Hitachi-HMA6500-pwr-sm维修电路原理图.pdf

SERUICE MATUA1 SPECIFICATIONS Continuous RMS power outpul Harmonic 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 factor Channel separation Slgnal-to-noise ratio (lHF, A network) Speaker impedance Power supply Power consumpllon Dimensio ns Weight English Deutsch Franqais 50 watts per channel min. RMS, at 8 ohms from 20 Hz Io 20 kHz, with no more than 0.02% total harmonic distortion. 55 w/ch + 55 w/ch (8 ohms, 1 kHz, T.H.D . O.O2%l 53 w/ch + 53 w/ch (4 ohms, 1 kHz, T.H.D .0.02%l Less 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 dB 4-16 ohms (A, B), 8-16 ohms (A+B) AC 120 V 60 Hz, - 120 v l22O V 1240 v 50/60 Hz 22OW or 320 VA (AC 120 V) 430 W (- 220-240V1 435 (W) x 153 (H) x 306 (D) mm 11-118 (wl x 6-1132 x 12-1116 Dl 9.4 kg (20.7 lbs ) No. 159 Specif ications and designs may be changed wlthout notice for improvement STEREO POWER AIhPI.ITIER Febru aryI 979 RadioFans.CN 收音机爱 好者资料库 t Sinusdauerleistung ( 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 aktor Kana ltrennung Geru schspannu ngsabsta nd (lHF, A-Netz) Lautsprecherim pedanz Netzspan nu ng Leistu ngsauf nahme Abmessu ngen Gewicht SOWKanal *SOWlKanal (g Ohrn;20 Hz -20 kHz, Gesamtkl irrfaktor 0,02%) 55 W/Kanal + 55 W/Kanal (8 Ohm,.1 kHz, Gesamtklirrfaktor O O2%l 53 WlKanal + 53 W/Kanal (+ Ohm,!. kHz, Gesamtktirrfaktor O,O2%l Wen iger als O ,02o/o Weniger als 0,003% 5 Hz - 60 kHz (8 Ohm, Gesamtklirrfaktor 0,05%) Gleichstrom-l00 kHz 1 Oa (Oiret Chassis ground Fig.4 The is because the POWER MOS FET is in the source case, and in order to maintain the capacity between FET and the radiation fan, stability deteriorates by this, so the FET is isolated from the chassis using a resistor of 47 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, since this may cut the lead wire of Rl or R2 and introduce nolse. 5q . Woshcr _kl) -4- . Precautions on troubleshooting and replacing parts (1) When the stabilized power circuit and the peripheral parts of Q701 and Q702 (D106, R752, R753 and their peripheral parts) are replaced, the adjustment of the input/output DC may drift, so be sure to check the input/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 the socket of the POWER MOS FET, polarity is indicated as B, C, E. Match it to the indications shown in Fig. 5 when replacing the POWER MOS FET and when checking. . Gautions on checking the voltage (1) Oscillations may occur depending on the voltmeter HITACHI HMA-6500 used when checking the gate voltage at FET 701 L/R. If this happens, measure the collector voltage of Q704 LiR as it is at the same potential as FET 701 L/R. The protection circuit may operate when checking the collector voltage of Q706 L/R and the base voltage of Q707 L/R. In this case, change the measurement position and measure the voltage between the respective electrodes. Gate (G) Fig. 5 (2) ADJUSTMENT . Adjusting idle current Perform adjustment with no signal and with the speaker switch turned OFF. Remove the wiring , shown in Fig. 6 and connect the side of the DC ammeter to the drain side of the FET 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 FETTOZL Fig.6 o Adjusting the input DC Insert the shorting pin to the input, set the DIRECT COUPLING/CONDENSER COUPLING switch to CONDENSER COUPLING, turn the speaker selector switch ON, and turn the powet switch ON with no load for more than about 8 minutes before performing the adjustment. To adjust Lch, connect the side of the DC arnmeter to 13 terminal of the main amp. PWB, and the Q 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 zero reading (within t 0.5V) with the 3mV range. (Fig. 7) o Adjusting the output DC Be sure to perform this adjustment after the input DC adjustment is completed. Insert the shorting pin in the input, set the DIRECT COUPLING/CONDENSER COUPLING switch to CONDENSER COUPLING, turn the speaker selector switch ON, and perform the adjustment with no load. Fig.7 Perform adjustment using R753L or R753R after con- necting the DC ammeter to the and Q sides of the speaker A terminals of Lch or Rch for a zero reading (within +5mV), with the l00mV range. (Fig. 7) Adjusting the meter Adjusting the meter sensitivity Adjust sensitivity of the meter after zero adjustment is completed. With no load applied to the speaker ter- minals, connect the audio oscillator to the input terminal (INPUT) to feed in a signal of lkHz. In this case, adjust the input so that the Lch pointer indicates 1W. Then adjust R955R so that the Rch pointer also indicates lW (Fig. 7). o (1) FETT02R Fig. 6 -5- HITACHI HMA.6500 CHECKING THE OPERATION OF When the output circuit is repaired by replacing the power MOS FET, etc., perform an operation check on the ASO (Area of Safe Operation) detection circuit and the speaker protection circuit. 