[BruceP]

We have a Bridgeport series II Boss 5 cnc converted to run Greecko box, our Y-axis motor went out and found a used motor (p/n 025805) and installed it. We have tried the motor and it will run for a quarter turn then stop..we have the jog set to move 1 inch on the Y-axis but but it barely moves the belt pulley only moves 1/4 turn. Also does the motor also act as a brake because once it tries to turn it locked up like the motor is trying to turn both directions, feels that way also. So i guess my question is what could be going on ..like bad encoder...or controller.

The old motor would run but the output shaft wont turn.

Thanks in advance..

[machintek]

No encoders on a BOSS 5 unless someone installed them. And a whole new control that uses them
What do you mean that the old motor would run but the output shaft would not turn?
These are stepping motors. If a output transistor is shorted, it will whine as the motor oscillates between poles but the shaft does not turn.

George

[BruceP]

Well maybe that transistor whine is what we heard on the old motor, but it sounded like the motor ran. The 025805 motor has 8 wires and I was under the impression that it had end coders from what I was told.

The motor we have now we bought used and like i said it tries to run but not long enough for the Y-axis to travel an inch when hitting jog button. Even took the drive belt off and motor only turned about 1/2 a turn and you couldnot turn the motor pulley by hand untill shut the machine off.

[machintek]

Check output transistors.

George

[keebler303]

What is a Greecko box? Do you mean Gecko? If so, the output transistors are not to blame.

A better description of the hardware you are using would be helpful.

Matt

[BruceP]

The motor we took out was confirmed dead by a motor motor repair shop..was not repairable.

Thats why i asked if the was anything else that could of been burned out from old motor.

I,m not familiar with how to check transistors on the motor.

[keebler303]

WHAT IS A GREECKO BOX??

The motor is a stepper motor, it does not have an encoder. The transistors are in the electronics of the machine, not the motor.

If the old motor shorted, it could have blown one or more transistors in the original stepper motor drive. This is assuming you are using the original drives. If a transistor is blown, the new motor will not work until the transistor(s) is replaced. The transistors are mounted in fours on the big black heat sink on the back of the control cabinet. There are dozens of threads describing how to find the transistors and check them here. Make an effort to search the forum and then ask questions to help you along. It helps to answer the questions of folks trying to help you!

Search for:
BOSS transistors
2N6547

I have posted in multiple threads so you could search my name on here.

Matt

[BruceP]

WHAT IS A GREECKO BOX??

The motor is a stepper motor, it does not have an encoder. The transistors are in the electronics of the machine, not the motor.

If the old motor shorted, it could have blown one or more transistors in the original stepper motor drive. This is assuming you are using the original drives. If a transistor is blown, the new motor will not work until the transistor(s) is replaced. The transistors are mounted in fours on the big black heat sink on the back of the control cabinet. There are dozens of threads describing how to find the transistors and check them here. Make an effort to search the forum and then ask questions to help you along. It helps to answer the questions of folks trying to help you!

Search for:
BOSS transistors
2N6547

I have posted in multiple threads so you could search my name on here.

Matt

Thanks Matt

Gecko i guess i hit the (r) when i posted..lol

[keebler303]

In that case, the output transistor issue is not relevant. That pertains only to the original stepper drives.

What software are you using? Mach3?
Which Gecko drives are you using? G203V, etc.
Did the machine ever run correctly on the "Gecko Box" or is this a new modification?

Matt

[BruceP]

In that case, the output transistor issue is not relevant. That pertains only to the original stepper drives.

What software are you using? Mach3?
Which Gecko drives are you using? G203V, etc.
Did the machine ever run correctly on the "Gecko Box" or is this a new modification?

Matt

My bad Matt..i was wrong on spelling again...ugh or misunderstood when info was relayed to me...its Greco systems...which i believe its referencing to floppy drive.

The unit is all bridgeport original stepper motors and controls as far as we know it has the 025805 stepper motors on it.


I posted yesterday from home while sick and was relayed info over phone to make my post.

sorry about confusion.

Thanks Bruce

[keebler303]

OK Bruce

We are back to post #7.

Search and read.

