罗兰Roland-SPA-240-Power-Amp-Service-Manual维修服务手册说明书含电器原理图

SPA-240SERVICE NOTESIMPROVEMENTS COMPONENTS CHANGESSecond EditionPROTECTION CIRCUITSSPECIFICATIONSThis issue makes the first editiom obsolete.The protection circuits incorporated in the SPA 240 of various versions lexopt aarly modell have undargone design changes to have more raliable parformance.The changes are mainly concentrated an DC Levelinput levalDectorand Low Impedance Sersor.+4dm1.23WTHD:bomor thun605转德d+4dm1.FeU情rCyg04et-m地，±9BOUTPUT DC LEVEL DETECTORUntalanced0时wct市0 Cbias at speoler terminal (radio wares of hig中rgg,hen indu3ed,sity ampified:sam时imsnput inped山rcaPowtr bandwidthe20业=0地to the extent to become asymmetrical waveform which canstitutes DC).And opan-tircuits speaker eircuit已d由星5对：Damping factor:befler than 7by energizing a nalay upon detecting DC exceeding predetermined leal,Change:Threshould-from 1.85V to 4V allowance for torelance.sN广A"waigheed:input shortedOutputbetlar Ihan 110dB3pm,0604t0160LOW OUTPUT IMPEDANCE SENSORSpeaket,monodio162Aose开h样g网ercrcuit wit价the relay when it becames less than4ghT际Pawer co0210WChange:Bias souree for the first transistor of this stoge -from pesitiv supphy to pround to make theOutput paw智0e一2江k田cirouit immune from an DC supphy1o410月301r0+IOW HOITEMPERATURE SENSORMerras on heat sink and activates relay when owerheated.No change.CURRENT LIMITERRegulates output ourrent.Suppresses input signel levl at power amplifler stage in propotion as speskerimpedan住dcr网Change:Loosen torelanes to extend dynamic range.Nat all of changes took place in porallel with,but with some modifications on diferent part.Theproductiond are prouped into four sections in this Servioe Notes.GroupSerial Number1840100004923890850062559092560.102729112730Ofb No is the latest and the remainder of vensions should be modifieds eesry.Modificationprocedures are on rulated poges as a reference for updatingRemowsl of top cover provides accestibility for amost all servicingPOWER TRANSISTORSBecause of dscontinuance at the manufacturer.Roland has changed power transistrs.SPA-340BLOCK DIAGRAMfrom25A100528A11825C256529c2773in replacing power transis时o作，the followin0 must be observed in Eght of tone chara试sri时ic.Use NPN and PNP transisters of the same hfe range IY ar Ol in a chonnel..Do not mixuse diffarant brand in a channel even they hove the same suffix IY orRolandrinted in与pan831