Micro850 Output Header

Unfortunately, I have discovered that the outputs 0 and 1, as indicated by my blue Sharpie marks, have continuity. I have inspected the circuit for hours, and cannot seem to find the source of the short. Could anybody please advise on where the short may be, and how to fix it?

Thank you for your time

  • \$\begingroup\$ check the rest of the PCB \$\endgroup\$
    – jsotola
    Jan 27, 2021 at 19:03
  • \$\begingroup\$ The chance that there is an internal short in the Terminal block while still looking like that (not melted or burned) is very much close to 0. \$\endgroup\$
    – crasic
    Jan 27, 2021 at 19:06
  • \$\begingroup\$ I've had this happen on the 850 myself, root cause was hooking up power on the top terminals (which aren't labeled very well) instead of the correct ones on the bottom. There is no fix except to send in for repair. \$\endgroup\$
    – Ron Beyer
    Jan 27, 2021 at 20:29

1 Answer 1


More than likely two output transistors have failed short-circuit and you're getting a connection through them via the VAC/DC. If that's the case you'll have continuity to VAC/DC as well.

enter image description here

Figure 1. Output connections from user manual.

  • \$\begingroup\$ I checked, and I do not read continuity between Output 0 VAC/DC. Same with Output 1. Any ideas? \$\endgroup\$ Jan 29, 2021 at 4:28
  • \$\begingroup\$ Post a photo of the top side of the board showing the output switching devices. \$\endgroup\$
    – Transistor
    Jan 29, 2021 at 7:15
  • \$\begingroup\$ I looked at the board for a while. It turns out, there is a defective MOSFET that needs replacing. I am glad you mentioned the transistors could cause the problem outside of the terminal bus. Thank you for pointing me in the right direction. \$\endgroup\$ Feb 2, 2021 at 5:22

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