Bridgeport CNC Series II Boss 6 is Dead!

[grigsby]

Powered up my Bridgeport CNC Series II Boss 6 after a peroid of being idle. Unit failed with the following symptons:

At power up the console readout display flashes 000 60007 then goes blank. The Run, Goto, and Hold LED's are steady for about 3 seconds and then extinguish followed by illumination of the ABS LED. The limit switch is illuminated but can be cancelled. Upon cancelling of the limit switch and a reset (tape drive cabinet) the spindle can be started. The only other item that does anything is the edit button can be pushed resulting in the Run LED illuminating. The Hold button will also illuminate the Run LED. Once the Run LED is illuminated it will extinguish after about 15 seconds. No other functions appear to work.

Things we have tried:

Removed and cleaned all PC boards using contact cleaner, soft toothbrush and low pressure compressed air. Used an eraser to clean the backplain contacts. Adjusted the voltages (small blue and violet wires above power module) to 05.00, 12.00, -12.00 VDC. All voltages are steady and do not change any when power is applies to the spindle.

Checked both regulated and unregulated voltages and nothing appears to be outside the norm.

Any help would be appreciated!

Wayne

[machintek]

I would be looking at replacing the LSI-11 board (KD11L module by Digital Equipment Corp.).

George

[grigsby]

George,

Thanks for your quick reply! One thing I forgot to say is that the stepper motors are locked when power is on. When you try and move them you can feel electronic resistance (slight vibration or hum). Would this indicate that the stepper motor controls are working as advertised? Do you have a source for the Processor LSI 11 that you recommend?

Thanks

Wayne

[grigsby]

George,
Do you know someone that has and wants to sell an LSI-11 board?

Wayne
grigsbyatwowwaydotcom

[machintek]

Stepping motors are interesting. Even when off, if turned by hand you feel the poles of the motor, like a growl. A old motor has less growl because the magnetic fields have decayed. When power is applied, it does hold the rotor strongly but can be overcome. Any resistance to the motor turning (keeping up with commands from the control) will result in the rotor being attracted to the trailing pole instead of the leading pole. You then hear a whine as the motor oscillates between poles. The same occurs if a output transistor is shorted.

I do not know of any LSI-11 boards that are available. Years ago I did a Google search of it and found a lot of data about it but I have doubts that any repair parts are still available.

You may be forced to consider a retrofit.

George

[grigsby]

Can anyone advise me if the LSI 11 processor board is the same in a Boss 5 and Boss 6?

Thanks

Wayne

[machintek]

Yes, they are the same.
The BOSS4 and earlier had a KD11-F module. This had 4 LSI integrated circuits.
THE BOSS 6.1 and BOSS 7 had half size LSI-11 boards.

George

[grigsby]

Just to be clear, if we find a board that has 5 of the large Digital IC's like the one pictured below it should work.

[scottly]

I have an LSI 11 from a Boss 5. It was working before I started retrofitting the control.

[amishx64]

Things we have tried:

Removed and cleaned all PC boards using contact cleaner, soft toothbrush and low pressure compressed air. Used an eraser to clean the backplain contacts. Adjusted the voltages (small blue and violet wires above power module) to 05.00, 12.00, -12.00 VDC. All voltages are steady and do not change any when power is applies to the spindle.

Checked both regulated and unregulated voltages and nothing appears to be outside the norm.

Have you tried baking the board to reflow the solder? I would try that if I were you. Just don't bake too long. Also, I wouldn't bake the board if it has DIP components on both sides or you'll only have half of your board.

[grigsby]

I have an LSI 11 from a Boss 5. It was working before I started retrofitting the control.

How much do you want for your board?

[scottly]

I don't know what a fair price is for the board? You may want to try reseating the 5 big chips in their sockets first. Here is a pic of my board: