Analysis and elimination of common electrical faul

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Analysis and elimination of common electrical faults of jj204 offset press

jj204 B-B folio double-sided roll simple paper offset press, which can print books, periodicals, folio Northcote said, "this poses a great pressure on us to batch newspapers. The machine operates automatically from paper feeding, printing to folding, with high efficiency, which is favored by many book printing enterprises. Now the author analyzes the common electrical faults of the machine in use, and summarizes the specific treatment methods according to the actual situation.

(I) Common faults of the bell and related circuits

1. Press the bell, and the bell doesn't ring

(1) there are 8 bell buttons connected in parallel. If you press one bell and it doesn't ring, you can press another one to try. If the bell still doesn't ring, the fault should not be the bell button itself. It is likely to be related to the lock-out, stop and safety bar protection circuit connected in series with the bell button

(2) the machine is equipped with 15 lock stop and safety bar protection switches from the paper feeder, I printing unit, II printing unit to the folding machine and the main console. If any switch is disconnected, the bell will not ring. If you check level by level from beginning to end, it will take more time. The faster way is to divide these switches into several parts for partition inspection and judgment. For example, first measure from the stop lock button sb5 on the operating side of the II printing unit. If there is AC220V voltage between line 9 and line 0, the fault point is after sb5; If there is no AC220V voltage between line 9 and line o, the fault point is before sb5. After roughly judging the fault range, use similar methods to find the middle point in the same fault range, and narrow the fault range again until the fault point is found

2. press the bell, the bell rings, but the machine still cannot rotate at low speed

first observe whether the 2.2kW low-speed motor M1 is started

(1) if it is not started, check the main electrical box ka2, KM1 relay and its control circuit

(2) if it has been started, but the machine does not rotate with it, check the DC voltage of the low-speed clutch. Measure the low-speed clutch carbon brush line 703 and the ground. If there is DC24V voltage, check whether the carbon brush and slip ring are in good contact and the low-speed clutch itself; If there is no DC24V voltage, check the rectifier bridge vc2 and its power supply in the main power box

(II) common faults of main drive DC motor control circuit

1. No operation faults

(1) check whether relevant relays and contactors (such as KC, js4, xlc, JJ) are normally engaged, observe whether fan FD rotates normally, or directly measure KC lines 42, 43, 44 to judge whether the voltage is normal

(2) check whether the change-over switch whk is in "II" position

(3) measure the given voltage taken out from potentiometer WP at 4 and 8 contacts of whk. If there is a given voltage, check the amplifier and trigger again. If there is no given voltage, measure the given voltage at the 3 and 7 contacts of whk to judge whether the switch whk is open circuit. If the whk is normal, measure the voltage at both ends of the regulator tube 2wy2 on the given circuit board, and then check the given circuit

(4) when the triode 3bg1 or 3bg2 in the amplification circuit board is damaged, the trigger circuit will not get the control voltage and produce no operation fault. When replacing the triode, pay attention to the model and β Value, its β The value should be 50, and the hook should not face up to 100

Regularly insist on whether the screws in each part are stable

2. No constant speed fault

when it is found that there is operation without constant speed fault, just check the parts related to constant speed

(1) check whether the given switching relay KA located on the constant speed buffer plate is closed and whether it has poor contact

(2) if the triode BG on the constant speed buffer board is damaged, 15V DC voltage cannot be applied to both ends of the printing speed selection potentiometer wt

(3) due to long-term use of the printing speed selection potentiometer WT, poor contact between the sliding ends or open circuit at the head and tail ends will also cause non constant speed fault

3. low speed fault

the speed of the machine is too low after entering the constant speed state. After eliminating the possibility of mechanical faults (such as heavy load) and loose main drive motor belt, the following checks should be done: use an oscilloscope to check the DC voltage waveform at the output end of the thyristor DC drive device. When adjusting WT, the voltage waveform should change synchronously when the three-phase waveform remains balanced

(1) when there is phase loss or unbalanced waveform, the motor load should be replaced with 100W and 220V bulbs for debugging to avoid the adverse impact of unstable output on the machine

(2) if the three-phase output waveforms at the output end are uneven, the potentiometers 4W1, 5w1 and 6w1 on the A, B and C three-phase pulse plug-in boards should be adjusted repeatedly until the waveforms are symmetrical, and then the potentiometers should be locked

(3) if the voltage waveform at the output end is out of phase, use an oscilloscope to check the waveform of 4ck3 test hole of the pulse circuit board. If the waveform is abnormal, observe the waveform of 4ck2 test hole again. If the waveform of 4ck2 is normal, check whether the thyristor 4kgz1 is damaged

(4) if there is no sawtooth waveform in 4ck2 test hole, continue to check the ladder synchronous voltage of 4ck1 test hole. If there is no ladder synchronous voltage, check whether the voltage stabilizer 4wy1-2 or diode 4bz1-2 is damaged

4. High speed fault

(1) when the machine speed is much higher than the preselected speed, the potentiometer 3W1 can be adjusted to limit the output value of phase-shifting voltage; Potentiometer 7w2 can also be adjusted to appropriately increase the negative voltage feedback

(2) if the machine speed is too high and cannot be adjusted, it is very likely that the thyristor kgz1-kgz3 is broken down and should be replaced

5. speed instability fault

(1) first check whether the print speed selection potentiometer WT is in poor contact and whether the carbon brush of the main drive DC motor ignites

