Voltage Help [resolved]

[pofofo]

Hi, Ive got the same problem, so instead of making a new thread, Im posting it here.

When I plug the power cord to the wall socket, it makes my multimeter go haywire, + and - in voltage and around -7 to +7 and its never stable. I used both alligator clips and tried without, same result.

Ive checked the fuse (it atleast makes my multimeter make sounds), tried two cables that I know work and used an outlet I also know works.


I live in Norway so the voltage here is 230 v.

[Deke609]

Just a couple shots in the dark: double check that (a) the meter is set for AC voltage, not DC voltage, and (b) the red lead is plugged into the Volts socket of the meter, not the Amps socket.

[pofofo]

Im thankfull for your shots in the dark, they where correct! I didnt set my multimeter correct... damnit, thank you so much!

[pofofo]

So Ive built it, and Im getting a couple of wrong voltages during the last safety check.

The measurements that are wrong are:

Terminal 16: 336v (should be 65-95v)
H4: -2v (should be 2.8 - 3.2v)
H7: -2v (should be 2.8 - 3.2v)

What causes this?

Edit: Some places where the * sign are at the measurements my multimeter give unstable readings, but if I understood correctly, thats ok?

[Paul Birkeland]

You may need to post photos for us to see why terminal 16 is high.  This is likely to be a poorly soldered component or a miswire.

H4 and H7 may show 2V if your meter doesn't have a low DC range.  What meter are you using? 

[pofofo]

Thanks for the quick reply.

Its a very cheap basic multimeter I bought some years ago.

Edit: Terminals H2 and H5 measured 3v, H4 and H7 measured -2v

[Paul Birkeland]

I would suggest reheating all of the solder joints on all of your terminal strips, especially the lower joints.  The solder needs to flow into the terminal strip, not ball up on the outside.  If you are using lead free solder, it may help to get leaded solder to make this easier.  If you have an adjustable soldering iron or soldering station, turning the temperature up all the way is also helpful.

[pofofo]

Ok, thanks. I used lead free solder, because its illegal in the EU (Norway based). My soldering station goes up to 450C and Ive been using it around 330C or so, because I was worried that I might burn stuff.

[Paul Birkeland]

It does not appear to be illegal in Norway, just expensive:
https://no.mouser.com/ProductDetail/Kester/24-6040-9703?qs=Tcwt6g1oMihgbjSiwNe%252B3g%3D%3D

This one is far less expensive:
https://no.mouser.com/ProductDetail/MG-Chemicals/4898-454G?qs=SUQPjvP5usWOUeeKotOC4Q%3D%3D

[pofofo]

Wow, I didnt know you could get that.

But, the heat! I upped the soldering station and reheated all the lower terminal strips, and wouldnt you know it, Terminal 16 now has 89v.

I guess I should check every other measurements before putting it to use?

And thanks for the quick replies and great help, Paul!

Edit: Everything is now within spec (10%), the lowest I got are Terminal 21: 368v (should be 400v)

The H4 & H7 still measure minus 2v (-2v), while H2 & H5 measures 3v

Edit 2: Nevermind, I searched the forums and found that it i suppose to be minus. Ill heat the solder joints on the terminal strips and remeasure.

[pofofo]

I reheated the solder points, but stil the H4 / H7 measures -2v.

Any ideas?

[Paul Birkeland]

You should be able to get a lot more resolution on that terminal than just 2V.  I would set your meter to the 20V range and recheck those and let us know what at least the first decimal point is after the 2.  +/-2.9V would be fine, +/-2.1V would not.

[pofofo]

Im such a massive noob. With the multimeter set to proper measurements, so I can get DECIMALS, the H4 measures 2.98v & the H7 2.97V.

Again, thanks for really good and fast responses and help, Paul!

[Paul Birkeland]

Awesome, those are exactly what you'd want to see!

[pofofo]

Got finally time to test it. It works great! Thanks for all the help