Cheaping out with a cheap multimeter

It is no mistery multimeters that are essential to any DIY electronic project or repair, yet we constantly buy very cheap ones because they are "good enough" but we shouldn't... YET WE KEEP DOING IT AND OFTEN REGRETTING IT!

One of the most if not the most common cheap-o multimeter is the (in)famous DT830B, manufactured by various vendors from about 30 years, what could possibly go wrong? Spoilers: EVERYTHING!

The DT830B in all his crappiness!

These multimeters usually come already with a 9v battery and fragile test leads, at about 3 to 5 Euros/US dollars. What do "I" do when the battery depletes? Buy a new relatively pricey battery? WRONG!

Since the pandemic is still with us after a whole year, I decided to stop for a couple of months at my parent's while sorting out some personal stuff, at the same time this doesn't mean I'm not working at any projects and so I recovered my old, fierce and crappy DT830B.... CRAP! Battery's out and there's still a pandemic going on outside with 10K new cases each day in my country (Italy). Time to hack something together!

This will be useful

Here at my parent's there's a very old multivoltage psu lying around with 9 volt battery leads so I decided to connect it to the cheap multimeter and call it a day... WAIT WHAT? WHAT'S THAT?!

I never seen one with such press fit contacts!

Opening the battery compartment it turns out this particular DT830B does not have the usual 9v "snap" leads and a wire that allows install, instead it simply has fixed contacts that allow the battery to press fit inside... Do I have to buy a battery now? NOT ON MY WATCH!

I've got another much much older DT830B lying around which had an accident many years ago that caused a big resistor to literally explode... Whoops! But, lo and behold, it does have the classic snap leads, time to source them, remove the crappy contacts from the newer working one and install these instead, a job that was done quick and dirty.

Going upstairs to finally use this multimeter, I used an LED together with the old PSU set at 3v to find the polarity and be able to set it correctly. After selecting the correct polarity and voltage I connected it to the multimeter... NOTHING! What is going on? Did I set the incorrect voltage? Are the battery leads soldered in the right spot? Everything looked alright so I set the PSU back to 3 volt to test it again with the LED and... Nothing again... 

At this point I tried the LED with other PSU's connectors, specifically a couple of jacks, and the LED turned on... Something must have broken inside the 9v battery leads, which led me to cut the plastic of said connector and in fact one of the wires snapped off, it is an old very used PSU after all.

I quickly added a bit of fresh solder, burned myself and soldered the wire back. I secured the leads with some electric tape while trying to make it a bit sturdier and... IT WORKS! I avoided buying another battery!

Time to go back to work and have some fun... eh... what? No.. Nooo... NOOOOOOOOOOOOOOOO! THE TEST LEADS BROKE! I even said those are fragile!

DO'H!

What did we learn from all of this? Just buy good multimeters or, if really, REALLY you can't do otherwise buy a new crappy one everytime the battery depletes because test leads are gonna break again sooner or later.

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