To avoid the elementary causes of the on-screen errors always follow the Installation requirements:
-Machines are to be used in a place where the relative humidity is from 30 to 75% and the ambient temperature is from 18 to 30° C. Otherwise use the air-conditioning system.
-Do not install the machine in a place that is very dusty or where a lot of vibration is present.
-Do not raise or lower the room temperature suddenly. If you do so, moisture in the air is likely to condense on the machine, causing laser guns fogging, malfunctions in the electronics and PCBs, etc.

Preface

-Before using the machine, read the manual carefully, then handle the machine properly. Be sure to store the Maintenance manual near the machine so it can be referred to immediately should you have questions about operation or should any problems arise.
-Ground this machine with the grounding resistance of 4 Ohm or less.

Due to many different on-screen errors which may appear during the lab's laser exposure process or set up procedures we will explain only a few common errors for your prompt reference and remedy actions to set the problem:

Ask a professional assistance to perform all necessary actions to define the cause of the error.

Here we just write a few words about the probable causes of common laser errors.
So please read Laser Troubleshooting Guides to perform all necessary actions to define the cause of the error.

[Occurs from time to time or permanently]

Cause: The temperature of the laser unit is out of a specified range.

1. Measure the ambient temperature and set it to the working condition. If the temperature is within the specified range but the error still persists proceed to the next checkpoint.
2. Open the top cover of a lab. (See the service manual please).
2.1. Using the vacuum cleaner clean the space around the laser unit. Do not use in-take mode of the vacuum cleaner. Blow a dust from laboratory by means of a strong air flow made by a vacuum cleaner. The fans under the laser unit also should be revised and cleaned. When you finished and reassemble it - turn the lab on and if the error persists proceed to checkpoint 3.
3. Check the heaters and sensors which responsible for the Laser Temperature management.
4. Check the quality of all wire connections. 
5. Reconnect all connectors on Laser In/Out PCB.
Note: On some models such message can be seen when your lab was not working for some time due to software ability to turn off the laser in idling mode. So just wait when laser will be warmed and go on printing.  

See the detailed procedures in Service Manual. If you do not have it - click here.

Resume: No laser repair required.

[Occurs from time to time or permanently]

Probable cause: Poor connection/communication by fibre optic.

According to the "Troubleshooting manual" you have to perform the corrective action as follows:
1. Press the key.
The error message will be canceled.
If it recurs- Contact your place of purchase.

Our recommendations:
1. First of all try to reconnect all connectors of Laser driver PCB and Printer Control PCB.
2. Look at the condition of fibre optic (ARCNET) network (most likely cause of this error)
Go to Menu -> " Maintenance" -> "System version check" and check the condition of the status of communication.
If this good - no need to worry with network and you have to search further.
If this blinking between "ok" and "not communicated" - need to refit the fibre optic cable.
You need to check optical connectors # 1516, #1517 on Laser Control PCB and  #212, #213 on Printer Control PCB.
Note: At the end if all was in vain:
Try to swap the board with the same PCB from another lab and see the result. Perhaps the board is defective.

See the detailed procedures in Service Manual. If you do not have it - click here.
Resume: No laser repair required.

Probable Cause: The laser dust proof glass is dirty.

Affects all models.

Resume: No laser repair required.

Probable Cause 1: Defective AOM driver

Probable Cause 2: Weak sample signal of BLUE laser module

Affects Qss 32** and higher models.

Resume: if the blue AOM driver is in good working condition - Laser repair required.

The Exit sensor detects no laser beam of the laser module.
Probable Cause 1: Defective AOM driver.
Probable Cause 2: Defective AOM crystal.
Probable Cause 3: Defective laser module.

Affects any lab

In other words: The synchronous signal does not enter within the specified period of time onto the detector of the synchronous sensor PCB. Over time the light from the laser diode gets dimmer: eventually the laser beam is not bright enough for the synchronous sensor to reliably detect it, causing the 6073-000# error message.
The purpose of the AOM’s are to make the laser beam diffract (onto the print) by introducing sound waves of varying frequencies. Normally it is the blue solid state laser diode that tends to fail first, followed by the green, then the red.
If the exit sensor detects no laser beam this error will be generated. To exclude the worst do the following - determine the cause of this error.

If you still have error - the next suspicious parts are:
- AOM crystal (located is inside the Laser unit).  In this case laser repair required.
- Laser In/Out PCB.
- Laser control PCB
Also:
- Disconnect and reconnect all the connectors to all the laser PCBs.
- Check all test points for the wrong voltage presence.
- Check the quality of all connections of each AOM drivers. No result - go further.
- Check the Laser driver power supply. If power supply is normal but the error persists - send the laser unit to us.

NOTE: There was a problem with F & G 3001 software that would randomly cause the 6073 error, even if the laser was unit was good.
That is what the patch software was for. However if the software version is H or later the most likely cause will either be one or more faulty AOM signal processors, or deterioration of the laser unit.

