Hitachi-HMA6500-pwr-sm 维修电路原理图.pdf

SERUICE MATUA1SPECIFICATIONSContinuous RMS power outpulHarmonic d istortion (both channels driven)(at rated output)lat 1 12 rated output)Power bandwidth (lHF)(at 1 l2 rated output)Frequency characteristics(at 1 W output)I nput sensitivity ( j mpedance)Damping factorChannel separationSlgnal-to-noise ratio(lHF, A network)Speaker impedancePower supplyPower consumpllonDimensio nsWeightEnglishDeutschFranqais50 watts per channel min. RMS, at 8 ohms from20 Hz Io 20 kHz, with no more than 0.02% totalharmonic distortion.55 w/ch + 55 w/ch (8 ohms, 1 kHz, T.H.D . O.O2%l53 w/ch + 53 w/ch (4 ohms, 1 kHz, T.H.D .0.02%lLess than 0.02%Less than 0.003%5 Hz-60 kHz (8 ohms, T. H. D. 0.05%)DC-1OO KHZ 1? dB (DIRECT COUPLING)5Nz-100 kHz 1? dB (CONDENSER COUpLtNG)1 V (SO kohms)50 (1 kHz, 8 ohms)80 dB (1 kHz, 8 ohms, input shorted)115 dB4-16 ohms (A, B), 8-16 ohms (A+B)AC 120 V 60 Hz, - 120 v l22O V 1240 v 50/60 Hz22OW or 320 VA (AC 120 V)430 W (- 220-240V1435 (W) x 153 (H) x 306 (D) mm11-118 (wl x 6-1132 x 12-1116 Dl9.4 kg (20.7 lbs )No. 159Specif ications and designs may be changed wlthout notice for improvementSTEREO POWER AIhPI.ITIERFebru aryI 979RadioFans.CN 收音机爱 好者资料库tSinusdauerleistung ( R MS)Klirrfaktor (beide Kanle betrieben)(bei Nennlelstung)(ei 1 12 Nennleistng)Leistungsbandbreite ( I HF)(bei 112 Nennleistung)Frequenzgang (bei 1 Watt)Eingangsempf ind lich keit( I mpedanz)Dampf u ngsf aktorKana ltrennungGeru schspannu ngsabsta nd(lHF, A-Netz)Lautsprecherim pedanzNetzspan nu ngLeistu ngsauf nahmeAbmessu ngenGewichtSOWKanal *SOWlKanal (g Ohrn;20 Hz -20 kHz,Gesamtkl irrfaktor 0,02%)55 W/Kanal + 55 W/Kanal (8 Ohm,.1 kHz, Gesamtklirrfaktor O O2%l53 WlKanal + 53 W/Kanal (+ Ohm,!. kHz, Gesamtktirrfaktor O,O2%lWen iger als O ,02o/oWeniger als 0,003%5 Hz - 60 kHz (8 Ohm, Gesamtklirrfaktor 0,05%)Gleichstrom-l00 kHz 1 Oa (OiretChassis groundFig.4The is because the POWER MOS FET is in the sourcecase, and in order to maintain the capacity between FETand the radiation fan, stability deteriorates by this, sothe FET is isolated from the chassis using a resistor of47 ohms.Accordingly, be careful not to cause an output by touch-ing the Q lead wire of the speaker to the chassis or dis-charge the electrolytic capacitor during servicing, sincethis may cut the lead wire of Rl or R2 and introducenolse.5q.Woshcr_kl) -4-. Precautions on troubleshooting and replacing parts(1) When the stabilized power circuit and the peripheralparts of Q701 and Q702 (D106, R752, R753 and theirperipheral parts) are replaced, the adjustment of theinput/output DC may drift, so be sure to check theinput/output/ DC voltage.(2) Since grade of hrs is specially classified into - fo. Q701 and Q702, replace them match-ing the proper grade with the proper channel.(3) Since the socket for transistor use is used for thesocket of the POWER MOS FET, polarity is indicatedas B, C, E. Match it to the indications shown in Fig. 5when replacing the POWER MOS FET and whenchecking. Gautions on checking the voltage(1) Oscillations may occur depending on the voltmeterHITACHI HMA-6500used when checking the gate voltage at FET 701 L/R.If this happens, measure the collector voltage ofQ704 LiR as it is at the same potential as FET 701L/R.The protection circuit may operate when checking thecollector voltage of Q706 L/R and the base voltage ofQ707 L/R. In this case, change the measurementposition and measure the voltage between therespective electrodes.Gate (G)Fig. 5(2)ADJUSTMENT. Adjusting idle currentPerform adjustment with no signal and with the speakerswitch turned OFF.Remove the wiring , shown in Fig. 6 and connectthe side of the DC ammeter to the drain side of theFET and the O side to the main amp. PWB.Next,adjust R75 lL and R75 lR on