Blowing Fuses on LCD screen

I have a Kenwood lcd screen that keeps blowing a 5 amp fuse when I hook it to a switched 12 volt source.  I can hook up other components (dvd player, auxiallary input device) to the same 12 volt source and they work just fine.  I actually had the lcd screen working for months and now it keeps blowing fuses.  I don't want to put in a higher fuse in fear of frying the brain box for the screen.  help?  thanks!

Does the fuse blow immediately? If so, you have a dead short which you need to address. If the fuse blows several seconds later, or minutes. You have a current draw / load problem. The first step is to varify the idel, and the running current of the unit either from the literature from the manufactor. Then next, to measure the actual current being drawn from the unit itself. Be logical in the trouble shooting procedure to eliminate the basic things in the problem(s) before you. Let me know if I can help out more. Regards EVIL Teken...

It blows immediately and worked just fine for a few months...  I'm a newbie.  What's a dead short?  Is it bad doc?

There are technically two types of electrical short circuit conditions in the field. ELECTRICAL SHORT CIRCUIT DEFINITION: Is a condition where a electrical component, wire, or entire circuit board provides a path of voltage / current to other area's where there was none. The following is just one example of a electrical short. 1) Semi-short: You have a 100 ohms resistor, which is rated for 1/4 watts. In this example suppose the original resistor only carried 1/4 watt which it was made for. But then, for what ever reason the current was increased / power output was allowed to go past the 1/4 watt rating. The resistor partially melts, or breaks down due to the increase in current load / power output. You then measure the same resistor and it now registers on the DMM as being only 50 ohms. Now the resistor is flowing twice the amount of current / voltage it was not intended for. And the other components down the path are also being over loaded with the same thing. That is a semi-short condition, as the resistor no longer provides the stated manufactured resistive value. 2) As we continue with the same analogy: Assume the same 100 ohms resistor with a 1/4 watt rating is allowed to over load. And all the byproducts that make it a resistor is now gone. You are simply left with a piece of wire. Which basicly offers zero to no resistance at all. Now the circuit is being left unprotected and loaded with full voltage / current / power. That is a full short circuit condition. A similar sitiuation would be you trying to pass through a power wire into the fire wall of your vehicles engine bay without the use of a grommet. Over time, due to vibration from the vehicle and shaffing the insulation wears down. At some point the +12 volt supply comes into contact with the bare metal of the vehicle which is the *chassis ground* or ground plane. The voltage / current / power would be shorted to ground. In this case your vehicle would either start on fire, or the vehicles electrical system would fail. In this example it is a dead short. As the voltage / current goes directly to ground with no resistance. ======================================================== Now since your fuse blows immediately. You have some simple things to do first. First, do what I asked above. Find out what the stated current draw is for this unit at idel, and while operating. Next, measure with your DMM what current is actually being drawn from the unit. The next obvious Q would be is the 5 amp fuse the correct one? As a fuse will blow if the load is too high also. Which does not mean you have a dead short, but a over current condition. Is the fuse the correct amperage for the unit? The next Q would be is this unit the only thing being powered by this wire which is fused? If you have tapped into it for another accessory, that too would cause a over load condition and blow the 5 amp fuse. Varify that this is not the case. Another very simple thing to check, and this also causes fuse(s) to blow. Is the fact that there is a intermittent ground somewhere in the system. It is basicly like you turning on the lights in your house. Each time you turn on the lights there is a surge of power / current. In your case, if the ground wire that leads to and from the unit is loose, or intermittent from corrosion. This will also act as though you just turned it on and off very quickly, and thus, will cause a hi and quick surge that will over rate the fuse in use. You will also want to ensure that the power wire is also large enough to supply the needed current, while reducing as much resistance as possible. Check all the above and let me know... Regards EVIL Teken...

Thank for the tips.  I'm trying to power a Kenwood screen using the power to the cig lighter.  I'm only powering the screen and it still blows.   I don't have a DMM to measure current etc.  The screen worked in the past and now it continually blows fuses.  I've sent it to Kenwood twice and it still doesn't work.  There is a "brain box" where the power, video, and ground etc. go to.  I'm guessing something is screwed up inside??? Kenwood keeps saying the have "soldered a cold joint" both times which sounds luck a bunch of bs?  I don't know but I sure am frustrated...  I'm going call them and see if I get get a new  "brain box".  thanks for the info... 

If they have *re-soldered* a cold joint. This means in plain English, that there was a circuit trace that was improperly soldered in the first place during assembly. If they have performed the exact same procedure on the trace *circuit path(s)* then it is still a problem. The easiest thing to do right now is to open the unit and inspect the work that was done. You will be able to see the area(s) that have been re-flowed with solder. As there will be roslin core residue around the area. A level 1 electronics technician, assuming they are following procdedures should have removed the excess roslin core with Isopropal alcahol, and you will not see it. But I have yet to see many level 1 tech's do this in 15 years. That's why they are still at level 1 ! When you open the unit up, you will be looking for any signs of cracking, or seperation of the trace from the PCB board itself. If you see that the trace is coming off of the plastic board, or when you flex it. You will have found your problem. ======================================================== It would be helpful to know the *current draw* of this unit, or for you to provide me with a link about this product so as I may read up about it. This will make the trouble shooting procedure alot easier on both of us. ======================================================== As a simple test right now, run a power wire from the battery to the unit, using at least a 12 guage wire. Power up the unit, and tell me if it blows a fuse then, with the same 5 amp fuse. If it does not immediately blow and continues to run for longer than 5 minutes, then you have found one of your problems. That being that cigerettes wiring may not be able to provide enough current for the unit, and may be sending out a surge / spike during the lulls *sags* when power is not required. ======================================================== Let me know what happens... EVIL Teken . . .