I am considering replacing the control with gecko's etc, but in the meantime, I really need to get my Y axis running again so I can make some parts!

The failure occurred during a 20 minute or so period of time when the machine was sitting idle.

Specifics:
I pulled the front belt cover off to expose the position indicator drive, and allow me to see any leadscrew motion... If I try to jog the Y axis, the leadscrew shows slight motion in one direction, then motion stops while I can hear the stepper motor whine increase in frequency... When single stepped, the axis moves a step in the same direction each time. Positive, or negative direction motion is the same. Two sequential steps feel pretty solid, the next two feel weaker when moving in the - direction. In the + direction, all of the steps feel a bit weak.

There are no blown fuses...

Is this a common failure, and if so, what components should I be looking at? I have a maintenance manual, so I should be able to locate parts/testpoints etc.

TIA for any tips anyone can provide!

A little more info:
I flipped the ACC board with no change, and swapped SMD with Z axis SMD, and no change...

replace 4 transistors on the transistor pack on the back door

I had the same problem the transistors will fix the problem. I keep an extra block of transistors as a backup. They seem to use these from time to time.

Thanks!

I will replace the transistors and let everyone know what happens!

Actually my troubleshooting so far has lead me in this direction, so this tactic is right on track with what I am finding on my own!

This forum is a great resource, and I am grateful for the advice. Bridgeport information, and repair advice is getting quite scarce these days!

/Craig.

Craig here is a link to some files if you scroll down thru them you will find some info on changing those transistors. Be sure to use the heat sink compound when installing the block back on the heat sink.

Good Luck
http://metalworking.com/DropBox/_2000_retired_files/

It is also possible that one of the 12 diodes on the board beneath the ACC card is bad. When on of these goes, it does what you have described. By putting a meter on the base of the transistor, I notice that they do not turn on and off crisply. Instaed they turn off half way then finally off fully. By the way, the ACC is symetrical and by turning it around, you switch the X and Z current circuit but not the Y. In twenty years of BPT service I have only found one blown SMD board.
I cut and pated another answer in part below. Just substitute Y for Z.
Put the machine in jog, setup, z axis and step. Press the minus button repeatedly. Each time you do watch the small shaft and dial benath the Z axis motor. Made sure that it does not step in the same direction for three steps and then reverse direction for one. This would indicate a shorted final drive transistor (2N6547). There are 3 groups of these on black aliminum heat sinks above the ACC board.
It is also possible that your voltage in is wrong, you have a bad bridge rectifier, your current is set wrong, you have a chip or washer between two diodes on the small board beneath the ACC card, a chip or washer in the motor terminal strip beneath the ACC card, or the wrong transistors, or a high resistance in the Z axis DC fuse (screw in type, tan in color), or your quill needs to be cleaned with kerosene and use Mobil Vactra number 2 for way oil. I also once had a bad opto coupler on the ZDI to the SMD. Drove me crazy.
That gives you a bit to check.

I will check the diodes as you described. I am at work right now, so I can't fiddle with the machine until later this evening.
I found the post that you pasted in yesterday evening while I was searching for more information that might help me fix this thing! After single stepping the axis, and not seeing the backstep, I decided that I should post my problem and see if anyone could help.
Your description in that post, and obvious knowledge of the inner workings of the stepper drive circuits is what prompted me to post my problem here! Thank you very much for being willing to help and share!
Based on what I read here, I now know that I may have a diode problem, and replacing the transistors could be an exercise in futility. I will have to determine if the diodes, or the transistors are at fault before I start shotgunning parts...

I will post what I find!

Just for fun, I am attaching a photo that my wife took of me working on interfacing my laptop with the BOSS6 so I could transfer gcode programs etc...

Craig here is a link to some files if you scroll down thru them you will find some info on changing those transistors. Be sure to use the heat sink compound when installing the block back on the heat sink.

Good Luck
http://metalworking.com/DropBox/_2000_retired_files/

I was able to locate files that appear to be related to diode replacement here, but I didn't see anything about the transistor replacement... Perhaps you can give me a filename? There are a LOT of files in that folder!
Thanks!
/Craig.

