I just realised that my post failed to add my qoute/questions that I included with the pics....I need a potentiometer that can handle the load of a black and decker 12v 250ma 4watt power supply. This is powering approx 30 feet rgb led strip lights that are framing 2 large wall mirrors in the corner of my bedroom. I want to keep them dimly lit at night but need to reduce the 12v down to 4v or less. A 5v usb phone charger is just a little to bright even with the 44 key remote control that runs the lights. My final thought on the repair is in the picture i posted you can see that whoever assembled the dimmer switch did not double check their work and soldered the 2 +input/output posts together. I have fixed that but still the only way I get full power from the dimmer switch is half way up and thats shorting out some how and will not let me change the light colors. It illuminated all of them. Hopefully this posts properly and I don't have to type this a 3rd time...saving to my clipboard incase.... thanks in advance and hopefully I included enough information.

 

For starters, it looks like the two terminals bridged also have the circuit board trace connecting them, so that would not be the problem. But if the application is using the device in the picture to control the brightness of the LED string to a single level, there are simpler ways to do that. And it is not reasonable to try and control the intensity of the lights by dropping the voltage to the power input of the controller, because that controller has a bunch of logic inside that needs the specified supply voltage. A series resister in the feed to the LED string will reduce the voltage more effectively, but it will be less efficient.
BUT, if reducing the voltage to the controller input is working, and 5 volts is just a bit too bright, then put a high-current rated diode in series with the 5 volt line. That should drop the voltage a bit more, to around 4.3 volts.

 

This gives full control I made it just to show but the video don't give the real look but it dim's down to there almost off

will using that dimmer replace my rgb controller and the color change effects it has? heres a pic of the unit that i accidently fried because i unplugged the wrong ac power supply before plugging in the usb power. the mirrors are wired the same except i now have a 12v 1 amp ac power supply that plugs into the controller w/o soldering to the board. i believe it was mr.al who commented pics dont show how its wired so here it is even though there isnt much to wiring them.on this unit being burnt out anyone have any thoughts to what would be the most likely thing to burn out plugging both the ac and usb power supply in? my thoughts would be the diode. however for the 2 or $3.00 dollars these controllers cost its not really worth repairing
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For starters, it looks like the two terminals bridged also have the circuit board trace connecting them, so that would not be the problem. But if the application is using the device in the picture to control the brightness of the LED string to a single level, there are simpler ways to do that. And it is not reasonable to try and control the intensity of the lights by dropping the voltage to the power input of the controller, because that controller has a bunch of logic inside that needs the specified supply voltage. A series resister in the feed to the LED string will reduce the voltage more effectively, but it will be less efficient.
BUT, if reducing the voltage to the controller input is working, and 5 volts is just a bit too bright, then put a high-current rated diode in series with the 5 volt line. That should drop the voltage a bit more, to around 4.3 volts.

For starters, it looks like the two terminals bridged also have the circuit board trace connecting them, so that would not be the problem. But if the application is using the device in the picture to control the brightness of the LED string to a single level, there are simpler ways to do that. And it is not reasonable to try and control the intensity of the lights by dropping the voltage to the power input of the controller, because that controller has a bunch of logic inside that needs the specified supply voltage. A series resister in the feed to the LED string will reduce the voltage more effectively, but it will be less efficient.
BUT, if reducing the voltage to the controller input is working, and 5 volts is just a bit too bright, then put a high-current rated diode in series with the 5 volt line. That should drop the voltage a bit more, to around 4.3 volts.

For starters, it looks like the two terminals bridged also have the circuit board trace connecting them, so that would not be the problem. But if the application is using the device in the picture to control the brightness of the LED string to a single level, there are simpler ways to do that. And it is not reasonable to try and control the intensity of the lights by dropping the voltage to the power input of the controller, because that controller has a bunch of logic inside that needs the specified supply voltage. A series resister in the feed to the LED string will reduce the voltage more effectively, but it will be less efficient.
BUT, if reducing the voltage to the controller input is working, and 5 volts is just a bit too bright, then put a high-current rated diode in series with the 5 volt line. That should drop the voltage a bit more, to around 4.3 volts.

i didnt realize this was going to be such a big issue to adjust the brightness of these lights. i just figured a potentiometer to control the voltage to the controller would work. all of the lights dont light up until aprox 7 volts is applied to the controller. im about to give up on this and just use the latest 5v leds that i got to where i can cut them at each led and just use a few of them on a seperate controller at night maybe beside the smaller mirror

