Grove TMS 870 – 5 section boom with PAT DS350G (old) boom control system

PAT DS350G Boom Control Repair

We recently repaired a DS350G boom control system on a Grove Crane TMS870 with 5 section boom. The system that is the original old type DS350G type boom control system designed by PAT (Hirschmann) for the Grove boom control application is a very complex bus system and not easy to service. The later type DS350 Modular with boom control bus extension system is easier to troubleshoot.  The customer complaint that the Auto Mode did not work at all for A & B Automode. He could only operate the crane in manual mode. Obviously during the crane inspection, the crane inspector pointed this out to the customer and recommended to get this fixed prior to certifying the crane.We checked all input and output signal. A short test was done to ensure the operation of the bus system by checking the additional interface output of the DS350G board, the decoder board receiving and sending, the digital input board receiving and sending, and the receiving and sending of the analog output board that make the proportional telescope valve work and is responsible to ramp signals down and up during tele section change over in Auto Mode.We checked the proportional output signal of the analog output board in Auto Mode. That signal supposed to be at 1.2A (1200mA) at maximum ramping and turned out to be only 0.2 A (200mA). There are three failure possibilities; either the proportional 2-way valve is defective, the wiring has a short circuit or the analog output board does not deliver the correct electrical current, thus it is defective.The resistance check of the valve 25 Ohms confirmed that the valve is ok. Unplugging the valve and checking the resistance of the wiring confirmed that the wiring was ok and resistance check to chassis ground confirmed that there was no short circuit. We kept in mind that the ground for the proportional valve is not the chassis ground (battery or crane ground). The system produces its own analog ground for the proportional valve. So, never use crane ground for that proportional 2-way valve.Further troubleshooting uncovered that the proximity switch signal for the Center-Mid Tele section fully retracted failed at the central unit. We found that the problem was not the switch; it actually was the 10 conductor length cable on the cable reel for the IM (measuring the inner mid tele section). The length cable as such didn’t look bad, but unfortunately over the years the very small gauge electrical conductors got brittle and some of them just lost continuity. Our customer ordered a new length cable and a new analog output board.  Though the analog output board is officially obsolete and not made anymore, we were able to procure on of the last ones for our customer.After the parts arrived we scheduled a return visit and replaced the analog output board and installed the new length cable for the inner mid cable reel. As a courtesy we checked the pressure transducers and reset the zero value of the two pressure channels. We took the crane out and checked it at A & B Automode, checked radius, boom angle and boom length, we lifted several test loads and performed cut off tests. The crane and the DS350G boom control system functioned correctly and to our customer’s satisfaction. Furthermore the inspector was present and certified the crane on the spot, which made our customer very happy.
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