Resume: If AOM drivers are in working condition and you have checked all other parts - laser repair is required.
(in some cases)

Probable Cause: Unstable rotation of a polygon mirror located inside the laser engine.

Affects any lab

Causes:
- poor contact iof connectors.
- defective Laser In/Out PCB
- defective polygon mirror.

What to do:
- reconnect all connectors on  Laser In/Out PCB.
- check 24V voltage availability on Laser In/Out PCB.

Resume: If Laser In/Out PCB is in working condition and 24 V presents on it -laser repair required.

Affects any lab

This error may be generated if the current has reached the highest limit.
Sometimes this can be erased by restarting the lab and the lab will work without any errors a certain time but the appearance of this error means that  the certain laser module works on the current that is VERY near to the highest allowed limit.
This will short laser's life very fast because all optics elements will be destroyed during the work with the current on this level.
We recommend not to wait for the very end of the laser module's live and send to us the laser for repair or obtain the new laser module.

It is useless to try to fix it by yourself.

Resume: laser repair required.

Affects type A (A1), Ff laser engines (Qss 30/31/32/33 etc.)

In the laser unit type B, this error message will not be displayed.

According to the Service Manual you need to check:
Laser Control PCB
Laser In/Out PCB
B laser driver (if you have 6074 code)
G laser driver (if you have 6075 code)

Laser power supply 1 & 2 (Each power supply is equipped with the over voltage and overheat protection functions. If these functions are operated, turn off the circuit breaker of the machine and wait for a while, then turn on again. If the overheat protection function is operated, check if each cooling fan is in operation).
Also a good idea is to perform Autotuning with Qss 30/31 Type A or Laser Reset button with Qss 32/33/37 Type A1 and Ff.
The last cause of this error is inside the Laser unit.
 

If you checked all above parts and you have the same error - the only way out here is to send to us your laser unit for repair.
It is useless to try to fix it by yourself.

Resume: laser repair required.

Probable Cause: Poor contact/Defective LDD20 PCB/Deteriorated Laser/

Affects any lab

3. But the most probable cause is LD condition: The current has reached so called "deteriorated detect level".
It shows that LD is not in good  condition (deteriorated).
Perform "B-laser optimal temperature setup" - sometimes it helps to postpone the problem for a while.
If you will have "B-laser optimal temperature setup - NG"   - > laser module must be repaired.

Probable Cause: red laser is out of order.

Affects any lab

Resume: laser repair is required.

Affects any lab

These errors mean that your minilab cannot get the "Signal of Synchronization" from a certain laser beam (different labs have different laser beams as a source of synchronization).

Probable Causes:
1. Defective AOM driver (synchronization is performed by the different AOM driver in different models of Frontiers)
2. Defective AOM crystal.
3. Poor connection between :
    3.1. AOM driver and Image Processing PCB (different labs have different name of this PCB)  
    3.2. AOM-driver and AOM (crystal)
4. Mirror is not in the proper reflecting position and cannot reflect the beam to the beam receptor.

First of all you need to do is:
1.Check the position of the mirror. If this look well and firmly fixed in its position go next:
2. Swap Red AOM driver with to Green AOM driver. Such way you will find out if your Red AOM driver working or not. If you swapped it and have no error - your R AOM driver is defective and needs to be replaced.

If you do not want to remove drivers and place them back - just change cables and see the result:

Resume: If AOM drivers work well - laser repair required.

Probable Cause of this issue - defective AOM driver

Affects any lab

If AOM drivers are in good working condition : laser repair required.

Affects any lab

There are 3 probable causes:
1. Weak or contaminated chemicals
2. Defective AOM driver
3. Defective AOM (crystal)
 

If the change of black has appeared within 2-3 days - replenishment procedures were performed in wrong way.
If it took more time to be visible - the probable cause is the defective valve in replenishment pump.

How to check the chemicals:
Exposure the paper by daylight (take out 10~15 cm of paper from the paper magazine and pull it back)
Place the paper magazine into the lab and run printing or paper feed. See result.

If you have black paper - the most probable cause is a defective AOM driver.
See above article how to determine which AOM driver is defective.
TWO wires of Blue channel swap with TWO wires of Green channel and see the result.
If the color of a test will change- AOM driver is defective.
If there will be no change- AOM crystal located inside the laser unit is dead.
In this case you will not be able to repair it by yourself.

But if you will have paper sheet not black but with a blue hue - the chemicals are weak or contaminated. 

Causes:
- contaminated CD P1 - replace the chemicals (working tank P1)
- low temperature - search the cause (burnt heater, lost values in software, etc)
- low replenishment rate (check all replenishment pumps)
- low circulation in working tanks (check all circulation pumps and filters for clogging)

In other words - replace the chemicals (working tanks) and search the cause of its weakness.

Resume: If the chemicals and AOM drivers are in normal condition - Laser repair required.

To be continued...