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Boss machine up and running again

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  • Boss machine up and running again

    I have secretly been working on fixing the drive board in my Boss Bridgeport. I know... I am supposed to be converting it. But I have been collecting parts for rebuilding the controller in this machine. I didn’t want the machine to know, it might want to up and break something really expensive which would keep me from moving forward.

    In all of this time, the machine had started to give me a funny sound on the x-axis. I posted some questions about the issue here in the following thread. HSM thread - rockrats Boss sounds funny.

    Well, so much good information was given to me on this that I dug out my old electronics book and started to read up on things more. During that time, the TV stopped working. I decided to dive in and see if I could fix it or shock the crap out of myself. The answer was a bit of observation during the operation of the TV. This lead me to replacing a capacitor and it is now working perfectly. So I decided, why could I not do this to the Boss as well?

    After a bit of reading and help from the above thread, I began trying to test transistors. A bit of reading got me to this link.

    And this link came from that.

    With a bit of work and using the online transistor cross-references available on the internet, I have been able to put the mill back in order again. I ended up replacing about 14 transistors to get the end result, but it runs so smooth and sounds so nice with its acceleration and deceleration steps (those with boss machines know this sound, kinda a nice sound to hear for a machine type of person.)

    Here is a shot of the board after with one of the old good boards next to it.

    You can see all of the little black zits on the old good board (left) have been replaced by little metal top hats on the now fixed board (right). I now am looking for a good oscilloscope which would have let me find the bad transistors without all of the trouble that I went through. But I only used a multimeter so that in itself is cool.

    Now, to start working on the big conversion, boss to pc. After cutting my teeth on this last issue, the next job seems like it will be a bit easier that I had once thought.

    [This message has been edited by rockrat (edited 11-06-2005).]
    Civil engineers build targets, Mechanical engineers build weapons.

  • #2
    I'm looking forward to your conversion asa I'm getting ready to convert mine over soon. The only thing holding me back is that I've been using the machine a lot lately.

    -Christian D. Sokolowski


    • #3
      Mr Rockrat jnr,
      Nice work and pleased that you got it running again.

      My MDI conversion has gone on back burner as it's that time of year again.

      Sir John.


      Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.


      • #4
        The more you learn the easier it seems. Electronics are easier for some. Unfortunately it will be hard to trouble shoot without prints.

        But you are actually in good shape. The reason being is you have an identical, working board.

        If you do get an O-scope I suggest you make a rough "print" or schematic. It is only for documenting waveforms and signals.

        Draw out the board using a block diagram. So your drawing will be representative of the board as you look at it. Make the drawing with enough space between runs and components so you can add notes.

        Make a couple of copies, maybe enlarge the drawing.

        Now yer set....With the machine energized you want to take measurements of voltages and any waveforms with the drive "static" and dynamic.

        It would be very helpful to have another person move the axis while you take the measurement (wifey would be good, get her interested). Be very, very careful to not short a run to ground, component or anything else.

        A needle sharp probe helps, you dont have to press as hard and no slipping (also punctures protective coatings.

        If you do get varying waveforms (other than 60hz) draw the wave with voltage levels. If you draw an approximation of the waveform it helps when you check the bad board. For example: if the good wave doesn't have any clipping or "is" square in shape and the bad board is not the same it can show component degradation.

        After you have the entire good board mapped out you can go the bad board. Take your time and check the entire thing. You may get lucky and find a bad component. Hopefully it is fully opened and not just degraded.

        It is easter egging but can work. It's always easier to go easter eggin when you got a map

        Even if you have a real schematic I would still map out some good wave forms and voltage levels. I used to do this on a very large electronic system when everything was up and running well. Then when she went down I had a good signal schematic.

        Lemme know if I can help. JRouche

        [This message has been edited by JRouche (edited 11-06-2005).]
        My old yahoo group. Bridgeport Mill Group


        • #5
          Oh, before I totally forget, a special thanks to all that helped me out includine Bruce Griffing and IBEW (where ever you are).

          Civil engineers build targets, Mechanical engineers build weapons.


          • #6
            Hey next time you guys are running your boss 5, when you shut it off, could you check the gold resistors on the inside top of the back door. Mine run quite hot, like burn the spit off your finger hot. I just want to know if this is normal or not. Glad to hear you got your mill running Rockrat. Sounds like you have had the same problems as I.

            When I got mine the first time I put power to it the smoke got out. Luckily as you have found out there are three separate identical systems, makes for nice comparing. If not I would have never figured mine. Some numbskull was messing around with the DC transformers on mine and put one of the ceramic resistors in the wrong terminal. It took me a wile to figure that one out. I always had a higher DC voltage on one and that is what was letting the smoke out. All and all the fix was cheep parts wise; it only took me a couple of years of tinkering to get it going.

            The day I finally figured out how to make a program to make it move was just so frigen rewarding I can’t explain it. I love to watch the mill do circular entropolation I think that is what you call it one motor speeds up slows down and reverses at the same time the other one is doing the same, that is just neat.

