Need Help!- Bridgeport mill power supply circuit

[JohnDG]

Hi, folks! My first post - after some help.

The workshop here has a Bridgeport vertical mill with a Heidenhain TNC150 controller. The other day the controller blew an input fuse, & after replacing the fuse, just plain doesn't work. I've taken the power supply board & mains transformer out & have it set up on the bench, but it's a bugger to work on without a circuit. Some of the supplies seem OK - theres an 11Vdc for the display, and what should be the +5Vdc line for the TTL stuff is sitting at about 6.3V off-load (but it's normal load is about 3.5A, so I'm not fretting about it). Not much else seems to work.

Found the Heidenhain service manual on the 'net, but there's a scruffy block diagram of the PS board & half a page about what the outputs should be, and that's about it. The block diagram suggests that the problem is in the flyback converter which seems to be somehow slaved to the 5V converter.

Does anyone out there please have a copy of or a link to a proper circuit diagram - even an annotated board layout would be a help.

Thanks in anticipation ...

[Al_The_Man]

You didn't say what the actual symptoms were? Is it completely dead or does it have a CRT that is not displaying, as you mention a Flyback, This term usually refers to the Horizontal output transformer.
If so it is most likely either the Transformer or the drive Transistor to the flyback. Txfr.
Al.

[JohnDG]

Hi, Al, thanks for the reply.

Symptoms: Machine Stone Dead! There are no lights at all on the control panel - the display is showing only a bit of rolling, flickering stuff.

There's an 11V supply to the display, which seems OK, and a 5V supply for the logic, which also seems OK-ish.

The flyback I'm referring to is a flyback converter, part of the power supply which (as far as I can figure out) cunningly uses the inductor in the 5V switching regulator as a transformer to produce supplies at +45V, +22V and +/- 15V.

John