The link that puller482 provided lead me right to the transistor plate! I found one of the power transistors to be shorted. I will be ordering + replacing. The transistor plate is a bit of a bugger to get to, easy to drop the screws etc.
Thanks a lot everyone! I will be making chips again soon!
/Craig.

How did the interface go? There are a LOT of posts about that in this forum also.
In another post I give a legthy description of how these drives work with voltage readings etc. If I find it I will post a link.

George W.

How did the interface go? There are a LOT of posts about that in this forum also.
In another post I give a legthy description of how these drives work with voltage readings etc. If I find it I will post a link.

George W.

The interface took some time to figure out, but once I had the pinout information for the amphenol connector, I made up a serial cable with a DB9 on one end, and nothing on the other. I pushed the individual wires into the correct locations on the amphenol! My intention was to get it working first, and connect more permanently once it was working. The hardest part of the whole thing was figuring out how to transfer files, and break off the connection once the file had finished transferring... I ended up using hyperterminal at 2400 baud. At the BOSS6> prompt, Hit K <enter> to empty memory, and put the BOSS into "Input" mode. Next I would use the send text file function in hyperterminal to push the Gcode across. Once the transfer was complete, I had to hit CTRL+Z to get the BOSS out of terminal mode. It was frustrating to discover that there is no flow control on the BOSS RS232, so I ended up having to run the interface at 2400 baud. Any faster, and it would drop random characters. Usually the first character of the gcode block here and there. At 2400 it is almost rock solid. I added a delay of 15msec between lines, and presto! I am still pretty disappointed that the memory is so small. The BOSS6 will only hold about 600 some odd lines of Gcode. Once I have saved my pennies for a set of Gecko 201's or 210's, I plan to replace the BOSS. In the meantime I will have to live with it's limitations. I also have a 4 axis Shoptask that I built a few years ago. I can use it for the few jobs that require more than 600 lines of gcode if I have to. However I really don't have a lot of interest in running jobs on the Shoptask now that I have experienced the obvious advantages of the Bridgeport! :D

/Craig

Procomm works well also. I have the BPT Communications bulletins on PDF format if you need it. Remember to use 2 stop bits, no parity, X on Xoff enabled. The large rectangular connector on the ERS is pulled out and left to dangle for RS232. The AMP connector is a reverse sex 8 pin type and I used to purchase it from Newark electronics. On a 25 pin, the pc side would have 4 to5 jumpered, and 6 to 8 to 20 jumpered. There is a VERY powerful editor built into the BOSS control. In PROCOMM, I use the CHAT mode for editing the program in the machine. If there is a program in the machine and you press the edit button, it will come up with BOSS _ editor. You can still upload a piece of code by using the INSERT mode. Two carraige returns returns you to the edit mode. KI will clear the memory and return you to input mode. There is an entire page of editor commands.

George W.

bud you look like like my brother but he hates machines.
Do you have the programing book ? You know i had the same problems with the droped cariator also.I had one boss machine that had 20 ma loop that worked better . Since all the transistor pack blown out i used other drives thay work wonderful . With maxnc software. :cheers:

ALL BOSS 3,4,5, and 6 machines could communicate in 20ma current loop. But it was extremely common to blow the transistor in the loop on the ERS board. 20ma was used with the Type 33 teletype. The Type 43 could do both 20ma and RS232. The problem is that the serial port on a PC is Rs232. Pins 1,2,3,4 and 5 on the AMP connector were used for 20ma. Pins 5,6,7, and 8 were used for RS232. Only the local port on the machine is available.

George W.

