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BMX SERIES III CONSOLE
CIRCUITRY
When the tape machine is stopped, current is fed to STOP LAMP isolator circuit R1, R2, R3, CR1, C1
and U1, forcing the NOT STOP LAMP line low, which, via U4C and pulse driver circuit R4, R20, CR8,
C10 and Q1, momentarily holds the NOT AUDIO RESET low (ensuring module turnoff).
When the tape machine is in the record mode, current is fed to RECORD LAMP isolator circuit R9, R10,
C3, CR3 and U3, holding the NOT AUDIO RESET low.
The NOT REPLAY line, strapped low by jumpering pins 14, 15 or J1 (i.e., reel to reel mode) via R11, R12,
C4, U5B and U5C, holds resistor U6B such that the START ENABLE line is always high. When the
STOP LAMP and START ENABLE lines are both high, via U5D, R14 and Q2, the NOT READY output
will go low. With the NOT START ENABLE line low, a START pulse input via R16, R17, C6, U4E
and U4D will trigger monostable circuit R18, C7, CR4 and U6A, which momentarily turns on driver circuit
R19 and Q3 and TAPE START relay K1 (starting the tape machine). A STOP pulse input via CR6 turns
on TAPE STOP relay K2 (stopping the tape machine).
Either the NOT STOP LAMP line's low state or current fed to PLAY LAMP isolator circuit R6, R7, R8,
CR2, C2 and U2 forces the NOT RUN line low, which, via U5A and U4A, asserts the CART line high
(i.e., there is a cartridge in place).
When used for cartridge machine operation, the NOT REPLAY line is left unstrapped to the high state.
Without a cartridge loaded, the CART line is low, which, via U5B and U5C, presets U6B such that the
NOT START ENABLE line is low. After insertion of a cartridge (CART line is high), a start pulse input
will, as in reel to reel operation, start the cartridge machine. The NOT RUN line will then go low, which,
via U4B, will clock the low state on the data input of register U6B, asserting the NOT START ENABLE
line high. When the cartridge machine recues and stops, the RUN line will go low and the NOT START
ENABLE line remains high, which inhibits further start pulses from triggering monostable U6A, and
prevents restarting the cartridge machine. Either the CART line going low (by removing the cartridge) via
U5B, or a STOP pulse input, via R13, C5 and U4F via U5C, will again preset register U6B, asserting the
NOT START ENABLE line low.
8.5.5 TT-3 Turntable Interface
The TT-3 Turntable Interface (PR&E #99-110) was designed for use with most commercial turntables.
Each TT-3 can accommodate up to two turntables. For a schematic of this interface, as well as a diagram
of the console to interface cable (PR&E #99-38), see Section 8.6.
CIRCUITRY
When the turntable is stopped, no current will be fed to isolator circuit R1, R2, C1, C2 and U1, allowing
the NOT RUN line to go high, which, via driver R3, R12, and Q1, holds the NOT READY output low
(i.e., turntable is ready) and momentarily pulses, via C8, the NOT AUDIO RESET line low (ensuring
module turnoff). With the NOT RUN line's high state fed to U2D, a START pulse, via R4, R5, C3, U2D
and U2B, will cause a CONTROL pulse output via isolator circuit R8, R9, Q2, U3, R10, R11 and C5,
REVISION B
211
PACIFIC RESEARCH & ENGINEERING
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