Electronic Flash Pc Boards; Sonar Pc Board - Polaroid Miniportrait 455 Repair Manual

Electronic Flash PC Boards (Figure 2-10 and 2-11)
Note: Text in boldface type denotes a difference between Model 455 & 403.
1. With the Power Switch ON, the Flash Unit set and its Power Switch ON, flash circuit
oscillation is started by push-pull oscillators Q7 through Q10 and step-up
Transformer T1.
2. The stepped-up voltage is rectified by high-voltage diodes D4 through D11 and charges
main capacitors C8 and C9. When the capacitor voltage reaches a specified level,
Q11 turns on, Q5 and Q6 cause oscillation to stop, and a floating charge phase starts.
Simultaneously, the READY LED lights and the READY SIGNAL is output by Q1 to the
Main PC Board ("Body Circuit"). (As mentioned previously in the Main PC Board
description, Flash charging is halted during shutter Motor run.
3. When charging is completed, Q3 turns on and the trigger circuit is biased, creating a
ready-to-be-triggered state. In this state, closure of the Sync Switch causes strobe
firing.
4. To switch between the GN35 (for ISO 80 films) and GN16 (for ISO 400 or 800 films), a
double-throw Switch is provided on the rear of the Flash Unit. In the GN35 position,
capacitors C8 and C9 are connected in parallel. In the GN16 position, only C8 is
connected.
Sonar PC Board (Figure 2-12)
IC1 is an analog signal processor, IC2 a digital signal processor, IC3 an oscillator,
and IC4 a distance measurement checker. Each IC indicates its own processing results.
1. Pressing S1 of the release switch ("SR CONTACT") powers the Sonar Circuit and
initializes IC4 at the time constants of R11 and C8.
2. As IC3 supplies an oscillation output to IC4, Q2 and Q1 are turned on by a VSW
signal, powering IC1 & IC2.
3. When IC2 receives an INIT signal from IC4, IC2 generates ultrasound burst signals.
These signals are output from the XMIT pin to Q3, stepped up by T1 and transmitted
by Transducer TD1.
4. Received wave pulses are input to IC1, amplified and fed to IC2. IC2 measures the
reflected pulses (echo return) and feeds this measurement to IC4 from its ECHO (RLOG)
pin 9.
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