The Various Power Supplies; Key Scan - Hammond XK-5 Service Manual

The name
of the
Power supply voltage
vacuum tube
12AU7 No.1
and around 35V)
12AU7 No.2
12AX7 No.1
(between -15V
and around 35V)
12AX7 No.2

2.2.7 The various power supplies

The main power sources are generated by +5V input from the switching power supply module
with using the switching regulator.
The power source of CODEC is generated by linear regulator which is using the power source
generated by the switching regulator.
The followings are the details of the each power source.
Regulator
The name
IC desig-
of the
power source
nator
+15V U17
-15V
+13V U18
+30V
+16V Lamp U25
+5V CODEC U32

2.2.8 Key scan

Operated by the microcomputer U19 NXP KinetesL.
The details of the operations are as follows.
• Scanning a three contact keyboard
around 35V
(between 0V
around 45V
Voltage Use
+15V Operational amplifier
-15V
Vacuum tube heater,
Analog volume control,
+12.25V
around
The power source of the
+35V
vacuum tube
+16.2V for EXP-100F lamp
+5V for CODEC analog power
supply
Bias voltage
adjustment range
0∼-3.3V(grid)
0∼around -1.0V
(between cathode and grid)
-15∼around -11.7V(grid)
Regulator U32
10-4
Bias adjustment
VR No.
VR1
VR4,VR2
VR5,VR2
Remark
Generated both positive
and negative by trans-
former T1. The feedback
is only for the positive
side.
Generated along
+13V by charge pump
with using D8, D10 and
C213.
Apply the resistance to
+13V in series and make
+10.5V.
with