SONY IFB-12A
Manual de Servicio

2 Video signal
Video signals input from the BNC terminal are passed through relays RY1, 2, and 3 (IFB-12 (OLD)), RL1, 2, and 3 (IFB-12 (NEW), IFB-12A) and are input to +6 dB amplifier ICs 19, 20, and 21. This input signals are usually terminated with the 75 Z terminator switches S3, 4, and 5 (IFB-12 (OLD)), SW3, 4, and 5 (IFB-12 (NEW), IFB12A). When JP 1 and 2 connectors are set to the G-R and G-B sides, only G signal is generated, and a black-andwhite image is output. RGB signals input from ICs 19, 20, and 21 are passed through RY7, 8, and 9 (IFB-12 (OLD)), RL7, 8, and 9 (IFB-12 (NEW), IFB-12A) and are output to CN3 (21, 25, and 29) (IFB-12 (OLD)), J1 (21, 25, and 29) (IFB-12 (NEW), IFB-12A) terminals.

(A17) (IFB-12 (NEW), IFB-12A) becomes MIDDLE or HIGH, this mode is set. IN/OUT terminal of CN3 (B23) (IFB-12 (OLD)), J1 (B23) (IFB-12 (NEW), IFB-12A) becomes LOW and informs the outside of the output mode.

1 Video signal
RGB signals input from CN3 (B3, B5, and B7) (IFB-12 (OLD)), J1 (B3, B5, and B7) (IFB-12 (NEW), IFB-12A) are terminated with the 75 Z termination resistors R50, 90, and 130, and are passed through buffer ICs 7, 8, and 9 to be distributed for four outputs. These signals become four signals in which high-frequency is emphasized by R and C, and cable compensation elements CR1, CR2, and CR3. Analog switch ICs 10, 11, and 12 are used to select one compensation rate required from these four signals according to the mode S8 (IFB-12 (OLD)), SW8 (IFB-12 (NEW), IFB-12A). These signals are amplified by the 7 times output amplifier ICs 13, 14, and 15, are passed through relay RY1, RY2, and RY3 (IFB-12 (OLD)), RL1, RL2, and RL3 (IFB-12 (NEW), IFB-12A), and are output to the BNC terminal. Q18, 19, 20, IC16, and IC17 serve as corresponding feedback clamp circuits, detects black level of output signals, and applies DC bias to the output amplifier.

3 SYNC signal
A 75 Z or 1 K Z termination resistance can be selected for SYNC/HD and VD signals input from the BNC terminal using terminator switches S6 and 7 (IFB-12 (OLD)), SW6 and 7 (IFB-12 (NEW), IFB-12A). Q10, Q11, and IC (1/2), and Q14, Q15, and IC (2/2), and Q12, 27 (IFB-12 (NEW), IFB-12A) serve as a peak detection circuit for SYNC/HD and VD signals. These signals are compared with the intermediate value of the peak value, are converted to TTL level SYNC signals by IC3 and output to CN3 (12, 14) (IFB-12 (OLD)), J1 (12, 14) (IFB-12 (NEW), IFB-12A). Also with IFB-12 (NEW), IFB-12A, when input signal is recognized as TTL level, SYNC/HD, VD, which is input from BNC terminal, is input to relay RL6 as it is, then it is output to J1 (12, 14) by control of this relay. When the SYNC signals are used to process signals synthesized with video signals, JP3 and 4 are set to the VIDEO side. By switching JP5 to GS side, SYNC signals CS and VS are input from IC2 for input signals such as SYNC ON GREEN, Y signal, etc.

2 SYNC signal
SYNC HS and VS signals input from CN3 (B8 and B10) (IFB-12 (OLD)), J1 (B8 and B10) (IFB-12 (NEW), IFB12A) are passed through buffer IC5 (IFB-12 (OLD) only) and relay RY4 (IFB-12 (OLD)), RL4 (IFB-12 (NEW), IFB-12A) and are output to the BNC terminal.

3 Audio signal
AUDIO L and R signals input from CN3 (B1 and B6) (IFB-12 (OLD), J1 (B1 and B6) (IFB-12 (NEW), IFB12A) are passed through relays RY6 and RY5 (IFB-12 (OLD)), RL5 (IFB-12 (NEW), IFB-12A), and output to the pin jack terminal.

4 Audio signal
AUDIO L and R signals input from the pin jack terminal are input to the buffers Q16 and Q17, and are output to CN3 (A7, A8) (IFB-12 (OLD)), J1 (A7, A8) (IFB-12 (NEW), IFB-12A) by the analog IC4 switch.

4 Others
When the NOR/MIX switch S12 (IFB-12 (OLD)), SW12 (IFB-12 (NEW), IFB-12A) on the board is switched to NOR or MIX, �HIGH� or �LOW� voltage is output to CN3 (B31) (IFB-12 (OLD)), J1 (B31) (IFB-12 (NEW), IFB-12A) terminal. The signal type to be output (monitor output or projector output) can be indicated to an external switcher, etc.

2-4. OUTPUT MODE
When the IN/OUT switch (S2: IFB-12 (OLD)), (SW2: IFB-12 (NEW), IFB-12A) is set to the OUT side and RGB/ VIDEO signal level of CN3 (A17) (IFB-12 (OLD)), J1 2-2(E)

IFB-12/12A