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BridgeportB BOSS6 Problem with power supply^

fredhh47

Aluminum
Joined
Nov 11, 2009
Location
Upstate New York
I have a Bridgeport BOSS 6 Series II CNC that has been working (mostly) faithfully since I bought it used in the 80's. It was made about 1982. I love this machine, not just for the 15" x 30" work envelope, but also for its' overall reliability. That is with the exception of blowing transistors on the SMD boards and a few other glitches that I can usually handle by myself. This problem has me stuck with a dead machine and nobody who knows how to fix it. I need a replacement power supply for the 5/12 circuitry**. For anyone with a BOSS machine, you know that is the metal box to the right of the card cabinet in the control enclosure on the side of the machine. Ithas the vertical strip of test points to check the 5 and 12 volt output. For some reason, the 5-volt REGULATED side of mine no longer puts out anything at all. The 12 volt side (Regulated and Un-Regulated) and the Un-regulated 5-volt circuits seem to be working.The Reguated 5 volts comes from theFPS board that plugs into the front of that unit. Unregulated 5 volts comes pretty much straight off a transformer, thru a couple diodes that probably work like a bridge rectifier to produce the 5-v DC, which can run as high as 15 volts. DOES ANYONE HAVE one of these units, possibly pulled out of machine that was retrofitted into the 21st century? If so, was it working when taken out? If it was a working unit, I would like to buy it. I only have 3 CNC machines, one of which is already in the middle of an update-retrofit. The other one was retrofitted with a Centroid control back in the 2000's. I am having to turn away work because I could do, but cannot do in the required time frame.
**You may ask why don't I just put in a couple off-the-shelf power supplies? I wish it were that easy. Bridgeport built solid machines, but I think the electronic controls were designed by a cadre of monkeys. In fairness, in 1980 solid state was limited to IC's and discrete components, and power was handled by big, heavy transformers. In this machine, Circuits overlap and some components seem to multi-task. The wiring is especially complex as a result. There just is (almost) no way to simply pull out the box and stuff in a couple switching power supplies instead. I can't afford the time and expense of totally gutting the control system and retrofitting it. I already have one machine in process and it's been almost 2 years so far (I'm working by myself). So, in plain English, HELP!
Fred Howe
 
If Terlecke isnt able to help you, then I don't know where to point you. Ever since Keith passed a few years back, he is the only person I know who was even remotely willing to help.

Jon
 
If you are not getting +5 VDC I would look for an LM7505 5 volt regulator. Center pin (3 pins comming out)and heat sink common. Of the other 2 1 pin should be unregulated 5VDC in and the other regulated 5 VDC out.
As far as other transistors letting smoke out. Have you checked larger capacitors? When they get old & "leaky" they essentially turn into resistors.
With what you have described and me not being able to see anything, that would be where I would start.
If you can post some pics or send them to me. A schematic would great. I have done a fair bit of reverse and forensic engineering on old electrical gear over the years and would be happy to help you.
Is this a linear or switch mode power supply, sounds linear but had to ask.
 
The occasional problem of blowing transistors on the motor driver modules is tolerable and I have no problem diagnosing and replacing them. They are 2N6547 or ERS-53's and are pushed right to their operating limit by the requirements or pushing all that iron around. Unfortunately, Bridgeport used their own in-house numbers for most components. I can identify a lot of components by their overall appearance (I know a diode from a capacitor from a resistor, from a bridge rectifier, etc)and I can do a fair layman's interpretation of some schematics, but when it comes to singling out specific parts, such as a LM7505 5 volt regulator*, I might as well be looking for pixie dust and unicorn horns. The power supplies are linear (they are from early 1980's), and do have a lot of large capacitors, there are a lot of diodes used in pairs (instead of bridge rectifiers, I presume), etc. The 5 volt supply is divided into two portions, an Un-regulated 5v output, which is right off a transformer and thru single diode. That output can vary from about 10 volts up to as much as 15 volts. And, when tested, it worked. Then, from the same tap, there is the 5 volt Regulated circuit, which feeds thru the collector side of a parallel wired set of 5 2N3055 transistors (mounted on a big fat heatsink), each with a .25 ohm resistor in series with the emitter leads to a common output that in turn is fed through a 20 amp fuse to the 5 volt bus. That is apparently 'more finely regulated, as the expected output is 4.9 to 5.1 volts. The logic boards and the operators control panel all run off the regulated 5 volt bus. That is the only part of the power supply that is not putting out any voltage. Bridgeport did not see fit to supply the schematic of their FPS board, which has the 12v+, 12v-, and 5v+ regulated outputs and adjustment pots. There are 3 UA723DC precision low voltage regulator IC's*(might these be similar to the LM-7505??), a couple 2N3055 transistors and some resistors and capacitors on it. This board stands ahead of the logic boards and the front panel. It just occurred to me as I was re-reading this that I should check out the 2N3055 transistors to see if one of them went bad.
If this is as clear as mud, I apologize, and if you'd like to contact me directly by e-mail, I could send you a picture of the schematic, the FPS board,or any other info that might help. My e-mail address is [email protected]
 
