Transcript
Repair Manual
Miniportrait 485 Electronic Flash Unit September 1996
Americas Business Center Technical Services 201 Burlington Road Bedford MA 01730 TEL: 1.781.386.5309 FAX: 1.781.386.5988
Table of Contents Page Section 1 - General Description ....................................................................... Description .......................................................................................................... Specifications ......................................................................................................
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Section 2 - Circuit Operation ............................................................................
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Section 3 - Disassembly ................................................................................... General Information ............................................................................................ Flash Unit Disassembly .......................................................................................
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Section 4 - Troubleshooting ............................................................................. Required Test Equipment .................................................................................... General Troubleshooting Guide .......................................................................... Detailed Troubleshooting .................................................................................... Main Capacitor Regulated Voltage Adjustment ................................................... Final Testing of Flash Unit with Camera .............................................................
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List of Illustrations Figure 1 2 3 4 5 6 7 8 9
Page Electronic Flash Unit.............................................................................. 3 Flash Circuit Block Diagram .................................................................. 7 Flash Circuit Schematic Diagram .......................................................... 7 Flash Components ................................................................................. 9 Block Diagram for Troubleshooting Reference ...................................... 15 Capacitor Voltage Adjustment Setup ..................................................... 17 Flash PC Board Layout with Component Ratings.................................. 18 Flash PC Board with Component Designations ..................................... 19 Flash Circuit Diagram ............................................................................ 20
List of Tables Table 1
Page Main Capacitor Regulated Voltage Values ............................................
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Section 1 - General Description Description This compact flash unit is designed for use with the Model 485 Studio Express Camera, and mounts on the Camera’s hot shoe. Light output is switch selectable for ISO 3000 or 80 films. As shown in Figure 1, on the back of the unit is an ON-OFF switch, ISO 3000 - 80 film selector switch, green LED Ready Light, socket for AC Adapter cable, and a Flash TEST button for firing the flash without exposing a picture. The unit operates on either four 1.5V AA alkaline batteries, four 1.2V rechargeable nicads, or a Polaroid 120 VAC Adapter (PID #614737).
Figure 1. Electronic flash unit
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Specifications Dimensions
2.75” W x 1.75” D x 4” H (70 x 44 x 102 mm)
Weight
9 oz. (255 grams)
Recharging Time - Approximate Number of Flashes 10 sec. 7 sec. 5 sec.
150 - 200 (1.5V Alkaline batteries) 75 - 100 (1.2V Nicads) - (AC Adapter)
Guide Numbers 5.7 (m) at 3000 setting 25 (m) at 80 setting)
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Section 2 - Circuit Operation Understanding the electronic operation of the 485 Flash can shorten troubleshooting time, by helping you narrow down the probable sources of a problem. In these explanations, refer to the 485 Block Diagram (Figure 2) and Schematic Diagram (Figure 3).
Operation of Blocks 1-12 (Figures 2 and 3) Closing power switch SW1 applies voltage to the bases of oscillator transistors T4 and T5, initiating oscillation. C1 reduces charging time. A stepped-up voltage at the secondary of Transformer TF is rectified by D2 and charges main capacitor C11. D3’s rectified voltage, approximately the same as the voltage across C11, charges C6. When D3’s voltage, divided by R6 - R7 -R8 (block 9 in Block Diagram), exceeds the voltage of zener D6 (block 10), current flows through D6. This sets the voltage at the regulated voltage value of the main capacitor C11. The setting can be adjusted by R7. Current flow through zener D6 also turns on T7 and T6, ceasing current flow into the base of T4 and T5. T4 and T5 turn off, oscillation stops and voltage across C6 falls. Current flow through D6 consequently stops. T7 and T6 turn off and oscillation starts again. As this cycle repeats, it maintains a constant voltage across C11.
Operation of Block 13 Oscillator control (block 11) turns on transistors T3 and T2, lighting green LED D1. When SW1 is off, the voltage across C11 is not applied to the output voltage sensing circuit (block 9), T7 turns off and D1 goes out.
Operation of Blocks 14 - 18 Operation of the LED circuit (block 13) turns on T1, causing C7 to charge. Next, a signal from the Camera sync contact (block 18) turns on T8. When the voltage across C9 reaches the specified value, D9 turns on and the charge stored in C10 flows to trigger coil TC. The high voltage this generates in TC’s secondary fires flashtube FT.
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Operation of Blocks 19 - 21 When the ISO 80 contact of Film Speed Switch SW2 is closed, voltage applied to C12 through D12 charges C12. When the Flashtube is fired, energy flows through D10 and D11. Conversely, when the ISO 3000 contact of SW2 is closed, Flashtube energy flows from the main capacitor C12 discharging through R17 and R16.
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Figure 2. Flash circuit block diagram
Figure 3. Flash circuit schematic diagram (See Figure 9)
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Section 3 - Disassembly General Information Caution: Shock Hazard! Capacitors C11 and C12 are charged with high voltages which can also migrate to other parts of the Flash unit. Before attempting repairs, discharge these capacitors by connecting a 100 ohm 5W resistor (or suitable dump probe) across the terminals!