Here is a copy of a post I replied to on the BobCAD forum a while about. The terminal/editor I am referring to in the message is Tera Term. It is free and I use it to talk to my Bport BOSS-5. Use the following link to go to the Tera Term page.
http://hp.vector.co.jp/authors/VA002416/teraterm.html
I purchased the cable from Jim Blasko about 2 years ago and have never had any regret in the purchase. He is still selling the kits/cable. I am in no way related to him and I do not make any money on any sales.
It is a pain in the ass to break up your program in 13K chunks but it works.
Hope this helps someone.
mc_n_g

beginning of post
*******************************************************
I have a Bport BOSS 5 Series I CNC machine I run with BobCAD generated Gcode.
I use a cable connection designed by JCM Blasko of Lake Oswego OR (near Portland). He has a RS232 kit for sale that bypasses the old connection and splices into the wires of the communications boards. You send your code to the machine via a Hyperterminal window (program). Basically you start an editor to 'talk' to the machine and download the code to it. Once the code is downloaded you turn the dial and hit Start button on panel.
I have reached a maximum file size of around 13,400 Kb file. Yes it is small but remember this is ascii text only so there can be several hundred lines of code. When my programs become too large I just break them up into smaller pieces and feed the program in chunks to the machine and run the whole program in several parts. For the most part this only comes into play when you are creating skins or very complex parts.
The cost is around $70 for the cable, directions, and terminal program.
It is well worth the investment rather playing with the old style serial port.
I noticed he is currently running an auciton on EBAY and selling some of the cable kits. The link is
http://cgi.ebay.com/ws/eBayISAPI.dl...&category=11805

If the link does not work look for Bridgeport RS232 as key words. You should find him with a few other listings.
He is a nice guy and can answer questions you may have about the set up of tha cable and the machine.

If you need more info contact me through the board.

mc_n_g
*******************************************************
end on post

Just as another note. I also have used the Metal Working Drop Box files for replacing the transistor/diode in the Bport. Make sure you use a heat sink when soldering in the new transistors. The cost of the transistors is around $10-$15 each.
Everything worked fine after replacing the 1 that blew.
One way to tell where your problem transistor is located is to swap the transistor boards. If your X-axis is not working right swap teh baord with one already working on the machine (say the Y-axis). If your problem transfers from the X-Axis to the Y-axis you know the transistor you need to replace is on your board and not on the large heat sink at the back of the machine. If your problem stays with the X-axis then you know to look at the transistors on the large heat sink at the back of the machine.
There are 4 transistors per board and 4 transistors mounted on the heat sink on the back of the machine for a total of 8 per axis. 24 total for the machine.

mc_n_g

A meter set to diode check (which measures voltage drop across a semi-conductor junction) is the quickest way to determine if a transistor is bad. First do the step test. If the mechanical counter goes forward, forward,forward, back, etc you have a blown (actually shorted) transistor and the voltage drop will be zero.
It is a lot quicker than swaping transistor blocks. Also the less you remove these, the fewer washers and screws you will drop onto the diode board or the motor terminal strip. Transistors are 2N6547 and any BPt tech carries a dozen, as well as a couple of bridge rectifiers. These final drive transistors are driven by the SMD boards. In twenty years of service, I have only replaced one of these.

George

Yep...I bought a bunch of these transistors in question. I have 9 of them brand new for sale if you want them. $35 shipped USPS Priority in the US. Contact me if interested. I no longer need them since I am converting to servos.

-Brady

Well Guess what...

I replaced the shorted transistor for the Y axis, and another one that was reading different than the others, but wasn't shorted... I figured this other one was marginal. After putting the thing back together, I put power to it... Y axis works great! Cool I thought... Problem solved. WRONG... The X axis won't jog now... I popped the machine open and put my meter onthe transistors for the X axis... One shorted, and another marginal... Replaced the shorted one... I vacuumed the control cabinet to make sure that I hadn't inadvertantley shorted womething by brushing a chip inside or something... I was careful with my repairs and didn't drop any screws etc... Powered back up, and no X axis jog... Powered back down, metered the X axis transistors... The marginal one is now shorted. I replaced it. I figured I must have done something while I was in there, so I double checked every connection, and checked for shorts before putting power to it this time... Damn X still not able to jog... Three steps forward, one step back! Multimeter confirms that the transistor I just installed is now shorted.
I have bought all of the 2N6547's that I could find within driving distance (4)... I need more, but I am concerned that I must have done somethig while I was in there that is killing transistors on the X axis now...
Any ideas? This is pretty frustrating!!!!

