# Sudden stop



## zerotact (Jun 12, 2019)

I have a H.F. 7 X 10--it`s in good condition and works well, however im doing some pretty tough stuff with it because I have to. I have no other way to do what I need to. I am building a Front loader for a Cub Cadet garden tractor and im making all the bushings and pins on this little lathe. I know--get a bigger lathe--I am looking for one I can afford. I am retired and have to be careful about how much I can spend on what. I probably have 30 thousand worth of tools, but they were accumulated over 40 years in the trades. Random tool buying kind of stops when you cant work anymore. So im making a die holder to thread a 5/8-11 taper bolt and the machine starts --like -whining --not bad, but I never heard this before, so I stop the lathe to check the gears. There was no visible damage, and very little chip fragments in the gear area. i cleaned out the area and started the lathe, and ran at low--RPM  while watching the gears--also, no signs of problems, so I sprayed a little lubricant on the gears to see if the sound abated--No--I stopped the lathe to reverse the motor to listen to it in reverse--I switched the lever in the back down to the reverse position and pushed the start switch---and--Nothing--I thought--what-?--so I put it back in Forward and pushed to start it again--and--Nothing again--now im getting worried. What could have happened between stopping and restarting the lathe and how could it have anything to do with switching to reverse. I then checked the fuse to see if it blew. It checked good with a DVOM, but I checked further with meter to follow the AC path. I had ac voltage from L1 in From power cord to L1 terminal --through power on switch--to-Fuse--through to other side of fuse, and had ac voltage all through to- PCB- terminal. Tried lathe again--Nothing-. Detached -DC-outs to motor--from terminal block switch and fed-12 v dc from a car battery directly to motor and it fired right up and ran fine--slow--but fine. So now im Lost. Sorry about the Long dissertation but ive always thought in life--More information is better. Any Help would be greatly appreciated . Greg---aka--zerotact


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## RJSakowski (Jun 12, 2019)

You have isolated your problem to the circuit board.  Without a schematic, it is hard to say definitively what failed but usual suspects are in the power circuit rather than the control circuit.  Check the rectifiers and output transistors.  Wth a little detective work, you should be able to narrow the problem.  

If you have a schematic, it would help us help you.


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## zerotact (Jun 12, 2019)

yes , figured I would have to trouble shoot the PC board--now--but that was not the original problem--I stopped to check a noise on the machine, and the lathe was running ok, but when I switched the Drive from forward to reverse and then restarted-- the lathe would not start--what could changing the drive direction have to do with the Lathe now not working at all-?


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## markba633csi (Jun 12, 2019)

There's a guy who specializes in repairing those boards-  www.olduhfguy.com
I think his name is Pete and it's a flat rate of 50$ (or used to be)
Mark


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## matthewsx (Jun 12, 2019)

This guy?









						MINI LATHE - MILL BOARD REPAIR SERVICE
					

Check out this GoDaddy hosted webpage! http://olduhfguy.com.




					www.olduhfguy.com
				




previous link doesn't work.


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## RJSakowski (Jun 12, 2019)

Starting and stopping create some of the greatest stresses for electrical circuits.  Particularly, if you reversed the motor while it was still running, a large back emf would be created.  Mosfet transistors are particularly susceptible  to transients.  There is snubbing circuitry to absorb the transients but it can only do so much.

Since you were able to run the motor on a battery, the problem with no run is the control board.  You will have to sort that out before moving on to the noise problem.


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## matthewsx (Jun 12, 2019)

zerotact said:


> yes , figured I would have to trouble shoot the PC board--now--but that was not the original problem--I stopped to check a noise on the machine, and the lathe was running ok, but when I switched the Drive from forward to reverse and then restarted-- the lathe would not start--what could changing the drive direction have to do with the Lathe now not working at all-?



It doesn't have to be related, but running any circuit at maximum output can fry it. Especially if it was built marginal in the first place. Old UHF Guy has troubleshooting on his website and seems to have quick turn around at a good price.

John


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## Firstram (Jun 12, 2019)

Used KB controllers on ebay are far superior to the oem units. Just buy the appropriate resistor.









