How to figure positive and negitive on this invertor

[treehog]

Pictures below show piture of my 150watt 12 volt to european standard 220 volts

Normally you plug it into the cigaerate lighter in the car and then plug in a home appliance liake a laptop

One day the plug melted from some sort of short and I went to replace it
Did something really stupid cut back the cable which has two wires both black so now I dont know which is positive and which is negitive

I dont have access to another unit to compare with whaat connection is what and I which I bought it for €20 eurol in Lidl Aldi which dont keep them in stock all year around

Nothing on the circuit bourd like a big positive

one wire is close to the tranformer and the other is close to a capsitor

I also have a volt meter if its possible to trace circuits
Any ideas ??? how to figure which is positive and which is negitive

Ralf

[Greywing]

I assume you are talking about the 12V input wiring. Given that is the case, it is probable that the wire going to the capacitor is the one; however you should verify this by examining the circuit on the back side of the circuit board and verify the the circuit trace from the wire attachment goes to the capacitor + terminal. This trace may go elsewhere as well.

Good luck.

[treehog]

I assume you are talking about the 12V input wiring. Given that is the case, it is probable that the wire going to the capacitor is the one; however you should verify this by examining the circuit on the back side of the circuit board and verify the the circuit trace from the wire attachment goes to the capacitor + terminal. This trace may go elsewhere as well.

Good luck.


Thanks Its big work to take the circuit board out as the big op amps are glued bolted to the walls to cool down.I looked the capasitor from the top and figured I could make out the positive symbol in probable direction of what might be the positive lead

I noticed from the pic a serial number on the cable on that cable and looked closer .There is a serial number all down one cable not easy to spot but molded in.
Using SWAG scientificaly wild assed guess I figured this writing is on the positive cable .That the green cable is linked to negitive so I decided to risk it for a bisciut and connect it up
I switched it on and green on light came on so now all I got to do is go out test it in the car( which I will do in a few hours when I get to work and plug in my old laptop that hasn't got a battery)

fingers crossed

Ralf

[Brandano]

Another hint would have been that yellow/green cable, which is usually ground for AC power. Since cars usually have the negative connected to the chassis, and you normally want your ground to be at the same potential as the surrounding ground, which in this case is the car's chassis, probably the yellow/green cable is shorted to the inverter's negative. Btw, I find it odd that the circuit shouldn't have an indication of polarity on its serigraphy.

[mjsas]

One side of the wire is smooth and the other side is ribbed. The ribbed side is ground.
In the US, all two wire cords have a smooth side and a ribbed side so the ground side is always marked.