After reading this forum for a long time I'm going to leap in and ask for some help. I have a 2004 Kobelco SK70SR YT02-04874 8000 hours with a swing speed issue, recent purchase, prior owner had same issue on swing. Swing brake releases and machine swings but has very low power when only using the swing control, rotation time about 9-10 seconds. Same issue in clockwise or anticlockwise rotation. Wiring to sensors fine, output to mechatro is in spec. Changing sensors around doesn't affect anything. When I actuate other controls, boom, stick, drive, suddenly the swing has great power. Service Manual points to PSV-B, checked, changed, has voltage, nothing changes it. At first I thought this was the result of the action of the hydraulic system. For example the stick spool is after the swing spool and does the same thing the PSV-B spool does in reducing or stopping path to tank of the P2 pump. Just one example. However I also noticed that the rpm will shift on all other functions to a higher rpm when actuated. Mechatro portion of SM shows that the stepper motor is involved in all hydraulic functions. Swing doesn't result in an increase in rpm. Speed control switch does work. In the process of searching all this out I also found three bare wires into the Mechatro unit, power in, ground out, and key switch in. Wires repaired with no change in function. Unfortunately in the process I accidentally hit the buzzer off switch while in test mode putting the unit into A programming mode. Shut it down immediately but still lost the stepper motor programming and have a flashing CPU switch. It simply won't reprogram and turn off the cpu flashing light and E-01 error. Removed and examined board of Mechatro, it's immaculate, looks like it just came out of the factory. Readout of the Mechatro shows all in spec, speed sensor, percentage of throttle, outgoing and incoming current correct. In running the A adjustment about 40 times I started logging the Expected RPM vs the Speed Sensor RPM. They do not match. They tend to be close at low rpm but as the rpm gets to maximum on the dial it's off by about 200 rpm according to the Mechatro controller. Stepper motor ohmed out in accordance with SM. Operation of stepper motor appears fine during A adjustment or use of speed dial. I do now have FC/S/H function of the system now that didn't work before. I know, this is getting long, sorry. Bucket curl speed also starts out fast, goes slow in mid stroke of piston, then fast again when operated by itself. Mechatro feeds ground back to fuse box via the switched side of the battery relay. Once power applied the fuse block has correct positive voltage. Ohmed out Mechatro power in and ground, shows rising and falling resistance almost like a capacitor when tested by an Ohm Meter. I've had a gent out who has worked on these, he didn't find anything else. I expect this is a problem in the Mechatro system parts not the Controller. I haven't checked the voltage from the speed sensor yet. Any thoughts or ideas you have are welcome as I've reached the end of what I think could cause this. Yes, the system is a little complicated but not that bad.
Ran this machine for a while again yesterday. When stick is run all the way out or all the way in until it hits relief the motor severely drops rpm and will stall if held. Same for pushing with the blade, once the machine can't continue to move the pile the rpm drops and motor will stall. Both of these functions do result in an rpm increase when triggered.
"...Service Manual points to PSV-B, checked, changed, has voltage, nothing changes it..." Service instructions are always correct. You have only checked the "VOLTAGE" of the PSV-B. But if the mechanical part of the PSV is stuck or the hydraulic hose from PSV-B to port Pd4 is clogged, there is still no hydraulic pressure acting on port Pd4. Therefore, I suggest you measure the hydraulic pressure going to port Pd4
Lachau, thank you very much for reading my post and thinking about the problem. I did purchase a new PWS Valve for the B function. I bench tested it with 24 volts at 1 amp and it actuated/moved. I also attached a pressure tester to the incoming line into the spool port on the valve block and got a reading of 370 psi. If I understand the PWS valve it uses the frequency of the signal from the Mechatro to operate more as a throttle than a switch like the Swing Brake Solenoid valve. Without an oscilloscope I don't have the ability to test that part of the function. I did change out my engine speed sensor today in hope that the original 20 year old part was the issue in my inability to successfully complete the "A" programming of the stepper motor. Unfortunately this didn't solve that issue.
As you can see in the attached images. There are just a few reasons why an adjustment cannot be completed: 1/- Engine speed sensor error. 2/- Link-Rod is wrong. 3/- Limit switch signal error. a)- Have you tested the voltage signal of the engine speed sensor? b)- Have you adjusted the length of Rod-Link to the correct standard? c)- Have you checked the step motor's limit switch signal? d)- Have you "Check to be sure that the engine emergency stop lever knob is fully pressed down. If the Mechatro-controller is adjusted in the condition where the knob is pulled out, the engine speed can not be set rightly". However, there are some very common causes that Kobelco SM has not mentioned. The following reasons also cause "A adjustment" to not be completed. 1/- Engine degradation leads to reduced engine power, causing engine rpm to not reach standard speed. 2/- The machine has a condition that we call "hanging load". Even when all control levers are in the neutral position, the hydraulic pump still has high pressure. So I suggest you again: 1)- Remove the Rod-Link of step motor, use your hand to pull the throttle to the highest level, then use a tachometer to check how much RPM is achieved? 2)- Measure the pressure of hydraulic pumps immediately after starting, while not in operation.
Based on this phenomenon: "When the stick is run out or in until it hits relief the motor severely drops rpm and will stall if held. Same for pushing with the blade" . I think your engine has been degraded!! To handle this, try adjusting the main pump regulator to see the results. Kobelco sk70-sr hydraulics I have a 2003 kobelco sk70sr that is having hydraulic issues. I just replaced the pump because the old one went out. Put the new pump on and it worked great for about 2 hours one day. Went out the next day and 15 minutes into working it started killing the engine. Replaced all the fuel filters... HeavyEquipmentForums
I did replace the engine speed sensor yesterday. I didn't check the AC voltage directly in it. I did use the 0-1 and 0-2 settings of the Mechatro Hardware Check Switch. The sensed rpm is close to set at lower speeds but starts to lag behind at maximum throttle. No difference from the switch I replaced. I don't think the motor is degraded as this machine is very strong with the exception of the functions noted. Unfortunately I don't have a matching model to compare with. I will read through all of what your wrote thoroughly and hopefully get a chance to check it in the next day or two. In yesterday's attempts to redo the A adjustment I noticed the throttle advance to the limit stop and then the stepper motor try to move it further counterclockwise. Seems like it was trying to still raise rpm. Thank you again for your thought.