Help with Transformer (plug type) wires

[Jsf721]

I have a GBC Plug in type transformer
Details off the unit :
Input 12VDC 60 Hz 5W
Output 12 VDC 100mA
Part # MP-100T
Model No DV-1220DC-2
Class 2 Transformer

It is providing power to a water bug ALARM controller that connects to a water sensor next to my water heater and boiler. The transformer is bad and the system is running on battery power. I cannot find the exact transformer new, and my issue is all the transformers I find have a tip which I can cut off and strip the wires, but the ground is marked with a gray stripe on the insulation and the voltage is plain black. How do i tell which is ground and voltage on a new transformer of a different brand, are they all marked with a stripe on the ground side ?

Pictures below to clarify and thanks for the repossess.

 

[gungatim]

Use a free Harbor freight DMM, put it on DC and test the wires. it will be negative if you have them backwards.

 

[Jsf721]

Thanks, I appreciate the response.

I'm Sorry, I believe the DMM is a multi meter and I have one of those but if I hook up the transformer incorrectly will I damage the board / controller ? What settings should the meter be set to ? Sorry I am a serious Noob. And what side does the neg and pos probes go on or doesn't that matter fore this?


While changing the board, I unplugged the transformer but the 2 wires touched while uplugged and I got a POP. That why I think the transformer is shot.

Use a free Harbor freight DMM, put it on DC and test the wires. it will be negative if you have them backwards.

 

[Ohmthis]

I’m not sure if the board is polarity dependent. I would think There would be a diode or something to keep the potential danger at bay. At any rate, leave the wires off and plug the transformer in. It doesn’t matter which lead is where. If your voltage is negative (-12.43, for instance) the wire that the red lead on is the - and the black lead is the +. Switch the leads and you should get the same voltage, but without the negative (12.43). Usually, and I say usually with a grain of salt, the wire marked with a line or dashes is the positive wire. Do double check to make sure though. Hope this helps.

 

[Jsf721]

Thanks for the response, That I can certainly do, but how do I know which is the ground?

sorry, if I am a little thick on this point.

I’m not sure if the board is polarity dependent. I would think There would be a diode or something to keep the potential danger at bay. At any rate, leave the wires off and plug the transformer in. It doesn’t matter which lead is where. If your voltage is negative (-12.43, for instance) the wire that the red lead on is the - and the black lead is the +. Switch the leads and you should get the same voltage, but without the negative (12.43).

 

[Sevenhills1952]

Right up my alley, a retired electronic technician!
It's easy.
That wall wart...I mean transformer is a transformer/power supply combo.
Output is 12VDC @ 100mA
Plugs into wall, other end shows a barrel connector. 5.5mm (O.D.) is common.
That connector the outside of connector is --negative, center +positive.
It looks like connector was cut off, wired into a screw terminal strip.
So, all you need is an a.c. adapter like that that outputs 12VDC at 100mA or greater.
If you find,say, a 200mA one it will work fine , 12 volts D.C. is important. More current just means it will be less load on the supply.
You should be able to find a supply anywhere...12 VDC is common. Our local Goodwill stores have loads of various supplies for $1-$2.
This is important! Be 100 sure output is 12 volts DIRECT CURRENT! (NOT 12vac). It MUST be 100mA or greater. 1000mA or 1 amp will work...but ridiculous. 100 to 300mA will be fine.
Radio Shack (If still around your area), even WalMart should have it in electronic department.
Connecting!
Cut connector off the new supply. Strip 1/4" insulation off end, twist wires tight.
Now with a VOM (multimeter) put it on , say, 15 or 50 vdc (whatever DC range you have over 12vdc)...put it across your car battery. Be sure it reads correctly (red to+)...around 12.5v.
Now check supply wires. One will have a stripe or other polarity marking. Meter across will show you which is +, other --.
Connect to your strip connector + & --.
That's it!