Before disassembling the Flash unit for troubleshooting/repair, check whether the batteries are fresh and battery contacts clean. If batteries have leaked excessively, the PC Board may have been damaged and require replacement. Frequent causes of problems include: Components or lead wires out of position; broken or cracked PC boards; poor solder joints; parts contacting each other. Carefully check for these conditions before doing extensive troubleshooting or disassembly. Disassemble the Flash unit only as far as necessary to correct the problem.
Flash Unit Disassembly (Figure 4) Note: (See the Parts List for a complete parts listing.) 1. Remove Batteries. 2. Remove cemented Rear Plate. 3. Remove screw A. 4. Remove two screws B. 5. Remove two Battery Labels.
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6. Remove Rear Case. 7. Discharge Capacitor (C12) 6 with a 100 ohm 5W resistor and remove the Capacitor. 8. Remove screw C. 9. Remove PC Board A. 10. Discharge Capacitor C11 with a 100 ohm 5W resistor and remove the Capacitor. Note: When reassembling, be sure the ON-OFF Switch Cover is positioned as shown.
Rear Plate
Screw A Rear Case PC Board A Capacitor C12
Battery Labels
Screw C Capacitor C11
Screw B
Switch Cover
PC Board A
Figure 4. Flash components
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Section 4 - Troubleshooting & Adjustment Required Test Equipment •
Digital Multimeter
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Regulated 6V 5A power supply with 0.7 ohm resistor (for Main Capacitor regulated voltage adjustment)
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BCPS Meter
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Four 1.5V Alkaline or 1.2V Nicad AA batteries or AC Adaptor
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Model 485 Miniportrait Camera & Film (for checking repaired Flash Unit)
Caution: Shock Hazard! Capacitors C11 and C12 are charge with high voltages which can also migrate to other parts of the Flash unit. Before attempting repairs, discharge these capacitors by connecting a 100 ohm 5W resistor (or suitable dump probe) across the terminals!
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General Troubleshooting Guide Block Diagram No.
Type of Trouble
Location
Fails to Oscillate
Power Source ON-OFF Switch Oscillator DC Power Jack
1 4 6 3
Oscillates but with low, abnormal noise
Oscillator Rectifier 1 Main Cap. 1 Osc. control 2 Osc. control 1 ZD-1
4 7 8 12 11 10
Oscillates but with high noise and fails to charge
Osc (Xfmr secondary open) Main Cap. 1 Out. Voltage Sense Rectifier 1 Input filter
6 8 9 7 5
Charges but LED fails to light
Osc. circuit Rectifier Main. Cap. 1 Out. Voltage Sense ZD-1 Osc. Control 1 LED Circuit
6 1 8 9 10 11 13
Charges, LED lights, fails to flash when shutter operates
Trigger Circuit Flashtube Camera Sync Contact Trigger Gate Circuit Trigger Gate Control
14 15 18 17 16
Charges, LED lights, oscillation doesn’t stop at rated voltage
Osc. Control 2
12
Flashes with Power Sw. OFF
Switch SW1
4
Fails to oscillate or reach flash level (GNo), with SW2 at either 80 or 3000
Main Cap. Rectifier 2 Rectifier 3
20 19 21
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Detailed Troubleshooting
Block Diagram Name
Trouble Occurrence + Often o Occasionally - Rarely
1
Power
+ Volt. drop
2
Source 1 & 2
+ Poor contact
4 3
ON-OFF Sw DC Pwr Jack
o Poor operation
Switch hard to operate: Won’t go to ON or OFF positions. Doesn’t always turn circuit ON.
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Input Filter
- Short
Won’t oscillate. Large current flows. Charge time 0.5 - 1.0 sec. too long. Charge time slightly long.
This malfunction almost never occurs.
Won’t oscillate. Large current flows. Won’t oscillate. No current flows. Oscillates but long charging time.
Often, Q1 & Q2 shorted. If it’s internal, charge time longer. If xfmr secondary open, oscillation occurs but with abnormal noise if xfmr. shorted. Large current flow.
Block Diagram Number
- Open - Other 6
Oscillator.
+ Short - Open - Other
7
Rectifier 1
o Short - Open
- Other
Type of Trouble
CKT. Conditions, Probable Trouble Source
No oscillation, oscillation but no LED, intermittent oscillation, fixed by tapping unit.
Oscillation with abnormal noise. Large current flow. Oscillation with high noise. Won’t charge, small current flow. Charge time too long. Current flow larger than usual.
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Block Diagram Number
Block Diagram Name
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Main Capacitor
Trouble Occurrence + Often o Occasionally - Rarely o Short o Open o Other
9
Output Voltage Sensor
o Short
o Open
10
Comparator.
- Short
- Open
- Other
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Oscillator Control 1
- Short
- Open
- Other
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Oscillator Control (2)
- Short - Open
- Other
Type of Trouble
Oscillation with abnormal noise; large current flow. Oscillation with high noise; small current flow. Long charge time; voltage below rating. Charge time and full charge current greater than usual.