1. Operation check of the ASO detection circuit for the power MOS FET Connect the audio oscillator to the INPUT terminals with the speaker terminals unloaded (speaker : dis- connect). Set the frequency of the audio oscillator at lkHz and adjust the level of the input signal so that the voltage 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 applied using a lead wire, etc. If this short-circuit makes the ASO detection circuit operate, no output appears at the speaker 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 indicates that the ASO detection circuit is operating normally. 2. Operation check of the speaker protection circuit Make sure that the relay operates(a click sound is heard) approx. 4 seconds after the power switch is turned on with the speaker terminals unloaded (speaker: discon- nect). ACvolmeler 0scilloscope Fig. 8 o Phenomena and remedy when the proection circuit operates THE PROTECTION CIRCUIT Next, when a resistor of approx. l0 kohms and2 dry cells (1.5V) are connected in series to R902 on the audio printed wiring board and the jumper wire , the relay turns off within I sec. When the dry cells are taken away, the relay operates again. Next, change the polarities of the dry cell and carry out the above- mentioned operation to check the operation of the relay. If this operation makes the relay activate, this indicates that the speaker protection circuit is operating normally. Moreover, pay attention during this operation check so that nearby parts are not short-circuited. of checking the POWER MOS FET Remove the FET. In the case of an N channel FET, it is normal : When touching the black test probe of the tester (ohm range ) to the drain of the FET, and the red test probe to the source, after applying the black test probe to the gate and the red test probe to the source at the same time, a current flows. And next, when brushing both the gate and source simultaneously with your hand, the current stops. In the case of a P channel, the red and black test probes of the tester are applied in reverse. TVpe of protection circuil Phenomenon when the protecion circuit operates CauseRemedy lMuting circuil No sound comes out about 4 rec. after the power switch is turned on Normal 2Protection circuit of the power l4OS FET (ASO protection circuit) I No sound comes out 2. When the power switch is turned ON the relay becomes ON, then OFF when the signal is applied Short circui of speaker output teminal Turn off the power switch, check whether the speaker teminal is short circuited or not, and tum ON again. 3 Speaker protection circuit (DC voltage detection / protection circuit) No sound comes out. Neutral point voltage is more thil i 2V After the power switch is tumed ON, rclay doesnt tum ON DC leakage of control amp , power amp. faulty, etc I ln care the input select switch has been set to DIRECT COUPLING: If the fault is corrected by setting it to coNDEN- SER COUPLING, control amp. DC is leaking so repair the control mp 2 In case the input slect vitch has been set to CONDENSER COUP. LINC: Repair faulty parts in power amp -6- DESCRIPTION OF THE NEW CIRCUIT o Protection circuit IC HA12002, an exclusive protection circuit, is used to protect the speaker and power amplifier. (1) Muting circuit This keeps the relay off for approx. 