Arcam-Alpha7R-int-sm维修电路原理图.pdf
《Arcam-Alpha7R-int-sm维修电路原理图.pdf》由会员分享,可在线阅读,更多相关《Arcam-Alpha7R-int-sm维修电路原理图.pdf(16页珍藏版)》请在收音机爱好者资料库上搜索。
1、H /P P SE MANALPHA ONE/7R/8R/8P AMPLIFIER SERVICE MANUAL1Arcam Alpha One/ 7R/ 8R/ 8P Amplifier Service ManualIssue 1 Serial Number 001 - (Paul Newton/ Haider Bahrani Sept 98)Circuit DescriptionThe Alpha One / 7R/8R and 8P share a commonpcb. The circuits are very similar and the maindifferences are t
2、he remote volume facility and extrapower output on the 7R and 8R and a switch tobypass the phono stage to enable its use as an extraline level input and the AV processor switch on theAlpha 8R integrated amplifier. The 8P poweramplifier utilises the same power amplifier circuit asthe Alpha 8R integra
3、ted amplifier. Power SuppliesThe ac output of the toroidal mains transformer isrectified and smoothed by D201-204 and C204, 205.This is then regulated to +/-15V by Z201, 202 topower the phono and tone control stages and thed.c. servo.The Alpha 7R and 8R transformers have an extratapping which is use
4、d for the remote volume circuit.The ac in is regulated to 5V by zener D902 andassociated components and this is then used topower the microcontroller Z901 and remote receiver.Phono Stage (Not applicable to Alpha One)The phono stage consists of a dual opamp Z305, oneopamp per channel. The RIAA equali
5、zation isachieved by the feedback components R703, 704,702 and C704, 705, 702 on left channel (R603 etc.as above for Right channel). R703 determines thegain and C703 the low frequency roll off.On the Alpha 8R this stage can be bypassed by useof switch SW302 to enable use as an extra line input.Tone
6、ControlsThe tone control stage is based around Z304 a dualop amp.The range of the controls is set by R507, 508 for thebass pot RV302 and R509, 510 for the treble potRV303.The tone controls and balance pot can be bypassedby use of the direct switch, SW304.Power AmplifierThe input to the power amplifi
7、er from previous stagesis fed to the differential input of Q112 and Q113. Q110 and Q111 form a constant current source for the differential input stage.The output devices are n channel mosfets SMF045.Zener diodes D103,104 limit the voltage swing withinsafe limits for the output devices & fusible res
8、istorsR105, 106 provide overcurrent damage to thedevices.A proportion of the output current appears across theprotection network R41,42. If this becomes too highQ17 is turned on and mutes the output. High D.C.levels at the output will also mute the output. Thereare no output fuses on the Alpha One,
9、7R and8R/8P amplifiers. The muting is done by the mute icZ303 and its associated compontents. The muteoperates on switch on/off and if an over current orover voltage condition occurs. The power led glowsamber when the mute circuit is operative and glowsgreen in normal use.Removing the Alpha One/ 7R/
10、 8R/ 8P TransformerThe toroidal transformer is extremely well secured tothe main pcb with a double sided adhesive gasket.To remove the transformer you must break thisadhesive bond by cutting through the gasket. Thiswill be easier if the transformer is warm.Use a cheese wire under the transformer, pu
11、llingbackwards and forwards under tension to graduallycut through. Once most of the adhesive is cut, youshould be able to pull the transformer away from thepcb.A less satisfactory substitute for cheese wire is to usesome 22 gauge tinned copper wire, stretched first toremove kinks, and two temporary
12、handles.Alpha One/7R/ 8R/ 8P Quiescent Current (IQ)SettingsWhen replacing the output transistors of the aboveamplifiers it is important to reset the quiescentcurrent (IQ) to the correct value to prevent theamplifier blowing again.The IQ should be checked and set by following theprocedure below:From
13、cold and with no load or signal connectedTurn both IQ presets (RV1 and RV101) down tominimum (fully anticlockwise) and set the voltagedrop across resistor R1 (R101 for right hand channel)to between 3.0 and 3.5mV for the Alpha One and 7RRadioFans.CN 收音机爱 好者资料库H /P P SE MANALPHA ONE/7R/8R/8P AMPLIFIER
14、 SERVICE MANUAL2amps or between 2.3 and 2.8mV for the Alpha 8R/8Pamps.Leave the unit for 1 minute and reset to these valuesif required.Leave the unit for a further 5 minutes and reset ifrequired.The IQ is now set and the unit can be connected tospeakers and fully checked out.Disassembly For Servicin
15、g1.Remove the top cover and front panel.2.Remove 2 screws securing the sub front to thechassis sides and 3 screws holding thesubfront to the chassis base.3.Remove 1 screw holding the pcb to thechassis. This can be found near to the mainsinlet socket.4.Remove 5 screws from the rear panel, one ateach
16、end and 3 along the bottom edge.5.Remove the transformer bolt.6.Release the PCB pillar located near to theserial number on the pcb.The pcb, with the rear panel, transformer andsubfront attached, can now be pulled backwards outof the unit.TEST POINT VOLTAGESTest PointDC Voltage Alpha OneDC Voltage Al
17、pha 7RDC Voltage Alpha 8R/8P132.8V35V37V227.8V29V31V315V15V15V4-32.8V-35V-37V527.8V-29V-31V6-15V-15V-15V7N/A0.09V0.09V8N/A0.10V0.10V90.3V0.27V0.27V103.4V3.2V2.9V1132.8V35V37V12-3V-2.7V-2.5V1332.8V-35V-37VBetween 14 & 153.0 -3.5mV3.0-3.5mV2.3-2.8mV16 (protection off)0.0V0.0V16 (protection on)0.6V0.6V
18、170.0V0.0V180.0V0.0V190.0V0.0VRadioFans.CN 收音机爱 好者资料库H /P P SE MANALPHA ONE/7R/8R/8P AMPLIFIER SERVICE MANUAL3Test PointDC Voltage Alpha OneDC Voltage Alpha 7RDC Voltage Alpha 8R/8P200.0V0.0V0.0V21 (protection off)1.6V1.6V1.6V21 (protection on)5.0V5.0V5.0V220.58V0.17V0.17V233.4V3.1V3.1V24-3V-2.7V-2.