CKT. Conditions, Probable Trouble Source
LED lights immediately. Lead wire out of place.
Some oscillation but stops immediately. Main capacitor voltage doesn’t rise. Oscillation doesn’t stop at rated voltage. Capacitor voltage approaches 400V. Some oscillation but stops immediately. Main capacitor voltage doesn’t rise. Oscillation doesn’t stop at rated voltage. Capacitor voltage approaches 400V. Unstable at rated voltage. Main capacitor voltage weak. Oscillation doesn’t stop at rated voltage. Main capacitor voltage approaches 400V. Fails to oscillate. Oscillation doesn’t stop at rated voltage. Main capacitorvoltage approaches 400V. Unstable at rated voltage. Main capacitor voltage weak. Fails to flash. Oscillation doesn’t stop at rated voltage. Main capacitor voltage approaches 400V. Unstable at rated voltage. Main capacitor voltage weak.
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LED light immediately.
Block Diagram Number
13
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Block Diagram Name
LED Circuit
Trigger Circuit
Trouble Occurrence + Often o Occasionally - Rarely
- Open
Type of Trouble
- Short
LED fails to light. LED lights dimly. LED fails to light.
o Short
Fails to flash.
- Open
Fails to flash.
- Other
Sometimes fails to flash.
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Flashtube + Open and o Other ReflectorAssy
Fails to flash. Sometimes fails to flash.
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Trigger Gate Control
o Short o Other
Fails to flash. Flashes before LED lights. Fails to flash.
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Trigger Gate Circuit
o Short - Open - Other
Fails to flash. Fails to flash. Sometimes fails to flash.
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Rectifier 2
- Short
Flash level is only ASA 80 or ASA 3000ER. Flash level is only ASA 80 or ASA 3000ER. Sometimes fails to oscillate.
- Open
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Main Capacitor 2
o Short o Open o Other
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Rectifier 3
- Short
- Open
Oscillation with abnormal noise; large current flow. Flash level is only ASA 3000ER. Charge time excessive: voltage below rating. Charge time and full charge current greater than usual. Oscillation with abnormal noise, large current flow, when S2 set at 3000ER. Flash level is only 3000ER.
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CKT. Conditions, Probable Trouble Source
Usually SCR D9 shorted. C10 may also be shorted. Usually, trigger coil broken. Usually, defective trigger coil. Lead wire out of place.
(S2 at ASA 80). LED lights immediately. Lead wire out of place.
Figure 5. Block diagram for troubleshooting reference
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Main Capacitor Regulated Voltage Adjustment If the Output Voltage Sensor (block 9 in the block diagram -Figure 5) or the Comparator D6 (block 10) is defective, the main capacitor regulated voltage must be adjusted even if the defective part is replaced with a new one. 1. Set the voltage of a regulated 6V 5A DC power supply to precisely 6.0 V. 2. Connect the 6 VDC output of the regulated power supply to the Model 485 PC Board, with a 0.7 ohm resistor in series with one leg, as shown in Figure 6. Refer also to the PC Board pictorials, Figures 7 and 8, and the 485 Circuit Diagram, Figure 9. 3. Set the ISO Switch SW2 to ISO 80 and connect a digital voltmeter across both capacitors C11 (60uF) and C12 (680uF) (Figure 9). 4. Now turn the power supply ON and carefully adjust potentiometer R7 (left center edge of board, at left of SW1 in Figure 8) to obtain the regulated voltage shown in Table 1 for the ISO 80 setting. Caution If voltage exceeds 340V, immediately turn off the power supply and wait for voltage to drop. Do not let the voltage exceed 350V! 5. Now set SW2 to ISO 3000 and connect the DVM across C11 (60uF). Adjust R7 to obtain theregulated voltage shown in Table 1 for the ISO 3000 setting. Note: The regulated voltage adjustment should be made carefully to obtain the combination of each capacitor regulated voltage and neon tube operating voltage shown in Table 1. Table 1. Main capacitor regulated voltage values
ISO
Capacity
Regulated Voltage
80
680uF +60uF
330V +/- 5V
3000
60uF
335V +/- 5V
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Digital Voltmeter Reflector
Regulated Voltage Power Source
PCB Assembly
Main Capacitor
DC 6 V 5A
Figure 6. Capacitor voltage adjustment setup
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Figure 7. Flash PC board with component ratings
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Figure 8. Flash PC board with component designations
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Figure 9. Flash circuit diagram
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Final Testing of Flash Unit with Camera After a Model 485 Flash Unit has been repaired, mount it on a 485 Studio Express Camera and take several photographs to check that it is operating properly and exposing film correctly. Check the following: 1. ON-OFF Switch. 2. ISO 80 — 3000 Switch. 3. Green READY LED. 4. Recharging time 5 - 10 seconds. (See Specifications, Section 1) 5. Front and Rear Cases and Hot Shoe securely attached. 6. Correctly exposed pictures of a person at various distances, with both B and W and color films, using the Guide Numbers shown in the Specifications (Section 1). Note:
If the Flash output is low or synchronization with the camera poor, the result will be underexposed pictures.
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