TIA!

/Craig.

Yep...I bought a bunch of these transistors in question. I have 9 of them brand new for sale if you want them. $35 shipped USPS Priority in the US. Contact me if interested. I no longer need them since I am converting to servos.

-Brady

I would like to take you up on your offer... My email is stevesys@snet.net If you can take paypal, drop me your address, and I will pop the money over right away...

Thanks!

/Craig.

You have mail!

Thanks!
-Brady

Check the current going through the X axis fuse. Does your meter go up to 10 amps? If so, WITH THE DRIVES OFF, remove the X axis DC fuse (fuse 12) and hook up your meter using alligator clips. Turn your drives on and set for 8.0 amps on the top pot of the ACC board. I am assuming you have snap in fuses. I hope you do not have the screw in fuse holders. They have been a big problem. The metal would actually run out of the ceramic fuse due to the heat generated by the corroded bad connection inside the fuse holder. Resistance generates heat. Shut the drives off and remove the meter and reinsert the fuse. Check your SMS card to make sure it does not have a blown fuse. It is a simple board with 3 fuses, three diodes, and three resistors on it. Advise us of your progress.

George

I do have screw-in fuse holders on the DC side. They are free from corrosion however...

X amps were at 7.6. I am fresh out of 2N6547's, so I can't replace the shorted one yet. I bought the transistors from Braidmeister, so once they arrive, I can replace the brand new shorted one on X. I set X to 8.0A anyway. Will setting the amperage to 8.0A with a shorted transistor set me up for trouble later?

I checked Y while I was in there, and it was at 8.02. I left it there for now. Y is working fine with it's new transistors.

SMS fuses are fine.

Should I replace the screw-in fuseholders with something else even though they appear to be free of corrosion? If so, what should they be replaced with? The AC side has snap in fuse holders.

This is somewhat frustrating, but with everyone's help I feel like I am at least moving toward getting the machine running again.

Thanks!
/Craig.

change allof them i onepack

You can check for resistance in the fuse holders by the voltage drop across them. We always replaced these fuse holders with the snap in type. If you remove these fuse holders, you will probably see a lot of heat related discoloration at the back.
Did you check the transistors out of circuit? I would check each removed transistor. It may be that your problem may be in the machine or in the transistor block. I had one machine where they replaced the transistors and lost one screw. They found a perfect replacement. It was just the right length to extend past the transistor block and short to the chasis behind it. That took a while to find. I had anothe company that replaced transistors and lost one of the little plastic isolators on the screws. Another forgot a mica (clear and hard to see) insulator beneath the transistor.
Remember that the transistors are electrically insolated from the chasis (ground).
If you have the small diodes on the transistors have you measured them for a voltage drop (good)?
Lastly I would check the resistance of the motor windings at the terminal strip. X1 to X5, X2 to X5 etc. to see if any vary.
What is the voltage to ground at each DC drive fuse?

George w.

I am reading 10 ohms across each of the screw-in fuses. All of the mica insulators are there, and each screw has a plastic insulator under the head of the screw. None of the transistor mounting screws appear to be long enough to short to the heatsink, but I will lay a straightedge across to make sure when I replace the transistors the next time around... Brady will be mailing the transistors to me tomorrow, so I hope to have them by the end of the week... The 1N457 diodes across each transistor appeared to be OK, so I used the old ones when I replaced transistors last time. I have three new diodes, so I will test each of the existing ones out of circuit to make sure they are OK before soldering them back, or replacing as required. Even though I am not reading excessive resistance across the screw-in fuse holders, I am concerned about them because of past troubles with them posted by Machintek. After thinking it over a bit, and realizing that the DC side fuses are only protecting the DC drive side of the stepper drivers, I think I can get away with using automotive spade type fuses and holders. My plan is to install them in parallel with the screw-in holders, remove the screw-in fuses, and install 10 automotive spade fuses. The automotive fuses may react slightly slower than the buss fuses, but I think they will do OK, and will not have the corrosion/resistance issues that the screw-in holders have. Please correct me if you believe my logic is flawed... I am also headed back to the AC side of the machine to measure outputs at the transformers just to make sure that the voltages are still reading what I think they are... I am thinking that if one phase of my rotary converter is lagging in voltage, it may explain my troubles here. One never can be 100% sure that the power company is delivering constant power right? At this point, I believe that going back and re-checking everything I have already done will be time well spent.
The assistance provided by a few folks on this forum has been quite helpful! Hope to have it sorted soon! Thanks!

