[jderou]

Well I got my Boss 5 wired up, and everything seems to work good except the z-axis, the belt is slipping at the screw. If I stick a screwdriver through the front I can turn the screw pulley, though it feels like it could be gummed up. Is their a way to tighten the belt? If not, do I have to disassemble the thing to free up the screw? Or can I just spray something on it (like liquid wrench, or some kind of solvent)?

Thanks!

[HuFlungDung]

Is this a toothed belt? Is the Z drive on the knee or the quill?

[jderou]

I was wrong, it isn't slipping, the stepper is losing steps. If you jog say an inch, it moves a little at low speed then slips, then moves again as it decelerates. Any ideas?

[HuFlungDung]

Your Honour, please instruct the defendant to answer the question

[machintek]

Bad transistor on final drive or it is gummed up. Remember that the control sends out pulses that the motor follows. The frequency goes up to rapid stays there and as the target is reached, the control decelerates the motor. If the transistors are not switching correctly or if there is drag on the motor, it cannot react to the faster pulse stream. Try flushing the quill with kero.
Another factor is the energy available to move the Z axis. If the voltage or current is not correct, it can cause a similar problem. Volts X amps = watts (energy). Do you have the screw in fuse holders?

George

[jderou]

Sorry HuFlungDung! Yes it is a toothed belt and it is on the quill.
I just tried jogging the axis at low feedrate, it moves ok up to ~ 40 ipm. It seems like it doesn't run as smooth as it should at low feedrates, though. Where are the transistors? Which fuse holders would be screw in? I don't recall seeing any. Where is the best spot to flush the quill, through the front cover?
Sorry so many questions, I have a lot to learn about this thing.

Joe

[machintek]

Are all 3 axis behaving the same?
In the set up of the RCK (clock board), a transition point on the board is 4.0 IPM which is input as 40 in the program. It does not use a decimal point in the feedrate, it is assumed.
Screw in fuse holders are NOT good. Typically they develop a high resistance, burn, the metal actually flows out of the ceramic fuses. Specifically fuses 12, 13, 14 are the DC side of the drives and are most vulnerable.
It is best to flush the quill through the front cover (it swings open).
You WILL need a maintenance manual.
Use Mobil Vactra number 2 way oil or equivalent.
You will need a meter that can measure 10 amps DC current as well as voltage and resistance. Fuses 12, 13, 14 should have 8 to 8.2 amps going through them at about 9 to 10 volts with the drives ON but at rest.
RCK set up cheat sheet is attached.

George

G

[jderou]

It is only the z-axis, the rest work fine. I tried swapping smd boards but it did not help. I will check the fuses.
Thanks!

[jderou]

I think its in the quill. I took the belt loose from the stepper and I can barely move the axis up and down by turning the nut with the belt. I don't think its in the nut because the nut will rotate freely a hair back and forth. What is the best way to de-gumm this? how hard would it be to remove the quill, can you just remove the bolts from the ball screw and pull it out?

thanks again

[machintek]

First flush it with kero. Just squirt it inside the hinge open cover that exposes the switches. If you can, try and lower the quill a bit and check for pealing chrome. I have seen this happen. Also if it frees up just past the set screw on the quill, then the set screw (preventing the nut from backing out holding the spindle into the quill) is too tight "egging" the quill and making it tight.

George

[jderou]

I flushed it out while moving it up and down slowly and re-lubed it. I may be a little better but still too tight. Haven't seen any peeling chrome. It actually gets tighter the farther you go down. I need to get a maintenance manual so I can see how this thing comes apart. The guy I bought it from has one, but he is on his honeymoon right now. Hopefully in the next couple of days I'll get it from him.

[jderou]

Well I was wrong again! While the belt was off I tried jogging the motor and it still wouldn't turn. So I went swapping stuff. I found the problem to be on the board that mounts to the rear heatsink (see pic). Now the question is how do I test the components on this, and where do I get them? Thanks for all the help!

Joe

[machintek]

What you have there are the final drive transistors (2N6547). The SMD board turns these on and off in the proper sequence. The beauty of this is that you have 4 transistors. You can set a meter to diode check and see what is the voltage drop across the semiconductor junction which should be about .5 volts. Or you can set a meter to OHMS and check each forward and backward (reversing the red and black leads). The bad transistor will show the same resistance forward and backward as it will probably be shorted. The base is the small blue wire to one of the pins. You will be checking collector to emitter which is the other pin (all 4 transistors are soldered together) to the transistor case. Hopefully, no one replace a transistor with a non spec unit and/or forgot the insulator beneath the transistor or the insulators on the mounting screws.
This is the MOST common problem with the old BOSS stepping motor machines. Followed closely with a bad bridge rectifier.
Check www.digikey.com or another electronic component source or call Alan at my office 1-800-245-2598 central time. I know he has some.
If a machine is tuned correctly, I have seen these machines run years without blowing a transistor. Proper and stable voltage in, proper fuse holders, current set correctly, a SMS card installed, and good preventative maintenance.

George

[jderou]

The transistors are on order, thanks!