Gymna Pulson 330, Service Manual

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The info of signals 1 to 4 are sent to the
µ
p which will
interprete these signals in order to determine output power, to
detect the quality of contact and to see which ;heads are connected.
The only information coming from the
µ
p is the wanted
US_AMPLITUDE ( see 8).
•
US_AMPLITUDE: Voltage between 0 and -3V which will eventually
determine the
AMP_US voltage.
The only factors which influence this voltage are the intensity
keys.
The US_AMPLITUDE is inverted by U3 and presented to the addition point
of the switched power supply. Q10 is connected to VUS_EN. In case of
processor hang-up Q10, immediately connects the input of U3 to ground,
which results in a output power of 0W.
The 5V used as a reference for the ADDA is also the base voltage for
an accurate 10V supply, which is used in the switched power supply. To
assure proper working of the opamp (U3), the incoming voltage is
divided in two. To get 10V out of 2.5V we need a dc-amplifier.
Q9 converts voltage into current and Q11 converts current into
voltage.
12.5 Output frequency generation.
A quartz connected to U5 produces a 6MHz signal. U7 ( 7492A ) is a
divider with an 1MHz output on QA and a 3MHz output on QD. These two
signals are inverted through U5 and fed to U8 ( 74HCT), a dual channel
multiplexer ( 2*4 inputs ), which will actually work as a switch. The
non-inverted signals are fed to channel 2 and the inverted signals are
fed to channel 1 of U8.
S0 ( 1/3 MHz ) and S1 ( ON/OFF ) are the selection bits; if S0=S1=0
then inputs 1I0 and 2I0 are selected and presented as outputs. In
other words, depending on the selection bits an input is selected.
This results in two outputs: DRIVE_FREQ and NOT DRIVE_FREQ, the two
signals we need to amplify at the output stage. See table on next page
for other possible combinations.
S0 S1 DRIVE_FREQ NOT DRIVE_FREQ
0 0 1MHz not 1MHz
1 0 3 MHz not 3MHz
0 1 VCC VCC
1 1 VCC VCC
12.6 Relay drivers
Q6: is the driver of relay 1
Q7: is the driver of relay 3, which is always the opposite of relay 1.
D16 lights when this relay is activated.
Q8: is the driver of relay 2.
D17 lights when this relay is activated.
See 5.7 for further information on the use of these relay.
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