Perhaps same brave people like to wake up in 7 am in the morning to a nice smell of burning electronics as well. Or risk the lab burning down due to fire started by $1 part, because “hey, it worked fine 20 years, she’ll be alright another 20!”. Right? RIGHT?…

Here’s what woke up me today and stinked the whole home – Fluke 732B-7001 charger used to power one of the new X9-D ADR1000 reference modules.
It was working fine for over a month, including the sweeps in air-bath over +45 °C but gave up in flames and fire started in tantalum capacitor C531 just a week after being plugged into array with other expensive zener standards next to it.

I assume there was a little fire with open flames because it is easy to see bits and pieces of materials sputtered all across the metal outer cover with a trail of charred surface. I’m lucky that nothing else catch fire. There is plenty of fire accelerant in nearby insulated box with foamed box, as well as AGM battery right under the PCB.

Mains 5 × 20 mm fuse, rated for 250V 250mA was also blown, so need to replace that as well before further repairs can be happening.

Have you replaced tantalum capacitors in your old Fluke 732B yet, or waiting for the fire and smokes too? DC standards such as 732B are commonly left running unsupervised for years and years and preventive replacement of capacitors would save you from risk loosing it all in a ball of flame. $50 for new caps every 10-15 years should be reasonable cost to keep peace of mind?

Here’s the choice of capacitors I’ve decided to use as replacement, rated for higher voltage where possible. I didn’t find 150uF tantalum with higher voltage rating that I like to replace the perished C531, so will install decent aluminum electrolyte instead. It’s there on the output +11.5 V rail to the zener core anyway, so no real need to have a tantalum type.