Hi,
I’ve got a control PCB from a Manitou telehandler, which seems to be defect.
When K16 (the relay at the bottom after an amplifier) is switched to radiocontrol, it operates the hydraulic proportional valve fine.
Since it’s a relay board, there isn’t really much that can go wrong. But..
When K16 is switched to onboard control, it fails to operate the valve.
The only “active” between the thumbwheel and the proportional valve is the amplifier.
I can measure ~30Mohm from the thumbwheel input and the black jumper after the amplifier, when no power is applied to the board. Is this normal?
The chip seems to be grinded or similar, it’s very hard to see some markings, even with a macrolens.
However, I think 358 is marked in it. So I guess it’s a LM358 dual opamp. Does it seem right with an opamp in that place?
First: Check voltage at pin 4 and 8?
Second: I’m clueless here. Can I test if the LM358 is operating correct?
Any other clues?