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I'm a hobbyist trying to diagnose a circuit board for a tape deck. One piece of advice I was given was to "check for any bad solder connections".

On this circuit board there are around 200 connections. All of these could be checked individually, but that seems practically infeasible.

Is there a practical way to comprehensively check all connections on a circuit board? If not, what is a diagnostic alternative that will achieve a similar result?

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  • \$\begingroup\$ For a board you didn't design yourself? Not that I know of. It's not even really practical for a board you did build yourself without flying probe robot. You need to troubleshoot and diagnose and narrow down where to look. \$\endgroup\$
    – DKNguyen
    Dec 23, 2020 at 0:45
  • \$\begingroup\$ use the cont tester on your DMM; many solder joints will be ground, so you can swipe dozens per minute. \$\endgroup\$
    – dandavis
    Dec 23, 2020 at 4:15

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Give it a visual inspection with lots of light, and use a head-mounted magnifier or a bino microscope if your eyes are not perfect. Get light from the sides as well as head on.

You can inspect a couple hundred joints in a minute or two with experience.

Knowing what to look for is the trick- you're looking for joints that have the lead with a hair around it showing they've broken free or pads that have a hair mark to the trace showing the pad has lifted. On dense SMT boards look for joints that are not smooth and rounded with an appropriate amount of solder.

Pay particular attention to heavy components, components that interact with the user's ham-fisted motions and around fixing points and connectors.

I would not suggest blindly re-soldering connections, you're more likely to cause problems than to fix them and you'll make it impossible to repair later.

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    \$\begingroup\$ Many companies (I know mine does) has a detailed document that specifies what a "good" solder joint looks like. Besides what Spehro mentioned, there's also the color or shininess of the the solder (a dull finish could indicate a cold solder joint), as well as too much solder as indicated by excessive solder up under the heel of the lead. \$\endgroup\$
    – SteveSh
    Dec 23, 2020 at 1:18
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    \$\begingroup\$ Sometimes it may help to gently push on pins with fine tweezers or something to see if they move or flex. If they move or flex the joint is probably bad. \$\endgroup\$
    – user57037
    Dec 23, 2020 at 1:36
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    \$\begingroup\$ As mkeith says, on through-hole parts you can wiggle them a bit. Any motion indicates a lead or a pad that has broken free. \$\endgroup\$
    – Spehro Pefhany
    Dec 23, 2020 at 2:07
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    \$\begingroup\$ you should also listen to wiggles and prods; creaking, cracking, or rubbing sounds indicate loose components or solder joints. \$\endgroup\$
    – dandavis
    Dec 23, 2020 at 4:14
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    \$\begingroup\$ @dandavis Good tip. Use all your senses (well, maybe not sense of taste). A sense of smell can lead you to a fried component more reliably than just looking for a browned circuit board. As can a fleck of missing epoxy from an blown-out chip or transistor. \$\endgroup\$
    – Spehro Pefhany
    Dec 23, 2020 at 4:17
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You usually resolder pretty much all of them or at least faulty circuit block if you know it without checking every time, is faster that way.

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    \$\begingroup\$ Thank you for the advice. So your answer to the OP is "no"? \$\endgroup\$
    – cheaterpushups
    Dec 23, 2020 at 0:50
  • \$\begingroup\$ When repair something usually this way I proceed. Start with transformers and components with a heatsink first. \$\endgroup\$
    – modoran
    Dec 23, 2020 at 0:54

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