Help needed - JPT 20W fiber laser stopped firing mid-job, still won't fire after replacing PSU and BJJCZ board

Community Laser Talk
1

Hi everyone,

I’ve been troubleshooting this for weeks and I’m running out of ideas. Hoping someone here has seen this before.

Machine: Hitec cnc HTJ-20F
Laser source: JPT YDFLP-E-20-LP-S (20W)
Original controller: BJJCZ HCU4-FIBER-M (LMC V4 FIB, Board Version 4.0.2)
New controller: BJJCZ FBLI-B-LV7 (purchased as replacement)
Software: EzCad2 (original board) / EzCad Lite (new board)

What happened:
Laser stopped firing instantly mid-job. No warning, no smell, no unusual sounds. Just cut off while marking.

What we found:
The original ±15V power supply (YSG-60-15N) had failed — outputting only 3V instead of ±15V. This PSU powers the BJJCZ board and galvo scan head.

What we’ve replaced/fixed:

  1. Replaced failed PSU with two Mean Well LRS-75-15 wired in series for ±15V — verified correct voltages
  2. Replaced BJJCZ board with new FBLI-B-LV7
  3. New DB25 cable
  4. 24V supply (Mean Well LRS-200-24) to JPT source confirmed working

What works:

  • Scan head fully operational — galvo movement, red pointer, show contour all working perfectly
  • BJJCZ board communicates with PC via USB
  • EzCad runs in full mode (not demo)
  • Red LED on BJJCZ board lights up when pressing Mark (F2) — board thinks it’s firing
  • Red light pointer works after assigning port 4

What doesn’t work:

  • Laser does not fire/mark
  • Test Laser button does nothing
  • No IO output indicators change during marking
  • Same result with both old and new BJJCZ board

Additional info:

  • Opened JPT source — no visible damage, no burnt components, internal fuses F1 and F2 both test good with continuity
  • The FBLI-B-LV7 board appears to have a known issue where it can frame but not fire (found another thread here with exact same problem — Cloudray couldn’t solve it and took the board back)
  • Old EzCad2 showed “read YLP laser failed” on COM3
  • EzCad Lite (new board) has no IPG/JPT settings menu under Laser menu

At this point I don’t know if the problem is:
A) The BJJCZ board(s) not sending fire signals through DB25
B) The JPT source being dead internally
C) Some EzCad configuration issue that’s preventing fire signals

Has anyone dealt with a similar situation? Especially interested in hearing from anyone who has experience with the FBLI-B-LV7 board and JPT lasers, or anyone who has used the JPT GUI software to diagnose a dead source.

Thanks in advance for any help.