4 sec after the power switch has been turned on to reduce shock sound during ON/OFF operation of the power switch. This is determined by the rise time constant of the voltage 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.6500 When a DC voltage appears at the neutral point of the output, a relay turns off when approx. l 3V is applied to pin of IC90l via R901, R902 R903 is the sensitivity adjustment resistor. Protection of Power MOS FET (ASO protection circuit) When overcurrent flows to th output, the voltage Vcs between the gzte and source of FET7OI increases, Q70 and Q707 turn ON, the voltage is applied to pinof tC901 and the relay is turned off. (3) FEATURES HITACHI 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 this POWER 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 to engineering only the best in sound quality. , 1. Design oriented toward low distoftion across wide band for the best in sound quality The POWER N/OS FET features a high input impedance and it is a voltage-driven device. These two merits provide a high power gain and a simply designed circuit configuration. This is why there is minimai noise or phase drift which has an adverse affect on the sound quality, and also why there is no deterioration in the distor- tion factor. ln addition, the frequencv response is excellent, the switching speed is fast, stable operation is ensured even in the high frequen- ciesand notch distortion is dramatically redued. The design makes for a low distortion factor across a wide band with a continuous power output 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 waveform power transmission The capacitors have been eliminated from the NFB loop and even the input capacitors have been put aside in this DC amplifier to effect a great improvement in the low-frequency-range phase characteristics. The first stage employs low noise transistors with a high withstanding voltage and well-matched pairing characteristics for a reduction in center point drlft. Further- more, there is a DIRECT COUPLING/CON DENSER COUPLTNG switch which is pro- vided to safeguard the speakers from damage caused by DC component eakage from the externally connected equipment (such as the control amplifier). 3. Connection facilities for two pairs of speakers This amplif ier can accommodate two pairs of speakers, 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 one speaker system in one room and from the other speaker systern in another room. 4. High-reliability protection circuitry ln order to protect the POWER MOS FET, a current limiter circuit which relles on the detec- tion of the area of safe operation and DC voltage detection circuit have been installed. This clrcuitry features high reliability which enables it to cope with accidents. 5. Large-sized power meters (peak rneters) The model comes with large-sized power meters which enable the balance between the left and right channels and also the output level to be checked. Their size and performance are what you would expect to find in a POWER MOS FET amplif ier The power meters adopt a loga- rithmic compression circuit for RMS value dis- plays of the detected peak values This is why they can track peak signals and enable the displayed values to be read out directlV / / -7 - HITACHI HMA-6500 WARTUNGSPUNKTE . 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 die Klemmen an den Punkten C803 und C804 mit einem Widerstand von etwa l0 Ohm (5W) berhrt werden. Wenn die Entladung ber die Erdung des Chassis er- folgt, besteht die Gefahr, dafl Rl oder R2 geffnet wird und Rauschen auftritt; das Entladen ist daher zwischen den positiven und negativen Q tclemmen des Elektrolytkondenston vorzunehmen. (2) Darauf achten, da$ die Klemmen benachbarter Teile nicht mit den Anschlssen des Gleichspannungsmessers berhrt werden, wenn dieser fr die Messung des Blind- stromes angeschlossen wird, da es ansonsten zu Strungen kommen knnte. Den Gleichspan nungsmesser vorsichtig behandeln. Isolationsband gegebenenfalls um den Schraubenziehre wickeln. o Einbau der Teile Bei der Montage des Gertes wurde besonderes Augenmerk auf Betriebssicherheit gelegt, so dafJ alle Teile besonders sorgfoltig eingebaut wurden. Zum Beispiel wurden bestimmte Leiter mit Kunststoff- sohluchen berzogen oder andere in sicherem Abstand von der Schaltplatne angeordnet. Beim Austausehen bzw. Reaprieren voR Teilen ist daher darauf zu achten, daf$ die ursprnglichen Sicherheitsmafrnahmen wiederum eingehalten werden. o Gleichstrom /Tiefenfilter-Schalter Da 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 die Lautsprecher-Treiber zerstren knnten. Mit Hilfe dieses