 

will using that dimmer replace my rgb controller and the color change effects it has? heres a pic of the unit that i accidently fried because i unplugged the wrong ac power supply before plugging in the usb power. the mirrors are wired the same except i now have a 12v 1 amp ac power supply that plugs into the controller w/o soldering to the board. i believe it was mr.al who commented pics dont show how its wired so here it is even though there isnt much to wiring them.on this unit being burnt out anyone have any thoughts to what would be the most likely thing to burn out plugging both the ac and usb power supply in? my thoughts would be the diode. however for the 2 or $3.00 dollars these controllers cost its not really worth repairingView attachment 144378
.

will using that dimmer replace my rgb controller and the color change effects it has? heres a pic of the unit that i accidently fried because i unplugged the wrong ac power supply before plugging in the usb power. the mirrors are wired the same except i now have a 12v 1 amp ac power supply that plugs into the controller w/o soldering to the board. i believe it was mr.al who commented pics dont show how its wired so here it is even though there isnt much to wiring them.on this unit being burnt out anyone have any thoughts to what would be the most likely thing to burn out plugging both the ac and usb power supply in? my thoughts would be the diode. however for the 2 or $3.00 dollars these controllers cost its not really worth repairingView attachment 144378
.

never mind on diagnosing damaged controller its now working again. initially when i plugged in the usb w/o unplugging the ac 12v unit it sut down instantly and i messed with it for about 10 minutes and never got it to power up again

 

i didnt realize this was going to be such a big issue to adjust the brightness of these lights. i just figured a potentiometer to control the voltage to the controller would work. all of the lights dont light up until aprox 7 volts is applied to the controller. im about to give up on this and just use the latest 5v leds that i got to where i can cut them at each led and just use a few of them on a seperate controller at night maybe beside the smaller mirror

The controller is not a simple thing, but instead it is a pulse width modulator circuit, and if there are three colors then there is also some logic to select colors by controlling all three colors of LED devices. And all of that logic needs to have at least some minimum voltage supply in order to function. So it is not a simple matter of just controlling the supply voltage to that controller, although I am certain that doing that affects the brightness some. But if the controller is truly "fried" then you need to do something different. A variable voltage regulated power supply is one choice, a variable Pulse Width Modulator is another option. BUT no matter which choice, you need to be able to limit the current to those LED strings to below some maximum limit to make sure they last more than a few seconds. So it does get complicated, but the great news is that it has already been done lots of times by lots of people, so you don't need to create anything new. Copying works very well. You can look at typical circuits on the "schematics for free" website in the section on lighting to see how some others have done it.

 

thank you everyone for helping me out with my lighting issues. i have since made a bulk order of lights and controllers and switched the mirror leds to 5050 rgb and swapped out the 12v controllers for usb rated between 5v and 12v @ 2a and put a separate controller for each mirror. still a little to bight to leave on at night but i decided on a 6" strip on each side of the room for night time. i kept some of these lights and controllers for myself and some family members and sold the rest for double what i paid in less than a week on the fb buy, sell, trade groups.who knows i may do it again but there is a lot of time and work in testing everything out thoroughly, soldering, ect. out of 160 ft of leds and 35 controllers i only had one 24 key with a bad usb cord and one 44 key with the red and green buttons being switched around. haven't seen if this is fixable and probably wont even mess with it. i also had about 4ft of leds that after being on for about 30 minutes the red started going orange and flickering and that just happens to be one of the ones i put on the mirrors. not to bad for what i paid for them.

 

thank you everyone for helping me out with my lighting issues. i have since made a bulk order of lights and controllers and switched the mirror leds to 5050 rgb and swapped out the 12v controllers for usb rated between 5v and 12v @ 2a and put a separate controller for each mirror. still a little to bight to leave on at night but i decided on a 6" strip on each side of the room for night time. i kept some of these lights and controllers for myself and some family members and sold the rest for double what i paid in less than a week on the fb buy, sell, trade groups.who knows i may do it again but there is a lot of time and work in testing everything out thoroughly, soldering, ect. out of 160 ft of leds and 35 controllers i only had one 24 key with a bad usb cord and one 44 key with the red and green buttons being switched around. haven't seen if this is fixable and probably wont even mess with it. i also had about 4ft of leds that after being on for about 30 minutes the red started going orange and flickering and that just happens to be one of the ones i put on the mirrors. not to bad for what i paid for them.View attachment 147212 View attachment 147218

You have certainly produced an awesome installation from what I see in this picture. It took a bit to realize that I was seeing two mirrors reflecting. And it seems that you have done quite well with the bulk purchases. It may be that you could start a business doing that, since I am sure that there are others who would want to have such a setup. Now for my question: Any more issues to be solved? I have a lot of repair and diagnostic experience and I am willing to answer questions.