All,
New to the forum. Helping a friend with some electronics problems on this 850K Series II. While I have experience with some machinery, I am not an everyday mechanic, BUT I am an electronics engineer with a lot of background in hydraulics, CAN, controls systems, etc. On to the problem...
Brought me the 850K travel joystick saying that forward and reverse movement was intermittent. Got to the point where it was a bear to operate because you had to hold the stick in the perfect spot to drive in any direction. We proceeded to disassemble to joystick to see what was inside. Two potentiometers and two pairs of microswitches. I checked all components with an initial outlook that all were "ok" with decent resistance readings while rotating the stick in all directions. Potentiometers can be finicky carrying current, depending on the type. Wrote down the numbers and began my research. Made by Contelec Swiss, 0-5K, basic stuff other than shafts are metal and 6mm in diameter. Couldn't find EXACT matches, but did find a VISHAY model that was similar with 1/4" shaft and exact type and overall dimensions. At $30 each, was worth a shot considering the cost of a new joystick. Received the new pots, disassembled originals out of stick to determine rotation and angular range. Originals were 225-240 degrees and infinite turns, new ones are 340 degrees and 1 turn. Not a huge difference, let's throw them in and if anything, it'll be slow. Sure enough, that was all true and original intermittent problem was FIXED, EXCEPT we had to tune each one to match the original calibration at neutral position. Did that with a few iterations between Forward and Reverse, Left and Right. Loaded onto the trailer to bring home to the shop so we could fine-tune the speed with some resistors added to match the original rotation angle.
Knowing my electronics, I added a 10K resistor across each pot to bring the total resistance down to 3.3K ohms. Resistors in parallel (5k * 10k) / (5k + 10k) = 3.3K. I determined the 10K resistor from an equivalence of X over 225 degrees to 5k over 340 degrees. I actually did this backwards first, but it made the machine run slower. It would not counter-rotate.
After adding the 10k resistor, it did NOT bring the machine back up to factory speeds. Now, I'm stumped. We had spoken to the local dealer before any modifications to the new pots, because I knew there had to be a calibration routine available. However, they are very reluctant to perform it, even if paid. They say it won't fix anything and we need to buy a new joystick.
Has anyone ever tried a repair like this?
Is there a calibration procedure we can run on the machine to reset range on the new potentiometers?
Thanks all ahead of time. We are hoping for a resolution, in any way.
2006 850K Joystick Issues