(2) connect a 100W, 200V bulb to the DC output to observe the oscillation. First adjust 7w1 so that the positive current feedback is not too strong. After eliminating the possibility of damage to 7c2 and 7C3, you can adjust 7w3 and 7w4 repeatedly, and observe the bulb and voltmeter at the same time until the light flashes faintly and rotates stably at various speeds

common faults of single control and program control

(III) the operation, constant speed, water, ink and pressure control of this machine are set with two control modes: single control and program control

1. there is no operation fault during single control

(1) press the operation button sbl5, ka4 to pull in and the machine does not rotate, then check according to the no operation fault condition described above

(2) press the operation button and ka4 does not engage, then check the single control and program-controlled transfer switch SA8 on the main console, the normally open contacts of lines 38 and 39 of the current limiting relay xlc in the rectifier cabinet, as well as the operation button SB15 and operation relay ka4

2. no fixed speed fault in single control

(1) press the fixed speed buttons sbl6 and ka6 to engage, and the speed of the machine cannot be adjusted by the printing speed selection potentiometer on the main console, then check according to the above-mentioned no fixed speed fault

(2) press the constant speed button sbl6, ka6 does not engage, then check the main console operation button sbl5, constant speed button sbl6, relays ka4 and ka6

3. there is no operation and constant speed fault during program control

(1) if ka5 is not engaged, first check the single control and program-controlled transfer switch SA8, operation button SB15, relays KA3 and ka5, etc

(2) if ka5 has been engaged, check the circuit board cxk of the program controller of the main electric cabinet at this time, and measure whether there is DC24V voltage between 706a and 702. If DC24V is normal, check relevant components of cxk circuit board

4. water, ink, and pressure failure

(1) if there is no water, ink, and pressure during single control, check the relevant water, ink, and pressure buttons and relays ka7, KA8, and ka9

(2) if there is no water, ink and pressure combination during program control, it should be checked according to 3 (2)

(3) if there is no action of water, ink and pressure combination during single control or program control, the corresponding solenoid valve should be checked

(IV) common faults of water and ink roller control circuit

1. the water roller or ink roller does not rotate during single action

(1) check the corresponding water and ink roller single action and automatic transfer switches and contactors

(2) check whether there is DC24V voltage output on line 708 and 710 of the given circuit board of the water and ink roller

(3) check whether the DC excitation power supply of the corresponding water and ink roller is normal

(4) check whether the corresponding 2.2k Ω speed regulating electric non corrosive medium level has adjustable voltage output

(5) check whether the ac70v and ac180v voltages of the water and ink roller speed regulating circuit board are normal, and whether there is adjustable DC voltage output at the output end

(6) if there is excitation and armature voltage applied to the corresponding water and ink roller drive motor, the carbon brush and its contact with the commutator should be checked. Generally, the carbon brush on the commutator surface is in poor contact due to carbon powder and oil dirt, which should be cleaned regularly, and the carbon brush should also be checked regularly

2. The water roller or ink roller does not rotate during automatic operation

(1) check the corresponding single acting and automatic transfer switches of water and ink rollers

(2) check whether the water and inking relays ka7 and KA8 are closed

3. the ink roller does not rotate during speed control

(1) check whether relay KA11 is engaged when it is placed in speed control

(2) observe whether the tachometer has corresponding indication when the machine is rotating. If there is no indication, check the tachogenerator g and its related wiring

(V) common faults of the version adjustment circuit

1. the version adjustment motor does not operate

(1) check the version adjustment change-over switch sa43 on the main console

(2) check the corresponding version adjustment buttons, limit switches, contactors and their wiring

2. The version adjustment motor is out of control

(1) check the corresponding limit switch and wiring

(2) check the phase sequence of the version adjustment motor, which is usually easy to be reversed after maintenance, resulting in the failure of the limit travel switch

3. no indication for version adjustment

(1) when there is no indication for all version adjustments, check whether there is DC voltage on 741 and 742 of the VC circuit board of the electric box under the main console

(2) if there is only one plate adjustment without indication, check the 1K Ω tracking potentiometer and its wiring under the plate adjustment limit travel switch on the transmission surface

(VI) common faults of tension control circuit

1. no tension of drum

(1) check whether there is DC voltage at the wiring terminal of drum coil. If there is DC voltage, it is mostly due to magnetic particle failure, resulting in no tension of the drum; If there is no DC voltage, check the single acting/automatic switch, 5A fuse and adjusting potentiometer on the paper feeder control panel

(2) check the electric control box located in the wallboard of the paper feeder operation surface, and check whether the red light-emitting diodes v2-25 and v2-26 on the magnetic particle tension control circuit board are on. If not, check the corresponding ac20v external voltage and rectification and voltage stabilization circuits

(3) measure the external power supply of ac30v and ac60v, and check the rectifier tube v2-12, v2-13 and thyristor v2-14, v2-15

(4) if the drum has no tension during automatic operation, check whether ka17 and ka18 work after pressing the bell

2. The tension cannot be automatically tracked

(1) check whether the transmission shaft of the mechanical sensing part of the tension mechanism is flexible. When the guide rod moves up and down, the straight slide potentiometer should not be stuck

(2) measure whether the voltage signal at the middle end of the direct sliding potentiometer rp15a/rp15b follows the guide rod

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