						KB Electric KBLC-240DS (3375D) 87VDC DC Motor Speed Control Controller 115VAC  | eBay
					

<p>KB Electric KBLC-240DS (3375D) 87VDC DC Motor Speed Control Controller 115VAC. </p><br><p>More information</p><br><p>-Input voltage: 115VAC / 230VAC</p><p>-Output Voltage: 0-87VDC</p><p>-Output Amperage: 6amps</p><br><p>Good working drive. Includes speed pot and 3/4HP resistor.</p>



					www.ebay.com


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## matthewsx (Jun 12, 2019)

Firstram said:


> Used KB controllers on ebay are far superior to the oem units. Just buy the appropriate resistor.
> 
> 
> 
> ...



Yeah, why just repair a tool when you can upgrade....

Next step CNC conversion


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## Firstram (Jun 12, 2019)

The noise problem is more than likely the plastic gears in the headstock. If you need to replace them replace the gear on the spindle with a steel one. When they break again you can replace the plastic one on the jackshaft without removing the spindle. They sell steel gears for both but they are noisy. It's also a good idea to leave one plastic gear in place to act a weak point to protect the rest of the drivetrain.


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## markba633csi (Jun 12, 2019)

I can vouch for the reliability of the KB controllers, they use an older SCR technology rather than mosfet- hard to kill 'em
Mark


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## Firstram (Jun 12, 2019)

I set up my 7x10 with a treadmill motor thru a speed reducing jackshaft controlled with a KB unit. Incredible low speed torque and Tons of power at high speed too. Pushing these tiny lathes will eat the hi low gears, I keep several replacements on hand. Little Machine Shop usually has everything in stock.


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## zerotact (Jun 12, 2019)

yes Im thinking of going to the treadmill motor setup--I have 2 of them right here, im just wondering what the cause of this is--trying to repair it as is just to know the cause and effect --so I know how to deal with these problems


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## zerotact (Jun 12, 2019)

markba633csi said:


> I can vouch for the reliability of the KB controllers, they use an older SCR technology rather than mosfet- hard to kill 'em
> Mark


then what do you think happened--remember this was not the problem in the first place--it was a whining noise that I went to investigate--only then did the machine stop working--Thanks for any help


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## zerotact (Jun 12, 2019)

ok--thats a good idea about leaving one plastic gear to be the weak link--but im trying to find out why the lathe stopped--remember-this was not the original problem--it was just the whining noise--but the lathe was running fine--it was only after I stopped and reversed the drive direction that the lathe stopped working--how is that possible-?---what does switching the drive direction have to do with the loss of power to the motor


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## Firstram (Jun 12, 2019)

You were pushing it too hard and smoked the controller would be my guess. Turn the chuck by hand and shift the lathe from hi to low, you should be able to feel if the gears are damaged.


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## zerotact (Jun 12, 2019)

matthewsx said:


> Yeah, why just repair a tool when you can upgrade....
> 
> Next step CNC conversion


Because of Money--im retired with no income


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## zerotact (Jun 12, 2019)

Firstram said:


> You were pushing it too hard and smoked the controller would be my guess. Turn the chuck by hand and shift the lathe from hi to low, you should be able to feel if the gears are damaged.


OK--But the lathe was running --and then I shut it off to investigate the noise--it was only after I switched the drive to reverse, then went to restart that the machine would not start--how can switching the drive direction cause a loss of power--they are two different functions--one mechanical--and one electrical-?


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## Firstram (Jun 12, 2019)

Power surge to restart the motor is higher than running amps. The final straw? Use the controller from a free craigslist treadmill, your 90 vdc motor is not very picky.


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## zerotact (Jun 12, 2019)

Firstram said:


> Used KB controllers on ebay are far superior to the oem units. Just buy the appropriate resistor.
> 
> 
> 
> ...


is this controller the same as the MC-60 Tread mill controller-?--Thanks


Firstram said:


> You were pushing it too hard and smoked the controller would be my guess. Turn the chuck by hand and shift the lathe from hi to low, you should be able to feel if the gears are damaged.


yes--not only did I do that but I took the back panel off and visually inspected the gears--not a nick on any gear in there--and they sound fine turning--it seams the sound is coming from the the lead screw--just found that out a few minutes ago--but still makes me wonder how it was working--when I turned it off--then only after I switched the drive direction--and went to restart the lathe--did it not work--thats what is baffling me


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## brino (Jun 12, 2019)

Does this lathe have any safety switches on gear covers, or other panels?

