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I just bought a DC 3 wired voltmeter and it was working perfectly. Here is it image:

enter image description here

I used the yellow wire for measuring the voltages. But for some reason, I desoldered the wires and soldered pin headers. Now it gives unknown reading like 0.XY (eg 0.37) whenever I just connect the positive and negative to battery. It was not happening before.
Can I be helped to troubleshoot what I did wrong? Have I damage the circuit?

Here is the underneath image of the one I soldered:

enter image description here

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    \$\begingroup\$ those pins do not appear to be soldered to the PCB \$\endgroup\$
    – jsotola
    Commented Jul 28, 2019 at 18:26
  • \$\begingroup\$ Is the battery voltage too low by any chance? \$\endgroup\$
    – winny
    Commented Jul 28, 2019 at 18:27
  • \$\begingroup\$ @winny I am providing it 5V. \$\endgroup\$
    – Nouman
    Commented Jul 28, 2019 at 18:28
  • \$\begingroup\$ Strange. It’s however my go to thing with incorrect readings on DMM (yours is similar but not a DMM) as low battery voltage often give high readings. \$\endgroup\$
    – winny
    Commented Jul 28, 2019 at 18:29
  • \$\begingroup\$ What are you connecting the 'pin headers' to? \$\endgroup\$
    – Bruce Abbott
    Commented Jul 28, 2019 at 18:32

1 Answer 1

Reset to default
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There's no reason I can think of why you'd get different behavior if you did the desolder/solder job well.

The underneath part you show doesn't show good solder flow around the added header pins. So perhaps there's an intermittent problem due to poor/lack-of soldering?

But otherwise, I don't know of a reason why replacing wires with header pins should change its behavior.

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