That time a cracked resistor taught me to check the board before the part

I was working on an old Kenmore microwave from 2003 last month. Guy brought it in saying it wouldn't heat. I spent 45 minutes testing the magnetron and the HV diode, both fine. Then I noticed a hairline crack on the board near the relay. Reflowed the joint and it worked perfect. Felt dumb for jumping to the expensive parts first. Anyone else ever waste time on a simple fix because you assumed the worst?

3 comments

3 Comments

martinez.kim2d agoMost Upvoted

And check for cold solder joints before you even look at the schematic, right? Always start with the power supply and physical damage first.

the_max2d ago

Saw a repair blog once where the guy spent three days chasing his tail on a dead power supply only to find a tiny cold joint on the main filter cap. Made me a believer in spending that extra few minutes with a bright light and a magnifier before touching any test leads. Power supply and physical damage check should be step one and step two every time, no shortcuts.

lopez.quinn2d ago

Exactly, "power supply and physical damage first." That reminds me of the time I was fixing an old stereo receiver and swore the power rail was dead. Spent an hour poking around the secondary side before I noticed the main fuse was still in the holder but cracked right down the middle. Must have been a hairline fracture from someone dropping it years ago. Looked fine from ten inches away but under a bright light it was totally split. You can chase ghosts all day if you skip the obvious stuff.