IT-B1 SERVICE MANUAL Canadian Model Central & South America Model Photo: WHITE Type IT-B1 SECTION 3 DIAGRAMS 3-1. PRINTED WIRING BOARD HANDSET SECTION IT-B1 3-2. SCHEMATIC DIAGRAM HANDSET SECTION " Refer to page 7 for IC Block Diagrams. Note: " All capacitors are in µF unless otherwise noted. pF: µµF 50 WV or less are not indicated except for electrolytics and tantalums. " All resistors are in &! and 1/4 W or less unless otherwise specified. " % : indicates tolerance. " ó : internal component. " C : panel designation. " U : B+ Line. " Connect J2 and J3 with handset cord. Power voltage is dc 12V and fed with regulated dc power supply from J3 with 100 &! in series. " Voltage is dc with respect to ground under no-signal condition. no mark : OFF HOOK ( ) : ON HOOK " Voltages are taken with a VOM (Input impedance 10 M&!). Voltage variations may be noted due to normal produc- tion tolerances. " Signal path. N : RX (from TEL LINE) O : TX (to TEL LINE) P : bell " Abbreviation MX : Mexican model LA : Latin American model 55 IT-B1 3-3. PRINTED WIRING BOARD CRADLE SECTION 3-4. SCHEMATIC DIAGRAM CRADLE SECTION JW " IC Block Diagrams IC2 TEA1112AT VCC GAR QR VEE MIC+ MIC- AGC IR 16 15 14 13 12 11 10 9 AGC CIRCUIT CURRENT REFERENCE LOW VOLTAGE CIRCUIT MICRO MUTE LED DRIVER ATT 1 2 3 4 5 6 7 8 LN SLPE LED REG GAS MMUTE OTMF MUTE IC3 HM91510AP R4 R3 R2 R1 MODE TONE PO HKS VDD 18 17 16 15 14 13 12 11 10 VDD D/A PULSE CONVERTER GENERATOR INPUT INTERFACE CIRCUIT ROW/COLUMN DECODER ROW PROGRAMMING & INTERFACE CIRCUIT COUNTER DATA LATCH LNB MEMORY KERNEL CONTROL CIRCUIT MEMORY COLUMN VDD INTERFACE CIRCUIT DIVIDER OUTPUT INTERFACE CIRCUIT OSC VSS 1 2 3 4 5 6 7 8 9 C1 C2 C3 C4 KT OSCI OSCO XMUTE VSS