the main amp. PWB.so that they are both 150mA.Attached the wiring , as they were, after adjust-ment is completed.IEI|OZR FETTOZLFig.6o Adjusting the input DCInsert the shorting pin to the input, set the DIRECTCOUPLING/CONDENSER COUPLING switch toCONDENSER COUPLING, turn the speakerselector switch ON, and turn the powet switchON with no load for more than about 8 minutes beforeperforming the adjustment.To adjust Lch, connect the side of the DC arnmeterto 13 terminal of the main amp. PWB, and theQ side to 14 terminal.To adjust the Rch, connect the side to l5 terminal,and the Q side to 14 terminal. Then perform the adjust-ment using R152L or R752R respectively for a zeroreading (within t 0.5V) with the 3mV range. (Fig. 7)o Adjusting the output DCBe sure to perform this adjustment after the input DCadjustment is completed.Insert the shorting pin in the input, set the DIRECTCOUPLING/CONDENSER COUPLING switch toCONDENSER COUPLING, turn the speaker selectorswitch ON, and perform the adjustment with no load.Fig.7Perform adjustment using R753L or R753R after con-necting the DC ammeter to the and Q sides of thespeaker A terminals of Lch or Rch for a zero reading(within +5mV), with the l00mV range. (Fig. 7)Adjusting the meterAdjusting the meter sensitivityAdjust sensitivity of the meter after zero adjustment iscompleted. With no load applied to the speaker ter-minals, connect the audio oscillator to the inputterminal (INPUT) to feed in a signal of lkHz.In this case, adjust the input so that the Lch pointerindicates 1W.Then adjust R955R so that the Rch pointer alsoindicates lW (Fig. 7).o(1)FETT02RFig. 6-5-HITACHI HMA.6500CHECKING THE OPERATION OFWhen the output circuit is repaired by replacing thepower MOS FET, etc., perform an operation check onthe ASO (Area of Safe Operation) detection circuit andthe speaker protection circuit.1. Operation check of the ASO detection circuit for thepower MOS FETConnect the audio oscillator to the INPUT terminalswith the speaker terminals unloaded (speaker : dis-connect). Set the frequency of the audio oscillator atlkHz and adjust the level of the input signal so that thevoltage at the speaker terminals is approx. 5V rms.Under these conditions, short-circuit the speaker termi-nals of the channel to which the input signal is appliedusing a lead wire, etc. If this short-circuit makes the ASOdetection circuit operate, no output appears at thespeaker terminals even if the lead wire used for short-circuiting is removed.Next, turn off the power switch and, after approx.10 sec., turn the power switch on again. When out-put comes out of the speaker terminals, this indicatesthat the ASO detection circuit is operating normally.2. Operation check of the speaker protection circuitMake sure that the relay operates(a click sound is heard)approx. 4 seconds after the power switch is turned onwith the speaker terminals unloaded (speaker: discon-nect).ACvolmeler 0scilloscopeFig. 8o Phenomena and remedy when the proection circuit operatesTHE PROTECTION CIRCUITNext, when a resistor of approx. l0 kohms and2 drycells (1.5V) are connected in series to R902 on theaudio printed wiring board and the jumper wire ,the relay turns off within I sec. When the dry cellsare taken away, the relay operates again. Next, changethe polarities of the dry cell and carry out the above-mentioned operation to check the operation of therelay. If this operation makes the relay activate, thisindicates that the speaker protection circuit is operatingnormally. Moreover, pay attention during this operationcheck so that nearby parts are not short-circuited.of checking the POWER MOS FETRemove the FET.In the case of an N channel FET, it is normal : Whentouching the black test probe of the tester (ohm range ) tothe drain