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Author Topic: LT40 power feed problem  (Read 2093 times)

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Online Dan_Shade

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LT40 power feed problem
« on: August 18, 2012, 06:31:33 pm »
My LT40 won't go forward, it will go backwards.

if I unplug the red wire to the potentiometer and plug it back in, sometimes the head will move a few feet.  Does anybody know what part is fubar?
Woodmizer LT40HDG25 / Stihl 066 alaskan
lots of dull bands and chains

There's a fine line between turning firewood into beautiful things and beautiful things into firewood.

Offline John_Haylow

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Re: LY40 power feed problem
« Reply #1 on: August 18, 2012, 07:06:57 pm »
I had the same problem last week Dan...the power feed motor belt was loose.
John
2004 Wood-Mizer LT40HDG28

Online Dan_Shade

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Re: LY40 power feed problem
« Reply #2 on: August 18, 2012, 07:26:44 pm »
it's not the belt.  I think it's one of the modules inside the control box.

the power indicator is lighted on the circuit board on the back panel.  another LED would flash.

there is a circuit board, a thing that looks like a mosfet block, and a thing that looks like an SCR.  I'm not sure which one is toasted.
Woodmizer LT40HDG25 / Stihl 066 alaskan
lots of dull bands and chains

There's a fine line between turning firewood into beautiful things and beautiful things into firewood.

Offline drobertson

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Re: LY40 power feed problem
« Reply #3 on: August 18, 2012, 07:27:09 pm »
sounds like your speed pot, has gone bad.  You might check the very small set screw that fastens to the pot shaft and see if it is slipping, 
Lt-40 super Cat 51hp, smith single head resaw, 362,310 stihl, and a nice real, nice small poulan!  585D Case loader, one real good rat dog, and one that is learning,

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Re: LT40 power feed problem
« Reply #4 on: August 18, 2012, 07:51:01 pm »
I'm pretty sure it's not the pot, but I didnt have a multimeter with me to check the pot.  I replaced the pot a few months ago.

Woodmizer LT40HDG25 / Stihl 066 alaskan
lots of dull bands and chains

There's a fine line between turning firewood into beautiful things and beautiful things into firewood.

Online pineywoods

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Re: LT40 power feed problem
« Reply #5 on: August 18, 2012, 09:16:42 pm »
I hope I didn't get the last one...Had the same identical problem...circuit board..
Call wm and talk to Rick...
1995 Wood Mizer LT 40, Liquid cooled kawasaki,homebuilt hydraulics. Homebuilt solar dry kiln.  Woodmaster 718 planner, Kubota M4700 with homemade forks and winch, stihl  028, 029, Ms390
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Online Dan_Shade

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Re: LT40 power feed problem
« Reply #6 on: August 18, 2012, 09:24:00 pm »
i'll send you my address :-)

Woodmizer LT40HDG25 / Stihl 066 alaskan
lots of dull bands and chains

There's a fine line between turning firewood into beautiful things and beautiful things into firewood.

Offline stavebuyer

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Re: LT40 power feed problem
« Reply #7 on: August 19, 2012, 05:31:17 am »
Had that happen on my LT70 and turned out to be the H-bridge.

Offline drobertson

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Re: LT40 power feed problem
« Reply #8 on: August 19, 2012, 08:21:22 am »
Yea this is weird, if the motor goes back, then there is voltage at the motor. and if it moves intermitantly there is voltage.  What about the drum switch on the foward/rev. ? Cant remember how these are wired, but they go through the pot, at least the foward does.
Lt-40 super Cat 51hp, smith single head resaw, 362,310 stihl, and a nice real, nice small poulan!  585D Case loader, one real good rat dog, and one that is learning,

Offline MartyParsons

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Re: LT40 power feed problem
« Reply #9 on: August 19, 2012, 09:22:25 am »
Hello,
Look at the black box, the LED lights.  Power light on? If not go back to the drum switch. In and Out light should get bright and dim as you turn the POT up and down. OV or OL usually states that the control box ( Black) is gone. OV = Over volt, OL is Over load.  The Pot works on a 5 volt reference.
The blue wire on the Mosfet. You can put 12v power to the terminal on the Mosfet the motor will run full speed forward if not the Mosfet is gone.  Not many issues here.  Most times it is the Control box.
There is a flow chart in the owners manual.  :P
OV could also indicate that there is a faulty bearing on the feed system, track or a bind. So remove the belt and push the saw head forward. It should move easy.
Marty

Hope this helps
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Re: LT40 power feed problem
« Reply #10 on: August 19, 2012, 10:02:32 am »
Thanks, Marty.

Woodmizer LT40HDG25 / Stihl 066 alaskan
lots of dull bands and chains

There's a fine line between turning firewood into beautiful things and beautiful things into firewood.

Offline Bandmill Bandit

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Re: LT40 power feed problem
« Reply #11 on: August 19, 2012, 12:13:49 pm »
I had this problem a while ago and went through the diagnostics process as described by Marty and found the little black controller box to be faulty.

Dont know if you have seen the following problem before Marty but here is a description of how mine was and how I fixed it. If you like I can tear it down and recreate the problem for the purpose of pictures to illustrate.

