BP Series I axis problems

[jho5820705]

Hi! I am new to CNCzone and CNC machines. I just purchased a BP Series I and got it wired up. Initially the Z-axis did not work. X & Y axis would jog fine. I pulled the transistors and replaced a bad one on the z-axis but it still does not work. Now the y-axis has a problem. The stepper motor seems to have power but will not turn the pully even with the belt removed. Did I mess up something when I changed the transistor? Or is this just another problem cropping up? Any help would be appreciated.

[NC Cams]

Frankly, if the axis worked before a repair and now doesn't now
, it is a good estimate the something got hurt in the process of "fixing" what ultimately didn't get fixed.

Try pulling the power transistors and bench testing them - if they pass current, it is probably in the drive circuit. Also, get hold of a wiring diagram for the control circuti and see if you have power going to the drive circuits and ultimately to the power transistors.

Swapping parts willy nilly can get stuff up and running but it can also result in more damage. This is especially true in "legacy boards" that have been heated and cooled and start to semi-conduct thru deteriorated solders or old, possibly frayed wires. You can even fry transistors via improper handling.

You're going to have to troubleshoot the circuit in an organized, logical fasyion to find out what's gone wrong - that is, unless someone had the exact problem you did and knows the 'silver bullet' fix.

Possible but I wouldn't count on it.

Welcome to the challenges of fixing/resurrecting legacy equipment.

[jho5820705]

I have ordered all the manuals for the machine and am waiting for them to arrive. I have traced the wiring and tested for signals and found the bad transistor in the z-axis, power going in none out. I have power to the y-axis but not enough to turn the motor. Guess until I get the manuals I will have to wait to test further. I am not sure what voltages I should have where.
Thanks.

[NC Cams]

The manuals will probably have the intereconnect wiring but I'd be surprised if they have circuit board wiring for amplifiers or drives.

If you have a functional driver/amp, you have a leg up. Start by comparing voltages at the gates of the drive transistors of the DOA board versus that of the good board and work your way back. BE CAREFUL as you're surely running out of bullets.

You might find that you may have to remove the pass element (drive transistor) as a short here can load down the drive and give bogus voltage readings. Look for burned or broken traces - perhaps even fried parts. Even a simple shorted diode can cause HUGE grief.

If you don't have voltage at a gate when you should have, or vice versa, that is a strong indicator that something is awry in the drive circuit.

If you did a lot of moving or R&R'ing of stuff to replace the funky transistor, you could have broken or cracked a trace on an old board. These can be a nighmare to find if they can be found at all.

If you can get a schematic for the amplifier drive, you'll be miles ahead with regard to troubleshooting your problem. Simply reading voltages for a circuit that you have not clue on how it works is a really hard way to fix something.

Sometimes it is simply easier to start replacing transistors (if you can find replacements which can be tough to do if they are old clunky darlingtons). I did that on some small power supplies and lucked out.

On more compicated boards, however, you really need a schematic to help you figure out what's wrong. Shots in the dark are not always on target.

Power going in but not enough going out suggests that the base drive current flow on the transistor (assuming it is a PNP or an NPN) is insufficent or totally non-existent. Then again, if the drive isn't pulsing or is pulsing out of phase, the motor won't commutate which points to a more complicated drive mallady.

Might want to locate someone who has experience with fixing amps like those you have. Might be money well spent, especially if you're not electronically proficient at reverse engineering circuits.

[machintek]

Sound like an older BOSS machine with stepping motors. Yes, the complete maintenance manual has all the board schematics.
The drives are very wierd. None of the fuses associated with the drives should be the screw in type. They develop a high resistance and you will see the fuse material melt out of the ceramic fuses. They were replaced with snap in type.
The current (DC) should be set to 8.0 to 8.2 amps using the ACC board. Never connect a meter or remove a meter or fuse with the drives on. You wil blow a transistor. Running into a limit at rapid will usually blow a transistor unless you have the SMS board.
If your voltage on T2 (back cabinet, top) exceeds 63 VAC, you will blow transistors like candy.
Many people have dropped a screw or washer onto the terminal strip for the motors and then that axis behaved like it had a blown transistor.
You do not want to know where the bridge rectifiers are!
Once set up correctly, I have these machines running very reliably.
It is normal for the Z axis to rapid up, hit the decel and feed the rest of the way, usually .200 inches. If it does not do this, it may mis-position.

