HHB-Circle5A_V3-spk-sm 维修电路原理图.pdf

Version 5.1 03.01.02Page 1Service manualHHB Circle 5A Powered Monitor speakerwith V3 electronicsManual: Version 5.2 23.12.2001This manual is subject to change without notice.Always check with HHB that you are using the latest version.Also available as an Adobe Acrobat V4 file.When printing this file, for clear sharp pictures on a black & while laser, it may be necessaryto adjust your printer drivers Print half tone settings. If you have a 600dpi printer, setting thehalf tone to around 45 lines per inch will give a clean sharp image, where as the default -around 60lpi may give a dark image to pictures.WARNING! DANGER OF ELECTRICAL SHOCKOpening mains operated equipment like the HHB Circle 5A incurs a risk of electric shock.DO NOT attempt to open this equipment unless you are qualified to do so, have thenecessary test equipment and are operating the Circle 5A from anISOLATED POWER SUPPLY.Ensure that only the correct mains voltage is applied, as marked on the module.NEVER OPERATE OR OPEN THIS SPEAKER IN DAMP OR WET CONDITIONS ANDNEVER ALLOW IT TO BE USED OUTSIDE. ENSURE THAT ALL POWER AND SIGNALCABLES ARE IN PERFECT CONDITION AND ARE CORRECTLY FUSED.IF IN DOUBT, CONTACT HHB IMMEDIATELY BEFORE PROCEEDING.RadioFans.CN 收音机爱 好者资料库Version 5.6 07.04.02Page 2ContentsPage 1: The cover and warningPage 2: (This) index pagePage 3: Section 1.0: External arrangement andcomments on connectors/controlsPage 4: Section 2.0:General arrangement, notes on testingPage 5: Section 3.0:Access to the Circle5A electronic module Page 6: Section 4.0:General inside views of C5A modulePage 7: Section 4.1Close-up view of C5A modules circuit boardsPage 8: Circuit diagram: C5AIPM input boardPage 9: Circuit diagram: C5APAMs rectifier/PSU/mute circuit Page 10: Circuit diagram: C5APAMs active filtersPage 11: Circuit diagram: C5APAMs power output circuitPage 12: Parts listPage 13: Fault findingPage 14: Modifications and updates Information contained in these pages is the intellectual property of Harbeth Audio Ltd. Harbeth Audio Ltd. 1997-2002 All rights reserved.RadioFans.CN 收音机爱 好者资料库1.0 External detailsThis is a view of the external controls on theCircle5A.1.1 Master Volume ControlThe function of the Master Volumecontrol is really that of a sensitivity control - to scaledown excessive input signals. In a set-up where thesignal level is scaled so that set to maximum (fullyclockwise) an input of 0.775VdBV, on the loudestpeaks, will fully drive the power amplifiers. Sincemany sources give a signal under normal pro-gramme that is significantly greater than 0.775V, it isexpected that in most situations the Circle 5As vol-ume control wil be set to about half way i.e. 12oclock. This would apply in many studios where the+4 signal reference is the maximum. Note: as youwill observe from the circuit diagram, the volumecontrol follows the input buffer stage, and the inputamplifier will overload and distort if the input signal isexcessive whatever the volume control is set to.1.2 Input sockets and selector switchThere are two input connectors: a master input, anisolated XLR following thenormal European wiringconvention:Pin 1 = shield (ground*)Pin 2 = Live, hot, + signalPin 3 = Cold, -, return signal* Pin 1 is connected to the ground of the C5As electronics. There is no connection from the audioground to the mains (safety) ground. The metalpanel is the only part of the C5As electronics that isconnected to the mains ground.Also provided is a secondary input: a Phono (Cinch,RCA) connector for unbalanced systems. The centrepin is signal +, and the connector case is the ground.The phono plugs case is connected to the C5as sig-nal ground, not the mains (safety) ground. Neitherinput is transformer isolated, and therefore caremust be taken to eliminate hum loops.The selector switch selects which of th two inputs isfed to the input buffer IC.Connect to EITHER the XLR or the phono, not both.Only use the mains cable supplied. Replace themains fuse with the correct type. The Circle5A mustbe earthed at all times, and is not suitable for useoutdoors.Version 5.6 07.04.02Page 3External view of C5As version 3 panel2.0 General arrangementAll the signal processing circuitry of the Circle5Aamplifier module is arranged on two PCBs - onepassive board, the C5AIPM holds the XLR, selec-tor switch, volume control and phono socket. Thisis connected to the C5APAM (filter/PSU/poweramp) board via a 6 way wire loom. There are nouser-adjustable parts.Although mains voltages do not appear on thePCB, but care should be taken when examiningand working on the module, since the secondary ofthe mains transformer (25-0-25 AC) is connected tothe bridge rectifiers and smoothing capacitors onthe board. These store considerable energy, andare capable of creating a spark many minutes afterthe C5As mains power is