Adcom-GFA5802-pwr-sm维修电路原理图.pdf

RadioFans.CN 收音机爱 好者资料库 RadioFans.CN 收音机爱 好者资料库 ADCOMServiceBulletin Date:August12, 1998 OrderingMatchedFETsandServiceManualCorrections Model#:GFA-5802 Bulletin#:GFA-5802-1 The GFA-5802 Service Manual notes on page 4 that anumberof the MOSFETsinthe amplifier are matched to ensure properperformanceFor repairs requiring replacement of these parts, equivalently matched parts must be used. In ordering these parts, these procedures must be followed. Failureof0169,0171,0176, 0178,063or073 For repairs requiring replacement ofanyoneof the transistors in input pair0169and 0171,cascade pair0176and0178or second differential pair063and073,both transistorsinthe pair must be replaced. That is, if0169fails, both0169and0171need to be replaced. Order both and specifyMatchedwith the part number. FailureofanyoftheIRF244outputtransistors The category of the output transistorsisidentified by a letter written on the bottom of the transistor. The markings will appearinone of two ways. 1)As a single or double repeated letter. (Example MorBB.Note:BandBBare different categories). 2)Asasequence of letters separated by a dash. (ExampleAD-AAorTB-O). When ordering replacements, indicateMatchedwith the partnumberand theexactletter codewritten on the transistor. The replacement parts will be of the same category. Note: there is no quality difference between transistors of different letter categories. Transistors of category CC are not better than those of categoryD.It is only important that the output transistors are of the same categoryforproper operation. GFA-5802Service ManualCorrections 1)On page1,change step 4 of theBIASALIGNMENTprocedure from The reading across these resistors should average33mVand all should be between 23mVand 43mV. to The reading across these resistors shouldbe amaximumof33mVandallshould rangebetween18mVand33mV. 2)On page 3, change the062,63, 73 part description from *Matched IRF961 0 to *Matched IRF9622 and the part number from 33009610 to 33009622. IRF9610s will be replaced with IRF9622s. These will be providedinmatched pairs as described above. ES 8/98