I changed it out and went about sawing as usual. With the new controller box in place I noticed immediately that I my feed speed switch position was quite a bit different than with the old controller and that I had a barely noticeable jerk like there was bark or something sticking on the chain that would cause this. I checked it every time it happened but never ever found any thing on the chain till one time the head stopped. There was a small knot piece that had jammed the between the chain and drive sprocket.

I gave the head a push with my hand to free the knot so I could get it out and as I did I noticed that the chain was not running square on the idler roller behind the drive sprocket. I couldnt see real well but took a long screw driver and pushed/pried the chain over to the center of the idler. I finished the last couple of feet of the cut and checked the chain postion and it was way out of line again.

I ran up the shop and grabbed a flash light so I could see properly and when I looked  with good light I found the chain was actually running on the CORNER of the idler and by the look of the drive sprocket had been for some time. I checked my chain adjustment and messed with that for a bit but no matter what I did that chain would not stay up on the idler properly.

Tear down time!

So took it apart and when I had all the guards off and could see everything I found that idler was very much out of line. After a through check of all the bolts and set screws I determined that nothing had moved from original assembly and found that there are a few large washers used as shims to position that idler properly.

I moved washers from the mill frame side of the idler to the saw head mast side till I had the chain running centered on the idler roller. I did have to swap out one thinner washer for a thick one out of my nut and bolt supply bin to get the chain running dead center but that was not an issue as the washers are regular 5/8th washers.  (if I remember right. might be 3/4)

Once every thing was aligned, back together and adjusted, I started cutting again. I noticed an even further reduction in the position of the speed switch to get the desired feed speed. It about a year or so ago that I made this discovery.

I have not any problems since and never thought to post it here. If it happend on mine it could be apart of the problem for others as well. With the chain binding between the sprocket and idler the way it was on my mill it is quite probable that the extra torque required to move the head would be enough of an overload to blow that controller. I would say that my feed switch postion is running about 30% lower on the curve than it was before I fixed this issue.

My mill is 2007 LT40HDG28.

Running the way it was kinda chewed up the drive sprocket and I will need to change that soon. Planing on putting on the LT40 Super feed and lift motors so have not  changed that sprocket yet.

Any questions as a result of this post just ask away. I will do my best to answer them

 
   

If you ain't livin on the edge you are takin up way to much room. Of course at my age if I get too close to that edge any more theres a good chance I may fall off.

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Re: LT40 power feed problem
« Reply #12 on: August 19, 2012, 04:40:07 pm »
If I jump 12v to the blue to the terminal, it runs full speed.  If I unplug the brown wire from the pot, it will run, but its not a constant speed. 

Just letting it sit, with the switch in forward, and the pot turned up,  the motor kicks on and off.
Woodmizer LT40HDG25 / Stihl 066 alaskan
lots of dull bands and chains

There's a fine line between turning firewood into beautiful things and beautiful things into firewood.

Offline MartyParsons

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Re: LT40 power feed problem
« Reply #13 on: August 19, 2012, 08:29:38 pm »
If you unplug the pot then what? What do the lights tell us? In out lights getting bright and dim? OV or OL lights on?
Do what you love. Continue to Learn. Appreciate your Friends. Listen Hard. Laugh. Practice Wellness.

Online Dan_Shade

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Re: LT40 power feed problem
« Reply #14 on: August 19, 2012, 08:41:48 pm »
I don't remember what the lights do with the pot unplugged.

The PWR is on when I put the side switch into "forward".

the OV or OL lights do not light up.

the out light will flicker a bit, I don't think the "in" comes on at all.

I didn't pay attention to the lights while the motor would intermittantly run.
Woodmizer LT40HDG25 / Stihl 066 alaskan
lots of dull bands and chains

There's a fine line between turning firewood into beautiful things and beautiful things into firewood.

Offline drobertson

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Re: LT40 power feed problem
« Reply #15 on: August 19, 2012, 09:02:15 pm »
Danshade, I hate to say it, but this is so simple.  you have a loose wire. or bad pot,  there is no other way. it is a simple fix, just track it down systematicaly. voltage in, voltage out.  If there is a bad board, well then it still is a bad connection. check the lights, get some help, slow down, and you will find it. This is simple wiring, and voltage. This is why we love WMZ products. Get some help with the controls, and check the lights and voltage, with a meter,  I know folks use test lights. but this just don't get it with me, WMZ controls are a bit sensitive, they need 12Vs  I am sure this is a simple problem,  finding it is not always simple, contradition in terms for sure, but simple the same. 
Lt-40 super Cat 51hp, smith single head resaw, 362,310 stihl, and a nice real, nice small poulan!  585D Case loader, one real good rat dog, and one that is learning,

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Re: LT40 power feed problem
« Reply #16 on: August 24, 2012, 09:19:10 pm »
it was the controller.

Thanks for the help from everyone.
Woodmizer LT40HDG25 / Stihl 066 alaskan
lots of dull bands and chains

There's a fine line between turning firewood into beautiful things and beautiful things into firewood.

Offline Magicman

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Re: LT40 power feed problem
« Reply #17 on: August 24, 2012, 09:27:12 pm »
Glad to hear that you got it "power feeding" again.   smiley_thumbsup
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Re: LT40 power feed problem
« Reply #18 on: August 24, 2012, 09:28:05 pm »
yep, back to sawing nails in half again
Woodmizer LT40HDG25 / Stihl 066 alaskan
lots of dull bands and chains

There's a fine line between turning firewood into beautiful things and beautiful things into firewood.