[Craigpat]

Hello,

I have sent the below information to Sherline. I'm out of warranty on bother PSU & box.

On Friday while using my Sherline lathe the motors would not turn and more or less stuttered when attempting to manually jog. It did come back after power cycling the box. I finished my task & went on another not using the lathe or control box. Box left on. After returning the stutter issue was present again. Power cycle did not resolve the issue. When the motors are attempting to turn it feels as if there not getting full power. When its powered up I can rotate the hand wheels by hand.


Diagnostics:

• I launched Mach 3 – power cycle box –NO CHANGE
• Reboot pc (Dell gx 260 dual core ~2 ghz) Ended unneeded programs - NO CHANGE
• Unplugged box power supply & allowed to discharge approx. 10 minutes- NO CHANGE
• Removed LPT1 junction between printer cable & box. This is used as a safe connection point to connect tool setter signal for Mach3. NO CHANGE
• Changed to Mach 3 mill screen NO CHANGE
• I have left box & power supply unplugged overnight. NO CHANGE
• Diskonnected all but one stepper motor to check for faulty motor NO CHANGE
• Swapped PC NO CHANGE
• Test Box power supply with volt meter. Output is 24V

I have a pre-2011 control box.

No burnt fuses
No blown caps (bloated tops)

When the box is plugged into the stepper motor(s) & power is turned on the power light comes on bright then dims. Led voltage is ~1.2v if I recall correctly. When the stepper is unplugged (no load) & box powered up; the power light is bright; NO DIMMING.
Voltage at the switch under load is 24v.
Voltage after all fuses (both sides ) 6.8v Voltage from the cap near the stepper plugs 6.8v

The voltage regulator does not get hot. It doesn’t even get warm. LM2575 - Looks a step down reg. I'm used to the stepper box getting pretty warm. No heat is being generated at all. I know that the 555's generate heat. There are 4 large chips on the plug side of the 555's. I don't know what these are.

I did find one of the 555 timer chips wasn’t fully seated. I don’t believe this to be the problem. It worked for years up to this point.

Being there is no visible damage inside the box. The dimming of the power light when the box boots. I'm leaning towards a power supply problem. I do live in Florida We are prone power outages.

Any thoughts would be helpful.

[Craigpat]

I FIXED IT


I had to remove the board from the case to trace the power leads. I was looking for a bad solder joint. I traced the power leads after the switch to the main board. All bottom solder points are in good condition. Power testing at the main board connection after the switch was ~18V at no load & 6.8v under load with one stepper connected. The power here should have been 24V. This required the switch to be removed. Further inspection showed melted wire shielding just after the heat shrink. Power up under load I felt heat building in the switch. I used an IR thermometer to see the increase in more detail. Removal of the switch confirmed the problem.

After all my frustration it was found to be $5.00 part. In the grand scheme of things good.

Hope this helps someone in the future.

Craig.

[Fastest1]

Great you found it and the fix was cheap. Many times it is just that simplpe.