It sounds to me like maybe you opened one to look for the noise, and then didn't close it.
Now the controller won't power the motor because it thinks you have your hands in there.

It's worth a check........

If that's not it, can you post some good close-up pictures of your motor controller.
Maybe someone can spot something amiss.

-brino


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## zerotact (Jun 12, 2019)

Firstram said:


> Power surge to restart the motor is higher than running amps. The final straw? Use the controller from a free craigslist treadmill, your 90 vdc motor is not very picky.


yeh--I guess im going to have to do that--how do I set that up--the Tread mill motor is much larger--it wont fit in there--am I going to have to place the motor behind the lathe like a south bend and go to a pulley drive and even change the --or--put a pulley on the back of the spindle to drive it with--e.t.c--e.t.c


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## zerotact (Jun 12, 2019)

brino said:


> Does this lathe have any safety switches on gear covers, or other panels?
> 
> It sounds to me like maybe you open one to look for the noise, and then didn't close it.
> Now the controller won't power the motor because it thinks you have your hands in there.
> ...


oh man--IDK--There is no stop switch on the control panel where the start switch--but in the back I dont know--good question--im going down to look at that possibility right now--Thanks--Greg


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## zerotact (Jun 12, 2019)

No, I would never reverse the drive direction without stopping the machine first--always--but what is baffling me is how can the machine be running ok--with just the new noise being why I stopped in the first place to check on it--then only after I reversed the drive direction--then went to restart the lathe--did it not run--thats what has got me crazzy


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## zerotact (Jun 12, 2019)

markba633csi said:


> There's a guy who specializes in repairing those boards-  www.olduhfguy.com
> I think his name is Pete and it's a flat rate of 50$ (or used to be)
> Mark


ok-Thanks for that info im prety sure I can trouble shoot and --maybe repair it myself--im a  CET--I went to electronics school--knowledge is not my problem--it`s--age--my hands cant do fine work like years ago---hell I cant even do regular electrical work anymore--im a 25 year Licensed electrician--but when you old and hurting--they wont pay to be slow--I got away with being the forman for years--being the answer man--but after the 2009 collapse and recession--that all went away--but im glad you guys are here to held us folks to fix think we otherwise might not be able to


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## markba633csi (Jun 12, 2019)

Hi Zero- you may never know exactly what caused the failure, in fact, the whining sound could be an issue with the motor itself, which then failed the controller.  In any case, it's dead now so you have a few options:
1) send the board off to Pete
2) try to repair the board yourself
3) replace the controller with another identical one, or an SCR type, or a treadmill one
The motor should be tested to verify proper current draw and no abnormal leakage to the case or interwinding breakdown;  if there is any doubt you should either replace it or if you decide to send the board off, send the motor too so they can be tested together.
These controllers have a history of failing under hard use unfortunately, probably because they are made so cheaply
Mark
ps you could cobble together a quick and dirty substitute control using an ordinary light dimmer driving a bridge rectifier. It won't give great load regulation but would at least get you back on the air


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## zerotact (Jun 12, 2019)

markba633csi said:


> Hi Zero- you may never know exactly what caused the failure, in fact, the whining sound could be an issue with the motor itself, which then failed the controller.  In any case, it's dead now so you have a few options:
> 1) send the board off to Pete
> 2) try to repair the board yourself
> 3) replace the controller with another identical one, or an SCR type, or a treadmill one
> ...


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## markba633csi (Jun 12, 2019)

Consider the light dimmer idea, you could at least get going again quickly within the original footprint and you could exercise the motor and see if it still whines (or smokes)- basically accomplish two things at once.   You would need a beefy bridge rectifier about 10 amp at around 400 volt on a small heatsink
M
ps if you want to try repairing the original board I can give you a few things to check- it might be something easy to fix- start at the input supply


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## zerotact (Jun 12, 2019)

markba633csi said:


> Consider the light dimmer idea, you could at least get going again quickly within the original footprint and you could exercise the motor and see if it still whines (or smokes)- basically accomplish two things at once.   You would need a beefy bridge rectifier about 10 amp at around 400 volt on a small heatsink
> M
> ps if you want to try repairing the original board I can give you a few things to check- it might be something easy to fix- start at the input supply


yes, I would like to do both--repair the original board to keep for a spare and switch to the treadmill motor for more torque. I have the motor controller from the tread mill but not quite sure how to wire it for the lathe just yet


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## markba633csi (Jun 12, 2019)

You mentioned it failed after you switched the directional switch- I wonder if that switch may be somehow defective and caused the failure. That switch is connected in between the controller and the motor.  If it was making a flakey connection during power up or power down the resulting voltage spike could kill the output stage


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## markba633csi (Jun 12, 2019)

Also what Brino said- you didn't accidentally bump the stop switch or joggle the protective cover switch?  Having a sudden failure like that seems suspiciously like an operator-caused effect


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## zerotact (Jun 12, 2019)

There is no stop switch on this Little lathe--but if there is a safety switch in the back where you remove the gear cover then i dont see it


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## royesses (Jun 13, 2019)

If you have the 7x10 with safety interlocks one of them could cause the problem. Also I had a similar problem and found the speed potentiometer had a switch on the bottom that had broken causing the problem. LMS has schematics for the HF 7x10.

Roy


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## zerotact (Jun 13, 2019)

I looked for one , did not see any--I wish it was only that--think I fried the board


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## homebrewed (Jun 16, 2019)

Little Machine Shop has a troubleshooting guide for mini lathe controllers.

-Mark


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## horty (Jun 16, 2019)

If I remember right, behind the speed control potentiometer is the safety switch, it might not have reset when lathe was overloaded.
I had some notes somewhere on this, not sure where they come from, I have more notes just need to find them somewhere..

If you cant get it going I will search for my notes for you..


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## zerotact (Jun 16, 2019)

Behind-?--do you mean inside the plastic housing the speed pot is mounted on


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## horty (Jun 16, 2019)

I believe that is right, can you access the wires there, could be different model lathe, not 100% sure

do you see terminals 3 and 5?

Damn, I know I got this info off the net somewhere, cant remember where


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## horty (Jun 16, 2019)

I found some more notes and all it says is to jump between terminal 3 and 5 to bypass interlock that will not reset..
sorry this is all I have

Hope I'm not making more work for you, I see that these lathes have change alot in the years they were made.. and not sure the info I have is for yours.
not sure but I think the pot has a resistor to be checked on the back,,,


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## zerotact (Jun 16, 2019)

I dont see anything in there--im trying to send you pics of the control box wiring--let me know if they come through


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## horty (Jun 16, 2019)

Yes i see them, look for a terminal 3 and 5 on board,, jump them  ... then try

I see that terminal 6 - 7 are safety switch you could also try jumping them also


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## zerotact (Jun 16, 2019)

ok--if 6 to 7 is the safety --why is there no switch for those leads and the how would i reset it to get the power working again---and thanks for all your help


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## horty (Jun 16, 2019)

I believe its self reseting

it might not have reset itsself

jumping 6 and 7 will bypass the switch


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## zerotact (Jun 16, 2019)

ok--so on the board--those 2 wires--6-and-7--come out of the Spindle Gear crank case and then go to terminal screws-6-and-7-on the PCB--like on the schematic---they do not go to a--Visible-- switch --like it shows on the schematic you sent--which--thanks for that--however--might this mean--that the--DAMN--switch is actually--in the gear crank case--please say--NO


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## horty (Jun 16, 2019)

I is possible, lots of changes over the years, but if you jumped 6 and 7 it should bypass and able to run

did you jump 6 and 7 ??

has it ever just stopped before ??

Might be stupid, a friend just called and he told me to ask if you turned speed contoller off and then on again


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## royesses (Jun 16, 2019)

Safety interlock switch #212 part of clear safety shield:





Reset switch(part of speed control switch this was broken on my 7x10 a plastic piece inside the switch cracked)