19、7V25-26V-29V-29VBetween 26 & 273.4mV3.4mV2.5mV28 (muted)35V35V35V28 (protection off)1V1V1V29N/A5V5V30N/A10.510.5V31(volume going up)N/A0V0V31(volume going down)N/A5V5V32(volume going up)N/A0V0V32(volume going down)N/A5V5VPARTS LISTSThe parts for all the units are as the Alpha 7 except where shown.RE
20、FDescriptionPart NoProductC1ELST 100U 100V2N710B7RC2PEST 47N 63V 10%2K3477RC3PCRB 100N 100V 5% RA5mm2H4107RC4PEST 47N 63V 10%2K3477RC5PSTY 33P 160V ENCAP1PF%2F0337RC7PPRO 4N7 63V 5% RA2D247N7RC8PPRO 100P 63V 5% RA2D110N7RC9ELST 100U 25V2N710A1C10ELST 22U 20V OSCON2P6227RC10ELST 22U 63V ELECT2N622A1C
21、11ELST 100U 100V2N710B7RC12ELST 100U 100V2N710B7RC13PEST 15N 63V 10%2K3157RC14PEST 15N 63V 10%2K3157RC15SUPPR CAP 4N7 250V2K2477RC16ELST 100U 25V2N7107RC17CERD 470P 63V 20% RA2A1477RC18CERD 1N0 63V 20% RA2A2107RC19ELST 100U 25V2N7107RC20CERD 470P 63V 20% RA2A1477RC21CERD 10N 63V 20% RA2A3107RC22CERD
22、 10N 63V 20% RA2A3107RC23SUPPR CAP 4N7 250V2K2477RC24PPRO 4N7 63V 5% RA2D247N7RC25PCRB 100N 100V 5% RA5mm2H4107RC26PCRB 100N 100V 5% RA5mm2H4107RC27ELST 220U 16V2N7227RC28PCRB 100N 100V 5% RA5mm2H4107RH /P P SE MANALPHA ONE/7R/8R/8P AMPLIFIER SERVICE MANUAL4C29ELST 1U0 50V 20% RA2N5108RC30ELST 22U 6
23、3V ELECT2N6227RC30ELLL 47U 10V ELECT2R647A1C30ELEC 10U 25V CERAFINE2P610CC8RC101ELST 100U 100V2N710B7RC102PEST 47N 63V 10%2K3477RC103PCRB 100N 100V 5% RA5mm2H4107RC104PEST 47N 63V 10%2K3477RC105PSTY 33P 160V ENCAP1PF%2F0337RC107PPRO 4N7 63V 5% RA2D247N7RC108PPRO 100P 63V 5% RA2D110N7RC109ELST 100U 2
24、5V2N710A1C110ELST 22U 20V OSCON2P6227RC110ELST 22U 63V ELECT2N622A1C111ELST 100U 100V2N710B7RC112ELST 100U 100V2N710B7RC113PEST 15N 63V 10%2K3157RC114PEST 15N 63V 10%2K3157RC116ELST 100U 25V2N7107RC117CERD 470P 63V 20% RA2A1477RC118CERD 1N0 63V 20% RA2A2107RC119ELST 1U0 50V 20% RA2N5107RC120CERD 470
25、P 63V 20% RA2A1477RC121ELST 1U0 50V 20% RA2N5107RC122ELST 100U 25V2N7107RC123ELST 100U 25V2N7107RC124PPRO 4N7 63V 5% RA2D247N7RC125PCRB 100N 100V 5% RA5mm2H4107RC126PCRB 100N 100V 5% RA5mm2H4107RC127ELST 220U 16V2N7227RC128PCRB 100N 100V 5% RA5mm2H4107RC130ELST 22U 63V ELECT2N6227RC130ELLL 47U 10V E
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- Arcam Alpha7R int sm 维修 电路 原理图