Troubleshooting my Melco EMC 10T

The needle is stuck down.

After powering off, unplugging, and rebooting the screen comes on, then goes blank. Prior to this, directly after the problem began, I was receiving a message "Bad Instruction"

I'm worried I might need to replace the circuit board. I feel it could be this because the green light is not coming on. I have another one but I don't want to do that if it's not the issue.

I'm looking for guidance on the fix, or any information anyone might have?

You're dealing with a couple of simultaneous issues on your Melco EMC 10T—both mechanical (needle stuck down) and electrical/software (screen blanking and “Bad Instruction” error, plus no green light). Let's tackle them step by step.

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Mechanical: Needle Stuck Down — Possible Z-Bind

A Z‑bind is a common cause if the needle becomes stuck down or the presser foot is trapped:

• Use the Emergency Stop to halt the machine.

• Lift the presser foot and slightly rotate the Z‑shaft by hand.

• Verify the presser foot isn’t binding on the Needle Block Clamp. If it is, gently pull the presser foot back and clear the bind.

• In more general cases (not tied to maintenance), follow Melco’s in-depth instructions to:

  • Remove the needle plate if the bind is below that area.

  • Check if the hook basket spins freely (remove the rotary hook if needed).

  • See if the grabber is stuck behind the needle bar.

  • Look for broken needle remnants in the hook and use compressed air to clear debris.

  • If drive studs and reciprocator are misaligned, carefully examine and possibly remove the needle bar to free the bind—though a Melco Certified Technician might be required.

These are mechanical fixes you can try before involving circuit boards.

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Electrical/Software: “Bad Instruction,” Blank Screen, No Green Light

You mentioned the message “Bad Instruction”, which indicates a fatal error from the CPU—meaning the processor received an invalid or unexpected

Additionally, the blank screen and absence of the green light signal that the main PCB (circuit board) might be failing or not receiving power/control.

Here's what Melco's technical support suggests:

1. Power Cycle: Turn the machine fully off; wait a minute; power it back on—and if needed, repeat. Sometimes this resets internal electronics.

2. Reseat the Ethernet Cable: Ensure the cable connecting the control panel (keypad/display) to the main PCB is firmly seated. Try power-cycling afterward.

3. Open the PCB Cover:

   • Remove the screws, slide out the main PCB tray, and inspect for power indication LEDs once the machine is turned on.

4. Reflash or Reconfigure (if relevant):

   • If your main PCB is the 34799 model, consider performing a USB reflash of the OS binary and ensuring filenames match the version.

5. Advanced Steps for Older PCBs (31058‑19 or earlier):

   • Disconnect Ethernet before powering on.

   • Disable any Ethernet hubs—connect directly.

   • Possibly update to AMAYA OS v10 if not already running.

   • Uninstall and reinstall software if needed.

6. Verify Motors or Other Faults:

   • If the green light returns after any of these steps, but you're still stuck, the issue might lie with motors or emergency stop circuits.

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Summary & Next Steps

Issue	Suggested Action
Needle stuck down	Release Z‑bind: use Emergency Stop, lift presser foot, rotate Z shaft, clear presser foot clamping.
“Bad Instruction” error	Indicates CPU/software crash.
Blank screen / no green light	Reseat Ethernet, power cycle, inspect PCB LEDs after opening panel, reflash OS

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Should You Replace the PCB?

Not necessarily—there are several intermediate steps before PCB replacement. I recommend:

1. Mechanically free the needle using the Z‑bind steps.

2. Power-cycle and reseat Ethernet, checking for LEDs.

3. If no sign of life, consider OS reflash (if main‑PCB model supports it).

4. If none of that works, then replacing the main PCB could be a final step—but only after consulting a trained technician, especially to avoid warranty issues or further

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Final Thoughts

• Start with mechanical clearance of the needle.

• Then verify connectivity and basic power functionality.

• Try software/firmware fixes next.

• PCB replacement should be a last resort, ideally done by a qualified technician.

Let me know which step you'd like to try first or if you'd like help identifying your PCB model before moving forward.

Thank you for your response Diver361!