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i had the power supply go south on a Boss 8 years ago. Just replaced it with an off the shelf Power-One. (Actually design by an engineer)

Ahh, would that I could. Problem one is that the BOSS 6 was "old school", just a slightly updated version of the BOSS 3/4/5 control system, where everything was integrated and intertwined. The power supply is spread over two different sub-cabinets, and some of it is mounted on the back door of the side cabinet. Problem two is that I cannot follow the schematics to all the many places that the circuits go. Bridgeport, in their infinite wisdom(?) did not include every schematic with the maintenance manual. Lots of critical details are left out. I presume they did that in order to prevent the average user from being able to actually maintain their own machine, and keep the service technicians employed. Now all but a few of the service techs are dead or retired and those that are still living and working get a small fortune for their services. $350 per hour, door to door, plus lodging, if overnight stay is required is way, way above my maintenance budget. Just a side note, in the case of the R2E3 control system, which came out just after the BOSS 9 and 10, Bridgeport themselves did not even have the schematic for the power supply. It was entirely manufactured by an Italian company and sold to Bridgeport with only instructions on how to hook it up to Bridgeport's controls. When we bought an R2E3 machine in 1984, the machine was shipped directly from Bridgeport Connecticut, and came in DOA. The cause was ONE broken (and I mean demolished) thermistor on the power supply unit, but without the schematics to tell them what it was, the only thing Bridgeport could do was to have one air-freighted to us from Italy. That machine had so many problems with the controls and servos that we had a Centroid CNC package installed in about 1987. The replacement control package, installed, set us back about $17K, but we finally had a working machine that is still working to this day.Speaking of ill-fated machines, we also bought a Bridgeport Discovery 308 machining center, straight from the factory. It was called a 308 because it had a 3hp motor and an 8-tool changer. It broke down a lot. In less than a year, the rubber gaskets that kept the windows in place dissolved from the water-soluble coolant, the tool changer would mis-position and jam, the z-axis would not reliably home to the same spot every time it was powered up,it would frequently be off by +/-3mm, which was exactly one full revolution of the z-axis ball screw, the coolant did not all go into the coolant tray, so coolant would seep out from under the machine. We had to defeat the operator access door latch/lock because it would lock the doors shut at random intervals. It was supposed to come with a hard drive, but arrived without one and we were told that Bridgeport "did not sell the hard drive" which was lavishly described in the brochure. And that is just the start of the list. At one point, I had to buy some DAC IC's from China to repair the mother board. They were already obsolete WHEN THE MACHINE WAS BUILT. But enough whining.
 
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On mine, it had an EXTRA power supply mounted in the upper left wire way where it gets absolutely zero air. I mounted the new one in the rear cabinet and used the sense lines to regulate the voltage.
Advantage I had was I had two of the pieces of shit, so I was able to use one to trouble shoot the other.
All I can say about BP electronics is, for every batch of new engineers, somebody's got to be at the bottom of the class.
 
It seemed to me like they hired stupid engineers and then had to hire very good techs. Part of the problem (IMHO) was that the engineers who worked for Bridgeport were so firmly rooted in the early solid-state era that they couldn't move ahead and keep up with the technology. It took them forever to come out with servo motor powered axes and they did a crappy job of it. My go-to tech support guy was factory trained and worked for several years for a Bridgeport dealer. When Bridgeport (Textron) had the brilliant idea of doing away with dealers and selling direct, which worked out soooooo well for them that they ended up closing the business entirely, my guy went independent and was working all over the northeast. He was extremely knowledgeable in fixes and work-arounds for the Bridgeport POS machines that came out between 1985 and whenever they shut down. Unfortunately, after a car wreck and several back surgeries, plus a heart attack, he hung up his tool belt and retired. I don't think Textron really had any intention of keeping Bridgeport Machines going. They just got every nickel out of it that they could and walked away. Selling the Knee mills to Hardinge sounded good, but I don't think Hardinge did a very good job of reviving them. They did move forward with the Romi lathes, but the knee mills never developed.
 
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