            Are any of you guys trying to interface a PC to download programs? I have had some successes but I think I have a grounding problem between systems. All is fine until I run the program. Something is frying my PC's. It’s a good thing you can buy a tower for 10 beens.
            Anyhoo if any of you BP Boss 5 owners have any advice or questions I would love to hear from you. I would love to share paper information and software for any interested.
            I moved this summer and have worked out a years storage with the new owner. I will be moving my mill to the new place in a couple of days so this has relit the CNC fire.
            Take care, Stephen


            • #7

              I'll be sure to check those resistors next time I'm running it. I'll have to check my settings but I am running the mill with programs from a PC. I just load them in with windows hyperterminal. I know it's 300 baud but I forget the rest.

              -Christian D. Sokolowski


              • #8

                [This message has been edited by hoffman (edited 11-08-2005).]


                • #9
                  Thanks Christian. I hope it is normal. It is just a guess but I think these may be current limiting resistors for the steppers or somthing of that nature.


                  • #10
                    A number of years ago, I worked in a place with a BOSS6 B'Port. Connected a DB-25 connector to the RS-232 plub on the machine, used a 25-conductor ribbon cable to connect a Radio Shack Model 100, and went to work. The Mod 100 is absolutely MADE to mate with the BOSS6!

                    I still have a couple of those machines around that I picked up for $10.00 or so at a HamFest.


                    • #11
                      I'm also a member of the Boss controller club. I know the feeling I had when I first brough my machine to life. It was scary and cool at the same time. I had to overcome quite a few problems, and I got a lot of help from some members of this board.
                      The scariest problem was a sticking jog switch. The machine would run away to the stops without warning.
                      Another problem that was predicted by a BP technician named George Wroclawski was in the fuse holders specifically the Z axis holder #14. These are for special ceramic "delayed" acting fuses that are slower than the slow-blow. It will blow and cause the Z axis to fail to retract and the machine will crash. I eventually replaced this one with a resetable breaker of the same amp rating and haven't had any further problems.

                      On the serial port issue I found that every diagram on the internet I came across, and references in old tech-notes were wrong. My theory is that the PC serial port description that we have now is not the same as it was back in the day. If I remember right it was the wire going to the 9 pin serial #1 pin labeled "chassis ground" was the culprit. Eliminating that wire and using only the transmit, recieve, and data negative wires was all that was needed. Of Course both chassis are electrically grounded to the same electrical ground anyway and so there was no need for this wire. It seemed to disable the PC port. Snip snip and no more problem. Of course you must then get the serial parameters right and set the ERS board for the fastest speed it will handle.

                      I would like to keep the Boss 5 controller in running condition, but I would also like to piggy-back a controller that could introduce the pulses and signals into the system to control the machine directly from the PC without having to download limited sized G-Code programs. The memory limitation is a bit of an obstacle.

                      Good luck. I'll try to check back here and see your progress.



                      • #12
                        I must have an older control on my Boss. Seems like I went searching for info to hook up the pc to the little round port on my machine. It does not have a rs232. I think that it is a 20ma loop. I just never finished working on it.

                        I kept thinking that if I were to put more money in it, I sould upgrade to pc and gain cutter comp. And I would also gain the ability to cross over the quadrants on a circle. Yes, my machine is that old.

                        As I reall, John has me beat with a machine that only uses one stepper card and switches between axis during operation.

                        Glad to see that we have members still playing with this control. Keeps me encouraged and hunting down parts.

                        Civil engineers build targets, Mechanical engineers build weapons.


                        • #13
                          Tell me a little more about your control. Does it have an ERS board? According to manual M-128 page 4-7 both capabilities are provided and the connection information is in manual M-130 section VI.

                          I don't have that manual.

                          You might find an interface card or an old IBM PC serial port card. If you go this route you should obtain a new motherboard that has an ISA buss. VERY few do any more. Otherwise you'll just have to use an old PC as an interface device or find a PCI card with a 20-ma serial port.
                          Check out this:

                          20mA current loop uses the absence of 20mA current for high, and the presence of current in the loop for low; this signal level is often used for long-distance and optically isolated links. Connection of a current-loop device to a compliant RS 232 port requires a level translator; current-loop devices are capable of supplying voltages in excess of the withstand voltage limits of a compliant device. However, the original IBM XT serial port card implemented a 20 mA current-loop interface, which was never emulated by other suppliers of plug-compatible equipment.



                          • #14
                            Mr Rat,

                            My Bridgy is a bit of a special, as in weird and not desirable.
                            These were fitted with servos and a Heidenhain 131 controller that could only do linear moves.
                            In this case it used servo motors with electromagnetic brakes fitted and swapped the one driver card between motors.
                            It was actually a good system for it's day, about time scale equal to a BOSS 4-6 as many repition jobs slots, drilling squaring up blocks are all linear.

                            So far it's been gutted and all the new parts are there waiting to be fitted, onlt time is missing.

                            Sir John

                            Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.


                            • #15
                              Sorry for the late reply. Things get going around here and I loose all track.

                              I have the following, RSI, RCK (that I think is the comm board, its been a while), BCC and LS1-11.

                              My notes are as follows. The lsi1-11 has 4 chips which means it is a boss 3 or 4 (mine is 3, too old to be 4).

                              I have notes for the 20ma loop noting that BlackBox makes a current loop adapter for the pc. RS422.

                              And some good info at

                              I had to run a short little program yesterday and it is still running like budda-. I am pleased and I might just try drip feed if I ever get around to the research for the 20ma loop.


                              Civil engineers build targets, Mechanical engineers build weapons.