removed.The very low level of self noise generated in the cir-cuitry means that, at idle, there is an extremely lowlevel of background noise generated in the circuitry.If the C5A is powered up the front panel power-onLED fitted to the tweeter face plate just above thebass unit will glow green, indicating that the speak-er is powered and awaiting a signal. If the power-onLED is the illuminated, by definition, the PSU isworking, and the two LEDs on the C5APAM will beglowing, confirming that the +/- 12V rails are opera-tional.To minimise power-on and power off thumpsappearing at the drive units, a circuit detects thepresence of mains 50/60Hz cycles, and should themains disappear (either because the user hasintentionally or unintentionally switched off thespeaker or because of mains supply failure) theC5A will revert to muted mode a virtually instanta-neously and the audio output circuitry will switchoff, and programme will not be heard.The power-on LED is driven from the rectified regu-lated supply rail, and is a positive indication that thetransfromer, rectifiers and smooting capacitors arefunctioning correctly. The bass unit is directly driven from a pair of ICpower amolifiers in bridge push-pull mode. Thetweeter is driven from one one IC. NOTE CAREFULLY:DO NOT CONNECT EITHER OF THE BASS OUT-PUT TERMINALS TO GROUND SINCE THIS MAYDESTROY ONE OR BOTH BASS POWER ICS.THIS WILL REQUIRE THE REMOVAL ANDREPLACEMENT OF ONE OR MORE POWERICS, A DIFFICULT AND EXPENSIVE TASK.Sec 3.0 Removing the Circle 5Asactive module from the cabinetIt is absoluletely essential that before removingthe module you have the necessary tools, aclear space, and sufficient uninterrupted time towork. Rushing leads to mistakes, and mistekescan be dangerous and impair the excellentperformance of your Circle 5A speakers.An isolated mains PSU is essential for yourelectrical safety: be sure you never work onequipment directly connected to the mains sup-ply. Ensure that the mains supply is discon-nectedand removed from the module, and is notreconnected until the module has been fullyrefitted.We suggest that you cover your work benchwith a soft material to protect the underside ofyour Circle 5As from scuffing duringremoval/replacement of the module. Also beaware that the module is heavy and that oncethe screws are loosened, it will tend to dropdownwards, and that the heavy aluminiumpanel of the module will readily chip the softerwood of the cabinet, exposing the white MDFboard under the black paint. You will need twoscrewdrivers:3.1: A 3.0mm cross head screwdriver of theSuperscrew or Pozidrive NOT Phillips type.The Superscrew type has 4 thin grooves intowhich the Superscrew screw driver securelylocates. If the Phillips type is used, the screw-driver will mash the heads, and then it maynot be possible to remove the module from thecabinet.3.2: A larger size (M4, 4mm, No.2);Superscrew or Pozidrive screwdriver.Section 3.3: Removing the screwsPlease follow these instructions exactly. Failureto do so may well destroy your cabinet and/ormodule.First, using your smaller Superscrew driver,check that the screwdriver makes a positive fitto the screws marked 1,2,3,4. Applying as littleforce as necessary, unscrew (anti-clockwise)the four corner machine screws in the order 1,2, 3, 4.These screws locate in metal inserts trapped inthe inside of tha cabinet, and the alignment ofthe module and the cabinet is precise.Then, using the larger screw driver, remove thescrews A, B, C, D, E and, as you loosed screwF, expect the module to drop down. Be readytocatch it!The module can then be removed a shortdistance from the cabinet, as the internal con-nections to the module are on short flexiblewires. Be ready to carefully note the colourcoding and position of the wires that connectthe module to the woofer, tweeter and LEDs.NB: This photo is of the earlier module,but the screw arrangement is identicalThere are four function blocks in the C5A elec-tronic module:C5AIPM: a small PCB carrying the XLR,phono,volume control and selector switch. Thisis secured to the panel by the nut of the vol-ume control and the two M3 nylock nuts thatsecure the XLR socket.The input signal, once selected by the userswitch is sent to the C5APAMMAINS TRANSFORMER:The mains primary is connected directly to theusers mains off-on switch. The single sec-ondary is connected to the C5APAM. Thetransformers mains operating voltage is notadjustable; various voltages are available fordifferent market conditions.Sec. 4.0 General view of C5A module viewed from the insideVersion 5.6Page 6Section 4.1 Close-up views ofinside of C5A moduleC5AIPM:note air holes are sealed withhot glue.Wire loom connecting C5AIPM toC5APAMC5APAMVersion 5.6 07.04.02Page 8Version 5.6 07.04.02Page 9Version 5.6 07.04.02Page 8 Version 5.6 07.04.02Page Version 5.6 07.04.02Page Version 5.6 07.04.02Page