Electronics and technology blog    /    Materials for March 2023 year

Today’s article is about repairing—or perhaps restoring—two power supplies from a mini PBX. These units are quite unusual and use some rather unconventional circuit designs, so this will be a long and fairly detailed article. I hope it will be useful for beginners and interesting for experienced repair technicians as well.

I hadn’t even thought about writing up this repair. Then I figured I’d just write a little and add a few photos. But I got carried away, and it ended up becoming an article about how power supplies behave when the voltage is too high, with a little extra theory about the circuitry of the chips.

As I mentioned before, along with the BL1850 and BL1860 batteries, I also received a charger for them. At first, I hadn't even planned to review it, but I tested it while checking the batteries, took it apart, and decided it was probably worth writing about after all.

So, I’ve just finished testing the second battery I received, and this one is the BL1860, rated at 6 Ah. Inspection, teardown, tests, conclusions—as usual.

Not long ago, I was asked to test and review some batteries for Makita power tools. Since this is right up my alley, and the batteries were expected to be good, I thought, why not? In short and subjectively: they’re solid. For the long, objective version, read on.

In my previous article, I wrote that repairing power supplies is usually not cost-effective, and even gave examples of cases where it really does make sense. But I just remembered a simple power supply I worked on fairly recently that’s a good example of when a repair is worthwhile.

Some time ago, I was sent several different pieces of equipment to repair, including a couple of power supplies. The repairs themselves weren’t particularly difficult, but they covered a fairly wide range of common failures. I’d like to use them as examples to show what’s what, what’s best avoided, and what you should definitely do.