10 Ohms is a significant amount of resistance. E=I x R 8 amps times 10 ohms = 80 volts.
In other words, to push 8 amps through 10 ohms, you need 80 volts. If you have only 60 volts, then you cannot push the requirted 8 amps through the fuse.
Tell me what the inside of the fuse holder looks like when you pull them out. Think of it this way, each fuse holder was dissipating 480 watts of heat.
Automotive fuse holders will work. My only concern is for a good connection to them.


George

The fuseholders I bought have a plastic socket with lid that snaps over the installed fuse. There is a wire that appears to be 10 gauge attached that has each end connected to the fuse legs. When I have used these in automotive applications, I just snip the sire and solder in etc. For the bridgeport, my plan is to snip the wire, strip each end, and install using the screws that connect the wires to the original fuseholders. I believe that the connections will be good. Would you explain why the resistance in the fuse holders would result in cooked transistors? Is this a simple E=IR thing? For instance, does the increase in resistance raise the voltage too high, and break down the transistors?
It is obvious to me that resistance will reduce the current available to the drives, but I am a bit sketchy about why this would break down the transistors...

I will install the fuseholders and post a photo...

Thanks again!
/Craig.

The fuseholders I bought have a plastic socket with lid that snaps over the installed fuse. There is a wire that appears to be 10 gauge attached that has each end connected to the fuse legs. When I have used these in automotive applications, I just snip the sire and solder in etc. For the bridgeport, my plan is to snip the wire, strip each end, and install using the screws that connect the wires to the original fuseholders. I believe that the connections will be good. Would you explain why the resistance in the fuse holders would result in cooked transistors? Is this a simple E=IR thing? For instance, does the increase in resistance raise the voltage too high, and break down the transistors?
It is obvious to me that resistance will reduce the current available to the drives, but I am a bit sketchy about why this would break down the transistors...

I will install the fuseholders and post a photo...

Thanks again!
/Craig.

I do not profess to be a EE. But my Service manager was one of the smartest people BPT had. He was of the opinion that it was the transistors turning OFF that created a short. Hence the SMS card. If you were in rapid and hit a limit or pressed the E stop, you would blow a transistor. If the T2 voltage exceeded 63VAC, you needed to invest in a tray of transistors. I could tell when a customer put in a non standard transistor as the static voltage would be a lot higher to have the same current. As I said the drives are strange. Static they are 9.5 VDC and 8 amps. At rapid they are 60VDC and 2.2 amps. If you do not have a SMS board and have a current clamp on the DC side and pree Estop, the current drops to zero like a stone. With a SMS card it drop to about half an amp and then decays. If one of the power resistors on the saturable core reactors went open (common in old machines, check for cracking on the borttom of the resistor), you would burn the SMS card and melt and burn your ACC card. The fan at the bottom of the logic card rack is critical. If it fails, your boards will fail due to heat. I have seen all of this more than once. I had a machine in Kearny NJ where the fan in the back quit. The insulation on all the wires became brittle and fell off. The ERS board has the BOSS software buned onto a chip at the bottom of the board. It has a tendency to collect dirt from the fan beneath it. This device runs hot to begin with and will fail if not kept clean. Preventative maintenance goes a long way with these machines. Many have been brought back to life by cleaning the boards and cleaning the edge connector with a pink eraser. The screw in fuse holders, when we came across them, were immediately replaced. They caused nothing but grief.

