[keebler303]

Referencing the picture you posted yesterday, the pin with the small blue wire soldered to it is the base (pin 1). The other pin (pin 2) is connected to all 4 of the emitters. This is actually ground with respect to the drive power supply. You will notice that the transistor body (tab) is insulated from the heat sink and these are actually what is going to the motor leads. It occurred to me it may be necessary to remove the transistors from the parent circuit to test them properly, I am not sure. I think you will be able to find one that measures differently from the others, this will indicate a failed transistor. If they are soldered, I would hold off on that until you run the tests. Some machines, including mine, have already been switched out to sockets so that no soldering is necessary. Lots of machines have this modification which should tell you how often the transistors are blown.

You are mainly just looking for continuity so the range is not too important. It should either be quite low resistance or it will be many million ohms depending on if it is conducting or not. 20k range should be fine. If it says 20k, its probably much higher than that (can try switching to the 200k range to see) if it says 0 (or close) it is conducting.

Matt

[BruceP]

Ok i thought tab was ground and yes they are all soldered in..so i cant really check tab without taking the whole panel out?

red 2 to black 1 - .71

red 1 to black 2 - .71

this was using 200K on the meter

these are the same for the same all 4 transistors

i used tab for ground so those readings are no good then right?

[keebler303]

it may not be possible to distinguish which is which but the big blue wires that go behind the plate attach to the "tab" of each transistor. I think that whole plate is only held on by 2 screws, there is no reason you can't just pull it loose and twist it around to get to the "tab" to make your measurements.

Matt

[BruceP]

it may not be possible to distinguish which is which but the big blue wires that go behind the plate attach to the "tab" of each transistor. I think that whole plate is only held on by 2 screws, there is no reason you can't just pull it loose and twist it around to get to the "tab" to make your measurements.

Matt

Matt..you must of read my mind

Ok i pulled the screws and pulled the panel out and measured at the tag.

red lead tag black lead post 2...0 on all transistors **0 meaning no continuity at any post**

read lead tag black lead post 1...0 on all transistors

black lead tag red lead post 1 ..0 on all transistors

black lead tag red lead post 2..0 on all transistors

red to post 2 black to post 1... .71 on all transistors

black to post 2 and red to post 1 ... .71 on all transistors.

This was with meter set to 20K

I posted earlier that it was 200K Which was wrong.

[keebler303]

Just to clarify, you are measuring resistance so 0 would mean a perfect conductor. Your stated value of 0 should in fact be reported as infinity.

As all the transistors are the same, I think they might not be the problem. Hopefully George will chime in with some useful commentary.

Matt

[BruceP]

Just to clarify, you are measuring resistance so 0 would mean a perfect conductor. Your stated value of 0 should in fact be reported as infinity.

As all the transistors are the same, I think they might not be the problem. Hopefully George will chime in with some useful commentary.

Matt

Just to clarify or confuse usually when you touch the 2 leads of an ohm meter together it will show zero...when i did the tag check to the pins the meter never did anything, it was just like you were not making any kind of connection just like if you was holding the leads apart.

Thanks again Matt and George

[machintek]

Additional test: Place meter on DC volts. Place on X1 (or whichever axis is in question), Other lead on ground. Have someone press STEP multiple times but give it a few seconds between each presses. You should see meter go high and then low. If I remember correctly, 2 presses apart. Repeat for X2, X3, X4.

George

[BruceP]

X being what George? the tab side of the transistor?

[machintek]

My Bad! There is a terminal strip on the bottom of the right side of the cabinet. Just below the transistors. This is where each motor is wired to.
Speaking of that. There is a small board with 12 diodes there. Those also go to the transistors. I have seen people drop those small screws that hold the transistor blocks and they land between two of these diodes causing a situation that imitates a shorted transistor. Also seen chips fall there and do the same thing.
Had one case where a customer lost a screw from the terminal strip for one of the transistor block. He found a replacement just long enough to hold the terminal tight and touch the frame beneath. That took a while to find! That also imitated a shorted transistor. And I have had numerous people forget insulators so just as mentioned all the transistors measured good but did not work in circuit.
The SMD board drives the bases of the transistors. In 30 years I have only had one bad SMD board. The step test may indicate bad switching. The SMD are interchangeable. The signal to the SMD comes from the ZDI through a opto-coupler. I have had one of these go bad in 30 years. Have to go to work now.

George

[BruceP]

Thanks George!

My terminal strip that the wires hook too is part of the panel that holds the 4 transistors..but i will check the voltage at the (tag wires)or big blue wires.

[machintek]

That right panel opens with those 1/4 turn fasteners. I stick a screw driver in the hinge to keep it open. The motor wires come in the bottom to that terminal strip. it should be the last item on the bottom.
The concept is to see if the output to each winding on the motor is switching thus verifying the circuit.

George

[BruceP]

After messing around with testing the trasistors the Y motor axis does nothing at all now the center 2 transisters had 4 volts at the big blue wires top and bottom transistor had no voltage. The X and Z axis works fine...also when trying to jog Y axis the digatail readout shows it is moving.

[BruceP]

I found out i was checking the wrong axis motor transitors, the Y axis transistor bank was behind the removable circuit boards..i checked them and they checked ok, but i can not check them live because the circuit board has to be removed to access them. I did change the circuit boards around x with the Y and the Y still doesnt work...when you hit jog the digital readouts says its moving..if there is a strange problem that no one else has ever seen then we usually get have that problem....lol

[BruceP]

I guess i scared George off

[machintek]

That is why I said to go to the terminal strip on the bottom of the side door. it can be checked live there. I have done it. Not unless the S2BOSS6 lacks this terminal strip?
(And I do have a job and life and do not scare easily! ).

George

[BruceP]

That is why I said to go to the terminal strip on the bottom of the side door. it can be checked live there. I have done it. Not unless the S2BOSS6 lacks this terminal strip?
(And I do have a job and life and do not scare easily! ).

George

You talking about that long white strip at the bottom of the door that goes almost all the way across?

How much voltage should i actually see at the wires there and can i just ground my black lead to the cabinet ground?

Just trying to make a funny George, i know you have a life and job....i really appreciate the time and effort That YOU and Matt have taken with me.

Bruce

[machintek]

The terminal strip has X1 through X5 + Y1 through Y5 + Z1 through Z5 and is labeled that way.
These drives have a very strange voltage situation. With the correct current set and the correct transistors, typically I see about 9Vdc with a stationary motor. At rapid, the voltage goes up over 50 VDC but the current drops from 8 amps to about 2 amps.
Any chassis ground will do. Remember you are stepping it so I would expect a reading of about 9VDC.
By the way there is a trouble shooting section in the maintenance manual too.

George

[MrBoss8]

Greco systems makes or made a cool stand alone unit the size of a lunch box. it accepts floppy disks. It can download and DNC drip feed to most cnc machines. The units I've used have RS232 and centronics outputs. If anyone is intrested, I have a Greco Box for sale that uses a 360K floppy disk.

[machintek]

A stepping motor BOSS machine cannot DNC. It needs a separate DNC loader that bridgeport built. In 30 years of field service, I have seen only one.
There are devices that are called BTR (behind tape reader) but I have no experiece with that either.
Bridgeport sold the same smart box you have and called it a EZFILE. Back then they got about 5 grand for it. (mid 1980s).
It does work with the BOSS 8 and 9 and above.

George

[heliosaucedo87]

Bridgeport Series II Operators Manual
hey guys!! i need t oknow where i can find the manual, thanks!!!