11.Technical Description
1.
AC Line Filter (PSH-83D)
The AC line filter board is comprised of inductor L1 and capacitors C1 – C5, a fuse and voltage
selector switch. The line filter prevents noise from the organ leaving through the AC line cord.
SW1 is voltage selector switch this allows selection of various line voltages available throughout
the world to provide power for the organ. The fuse value is selected depending on the source AC
voltage the organ is using.
2. Power Supply Board (PSH-72B)
This board takes the AC voltage from the secondary of the power transformer PSH-119, rectifies it
and makes the DC voltages needed to operate the organ (+5V, +6V, +/-18V). The Regulator U3
provides the +5V for the MGH-91A. Regulator U4 provides the +6V used for the heater of the
vacuum tubes on the PAH-72A board. The +/-18V is used for the amplifier ICs on MXH-35A
board. The regulator U1 a 7818 creates the +18volts and U2 a 7918 creates the –18volts.
3. Main CPU, Sound generator and DSP Board (MGH-91A)
This board has two CPUs, two VASE3 sound generators a digital signal processor and three D/A
converters. The main CPU controls the tone wheel generator and multi-contact keying and the
DSP provides the effects, reverb, vibrato, Leslie and tone control.
3-1. Main CPU
U1 is main CPU (SH7017). This CPU has internal flash ROM. Update of the system’s program
is from an outside 16M flash ROM U4. New system software is loaded from CompactFlash card
“CF card.” The Main CPU also controls the VASE3 generators U37 and U36, U2 the DSP, LCD
display and switch scan functions.
3-2. Sub CPU
U3 is sub CPU (3007). This CPU is a high-speed processor it controls the key scan and tube
overdrive circuits.
3-3. Main Memory
Main software is stored in 16M bit flash memory of U4 (29F160B). U57 and U58 is 1M bit SRAM
preset and panel switch data is saved in this pair of chips. These chips are battery backed up by
BAT 1. U5 is 16M bit DRAM this is workspace memory.
3-4. System Reset