of the FET, and the red test probe to the source,after applying the black test probe to the gate and the redtest probe to the source at the same time, a current flows.And next, when brushing both the gate and sourcesimultaneously with your hand, the current stops.In the case of a P channel, the red and black test probes ofthe tester are applied in reverse.TVpe of protection circuilPhenomenon when theprotecion circuit operatesCauseRemedylMuting circuilNo sound comes out about4 rec. after the powerswitch is turned onNormal2Protection circuit of thepower l4OS FET (ASOprotection circuit)I No sound comes out2. When the power switchis turned ON the relaybecomes ON, then OFFwhen the signal is appliedShort circui ofspeaker outputteminalTurn off the power switch,check whether the speakerteminal is short circuitedor not, and tum ON again.3Speaker protectioncircuit (DC voltagedetection / protectioncircuit)No sound comes out.Neutral point voltageis more thil i 2VAfter the power switchis tumed ON, rclay doesnttum ONDC leakage of controlamp , power amp.faulty, etcI ln care the input selectswitch has been set toDIRECT COUPLING:If the fault is correctedby setting it to coNDEN-SER COUPLING, controlamp. DC is leaking sorepair the control mp2 In case the input slectvitch has been set toCONDENSER COUP.LINC:Repair faulty parts inpower amp-6-DESCRIPTION OF THE NEW CIRCUITo Protection circuitIC HA12002, an exclusive protection circuit, is used toprotect the speaker and power amplifier.(1) Muting circuitThis keeps the relay off for approx. 4 sec after thepower switch has been turned on to reduce shocksound during ON/OFF operation of the power switch.This is determined by the rise time constant of thevoltage applied to pin of IC90l and is set by R907,R908, and C905.(2) Protection of the speaker (DC voltage detection/pro-tection circuit)HITACH HMA.6500When a DC voltage appears at the neutral point of theoutput, a relay turns off when approx. l 3V is appliedto pin of IC90l via R901, R902 R903 is thesensitivity adjustment resistor.Protection of Power MOS FET (ASO protectioncircuit)When overcurrent flows to th output, the voltageVcs between the gzte and source of FET7OIincreases, Q70 and Q707 turn ON, the voltage isapplied to pinof tC901 and the relay is turned off.(3)FEATURESHITACHI have developed a complementary MOS FET which displays superb characteristics as a power amplif ica-tion device for audio applications. Since both the N-channel and P-channel complementary characteristics of thisPOWER MOS FET are top-class, thls model features a simple 3-stage circuit conf iguration including the poweram-plification stage. This is a design which makes for a low distortion across a wide band and which is devoted toengineering only the best in sound quality.,1. Design oriented toward low distoftion acrosswide band for the best in sound qualityThe POWER N/OS FET features a high inputimpedance and it is a voltage-driven device.These two merits provide a high power gain anda simply designed circuit configuration. This iswhy there is minimai noise or phase drift whichhas an adverse affect on the sound quality, andalso why there is no deterioration in the distor-tion factor. ln addition, the frequencv responseis excellent, the switching speed is fast, stableoperation is ensured even in the high frequen-ciesand notch distortion is dramatically redued.The design makes for a low distortion factoracross a wide band with a continuous poweroutput of 50 watts per channel, min., at 8 ohms(2O Hz-2O kHz) with no more than 0.A2%total harmonic distortion.2. DC amplifier featuring accurate waveformpower transmissionThe capacitors have been eliminated from theNFB loop and even the input capacitors havebeen put aside in this DC amplifier to