chartman
23rd December 2006, 13:36
In car Charger fault
Do this to save your precious tomtom.......
The in car charger takes 12V from the cigar socket and converts it to 5V via a switch mode regulator chip( SMPS). Thing is, TT got too clever and decided it would be a good idea to run a thin voltage sense wire down the cable to the power plug for the TT. Thing is, they didn't reckon on it breaking. When it does, the sense circuit inside the charger jacks up the voltage to 12 volts to try and maintain 5 volts at the plug end. Very nice idea, except the chips inside the TT are only rated at 5v input max. Result is a lot of smoke and a nasty burning smell , followed by ' OH ****'.
Anther big mistake by TT design engineers. There are hundreds of SMPS chips that are >12V+ compliant. WTF didn't they use these????
So this is what you do. Take a look at the pictures for exact details.
Drill a hole or holes as per the picture.Don't drill too hard or you'll drill right through the PCB- we don't want to do that! You will see two solder blobs- one is the +5V line, the other is the sense wire. Now just carefully put a nice big fat solder blob across the two to short them out! Job Done. To finish it off, fill the hole with hot melt glue, or put some tank tape over the hole. Now if the sense wire braks, it won't matter as the sense is shrted to 5V inside the charger so it will only ever put ot 5V.
Down side? None reallly, except the 5V at the tommtom may go down to 4.9 when the battery is dead flat. Big deal, it will take another 10 mins to get a full charge into the batery.
If you don't fancy drilling the case, you can open it up with a screwdriver + knife. It's glued together so it's not so easy to get apart and will need gluing afterwards to make it look neat.
Pic 1 shows where to drill the hole. Pic 2 shows a bare pcb with the solder blob.
Do this to save your precious tomtom.......
The in car charger takes 12V from the cigar socket and converts it to 5V via a switch mode regulator chip( SMPS). Thing is, TT got too clever and decided it would be a good idea to run a thin voltage sense wire down the cable to the power plug for the TT. Thing is, they didn't reckon on it breaking. When it does, the sense circuit inside the charger jacks up the voltage to 12 volts to try and maintain 5 volts at the plug end. Very nice idea, except the chips inside the TT are only rated at 5v input max. Result is a lot of smoke and a nasty burning smell , followed by ' OH ****'.
Anther big mistake by TT design engineers. There are hundreds of SMPS chips that are >12V+ compliant. WTF didn't they use these????
So this is what you do. Take a look at the pictures for exact details.
Drill a hole or holes as per the picture.Don't drill too hard or you'll drill right through the PCB- we don't want to do that! You will see two solder blobs- one is the +5V line, the other is the sense wire. Now just carefully put a nice big fat solder blob across the two to short them out! Job Done. To finish it off, fill the hole with hot melt glue, or put some tank tape over the hole. Now if the sense wire braks, it won't matter as the sense is shrted to 5V inside the charger so it will only ever put ot 5V.
Down side? None reallly, except the 5V at the tommtom may go down to 4.9 when the battery is dead flat. Big deal, it will take another 10 mins to get a full charge into the batery.
If you don't fancy drilling the case, you can open it up with a screwdriver + knife. It's glued together so it's not so easy to get apart and will need gluing afterwards to make it look neat.
Pic 1 shows where to drill the hole. Pic 2 shows a bare pcb with the solder blob.