Marantz 105 B Service Manual
This is the 19 pages manual for Marantz 105 B Service Manual.
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Extracted text from Marantz 105 B Service Manual (Ocr-read)
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.......... .... ";;i//L TABLE OF CONTENTS SECTION PAGE
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INTRODUCTI ON This ser vice man u al w as prepared f or use by Auth or ized Warranty Stations and contains service i nformation for M arantz Mod el l 05B Stereophonic T un er. S ervic ing in for m at ion an d v oltage data i ncluded in this manual are intended for use by the k no w ledge abl e and exper ie nce d technician on ly . All instruction should be read carefully. No atte mp t shou ld be m ade to p roc eed wit hout a good understanding of the operation in the t u ner . The part l ists fu rnish infor m at ion by w hich replacement part may be ordered from the Maran tz Co m pa ny . A simple descr ip tio n is i n cl uded fo r parts which can be usually be obtained th roug h local suppliers . Th e Mod el 1058 is a tu ner version of the Marant z 's Model 20 15 Tu ner/Amplifier and almostthe sam e c ircu itr y a s u sed in th e Mode l 201 5 is em pl oy ed except the audio Amplifier, and power supp ly circu it. 1. AM Tuner A ll com po nents exce pt ferri te bar an tenna are m ounted on a printed circuit board Pl00. The AM signals in d uced in a ferrite bar a ntenna are appli ed to the base of converter transistor H113 th ro ug h a capacitor of C171, whil e t he loca l o sci llat or voltage is injected to the emitter of H113 th rough a capacitor C172. Bo th AM sign a ls and oscillating voltage are mixed at the base- em itter junctio n and converted int o 45 5KHz intermediate frequency. The resulting I F signal is ap plied to th e f irst I F tra nsf orm er L 116 co nsisting of one ceramic filter and two tuned circuits. T he o utp ut of L11 6 is led to the tra ns isto r H 1 04 which in turn apply its output to the t ransi st or of nex t st age Hl05. The fu ll y ampli fie d IF output is then applied to the diode H123 to detect aud ibl e signa l th rou gh th e det ector tra nsformer L 117. The detected audio signal is filtered and th e final au dio out pu t is obtained from pin terminal J118 and applied: to the output jacks th ro u gh the fu nc t ion sw itc h . T he DC c om ponent of the detected I F sig nal is used as a AGC voltage to control emitter curr en t of H 104 throug h the resistor R 185. A part of I F signal output is also applied to the diode H 124 through a capac itor C1BO and rectif ie d to obtain DC current for energizing the AM signal str e ng th met er M0 01. 1.1 Suggestions for AM Tuner trouble shooting C he ck fo r broke n AM bar anten n a, nex t try to tune station by rotating fly-wheel tuning knob slowly and observe the AM sig nal streng th meter whether it deflects or not. If the signal strength m e ter give s a deflection at sever al fre que nci es received, no failure may exist in the stages at least pr ec ed in g fin al I F trans f or mer L 117. N ext conne ct a oscilloscope to the pin terminal J118 and ch ec k for audio signa ls w it h th e tuning meter deflected. If the signal strength meter does not deflec t, check the local osc ill a tor circu it. Norm al oscillating voltage at the hot end of the osci llator tuning ca pacitor is a bo ut 2 or 3 volts, varying with tuning capacitor position. When me asu ring osc illati ng voltage use a RF V TV M, no circuit tester gives correct indication. If the l ocal oscillato r volt age is normal , check all voltag e dist rib ution in the AM circuits by using a DC VTVM and compar e th e m easur ed values with those given in the schematic diagram. 2. FM Tuner A ll com ponen ts are mou nte d on a pri nte d circ uit board P100. FM signa ls induce d by a FM an tenna are l ed to FM antenna coil L 101. These sig n als are then applie d to the FET RF amplifier which in turn applies its output to the next transis to r m ixer Hl02 th ro ugh a hi gh Q tuned circuit. The mixer convert its in put sig n al int o 10.71V1 Hz intermediate frequency and amplifies it at the same time. The H1 03 is a local o scillator and its output is injected into the base of mixer tran sistor, t he inj ectio n vol tage is abo ut 4 0 m V. 1