The head control box observes the 24V trigger signal from the power supply, and the output of an energy meter between the amplifier and the frequency doubler, and generates the voltage and timing signal for the q-switch as well as a mechanical shutter in the oscillator.
The box contains a motherboard, a high voltage power supply card, and a logic card. The logic is mostly 4000 series CMOS, with a supply voltage of 14V. There are a couple of TTL timer chips, and 2N2222 transistors for level conversion.
The logic card contains: (these are board coords)
A1 4020 14 bit counter A2 555 timer, running as a 1kHz clock B1 4013 Dual D flipflop B2 4020 14 bit counter B3 40174 hex D flipflop B4 4512 8 input multiplexer C1 4071 quad or gate C2 4049 hex inverter C3 4013 Dual D flipflop C4 40106 hex schmitt trigger C5 14538 dual monostable multivibrator C6 74221 dual non-retriggerable monostable multivibrator C7 74221 dual non-retriggerable monostable multivibrator
Connections to the control card are labeled con.1 to con.100, and are the pins on the edge connector.
The power supply card goes into a slot on the motherboard, and has a pice of
high voltage wire to a BNC for HV out. The slot has 44
pins, half of which are ground. The top of the connector is 1 to 22, and
the bottom is A to Z, omitting letters G, I, O, Q.
Schematic in postscript
Schematic in gschem format
The power supply card contains three separate circuits:
This takes several thousand volts DC from the power supply, and a low level
trigger signal, to generate the pulses for the Q-switch. It is physically right
beside the resonator, to keep things short.
Schematic in postscript
Schematic in gschem format
The energy meter has a couple of photo diodes, to observe the laser beam, for timing and a power bar graph on the remote control. The photo-diodes have IR filters on them, and just sort of look at where the beam goes by. There are no real optics.
Schematic in postscript
Schematic in gschem format
Connections to the energy meter are numbered EM.1 to EM.8 or so. They are numbered according to the header on the motherboard, and consistantly labeled everywhere. Which is why they are not in order on the EM board.
The remote control has buttons for shutter, fire, norm, and how frequently to fire the qswitch. I'm not sure what the norm button is supposed to do... There were notes attached to my laser indicating it should be pressed.
The power for the shutter in the oscilator goes through the remote, the laser will not operate without it. The pins on the remote control are labeled D15.1 to D15.12 on the remote control, but RC.1 to RC.12 on the motherboard.
The shutter will not open if the remote control is not plugged in.
Schematic in postscript
Schematic in gschem format