New video of fried out CX700 lathe problems
- Thread starter DPittman
- Start date
There might be a tag on the motor with a schematic. If the tag says it is an induction motor then it is brushless.
Have a look on YouTube for treadmill motor brush replacement and you'll see what a brush type motor looks like. It should have a small cover over the brush holder.
Yeah, I think your right, so much for that idea.
I looked at the Precision Matthews variable speed 1127 lathe schematic and it is similar to your Busy Bee lathe. It also shows the R/F switch connects the positive and negative circuits together with switch contacts 9-10. I don't understand what that is for. The PM machine uses a magnetic switch between the rectifier and the speed control instead of the manual switch before the rectifier that yours has but it is basically the same other than that.
I looked at the Precision Matthews variable speed 1127 lathe schematic and it is similar to your Busy Bee lathe. It also shows the R/F switch connects the positive and negative circuits together with switch contacts 9-10. I don't understand what that is for. The PM machine uses a magnetic switch between the rectifier and the speed control instead of the manual switch before the rectifier that yours has but it is basically the same other than that.
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That's kind of what I was getting at with your 12v battery test. I think you bypassed the entire control circuit & fed 12vDC to motor. The motor worked & in both directions which I interpret as motor is ok, or at least at that low, single ~12v level.
I'm no motor expert but I think generically 'brushed' means your typical variable voltage supply = variable rpm, power is conveyed mechanically through direct contact of the brushes. Brushless motors typically mean solid state speed control board that commutates power without mechanical conductors (typically 3-wires) & rpm result of synchronizing frequency. Where it gets confusing is that both can be 'DC' and 'speed control' is a just generic term. https://sciencing.com/difference-between-brushed-brushless-motor-7805274.html
Why I mention is the ebay controller might be DC>DC (I don't see spec on input voltage type). Somewhere in the lathe must be a do-dad that converts 120vAC to variable DC control. The question is that 2 separate components or somehow integrated on one board? But I'm just guessing now.
I'm no motor expert but I think generically 'brushed' means your typical variable voltage supply = variable rpm, power is conveyed mechanically through direct contact of the brushes. Brushless motors typically mean solid state speed control board that commutates power without mechanical conductors (typically 3-wires) & rpm result of synchronizing frequency. Where it gets confusing is that both can be 'DC' and 'speed control' is a just generic term. https://sciencing.com/difference-between-brushed-brushless-motor-7805274.html
Why I mention is the ebay controller might be DC>DC (I don't see spec on input voltage type). Somewhere in the lathe must be a do-dad that converts 120vAC to variable DC control. The question is that 2 separate components or somehow integrated on one board? But I'm just guessing now.
Johnwa
Ultra Member
Yeah, I think your right, so much for that idea.
.It also shows the R/F switch connects the positive and negative circuits together with switch contacts 9-10. I don't understand what that is for.
My guess is that it serves to latch the magnetic switch. When you operate the F/R switch the magnetic switch should drop out and you have to press start again. That way you can’t slam it into reverse while going forward at full speed.
In any case after start is pressed there should be line voltage between terminals 14 and. 24 of the control board. After a thorough visual inspection I would check for line voltage between 13 and 23 on the magnetic switch. Then press start and check voltage between 14 and 24 on the control board.
UPDATE....MY LATHE IS BACK WORKING!!
Wow! After about 4-5 hours of having a skilled technician working on my lathe problem we found the actual original problem was very small and simple.
I had blown fuses and replaced them...no fix.....
then I tested motor..seemed fine....
so then I assumed circuit boards were bad....ordered new boards from China/Busy Bee...
replaced boards in various combinations and problems seemed to get more complicated.....
replaced forward/reverse switch a couple of times.....once with improper wiring on my part caused more problems yet to be determined...
tested/replaced speed control switch....
replaced one of the two glass fuse holders to take a more conventional size of fuse as I was blowing fuses like mad in my testing/ignorance...
didn't understand wiring schematic but had John C and electronic technician comment that something looks funny as there is a dead short in it....
found out the original power supply circuit board did in fact have a purposely made jumper/short in it that the new replacement board did NOT have in it....
technician diagnosed the new speed control board I had replaced was fried out...no doubt from one of my incorrect forward/reverse switch replacements...
put in both original circuit boards again (which were testing fine)and then the technician found the fuse holder that I had not yet replaced was bad!!!!!
