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More electronic questions

Electronics Power and Sound
#1

So I bought a bridge rectifierand and attempted to put in a 12v regulator. Here’s what happens.
From the + out side of the rectifier I ran into the 12v regulator. Thats it I have done nothing more.
From the - side of the rectifier I get the same voltage as the power pack I am using 21v. BUT from the center pin (the -) on the 12v regulator I also get the same voltage from the power pack 21v.
I first thought the regulator was bad but it does it on the three other regulators I have a 5v and a 1v.
Can I not run a regulator behind a bridge rectifier? I’m lost here.

Terry

#2

Yes,
If the reg is a 7812 type connect the in side of the reg to + on the bridge.
Connect the middle leg of the reg to - (ground) on the bridge.
Put a small monolith filter cap, say .1mfd (#104), across the input.
The output of the reg is positive, (+ 12 volts) and the middle leg is ground.

#3

Sounds like you don’t have the leads connected right somehow… maybe you have the input and output of the regulator reversed?

Greg

#4

I checked it at least 4 different times. I gave up.

#5

What is the # on the voltage reg?
Did you connect the common - (ground)

#6

Dunno Tony. I got pissed and threw it all in a box.
If i ran the +12v reg alone on my power source it would work fine as soon as I added the bridge rectifier that was where my problems started.
Maybe the rectifier was bad? The wiring seemed simple two AC in tabs and one + and one - out tab.
The volt reg had a + in, ground and + out tab. When hooked to the rectifier the ground tab would show the same voltage as the + in. Without the rectifier, the volt reg works fine…

Here is my one and only thought on this. is it possible that the rectifier will not allow the the neg (ground) current to return and the volt reg is tripping? it’s the only thing I can come up with.

Just another reason why I like battery power…
Terry

#7

If you have trouble with right and left, like I do, the risk of reading the pin-out diagram backwards is high. I do that a lot and so always buy spares for the learning curve.

#8

Terry, were you feeding it with AC?

If so, you needed a filter cap on the output side, not just a .1 capacitor

But it sounds like you were running the bridge from DC… that should be fine too.

Maybe you got a negative voltage regulator, that would explain a lot… you need to gve us the part number of the regulator… like 7812 or 7912 …

Something is strange…

Greg