George

One of the things I did when I first put power to the machine was to verify all of the fans were running! I have the installation manual, so I stepped through the manual for the most part. The one thing I didn't do was adjust the regulated power supplies, or adjust the drive current for each axis. I have found with other old electronic equipment I have worked on that old machine may need to run at slightly higher or lower voltages to be happy. Logic chips that have run for years at 5.5V suddenly quit when the 5VDC power supplu is "correctly" adjusted back down to 5V! The regulated voltages were within .1V, so I left them alone for this reason.

I didn't check the drive amperage because I didn't have a clean way to put my meter in the circuit. Everything else had checked out, so I did the "Assume" thing. This may have turned out to be a mistake, or maybe not...

Both cabinets have some funk in them, but the circuit boards and terminal strips are relatively clean. I found dirt inside, but no chips. The filter on the control cabinet door was fairly clean, as was the filter on the backside of the power cabinet. Whoever had the machine before me appears to have been keeping up with filter replacement.
I did find a bit of mung on the bottom components on the ERS board, but it is mostly dust. I used compressed air to blow most of it off, and left it at that. As far as I can tell, the control doesn't have show signs of brain damage, and it seemed to run OK before It started eating power transistors.

I have an SMS card. My ACC card is discolored, showing signs ov overheating in it's past. It is also obvious that transistors on it were replaced in the past. The ACC card didn't seem to run hot when I checked it after running a part for about 20 minutes shortly after I bought the machine. I considered cleaning the card edges of the cards in the cage, but they look clean, and I have not seen evidence of logic trouble. The card edges of the SMD's, and ACC look good too, however I will hit them with the eraser to eliminate the possibility of intermittants at the connectors.

One of the two fans behind the tape drive has started whining like it's bearings are dry. The fan is quiet, then growls a bit, then quiet again... I have not dug in there to replace it yet because of the transistors problem. It is still moving air, and my garage is pretty cool due to the season. It can wait for now. No sense in throwing money at a new fan if I end up deciding to gut the cabinet...

I noticed that it lost a couple of steps during machining one of my parts, but I kind of expected this from half stepping drives (resonance). I ended up with a usable part, and decided not to persue it at the time. My intention has always been to replace the control, so I was willing to live with minor issues until I could replace the control. I am hoping to get a few more months of use from the old boss control before having to replace it, and I believe I am on track to be able to do this. Hopefully I can decrease it's appetite for power transistors so I can make a few parts! I would rather invest in cutters, and blanks right now.

Applying these great ideas, certainly can't hurt!

Machintek--

I really appreciate your willingness to share your knowledge and experience! Once the machine is running again, do you have any ideas on how I might increase the memory? Is 600 lines of Gcode about what it should be able to hold? I read somewhere that the BOSS 6 can hold 3000 lines of gcode... Another place I read that it holds 13K... Were there different versions with differing amounts of memory in them? If so, more memory could be just a card swap away?

Thanks!

/Craig.

I am looking for DNC somehow for more than 1 person. I will advise what I find.

George

Update:

Well I said I would write how everything is coming along... So here it is: The transistors arrived on Thursday, and I installed a set on Friday evening. I also installed my automotive fuseholders. I powered up the machine and hit the limit override button... All three axis jogged! I ran X back and forthe for a couple of minutes to make sure it wasn't going to quit again. Worked fine. So I figured I would close the control cabinet... Closed the rear door, and latched all the screws. Installed the side door+filter etc. Powered the machine back up, and hit the limit override again. X moved about 1/4", and quit again... Same symptoms. I replaced the two blown transistors after turning the amperage on X back down to 7.6A where I found it originally. I figured that it must have been turned down for a reason... Powered up to test, and blew another transistor... At this point, I am fairly certain that the problem must be within the wiring loom that connects the back panel components to the control cabinet components. Maybe old insulation or?? I will probably cut all the wire ties on the loom and see if I can find anu visible signs of damaged insulation etc...
At this point, I really don't feel good about this control, and don't know if I will ever trust it to machine parts... It is so flaky... I will be pulling it apart, and disposing of the control cabinet contents on ebay etc within the next month or so. I will be retrofitting with Gecko drives and EMC control, utilizing existing transformer etc for Gecko's power supply...