Replaced fuse holder and PRESTO my lathe works! It was originally just a friggin fuse holder that was bad!
Wiring schematic for my lathe was not drawn properly and even more troubling was the fact that the new replacement circuit board was NOT correct and had to be modified if it was to work with the way the lathe was wired up. I never would have figured that part out myself.
In the end it cost about $500 for parts, labour and shipping but it was actually only a $5 fuse holder that needing replacing. I'm slightly embarrassed and broke.
Don
Wow! After about 4-5 hours of having a skilled technician working on my lathe problem we found the actual original problem was very small and simple.
I had blown fuses and replaced them...no fix.....
then I tested motor..seemed fine....
so then I assumed circuit boards were bad....ordered new boards from China/Busy Bee...
replaced boards in various combinations and problems seemed to get more complicated.....
replaced forward/reverse switch a couple of times.....once with improper wiring on my part caused more problems yet to be determined...
tested/replaced speed control switch....
replaced one of the two glass fuse holders to take a more conventional size of fuse as I was blowing fuses like mad in my testing/ignorance...
didn't understand wiring schematic but had John C and electronic technician comment that something looks funny as there is a dead short in it....
found out the original power supply circuit board did in fact have a purposely made jumper/short in it that the new replacement board did NOT have in it....
technician diagnosed the new speed control board I had replaced was fried out...no doubt from one of my incorrect forward/reverse switch replacements...
put in both original circuit boards again (which were testing fine)and then the technician found the fuse holder that I had not yet replaced was bad!!!!!
Replaced fuse holder and PRESTO my lathe works! It was originally just a friggin fuse holder that was bad!
Wiring schematic for my lathe was not drawn properly and even more troubling was the fact that the new replacement circuit board was NOT correct and had to be modified if it was to work with the way the lathe was wired up. I never would have figured that part out myself.
In the end it cost about $500 for parts, labour and shipping but it was actually only a $5 fuse holder that needing replacing. I'm slightly embarrassed and broke.
Don
So glad to hear you isolated the problem. It is somewhat disturbing to hear of undocumented board design changes on the fly &/or schematics not matching what's actually in the machine. That just makes troubleshooting that much more challenging. Unfortunately, this isn't the first time I've read about similar issues.
Can you elaborate on what is defective in the fuse holder itself (like the fuse end contact points, or where it mounts to board, or internal crack somewhere embedded in the fixture.... etc).
How did you ultimately diagnose? I assume with a known good fuse in place it should have nil resistance across it, but for example does it act buggy only at higher current rate?
Can you elaborate on what is defective in the fuse holder itself (like the fuse end contact points, or where it mounts to board, or internal crack somewhere embedded in the fixture.... etc).
How did you ultimately diagnose? I assume with a known good fuse in place it should have nil resistance across it, but for example does it act buggy only at higher current rate?
Yes the fact that the replacement parts were not exactly the same as what was required and that the wiring diagram was not correct made repair very difficult even for my knowledgeable technician, and for me, impossible.
I just reexamined the faulty fuse holder and while its not real obvious, one can see the contact points do look like they are a bit questionable. That was the first fuse that blew originally and obviously it compromised the holder at the same time. The technician finally checked for continuity between the fuse holder, we had checked EVERYTHING else up to that point.
I'm now back at blowing fuses cuz I'm turning a big chunk of 4140 with less than ideal angles. I know its not ideal but im just about done the project. Easy does it! LOL
Don
I just reexamined the faulty fuse holder and while its not real obvious, one can see the contact points do look like they are a bit questionable. That was the first fuse that blew originally and obviously it compromised the holder at the same time. The technician finally checked for continuity between the fuse holder, we had checked EVERYTHING else up to that point.
I'm now back at blowing fuses cuz I'm turning a big chunk of 4140 with less than ideal angles. I know its not ideal but im just about done the project. Easy does it! LOL
Don
Glad you got it running Don.