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[Sevenhills1952]

Part 2...
Pictured is one on WalMart site. It's $5.67 free shipping. It's 12VDC 1000mA. It will work fine, 10 times the power. The back has a red LED which I like.
It has a barrel connector, barrel outside is negative, center +.
Cut it 1" or so from barrel end. Strip wires back. Say the two wires inside are purple and green. Meter on ohms (continuity) check...say purple checks to barrel center. Green to outside. Now you know purple is +, green is --.
Hope this helps.

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[Jsf721]

Guys thank you for helping me get through this. Can you please let me know how I can determine whitch is ground and voltage?

Thanks

Right up my alley, a retired electronic technician!
It's easy.
That wall wart...I mean transformer is a transformer/power supply combo.
Output is 12VDC @ 100mA
Plugs into wall, other end shows a barrel connector. 5.5mm (O.D.) is common.
That connector the outside of connector is --negative, center +positive.
It looks like connector was cut off, wired into a screw terminal strip.
So, all you need is an a.c. adapter like that that outputs 12VDC at 100mA or greater.
If you find,say, a 200mA one it will work fine , 12 volts D.C. is important. More current just means it will be less load on the supply.
You should be able to find a supply anywhere...12 VDC is common. Our local Goodwill stores have loads of various supplies for $1-$2.
This is important! Be 100 sure output is 12 volts DIRECT CURRENT! (NOT 12vac). It MUST be 100mA or greater. 1000mA or 1 amp will work...but ridiculous. 100 to 300mA will be fine.
Radio Shack (If still around your area), even WalMart should have it in electronic department.
Connecting!
Cut connector off the new supply. Strip 1/4" insulation off end, twist wires tight.
Now with a VOM (multimeter) put it on , say, 15 or 50 vdc (whatever DC range you have over 12vdc)...put it across your car battery. Be sure it reads correctly (red to+)...around 12.5v.
Now check supply wires. One will have a stripe or other polarity marking. Meter across will show you which is +, other --.
Connect to your strip connector + & --.
That's it!


Sent from my SM-S320VL using Tapatalk

Part 2...
Pictured is one on WalMart site. It's $5.67 free shipping. It's 12VDC 1000mA. It will work fine, 10 times the power. The back has a red LED which I like.
It has a barrel connector, barrel outside is negative, center +.
Cut it 1" or so from barrel end. Strip wires back. Say the two wires inside are purple and green. Meter on ohms (continuity) check...say purple checks to barrel center. Green to outside. Now you know purple is +, green is --.
Hope this helps.

Sent from my SM-S320VL using Tapatalk

 

[dogdog]

Guys thank you for helping me get through this. Can you please let me know how I can determine whitch is ground and voltage?

Thanks

I think it is easier if you watch some youtube videos on how to use a multimeter to measure DC voltage.... basically it's like this...

1) Set your miltimeter to DC voltage at range above the voltage range you are measuring... ( since you wanted to find polarity, it doesn't matter what range, just above your suspected range)

2) connect black multimeter lead to com, red lead to volt on the meter ( NOT AMP, dependent on your meter, you should know)

3) cut that lead off and expose some wire on that wall plug..., so it won't short, basic common sense safety...

4) just take a guest place black lead on one of the wire, and red lead on the other wire....



The logic of this...

5) if you have digital multimeter, and you'll see a voltage display, if it have display a Negative sign, that means the leads are reversed.... at this state.... your black is Positive, and your red is negative...

6) if you have a digital multimenter and you'll see a voltage display, No Negative sign on the far left of the LCD..... that means the black is negative and red lead is positive...

7) if you have a analog meter, the needle move to the right , that means the black is negative , and the red is positive..

8) if the needle tries to move to the left and off the scale, it means the black is positive and red is negative...

Simple as that...

 

[Sevenhills1952]

This is why my suggestion to the OP was simply do this...
1)Meter on DC volts scale...15volts or higher
2)put it across your car battery...correctly (red+,black--) see that it's about 12.5v
3)reverse leads...should read --12.5

Now you know how meter works...leave it on that setting

4)check then transformer wires...when it reads properly like car battery all is well.
It may read a little high because it's not under load & depends on how well it's regulated
5)also like in your picture transformer back shows the connector polarity...which you'll cut off, an inch or so away. Ohm scale tells which wire to plug is +, which is --


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