Bridge Rectifier Location

[cbarsh]

Hello,
This is my first post to this website. I have a Bridgeport Series 1 CNC with a Boss 9 Controller. I recently ran into a problem with the "Y" axis not jogging anymore. The usual fix for me is to test the board and replace the bad speed control diode (whatever that soldered component with the 2 prongs coming off it). This time that fix did not work. I had a guy over and I think we narrowed the problem to the "Y" Axis Bridge Rectifier. Problem is that he traced the wires on the schematic (Bridgeport Maintenance Manual M-154) to BR4 (Bridge #4). But he can't find it. Before, I tell him to rip the machine apart, any direction we should look to find these bridges?

I did a search on the internet and CNCZone came up. Hope you guys can help.

If I called any components by the wrong name, my apology.

Thanks,
Chris

[HillBilly]

The BOSS 9 had one DC power supply ( One transformer, one bridge and one capacitor.) for all the axis. It sounds like you are describing a BOSS 4-6.

Darek

[cbarsh]

Darek,
I appreciate the reply. Then I guess I have a Boss 6.
Where on the machine itself will I find these bridges? From what the repair guy tells me, the transformer is reading approx 60 volts and afterward at both the "X" and "Z" it reads approx 12 or so. He says this is what it should be doing. But on the problem axis, "Y", it drops to 4 volts and he came to the conclusion that since the volts are low, then that is why the axis will only moves in 0.001' steps and nothing greater. He switched powers supplies between the "X" and "Y" and the same problem came up. So unless there is something else that could be causing my problem, he figures it the "Y" bridge.

Thanks,
Chris

[HillBilly]

The bridges are on the back side of the chassis with the terminal strip and fuses on it. Right below the tape drive in the attached pic.

Darek

[cbarsh]

Darek,
Thanks for the help. I will take a look tomorrow.

Chris

[machintek]

I usually remove the tape reader for better access. Remove the wires from the fuse holders on the right side of the terminal strip. This prevents breaking the fuse holders. Remove the 4 screws that hold the white horizontal capacitor assembly and pull the right side out. You will see a black heat sink on the back of this assembly. Remove the screws holding it. You will wonder why they are so long. The bridge rectifiers are mounted on the inside of this heatsink.

Good luck

George