http://www.jameco.com/Jameco/worksh...1&spJobID=343082989&spReportId=MzQzMDgyOTg5S0
Max.

 

http://www.jameco.com/Jameco/worksh...1&spJobID=343082989&spReportId=MzQzMDgyOTg5S0
Max.

The MkI pointy finger is handy for seeking out those overheating electrolytics - but with exposed tops of aluminium cans, you can detect something you didn't want to on the PSU primary side!

 

theres also the cat urine smell of bad electrolytic caps.

 

theres also the cat urine smell of bad electrolytic caps.

I've also encountered "rotten fish" and "burning rubber" smells from dodgy electrolytics.

Since the arrival of RoHS solder; its been usual to inspect for bulged electrolytics then flip the board over and rework all the dodgy soldering.

The heat from this procedure usually gets any nasty niffs from dodgy electrolytics wafting out from under the upturned board.

 

theres also the cat urine smell of bad electrolytic caps.

I usually associated that with Selenium rectifiers which were bad for the same smell.
Max.

 

"Using all your senses" is a very difficult thing to teach!
The color and amount of smoke, using the infrared sensors in your face to find hot places, the different odors, like ozone or burnt resistors, "Is it a leak or is it glue?", catching a spark with your peripheral vision, hearing relays click, the distinctive crackle of exploding thermoplastic, how much, where, and what color a vacuum tube should glow, knowing if a motor sounds like it is running unloaded, insulation that is burnt next to where the wire connects...These things are not covered by V=IR or P=IE, but they are very valuable clues.

 

Yes, I do the same human sense tests all the time. Best if you can catch where the smoke is coming from before the supply shuts down.

 

My father told me he repaired tube radios when he was a teen (1940s). He had no equipment, just some hand tools. He tested for voltage by swiping his finger across the circuit. That's using your senses.

 

I usually associated that with Selenium rectifiers which were bad for the same smell.
Max.

One of the last hybrid CTVs I sold all those years ago had selenium tripler diode-sticks - I wasn't too popular with the pub I sold it to when it blew up!

 

My father told me he repaired tube radios when he was a teen (1940s). He had no equipment, just some hand tools. He tested for voltage by swiping his finger across the circuit. That's using your senses.

My father used to check for open cartridge fuses (essentially a 6 inch tube with a metal tab either end) by spreading his index finger and pinky and swiping at them. If he felt a tingle it was a bad fuse.

I SCREAMED at him after he told me this, as the fuses he was testing supplied power to the rails for the Long Island Rail Road. 600 volts DC at enough current to run a train and he touches the dang things.

Oh well… never hurt him any.

 

600 volts across his hand?

I can't understand why he wasn't called, "Lefty"!

 

That is why they fired him from the Railroad, He was a bad conductor. (snare drum).
Max.

 

Yes, I do the same human sense tests all the time. Best if you can catch where the smoke is coming from before the supply shuts down.

This reminds me of my first job as a pre-test technician. I powered up the newly assembled boards the very first time so I got to see all of the assembly errors.

The circuit subsections all had 10 ohm resistors and 15 uF tantalum capacitors for power supply bypass. There were dozens of these resistor/capacitor pairs on each board. The resistors often smoked because of solder bridges. As a new technician, my initial reaction was to quickly turn off the power to save the resistor. The senior technician told me to leave the power on until I could tell which resistor was smoking! Then it was an easy matter to find the short that fried the resistor, remove the short and replace the damaged resistor. This saved a lot of time for the small price of a resistor.