Thanks again everyone for the help in attempting to get the BOSS6 running again!

/Craig.

I have had many a problem with these machines that made me tear my hair out. One time I found an open 12 guage wire from the T2 transformer to one of the bridges. This wire does not move, how could it go open? It took a while to find. At Smith and Nephew in Memphis someone rewired T2. X moved great, Y maybe and Z, well, forget about it. Turned out X was at 60 VAC, Y at 30, Z at 15.
I do not bother to work on the old NC2s. The wires and connections are so old and corroded that they are not worth the time and effort to repair. My point is that, depending on the life your machine has had, it is very possible that you may a problem with the wire loom that runs to the door with the final drive transistors, SMDs, ACC, all those diodes and resistors. Just look at all those pins with the wires crimped on for the SMDs and ACC. Can you assure me that those connections are 100 percent?
On the positive side, you do seem to have isolated the problem to that wire loom. I have a lot of shops still running these machines and once you learn them, they run very well. Ie. Perry from B & W machine has not called me in years. Finally his BOSS 5 died. He needed a UFP board (behind the operator display). He plans on running it for years more. Now he wants to DNC. Just GOOGLE "behind tape reader" and all sorts of possibilities come up including DNC.
I had a BPT TC22 that would blow a relay after 7 hours of running like clockwork. I found that after that period of time, the soft field wires that were in a cable clamp would soften more from the heat of current and short blowing the relay. Some answers take patience and persistance. keep at it.

George

Update!
I ran out of patience with the Boss6, and retrofitted. The machine is now under the control of EMC running on a P3 500mhz. The PC is driving the machine through the parallel port and a Pico Systems Universal Stepper controller card. I purchased the new G202 Gecko stepper drives that have been enhanced to survive rough duty on a machine this size. The current power supply for the steppers was built from the 40V transformer from the Boss6, a bridge rectifier, and a large capacitor from the Boss6. The power supply is my limiting factor at this point, and is limiting me to about 90ipm with no step loss. A larger power supply is on the wish list, and will be added soon!
One of the features of the Pico Systems board is the ability to run the steppers closed-loop, which eliminates the step loss problem completely and permanently. At this point, I don't have encoders on the machine, but the motors run so smooth that encoders are really not required! Using this board also removes the burden of producing a clean step pulse train from the PC!
This was not a simple conversion, and was a long time in coming, but definately was worth the effort for me! I was pleasantly suprised when the smooth pulse train from the Pico Systems Board, and Gecko drives provided me with 90ipm rapids! After reading about other conversions that used 56VDC for the stepper power supply I didn't expect to get beyond 70ipm... Once the stepper power supply is upgraded to 75 or 80VDC, I expect to be able to easily exceed the original Boss6 maximum speed of 120ipm with feedrate override...
I am still working on wiring the spindle control to the I/O board. Currently the machine has the original controls working as they did from the factory. Once the spindle wiring is tied in to the I/O, I will have full control of fwd/rev, brake, and speed up/down.
If anyone else is considering doing this retrofit, be sure to spend some time reviewing the schematics! I removed more of the original wiring than I needed to, and had to re-install portions of it! One other source of confusion was wiring the stepper motors. I found several documents regarding how to wire the steppers online, and only one of the documents was correct according to resistance measurements i took across the motor connectors! My machine has Superior motors on it, and are wired parallel. so far I have about two weeks worth of evenings invested in the conversion including the time to remove the old Boss6 components which would not be needed for the conversion.

Anybody interested in some used Boss6 electronics?

/Craig

Craig,
That sounds great! I bet you are pretty stoked right now!

I too have been considering the new 202/212 drives for my BOSS5. It seems that with the extra protection of the drives, it should prevent anyone else from reporting a smoked Gecko...plus boost sales. As you know, plenty of us are on the fence about steppers vs servos. I have some suitable DC motors for servos...but since Rutex is still farting around with the much awaited 2000 series...I am leaning towards the 200 series Geckos to just use the machine!

