Electronics > Beginners

New PCB - adding wires to contacts make the voltage drop significantly?

<< < (2/2)

ArthurDent:
That is a 2-sided circuit board and there is a possibility that the through hole plating is defective so there is almost no connection through the board. Try soldering the bare ends of the wire on both top and bottom of the board to see if that corrects the problem. If the plated hole is good then when solder is applied to one side of the board with enough heat, the solder should flow on the pads on both sides of the board.

KaneTW:
That sounds like a flaky connection. Disconnect the battery and measure the resistance between the wires and the battery connector.

mariush:
Also try cleaning the board, the solder joints, and the tips of your probes... sometimes flux residue can cause improper connection.

mortrek:
Alright, I figured it out but I'm still confused... it must be a weird coincidence.

The power plug for the 8.4V rail was not making a good connection or something, but I moved it all around and tested the board on its back and front and the contacts were the right voltage but, without even moving the board, the voltage at the ends of the wires were not. However, once I suspected the plug, I started spinning it around and could make it 'come good' at the wires as well.

So maybe it just happened to reliably mess up only when I was testing the wires and not when testing any other part of the circuit? It should have shown the wrong voltage elsewhere as well... I'm still confused about exactly why it behaved the way that it did, but replacing the plug fixed it, so it must be the plug.

Thank you for the suggestions.

jmelson:

--- Quote from: alanb on January 14, 2020, 05:24:18 pm ---I would be interested in seeing what is driving the pads. Is there any possibility that the circuit is oscillating?

--- End quote ---
Yes, good thinking.  One time, I had a 5 V regulated supply feeding some logic.  It wasn't working right, so I checked the 5 V with a meter.  I got a reading of 120 V, which I instantly knew
was absolutely impossible.  Noise on the DC supply was making the meter show a totally outrageous value.

Jon

Navigation

[0] Message Index

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod