle charge facility, auto-sensing fan cooling, plus overload, short circuit and over temperature protection. Power Switch This switch controls the switching of AC power to the amplifier. A blue On LED will indicate whether the amplifier is switched on or off. This switch will not switch DC power on or off in DC operation. In DC operation mode, the amplifier is always on and the blue power LED will always be illuminated. If both AC and DC voltage supply are connected and the AC power switch is in the off position, the amplifier will continue to operate normally from the DC supply and the mains fail LED will indicate. Level Control The output level control is located in the centre of the front panel. It is a fully recessed screwdriver adjustable pot. Turning this pot cw will increase the gain of the amplifier. At maximum setting the input sensitivity is 300mV. The amplifier ships from the factory with the sensitivity set to 1V. Amplifier Status Display This VU meter indicates the output level of the amplifier. The sensing for the circuit is taken on the amplifier side of the output transformer. The 0dB level is referenced to 100V. This is an RMS meter, not a peak meter. Protect The protect LED will illuminate when the amplifier cuts out because of either over current or high temperature. The amplifier will switch back on after approx 4 sec for an over current trip. The amplifier will switch back on after the amplifier has cooled to 60degC for a thermal trip. Limiter The limiter is a hard limiter with an attack time of about 1msec. It is defeatable by removing the jumper on the solder side of the front pcb. This however is not recommended as voltage overload and speaker transformer current saturation may cause the amplifier to cut out under normal program material. Current Limit and Setup Current limit is controlled by a microprocessor (PIC12C509A). The detection is done by sensing voltage across the emitter resistors. Trimpot P1 on the front pcb is accessible through the hole in the top right of the chassis return (only visible with the lid off). Turning the trimpot ccw will decrease the point at which the amp cuts out ie the amp will cut out earlier. (P1 resistance is increased.) To set the current limit: 1. Reset the trimpot P1 turning fully clockwise. 2. Connect the amplifier to half its minimum load (10ohm for DCM500, 20ohm for DCM250, 40ohm for DCM120). 3. Run an rms 1kHz sine wave into the amplifier and set the input level so that you read 425mVDC (DCM250/500) or 825mVDC (DCM120) across the emitter resistor, measuring the side which has the higher current (measured as a voltage across the emitter resistors). 4. Turn the trimpot P1 ccw till the amplifier cuts out. The amplifier is set to the factory default. Thermal and Fan control and Setup The thermal cutout and fan is controlled by a microprocessor (PIC12C509A). The temperature is sensed using a 10k25degC NTC. The fan is normally off and turns on to full speed at 60degC. This temperature is fixed and not adjustable. The thermal cutout temperature is set using the trimpot accessible through the hole in the top left side of the chassis return (only visible with the lid off). Turning the trimpot cw will decrease the point at which the amp cuts out ie the amp will cut out earlier. Power Amp The power amplifier is a push pull single supply amplifier driven by a class A transformer coupled front end. The drive is provided by HEXFETs (RF9520/9530) into NPN BJTs (TIP35C). When replacing the FETs it is recommended that