Additionally, if the motor shop told you your stepper had an encoder, I am not sure that I would trust them to say the motor was dead. Did they even know it was a stepper motor? It is possible for the motor to fail and kill the transistors but it'd be much more likely that the transistors failed due to age or something and gave the appearance that the motor was not working.

Matt

[BruceP]

I can not turn my motor once its been activated or after i try to run it...before trying to run it i can turn it...i read somewhere where you said the transistors should be ok then? if i read it right...


Oh by the way is this what im looking for

[machintek]

Yes. One or more of those may be shorted which is how they usually fail.
Compare emitter to collector resistance readings of the 4. Or use diode check on the meter. Replace with motorolla 2N6547 as stated. Buy spares.
Is the AC voltage on T2 is over 63VAC, you will blow a lot of these. If your DC current is not set between 8 and 8.2 amps using the ACC board to set current measured at fuses 12, 13, and 14, you will blow transistors. Do not disconnect or connect a meter for current while a circuit is energized, that will also blow transistors.

George

[BruceP]

Yes. One or more of those may be shorted which is how they usually fail.
Compare emitter to collector resistance readings of the 4. Or use diode check on the meter. Replace with motorolla 2N6547 as stated. Buy spares.
Is the AC voltage on T2 is over 63VAC, you will blow a lot of these. If your DC current is not set between 8 and 8.2 amps using the ACC board to set current measured at fuses 12, 13, and 14, you will blow transistors. Do not disconnect or connect a meter for current while a circuit is energized, that will also blow transistors.

George

Mine do have the diodes across the transistor legs, but checking it with an ohm meter they seem to have the same resistance either way i go with the test leads on all 4 transistors.

What about what Keebler said in another post that after you try to jog motor and motor wont turn that it feels bound up in either direction that it may not be transistors.

or did i get confused reading everything.

[keebler303]

When a stepper motor is energized, it is "locked" in place. When it moves, it takes a step (1.8 degrees) and then locks there. Each time it steps, the transistors are turned on/off to make it step to the next position. If one or more transistors are damaged, the motor may still "lock" in position, but it will not get the necessary voltage to step to the next position. I think this is what you are seeing.

Matt

[BruceP]

Im going to recheck those transistors again here in a bit, and they should not read the same when reversing the meter leads ..correct?...

Thanks Matt and George


It would of been nice if i had a repair manual...lol

[keebler303]

Sorry for the earlier confusion, I thought you had Gecko drives which replace the existing drives. You obviously do not so it is most likely that you do indeed have a transistor problem.

Each transistor has 3 terminals (2 leads plus the case). Check the continuity between each pair of terminals both ways (test it then switch the red and black leads and test the same terminals again). The case is connected to the collector, the two leads are the base and the emitter. http://www.st.com/internet/com/TECHN...CD00002665.pdf

The base-emitter (BE) junction should behave like a diode and conduct one way only.
The base-collector (BC) junction should behave like a diode and conduct one way only.
The collector-emitter (CE) should not conduct either way.

If any of these conduct both ways that would indicate a shorted transistor. You need to do 6 measurements on each transistor. Do this for each transistor. You will probably find that one (or possibly more) is not like the others. As George said, order plenty of spares so you have them when you need them. It's not a bad idea to replace all 4 as the newer ones are probably more robust than the old ones. I would say just forget it and replace all 4 but we aren't sure that's the problem yet so we better see if one looks obviously bad.

Matt

[BruceP]

OK! here we go ..

From ground with black lead(-) red lead(+) to legs of transistor i show continuity of resistance. With red lead(+) to ground and black lead(-) to legs i show nothing.

Either way i go across the legs of the transistor i get a reading of resistance...ohm meter set to 200K i get a .6 reading or at 20K i get a .69.

I hope i explained this right..lol


Bruce.

[keebler303]

Bruce

You've lost me. Attached picture shows the 6 tests you need to do for each of the four transistors. You should come back with 24 measurements.

Matt

[BruceP]

Bruce

You've lost me. Attached picture shows the 6 tests you need to do for each of the four transistors. You should come back with 24 measurements.

Matt

Ok so what setting do i use on the meter then ..like 20K...200k or what?

Also is tab considered ground......the transistor bank are still mounted in cabinet so hard for me to tell pin 1 from pin 2.