Problem 1, Swing break down.                   
Last summer the Demag AC 120, new 2000, began to get problems now and then. The master console lost all its information content, and displayed error: E25,E93 or E94. When reading the manual, there is a long list of possible faults.
Some days later the crane had a problem with the swing and telescope. After some inspection, this fault was located in left joystick. A small wire innside the joystick, the supply for the digital input unit, had burned over. The joystick was replaced, and the reason for the overload was fixed.
Normaly,when the CPU have a fault, there is possibility to operate the Demag AC 120, in emergency mode. This is activated with a key-switch in the front panel. This mode will let you operate one movement at the time, and the speed of the movement is controlled by a potentiometer located near the right joystick. 

This Demag AC 120, and probable all Demag AC 120, that have been rebuilt with a foot pedal swing-brake, has lost the possibility to operate the swing in emergency mode. The problem is located in the wiring of the solenoids,Y70&Y71. The solenoids were connected directly to the digital inputs, and the curent the solenoids consumpt, may burn the switch in the joystick. To verify if your Demag AC120 has the same problem with incorrect connected solenoids Y70 & Y71, ( normaly cranes with swing-fot-brake attach.) test swinging the crane in emergency mode. (key in frontpanel, single movements, speed control by potensiometer at the right joystick). If all movements are okey, you're AC120 don't have the problem no. 1.     

27 Desember 2002 I repaired a customer's Demag AC 120 with 100% results. The schematic diagrams of this change was sent to Demag, and they can also be downloaded from my server. Download by the following link, and compare the diagrams with the original one, belonging to your Demag AC 120.
Download now for free. Click HERE!                                                 www.mobilcrane.com

The emergency-mode key in the frontpanel of the Demag AC 120, in the yellow circle.  


Problem 2, CPU Error (E25,E93 & E94)
After the repair of the Demag AC 120, there still was a problem with the CPU, and after some trouble shooting (every signal to the CPU was tested), the main problem was located in the main CPU-unit. The repair was done within 2-3 hour.  
There is an internal power supply, +5V. By testing this voltage constantly,  I discover that the voltage was unstable. Every time the voltage dropped under 4,8V, the CPU had an error. See photos how the problem was/is easily repaird. I removed the cable shoes (Abiko), and solder all low-voltage terminals. It has now been operating for almost one year without any CPU Errors.   

THIS PROBLEM I BELIVE WILL BREAK OUT ON THE MAJORITY OF THE DEMAG AC 120, AFTER SOME TIME.

Please notify www.mobilcrane.com , if urgent need of assistance. 

Certified:  Manager K.Skailand.

The Demag AC120, CPU unit seen from top.                                      www.mobilcrane.com

The Demag AC120, CPU from under.                                                   www.mobilcrane.com


The points that needs to be soldered, the 5V supply and ground in both ends, and the
connections for the sence cables.                                                   www.mobilcrane.com

 
Left side before repair, right side after repair.                                www.mobilcrane.com

For more details, please contact Skailand Kranservice at www.mobilcrane.com

Rev. 20080224 www.mobilcrane.com