LT40 super hydraulic forward / return problem

woodchuckc · September 10, 2024, 03:47:53 PM

I have a 2001 LT40 SH that I have been working on to get back in working order (it had been sitting outside, not used, for several years before I bought it). Getting pretty close to being able to saw with it, but I am having a problem with the carriage forward / return system. It will only go forward (cutting direction) at full speed, and it returns at full speed (as it should). It doesn't matter what the potentiometer setting is going forward. I have cleaned all the contacts on the drum switch and put new contact grease on them and have replaced the potentiometer also. Occasionally, if the potentiometer is turned all the way down when I engage the drum switch, the carriage will not move, and as I slowly turn up the potentiometer, there will come a point where it acts like a switch and the carriage will move forward at full speed, but most of the time it doesn't matter where the potentiometer is set - it just scoots down at full speed even turned all the way down. I am at a loss as to what to troubleshoot next - any suggestions from anyone?
Thanks!
woodchuckc

Ben Cut-wright · September 10, 2024, 04:19:41 PM

What are the "LED" indicator lights telling you?

woodchuckc · September 10, 2024, 05:23:49 PM

Good question - I don't know. I knew that there were some LED diagnostics, but don't have a clue about where to look or what they tell me. I need to get a manual for the mill really badly!

YellowHammer · September 10, 2024, 06:19:08 PM

The most likely answer isn't good, but before you get to that, make sure the belt isn't slipping (pull the cover) or binding (remove the belt and hand push it backward and forward, it should move freely).

Otherwise you may be looking at a new control board, which is what happened to me, the primary symptom is no speed control, just full speed either direction.

Hopefully not...

woodchuckc · September 10, 2024, 07:00:08 PM

Quote from: YellowHammer on September 10, 2024, 06:19:08 PMThe most likely answer isn't good, but before you get to that, make sure the belt isn't slipping (pull the cover) or binding (remove the belt and hand push it backward and forward, it should move freely).

Otherwise you may be looking at a new control board, which is what happened to me, the primary symptom is no speed control, just full speed either direction.

Hopefully not...

Yeah, that was the answer I was hoping not to hear but think is the most likely too. I'm pretty sure that the belt is not the problem, but I have not removed it to check the ease of carriage travel. I may just have to bite the bullet and in the short term manually push the carriage to get through a few logs that I am supposed to get milled by the end of the month. That really doesn't sound like fun, though!

SawyerTed · September 10, 2024, 07:39:02 PM

The manual is available on the Woodmizer website under Resources and Customer Support.

https://apps.woodmizer.com/Manuals/EngDoc.aspx?man=sawmill%2foperation%2fpdf2%2f757.pdf#page128

barbender · September 10, 2024, 10:25:19 PM

Yeah, I don't think you're going to finish any sawing jobs pushing the head, unfortunately. It's pretty heavy.

rusticretreater · September 11, 2024, 02:01:47 AM

You might try testing the potentiometer for proper operation. Plenty of websites explaining how to do it. You just need a volt/ohmeter.

woodchuckc · September 11, 2024, 09:23:28 AM

Quote from: rusticretreater on September 11, 2024, 02:01:47 AMYou might try testing the potentiometer for proper operation. Plenty of websites explaining how to do it. You just need a volt/ohmeter.

I checked the pot that was on the mill with my ohmmeter and it was ok, but I had a spare one that I got with the mill so I put it on it and it behaved the same way, so I'm pretty sure it is not the pot.

woodchuckc · September 11, 2024, 09:26:44 AM

Quote from: barbender on September 10, 2024, 10:25:19 PMYeah, I don't think you're going to finish any sawing jobs pushing the head, unfortunately. It's pretty heavy.

I know it would be a ton of work to do that, but I was just thinking that if it was possible I could do it in the short term for the few logs that I need to get sawed ASAP. I know that I will have to get the power feed fixed, even if it costs $$$$ for a new power controller.

barbender · September 11, 2024, 11:02:08 AM

I've never pushed mine with the carriage drive belt disconnected, and mine has a diesel so it's more weight. But from the bit I've pushed mine to and fro, I wouldn't even consider push feeding it. Maybe to finish one cut.

Magicman · September 11, 2024, 11:06:49 AM

Remove the drive belt.

Ben Cut-wright · September 11, 2024, 11:30:25 AM

You were provided with a link to WoodMizer manuals. Using the instructions there should give direction as to where the fault lies. Remove the belt during testing, note the LEDs and compare with what the manual says.

Did you test the pots with a digital or analog ohm meter? IF the pot 'ohm' tests bad...it's bad. The pot may ohm test OK but may not *function properly. A dynamic voltage test can determine if the pot functions properly when installed.

AFA pushing the saw head in the cut, it's not that hard. I've had to do it a couple times in order to finish a job. A dull blade becomes much more evident when pushing the saw head. Pushing the head will encourage the operator to get the speed control working again though.

woodchuckc · September 11, 2024, 11:50:40 AM

Quote from: Ben Cut-wright on September 11, 2024, 11:30:25 AMYou were provided with a link to WoodMizer manuals. Using the instructions there should give direction as to where the fault lies. Remove the belt during testing, note the LEDs and compare with what the manual says.

Did you test the pots with a digital or analog ohm meter? IF the pot 'ohm' tests bad...it's bad. The pot may ohm test OK but may not *function properly. A dynamic voltage test can determine if the pot functions properly when installed.

AFA pushing the saw head in the cut, it's not that hard. I've had to do it a couple times in order to finish a job. A dull blade becomes much more evident when pushing the saw head. Pushing the head will encourage the operator to get the speed control working again though.

Pulled the drive belt off and checked out the LEDs. I think it is doing what it should, in the the "IN" led is off with the pot turned all the way down, and then come on dim and it gets brighter as I turn up the pot. However, the drive motor doesn't progressively increase in rpms as I turn up the pot - it just suddenly starts at full speed when I move the pot from its lowest position (fully off). Carriage return looks right - the "OFF" LED comes on bright, along with the "PWR" LED and the motor turns full speed. So, to me it sounds like the control module output is what is problematic, not the input from the pot.

Magicman · September 11, 2024, 12:14:58 PM

From your test, I would agree. Call Wood-Mizer tech support.

SawyerTed · September 11, 2024, 02:38:47 PM

When you call Wood-Mizer use the menu to go to the electrical support area.

Stephen1 · September 14, 2024, 08:12:31 AM

Download the manual 1st then call WM.
You have lifetime Technical support from WM once you register that mill with them that you are the new owner.
Good luck.

woodchuckc · September 14, 2024, 12:01:13 PM

Called WM tech support, described the problem and what I had done to troubleshoot the issue. The tech told me to pull the blue wire going from the control module to the MOSFET board and see what the LED lights on the control module did when I engage the forward drive. That test determines whether it is the control module or the MOSFET board. According to that test, it is the control module that is bad. I ordered one on Thursday, and hopefully it will arrive soon (I would have thought it would be shipped by now, but not yet).

Thank you all for the advice, suggestions, and guidance!

woodchuckc · September 14, 2024, 12:02:59 PM

Quote from: Stephen1 on September 14, 2024, 08:12:31 AMDownload the manual 1st then call WM.
You have lifetime Technical support from WM once you register that mill with them that you are the new owner.
Good luck.

Yes, I registered the mill right after I bought it, but I hadn't downloaded the manuals then. I have now, and have copies on my desktop computer and 2 laptops, so I should be set. Thanks!