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I want to give you a real heads-up for your desire to enable such people as I to acquire the information I need to maintain the older types of equipment such as this Akai HXA351W. You do a swell job with all the processes you have to perform so I can have a legible, thus usable
document which does not send me crazy trying to figure out the blurry text of a bad copy.
Very well done, Thomas.
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This manual is very well presented and after printing out looks about as close to an original as I think you can get. The quality is second to none.
The content of the manual is comprehensive and I think it would be well suited to an audio repair professional which I'm not but I did find it very informative and helpful.
The cost of the manual is more than covered by the money I'll save when I change the keep memory battery now I have the relavant info.
Very pleased with my purchase and can recommend it wholeheartedly as I can other manuals I've downloaded from this site.
Regards
Limey Alex
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Complete manual including mechanical part in good pdf quality. Shaded greys of the pcb due to pdf not perfect but usable.
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Nice pdf file of the manual sent promptly. Thanks.
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Complete MFG Service Manual at a good price FAST !
3. ADVANTAGE OPERATION AND OF POWER AMPLIFIER CIRCUITRY SECTION
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QThere is neccessity to decrease not the phase response till DC rangein order to increase the musicsignalresponse of extremely low frequencyrange. Therefore, amplifier is this employingno capacitors exceptonesfor phase compensation, and has an almostperfecttransient characteristics. OThe first stageFET(2SK97) a dual FETof even characterisis tics and has a large Cm and no-leakage currentat normal temparature. To avoid the influenceby temperature drift, such as center voltage(0V) deviation, this FETis used as differentialamplifier and operatesat cross point which is the optimum point of drain current(at about 3mA) against the temperature drift. QTransistors, TR05and TR07,the push-pull pre-driverstage functionsas currentdifferential amplifierthat the stabilized operationcan be obtained. In addition,the collector current of these transistors enough high to make linearity is excel lent. OSincethis Amplifier employsphaseadvancer circuits [C06, C08, C15, R29, C16 and R30J,which have not been frequently used,to compensate the phasecharacteristics on high frequencyrangeand is also made to have enough
3-1. Advantage
current on each stage to increase the through-rate, the performance on high frequency range is conspicuously improved. OTo avoid the voltage deviation, regulatedpower supply circuit composedof ZD0'1, ZD02 is employed.
3-2. Operation
The use of differentialamplificationat first stagedual FET, (FET01, FET02) and connectionof the FETto the differential amplifier composedof TR01,TR02,make possibleto obtain enoughgainand remarkable low distortion. The output signalsof TR0'1 and TR02are untiphase. The output signalof TR02addsto TR05,on the other hand, the output phaseof TRO1 invertedbyTR03,then,it becomes is input signalof TR04and TROZwhich cascoded are connection. The output signals TR05and TR07are inphase at that the operationof this stageis push-pulldrive and currentdifferential amplification.The power amplifierof the f inal stageis composed of SEPP (SingleEnded push-pull)symmetry comple mentaryin 3-stage darlingtonconnectiontype. TR@and TR10arecomposing currentlimitercircuitto protect power transistor from break-down overload. by
4. ADJUSTMENTS
4-1. Driver Circuit BoardAdjnstments (Seethe picture of top view on page 3.)
N o t e :1 . M a s t eV o l u m e . . . . . . r 1. Room Temperature. ......Minimum 3. For adjustment, run the unit for more than 3 minutesafter the power is switchedon.
suBfEcr ,or,r"r*, |
DC Volt Meter Sameas above
MEASURE OUTPUT Speaker Terminal Sameas above
ADfusr I oolrrr ro*
F-2721 vR01, vR02 F-2722 VRO1, VRO2 F-2721 VRO3
CONDITION " Set VR01 and VR02 to center oosition. o Then, for the purpose of proceeding the accurateadjustment, set the voltaeeto 0 volt by VR01first and V-RO2 next. o By turning VR03counterclockwise, the-bias current is decreased gradually.
D C0 V + 5 m V
DC 0V+5mV
Sameas above
T PT e r m i n a + ) ( - ) (l ot F-2721 of F-2723
DC 20mV+1mV
Sameas above T PT e r m i n a + ) ( - ) (l
F-2722 VRO3
DC 20mV+1mV
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