effect agreat improvement in the low-frequency-rangephase characteristics. The first stage employslow noise transistors with a high withstandingvoltage and well-matched pairing characteristicsfor a reduction in center point drlft. Further-more, there is a DIRECT COUPLING/CONDENSER COUPLTNG switch which is pro-vided to safeguard the speakers from damagecaused by DC component eakage from theexternally connected equipment (such as thecontrol amplifier).3. Connection facilities for two pairs of speakersThis amplif ier can accommodate two pairs ofspeakers, and by selecting them with the speak-ers switch, you can compare the sound re-produced by each system.You can also listen to the sound from onespeaker system in one room and from theother speaker systern in another room.4. High-reliability protection circuitryln order to protect the POWER MOS FET, acurrent limiter circuit which relles on the detec-tion of the area of safe operation and DCvoltage detection circuit have been installed.This clrcuitry features high reliability whichenables it to cope with accidents.5. Large-sized power meters (peak rneters)The model comes with large-sized power meterswhich enable the balance between the left andright channels and also the output level to bechecked. Their size and performance are whatyou would expect to find in a POWER MOSFET amplif ier The power meters adopt a loga-rithmic compression circuit for RMS value dis-plays of the detected peak values This is whythey can track peak signals and enable thedisplayed values to be read out directlV/-7 -HITACHI HMA-6500WARTUNGSPUNKTE. Da dieses Gert mit einer Stromversorgung hoher Kapa-zitt ausgerstet ist, mssen bei Prfungen bzw. Re-paraturen die folgenden Punkte beachtet werden.(l) Fr das Prfen bzw. Repaieren der Schaltplatine un-bedingt die Stromversorgung abschalten und das Netz-kabel von der Wandsteckdose abziehen.Die Leistungskondensatoren entladen, indem dieKlemmen an den Punkten C803 und C804 mit einemWiderstand von etwa l0 Ohm (5W) berhrt werden.Wenn die Entladung ber die Erdung des Chassis er-folgt, besteht die Gefahr, dafl Rl oder R2 geffnetwird und Rauschen auftritt; das Entladen ist daherzwischen den positiven und negativen Q tclemmendes Elektrolytkondenston vorzunehmen.(2) Darauf achten, da$ die Klemmen benachbarter Teilenicht mit den Anschlssen des Gleichspannungsmessersberhrt werden, wenn dieser fr die Messung des Blind-stromes angeschlossen wird, da es ansonsten zuStrungen kommen knnte. Den Gleichspannungsmesser vorsichtig behandeln. Isolationsbandgegebenenfalls um den Schraubenziehre wickeln.o Einbau der TeileBei der Montage des Gertes wurde besonderesAugenmerk auf Betriebssicherheit gelegt, so dafJ alleTeile besonders sorgfoltig eingebaut wurden. ZumBeispiel wurden bestimmte Leiter mit Kunststoff-sohluchen berzogen oder andere in sicherem Abstandvon der Schaltplatne angeordnet. Beim Austausehenbzw. Reaprieren voR Teilen ist daher darauf zu achten,daf$ die ursprnglichen Sicherheitsmafrnahmen wiederumeingehalten werden.o Gleichstrom /Tiefenfilter-SchalterDa es sich bei diesem Gert um einen Gleichstrom-Verstrker handelt, mssen die Lautsprecher vor un-be absichtigten Gleichstrompotentialen geschtzt werden,die durch andere Bausteine eingefirhrt werden und dieLautsprecher-Treiber zerstren knnten. Mit Hilfe diesesSchalters knnen solche ungewnschten Gleichstom-komponenten ausgesiebt werden. Falls es aufgrund einesGleichstrompotentials zu Strgeruschen in den Laut-sprecherboxen kommt, diesen Schalter sofort auf Posi-tion CONDENSER COUPLING umlegen.oR1Die Erdleitung der Signalleitung und die Erdung desChassis sind mit Hilfe von Rl (47 Ohm) miteinanderverbunden wie es in Abb. 4 gezeigt ist.Der Grund dafr ist der Leistungs-MOS-FET; umnmlich die Kapazi6t zwisc