Milltronics Brought This Broken Milltronics CNC Lathe Back to Life

Wes got a 25-year-old Milltronics ML15 CNC lathe at a fantastic price. But despite looking like it had never been used, it had a number of electrical gremlins that were preventing it from working. Milltronics and the servo driver manufacturer, Glentek, weren’t any help. So, Wes did a reverse engineering deep dive to revive the old machine.

You can get really great deals on old machine tools at auctions. Those tools tend to be too heavy for hobbyists to transport, too big for them to store, and too difficult for them to power with household circuits, so they don’t bother. But they’re also too old to still be in service and supported by the manufacturers, so professionals don’t want to take the risk. Therefore, there are deals for those who can accommodate the quirks and headaches.

Wes is exactly that kind of person and he got the Milltronics ML15 at a low price at auction. He believes it came from a school that never used it, because it doesn’t seem to have a single chip in the tray or chip in the paint. But it wasn’t working and the electrical issues proved to be pretty dang frustrating.

The first couple of issues were easy to solve. One was fixed with a quick CMOS battery replacement. The other required a display change in the BIOS settings to get the correct resolution for the screen.

From there, the problems were much harder to handle. The Z axis wasn’t moving and the computer was showing a fault code. By switching the X axis and Z axis, Wes determined that the servo driver board was bad. Glentek made that driver, but obfuscated the relevant broken components with their own part numbers. Entire driver boards and those individual components were all incredibly expensive.

Fortunately, after an absurd amount of effort put into reverse engineering, Wes was able to figure out which specific components were faulty and find modern replacements that are both available and compatible. After swapping those, the driver board came back to life.

The final problem was with the encoder for measuring spindle speed. It was toast, but luckily replacements are pretty easy to find. Wes did have to machine a replacement shaft to get the replacement to fit, but that was a quick fix.

Now Wes has a nice CNC lathe that performs well, which he got for pennies on the dollar.