Roy


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## zerotact (Jun 16, 2019)

ya--I do that every time----but no I did not jump the --6-7-wires---because I have the 2 -mosfets -out of the board right now--every thing I read on this situation said they are the first and most likely thing to go first--and I could not find any reset switch--and I did test the Bridge rectifier--so I ordered new -MOSFETS---which im waiting for--and while I do, im building a PWM circuit--and connecting it to a 4 leg pack bridge rectifier--Chip #--d4sbL40--which has 5 amp load ability--2 amp higher than the motor pulls---then caps for smoothing the dc out--and see if this solves the problem--but --I do want to know what the hell happened--so--when I put the new --MOSFEts in--i will look in the gear case to see if thats where the damn switch is--if so--I will jump the--6-7-wires out and try it--if it works--I am Moving the damn switch to where I can see it---UNLESS--it`s in the gear case to measure gear oil or something that im not aware of. yes--the machine has stalled out before while turning  heavier stuff--but always came right back on--so Idk---Greg-------Thanks again for all the help


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## zerotact (Jun 16, 2019)

Well--yes---I do have the 2 wires on the bottom of the speed control ---but those are--#-3-and-5--and how do you reset them--or are they supposed to reset when you turn the knob off and on


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## horty (Jun 16, 2019)

My friend says that is suppose to reset, it does on his, took him a day to figure that out, 
Hope you get it working, I know what its like,,
I'm not the smartest but like to help out.
Good Luck, just sitting here melting aluminum and sucking beer anyway,,,Retired so can do what I want,,,


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## zerotact (Jun 16, 2019)

Ya--I want to melt some aluminum to--I want to cast some plates to use for a CNC router build--but for now Ive got to fix the Lathe--and then the Band saw that broke 2 days after the lathe, then get back on the mini Front loader build---and ya--im retired to--and hurting every day--but goyta keep moving--Thanks for all your help---and if you ever need any plumbing or electrical questions answered--just ask me---im a 40 year plumber and a 25 year electrician, and I be glad to help out---with something I know about---fixin lathes--Nope---Greg


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## horty (Jun 16, 2019)

zerotact said:


> Ya--I want to melt some aluminum to--I want to cast some plates to use for a CNC router build--but for now Ive got to fix the Lathe--and then the Band saw that broke 2 days after the lathe, then get back on the mini Front loader build---and ya--im retired to--and hurting every day--but goyta keep moving--Thanks for all your help---and if you ever need any plumbing or electrical questions answered--just ask me---im a 40 year plumber and a 25 year electrician, and I be glad to help out---with something I know about---fixin lathes--Nope---Greg


Your very welcome Greg, always something to do, it seems I had more time before retirement, I think I'm trying to make up for lost time..
The old bones and joints take a beating over the years,,,I use to just have an ache and pain then it would go away, not anymore, 
Then fell head first 20ft onto my cement floor about 10 years ago, that did me in good,,, at least I'm still kickin..
We'll Make It, and I'll keep you in mind..and if you need some info on metal casting I'll try to help ya out.
Tim


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## brino (Jun 16, 2019)

@zerotact and @horty 
Greg and Tim,

I am so glad you guys are here.
You both have such varied experiences and projects and you are both so willing to help someone else!
That's exactly the attitude that keeps me coming back here. 
I try to give as much as I can, but always feel I take away more than I give.

Thanks!
-brino


Greg,

I believe you should be able to test that safety switch. 
If your machine is like @royesses posted above, then that safety switch is activated by lowering the clear safety shield around the chuck. 

You could either:
1) re-connect everything to the board and then test raising and lowering the safety shield, or

2) unplug the lathe and put an ohm-meter across that switch. Raising/lowering the saftey shield _should_ change the switch from open to short.

Good Luck!


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## zerotact (Jun 16, 2019)

cool, I will have some--probably many questions about metal melting and casting--when and if can only get the time


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## horty (Jun 16, 2019)

zerotact said:


> cool, I will have some--probably many questions about metal melting and casting--when and if can only get the time


Anytime your ready...
Disregard any mess ups here, cat just ran across key board and really did it....


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## horty (Jun 16, 2019)

brino said:


> @zerotact and @horty
> Greg and Tim,
> 
> I am so glad you guys are here.


Thanks brino,


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## royesses (Jun 17, 2019)

zerotact said:


> Well--yes---I do have the 2 wires on the bottom of the speed control ---but those are--#-3-and-5--and how do you reset them--or are they supposed to reset when you turn the knob off and on



Yes when you turn the speed knob to the off position it resets the safety lockout for the next cut.

Roy


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