I have to change the tip (jack? what is it called?) on a replacement 12v power supply for my keyboard with the original tip. I'll cut the wires on the old and new power supply and solder and tape them together. Not the best solution, I know, but bear with me (yes, I ordered a replacement from acadaptors-r-us and of course it was the wrong tip; did they reply to my complaint? Of course not).
How do I test with a multi-meter that I have wired it properly to centre-negative?
The tip looks like a regular 9-volt tip you find going into a guitar pedal.
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Do I then simply insert the red cable into the centre of the barrel (and put the black cable on the outer barrel)?
I want to measure +12v.
Before I start cutting, I will perform the test with the functioning unit, get the desired 12v+, and then cut and wire up a different sized barrel.
You can test if you have this right by putting the meter on a battery and see'ing if it identifies the voltage and polarity of the battery.
If you cut and reverse the polarity of the cable then here's a neater way of doing it that's also immune to shorting
Now that you mentioned it, my 9 year old son and I had fun measuring old batteries to discover that a good 40% are good to go. My son now has greedy eyes on the battery recycling bucket at our local market.
Thank you, @Danny1969
Once again, thank you, @Danny1969