We have unblinded the Z,

We unplugged the Ethernet cables, cleaned, replaced and cycled through,

The lights on the PCB have changed from the previous configuration.

We went ahead and tried a voltage test by putting Red on TP3 and Black on TP4. The voltage is reading zero like that.

Another note is we have noticed that on ENS on the computer in the bottom right-hand corner my E is black.

Does this indicate that the PCB does in fact need to be replaced? Should we go forward into an OS reflash, and how might I do that?

Thank you again,

Maine Point

🔍 What Your Test Results Suggest

• Zero volts at TP3–TP4 → the 5V (or logic rail) is not being generated.

• That points to one of two root causes:

  1. The PSU isn’t delivering input voltage to the board.

  2. The onboard regulator on the PCB has failed.

• Since you noted that the screen briefly lights up and then goes blank, that means some initial power is there, but the logic rail collapses quickly — very common when a regulator or capacitor has failed.

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🛠 Steps You Can Try Before Swapping Boards

1. Check PSU output:
   With a multimeter, test the PSU lines coming into the main board (before the regulators). If there’s no DC voltage coming in, the PSU is bad, not the board.

2. Look for LED indicators on the PCB:
   Some Melco boards have tiny green/red LEDs near the regulator section. If they flash briefly and go dead, that’s another sign of failed regulation.

3. Inspect the board visually:
   Look closely for:

   • Bulging or leaking capacitors.

   • Burn marks around the regulator ICs.

   • Loose connectors/pins where the PSU plugs in.

4. Reseat all connectors:
   Fully disconnect and reconnect the PSU and Ethernet/control panel cables. Even oxidation on contacts can cause “Bad Instruction” CPU errors.

5. Try an OS reflash only if:

   • You have a 34799 PCB (later type, USB reflash supported).

   • You can confirm at least some voltage rails are alive.
     If TP3–TP4 is truly dead, a reflash won’t even start.

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⚡️ Does This Mean the PCB Is Dead?

Not 100% yet — but with:

• No green light,

• “Bad Instruction” earlier,

• Now TP3–TP4 = 0 V,

…it is very likely the regulator section of the main PCB is toast.
If your PSU tests fine, then yes — you’re looking at a main board replacement.

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✅ Recommendation:

• Test the PSU output to confirm.

• If PSU is good and TP3–TP4 stays at zero → replace the PCB.

• Only attempt an OS reflash if you confirm some power rail is alive (otherwise it’s wasted effort).

🔄 Melco 34799 PCB – OS Reflash Guide

🧰 What You’ll Need

• A USB flash drive (2–8 GB is ideal, formatted FAT32).

• The correct Melco OS binary file (usually provided by Melco support or found on your machine’s software CD/installer package).

  • File often named something like: amayaos.bin or similar.

• Access to the USB service port on the main board.

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🪛 Preparation

1. Format the USB stick to FAT32 (do a full format, not quick if possible).

2. Copy only the OS file to the root of the USB drive.

   • Do not rename unless Melco documentation specifies (older firmwares were picky about exact file names).

3. Power off the machine completely.

4. Insert the USB stick into the service USB port on the PCB.

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⚡ Entering Reflash Mode

1. On the 34799 PCB, locate the boot/reflash button (tiny pushbutton, usually near the USB port or the board’s lower edge).

   • Sometimes labeled SW1 or BOOT.

2. Press and hold the button, then power on the machine.

3. Keep holding until you see the status LEDs change (usually flash in sequence).

4. Release the button — the board will look for the USB binary.

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🔄 Flashing Process

• If successful, the green LED will blink steadily while flashing.

• The process usually takes 2–5 minutes.

• When complete, the board will reboot automatically.

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✅ After Flash

1. Remove the USB stick.

2. Power cycle the machine again.

3. If successful:

   • The green LED should stay on,

   • The screen should remain active,

   • And ENS software on the PC should now recognize the machine.

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⚠️ Notes & Warnings

• If the board has no power rail at all (like your TP3–TP4 = 0 V reading), the reflash will not even start.

• If LEDs never light or react when you attempt the boot process, the regulator section of the PCB is likely dead → at that point, swapping boards is the only option.

• Always ground yourself to avoid static shock to the PCB.