Any particular reason why you went with the Pico board? It would seem to me, given the limits of the motor and gearing, that Mach2 on a decent computer should be more than enough to generate a good data stream. Have you tried running without the board? Just the 202s?

-Brady

Hi Brady--

I went with the Pico board for a couple of reasons. The first was the ability to run encoders for closed loop. My old shoptask CNC conversion had step loss problem that I never did get ironed out! The second reason is the Pico board generates the step pulses with a microprocessor. There is no way a PC can generate as smooth a pulse train as a dedicated microprocessor does. The board is also capable of generating about 300K steps/sec! I am currently driving the board with a really old, slow PC. I guess the more I investigated the available parts options, the more I was drawn to the Pico board. I don't think there is anything else like it out there right now. Geckodrives is working on a similar technology device that may be a bit more capable... Or not... The only downside to the Pico board that I could find is that it is not supported by the MACH controller software. I downloaded the MACH2 software, and spent some time reviewing it's features. It is definately a nice system. I was considering it all along, but decided to go with EMC because I am kind of partial to Linux, and MACH doesn't support the Pico board. etc. Initially I had a problem with the startup pulsewidth of the Pico board not being wide enough to trigger the G202's, but Jon Elson worked through the problem with me, and we fixed it within a couple of days! Jon ended up making some modifications to his EMC driver software which will eliminate the problem for other users as well. I am quite happy with the end result! Better than anticipated!

The reason I went with the Gecko 202's is mostly due to economy. Comparing the price of three G202's to a set of three servo motors, three encoders, and three servo drives sort of makes the G202's with the factory steppers the economy answer!

The G202's get warm when moving at slower speeds, but nothing to worry about. I have them mounted to a .125" thick aluminum plate which is in turn mounted to the bottom of the huge heatsink that takes up much of the rear door of the control cabinet. This location allowed me to use the original stepper wiring! I didn't use any cooling fans for the G202's because I felt the big heatsink would do the trick... It works fine! I just used heatsink compound on the back of the G202's, and along the areas where my mounting plate contacts the big BP heatsink.

The motors run really smooth with this setup! At times I can't hear the steppers at all when they are moving!

If you decide to run the steppers with G202 drives, be really careful about how you wire the steppers! In order to get the maximum speed/performance from them they need to be wired parallel. There are several wiring diagrams on the web, but of the ones I found, only one matched my motors based on reading the winding resistance at the motor terminals...

The steppers on my machine are the 900 oz-in Superior motors.

/Craig

Craig,
How did you determine the 900 Oz/in rating of the Superiors? I have them on my BP as well...but thought that they were a higher rating than that...Would be interesting to find out if mine are the same @ 900.

I like all of the features that the Pico board has...except it's incapatability with Mach2/3.

-Brady

I have a nameplate from the end of one of them!

Hmm....Mine doesn't have that; Instead it has a wiring schematic...

-Brady

Yup. Saw that one too. On the backside of the outer cover that is screwed to the heatsink there is a wiring diagram for the boss stepper drive. The cover in the photo came from the stepper motor itself and was under the cover that had the boss diagram! the cover was only on one of my motors, and I didn't put it back due to wire clearance! I imagine that there are a lot of covers that were not replaced by bridgeport techs over the years! I must have gotten really lucky to have one I guess...

/Craig

I know this is an post,but I bought a BPT Boss6 which has been sitting around for a couple of years and had the same problem with the transistors,( blew one on each axis). When I checked it out there wasn't any two that were the same make or number so I pick one (NTB53) I bought 12 which is enough for each axis from NewakInOne(www.newarkinone.com) and they work fine. Just another source for transistors In case someone needs them.

I noted that the motor end plate says 3.9 volts at 6 amps yet the machine feeds them 8 amps at 9.5 volts static which at rapid goes to 2.5 amps at 56 volts.
Interesting.

George