Shure SR105 service manual Printed Circuit Board Removal

R 3 9 R 4 0 Dl2 R36

T2	C14	C15	R 31	Q8 R35	Q7	R 4 3	PL2	MI	PL3
							(XPL2)		(XPL3)

Y SRIOSA MODEL ONLY

FIGURE 13. SR105 POWER AMPLIFIER TOP VIEW,

COVER REMOVED (SRlOSA MODEL SHOWN)

adjustment screw below the meter face until the needle is properly positioned. With no load on the Amplifier (speaker disconnected), connect an ac voltmeter across one of the DIRECT OUTPUT Terminals. Turn the Amplifier on and ap- ply a 1 kHz sine-wave signal at approximately 3 volts rms to one of the Amplifier inputs. Adjust the VOLUME Control for 28.3 volts at the output. Remove the bottom cover and adjust the Meter Adjust resistor (R27-METER ADJ. located on the Main Circuit Board under the chassis as shown in Figure 14, Page 14) for a 100% reading on the OUTPUT VOLTAGE Meter. No further adjustment is necessary. Re- place the bottom cover.

To calibrate the meter for a 100% indication with 70.7V output, connect the voltmeter and an appropriate load across the 70V OUTPUT terminals and proceed as above.

PRINTED CIRCUIT BOARD REMOVAL

The underside of the SR105A Amplifier chassis contains two printed circuit boards: a Main Circuit Board and a Filter

Circuit Board. (The SR105B Amplifier contains only a Main Circuit Board.) The foil side of the boards may be made accessible for servicing without disconnecting any leads by removing the four Phillips head screws securing the board. The boards may be completely removed as follows (see Figure 14, Page 14). Remove the bottom cover. On the Main Circuit Board, remove all 15 interconnecting leads from the push-on board terminals, noting connections as listed in the table below.

CAUTION

Similar wire colors are used in different circuits; make sure proper re-connections can be made. Take care not to bend or break the push-on terminals.

Remove the four Phillips head screws from the board and remove the board from the chassis.

The Filter Circuit Board may be removed in the same manner. Replace bottom cover after servicing boards.

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