Jvc 4VN 770 Service Manual

Page 2

ADJUSTMENT (for TAD-95J Power Amp. Section and TAC-177J Protector Section)

1. CENTER VOLTAGE TEST
Connect probe of DC. V.T.V.M. to positive pole of Speaker Terminal. And connect ground or earth lead of V.T.V.M.
to Speaker Earth Terminal or Chassis.
And turn to Power Switch On. V.T.V.M. should read 0 volt. If V.T.\.M. read no 0 volt adjust the VR. (R437, R438.
R439. R440) for V.T.V.M. read in 0 volt.
Note: Set the VR (R437~R44»0) at middle position before switch on.
2. IDLING CURRENT TEST
Connect DC. V.T.V.M. to the check point of Resistor (R485, R486. R487. R488) at both ends.
And V.T.V.M. should read 10 mv. If V.T.V.M. doesn't read 10 mv. adjust the VR (R453, R454, R455, R456) deliberately

for V.T.V.M. readin 10 mv. (Idling Current: 20 mA)

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3. PROTECTOR ADJUSTMENT
The protector circuit dosent operate at 49 load, 7.5 volt (14 watt) output. (All channels are driven.)
Adjust the R522 in order to actil activate the protector circuit by grounding the speaker terminals when the out put

is 2 volt at 89 load.
And adjust R514 in order to activate the protector circuit by appling DC 0.25 volt to point A.

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