George

[machintek]

By the way, the transistor Bridgeport called out was a 2N6547. At rest the voltage at fuses 12, 13, and 14 was between 9 to 10 VDC, current 8 amps.

At rapid the voltage would rise to ^)VDC and the current would drop to 2 to 2.5 amps.

Heat and age affects the motors. You cannot take them apart. As they age and the magnets decay, the power (torque) diminishes and the rapid current goes up. I can get more life out of them by turning down the rapid rate on the RCK or ZCK board.

George

[jho5820705]

Originally Posted by machintek By the way, the transistor Bridgeport called out was a 2N6547. At rest the voltage at fuses 12, 13, and 14 was between 9 to 10 VDC, current 8 amps. At rapid the voltage would rise to ^)VDC and the current would drop to 2 to 2.5 amps. Heat and age affects the motors. You cannot take them apart. As they age and the magnets decay, the power (torque) diminishes and the rapid current goes up. I can get more life out of them by turning down the rapid rate on the RCK or ZCK board. George

You are right this is a BOSS 6 machine. The transistor is changed is one of 4 on the heat sink behind the SMD boards. I didn't touch the transistors for the y-axis so I can't understand why that is not working correctly. It will job if the switch is in step but not in jog, 1, .1 or .01 positions. The display does not give me the y or z positions when selected in jog mode. It does display the x position. I am beginning to think that I may have a controller problem also. Maybe it is time to upgrade to MACH3 and Bob.

[jho5820705]

Just checked the voltage at Fuse 12, 10.2V at rest and 56V in rapid traverse. Fuse 13, 9.1V at rest and 12.3V in rapid traverse. Fuse 14 is .215V.

[machintek]

X axis is normal.
Check fuse 17, the Z axis AC fuse.
Also in setup you CAN display the axis position. The keyboard is color coded for what mode you are in and you can press the appropriate key to display that axis.
Does not sound as if the Y axis is really moving.
If the axis does not move and you hear a whine it is actually the motor oscilating between poles usually due to a blown transistor.
A quick check is to put that axis in step and step it. If it steps forward, forward ,forward and then backward, it has a bad transistor.

George

[jho5820705]

It appears that the y-axis has a blown transistor, it moves forward 3 steps and then hesitates. I can't see it moving in reverse but it does not move forward on the fourth step. I don't have any blown fuses that I can find, but could not find a fuse labeled 17. There were three fuses in the power cabinet that I checked also and they were all good. I guess I am going to have to wait and hope that the manuals will show me where everything is. There are a lot of labels that are missing or unreadable in the cabinets.

[machintek]

If I remember correctly Fuse 12, 13 and 14 were X Y and Z DC side.
15, 16 and 17 were X Y and Z AC side of the bridge and were in the back cabinet.

George

[bbuonomo]

Originally Posted by machintek Sound like an older BOSS machine with stepping motors. Yes, the complete maintenance manual has all the board schematics. The drives are very wierd. None of the fuses associated with the drives should be the screw in type. They develop a high resistance and you will see the fuse material melt out of the ceramic fuses. They were replaced with snap in type. The current (DC) should be set to 8.0 to 8.2 amps using the ACC board. Never connect a meter or remove a meter or fuse with the drives on. You wil blow a transistor. Running into a limit at rapid will usually blow a transistor unless you have the SMS board. If your voltage on T2 (back cabinet, top) exceeds 63 VAC, you will blow transistors like candy. Many people have dropped a screw or washer onto the terminal strip for the motors and then that axis behaved like it had a blown transistor. You do not want to know where the bridge rectifiers are! Once set up correctly, I have these machines running very reliably. It is normal for the Z axis to rapid up, hit the decel and feed the rest of the way, usually .200 inches. If it does not do this, it may mis-position. George

THANK YOU! This answers why I blew 2 power transistors this week. I was jogging Z and when I jogged Z + and hit a limit switch, it stopped working (aka blew transistor). I'm guessing the BOSS5 controller on my system used to handle the decel, but now I'm using MACH3 and a BOB Controller (Hillbilly's board), it didn't decel and zzzaaaappp.

BTW, I'm very happy with the BOB Controller and MACH3. Still a lot to learn, but I was able to run some code today to test it all out and all seems good so far. Still learning how to set offsets and setup in MACH3.

Thanks!

Brian