FM modulator light only and no transmitting

[pharaon]

my car mp3 FM modulator was working fine this morning and suddenly it stop transmitting frequency and just give me light screen.. wonder if any one can help me about the item that cause that failure in the circuit.
here's is some pictures of the modulator circuit.

 

[Gryd3]

There is a bit of a problem...
That little black hardened puddle has a mystery inside.
The only thing I can think of is testing the chip beside the usb plug. (can you give us the numbers on it?)

 

[pharaon]

can you tell me what type of this item is it IC or transistor

 

[Gryd3]

can you tell me what type of this item is it IC or transistor

https://www.fairchildsemi.com/datasheets/KS/KSE13003.pdf
Looks like a transistor. I didn't even consider the power source because you still had light...
Do you have a multi-meter? Put the plug back together and measure the output voltage on the main portion of the FM transmitter where those 3 wires come in. (Careful not to short the wires with the meter leads)

 

[pharaon]

you want me to measure the voltage of the 3 wires in the main portion which have the screen right?
and you want me to measure the volt between what wires exactly like
black - red
black- white
white- red

 

[Gryd3]

you want me to measure the voltage of the 3 wires in the main portion which have the screen right?
and you want me to measure the volt between what wires exactly like
black - red
black- white
white- red

Exactly. Yes Please.
I just noticed the 3 wires. So it is completely possible that there are two different voltage supplies, and making sure they both work will help.
Can you also please get be the part number from the IC beside the USB port?

 

[pharaon]

sorry for the delay


G - V = 5.13
G - A = 1.65
V - A = 3.46

 

[Gryd3]

yeesh..
Found info on that chip : http://www.hobbielektronika.hu/forum/getfile.php?id=70355
It's got 2 different grounds and 2 different power sources. (One for control, and one for RF...)
I am not familiar in RF to be sure how these work together...
The 1.6V from G-A seems pretty low to me though.
Perhaps someone else has some better ideas.

 

[pharaon]

do you suggest to change the KSE13003?

 

[Gryd3]

do you suggest to change the KSE13003?

I don't understand the KSE13003 enough.. even with the datasheet.
I'd like to have a second set of eyes on this, but judging by the numbers you measured at A, G, and V, I would try to make certain that the components in the plug are working to ensure that the voltage you measured is actually supposed to be those numbers.
G-V should be right... as that board would need a 5V source, but I expected G-A to be a higher number.
While we wait for a second pair of eyes, can you please take some nice clear pictures of both sides of the plug? We would ideally need to be able to follow the lines and read most of the components.

 

[pharaon]

that's all no lines at the back and no more components

 

[Gryd3]

I don't see enough components on there to provide 2 different regulated voltages.
My gut is telling me white should be 12V...

Can you please set your meter to test resistance, and measure the resistance of each of the 3 wires from the plug to the main board.
Red - Red, White - White, and Black - Black.
They should all be the same. A very low resistance.
This will tell us if there are any breaks in the wire.

If there are no breaks we need to trace the lines in the plug... which may be tricky because some are covered and the board looks messy

How are you with electronics?
If you're comfortable with a soldering iron, I'd remove that 13003 transistor and get some head cleaner to clean up some of that gunk on the board. This will also give us a clear look at where the lines go that pass under the transistor.

 

[Arouse1973]

The white wire might be a control line for voltage regulation or over current, it looks like it's connected to the base.
Adam

 

[Gryd3]

The white wire might be a control line for voltage regulation or over current, it looks like it's connected to the base.
Adam

Good catch. I'm having trouble following the lines there, and I based my gut feeling on the possible 12V on the specs I found for the AS6001 being able to use 2 different voltage rails.

 

[pharaon]

hope this will help

 

[KrisBlueNZ]

The circuit in the plug, using the KSE13003, looks like a standard emitter follower regulator with zener, but... the transistor seems to have been installed backwards! In other words it should be fitted so we can see its partly exposed metal face, not its plastic face with the part number marking!

The circuit is probably there to keep the automotive noise and spikes away from the main PCB. It will provide good protection against positive spikes but no protection against negative spikes; the addition of a diode (e.g. UF4007) between the end spring (anode end of diode) and the rest of the circuitry (cathode end of diode) would help.

Once the transistor is replaced, the output will be on the red wire, with the black wire being the 0V return.

According to your drawing, the white wire only connects to one side of C2, but I don't think that's all. Is it also connected to the black wire? It might be used as a second 0V conductor.

The output voltage is determined by the zener voltage, which we can't see. I would expect to see another regulator on the main board, taking the voltage from the red wire and dropping it down for the parts on that board, since this regulator is crude and not very accurate.

 

[pharaon]

The circuit in the plug, using the KSE13003, looks like a standard emitter follower regulator with zener, but... the transistor seems to have been installed backwards! In other words it should be fitted so we can see its partly exposed metal face, not its plastic face with the part number marking!

The circuit is probably there to keep the automotive noise and spikes away from the main PCB. It will provide good protection against positive spikes but no protection against negative spikes; the addition of a diode (e.g. UF4007) between the end spring (anode end of diode) and the rest of the circuitry (cathode end of diode) would help.

Once the transistor is replaced, the output will be on the red wire, with the black wire being the 0V return.

According to your drawing, the white wire only connects to one side of C2, but I don't think that's all. Is it also connected to the black wire? It might be used as a second 0V conductor.

The output voltage is determined by the zener voltage, which we can't see. I would expect to see another regulator on the main board, taking the voltage from the red wire and dropping it down for the parts on that board, since this regulator is crude and not very accurate.

so you suggest that I replace the transistor KSE13003?
that will fix the problem?

 

[KrisBlueNZ]

I'm not sure. According to post #7 you have about 5V between red and black. Is the polarity right? The red wire is positive relative to the black wire? If so, perhaps the regulator is working properly - perhaps the transistor was manufactured by a different company, and they used a reversed pinout.

I don't think we can be sure of anything until we figure out what the white wire does. Check for continuity from the white wire to all other points on the plug board. I can see that it connects to one side of the capacitor marked C2 but I think it probably connects to other places as well.

Also can you upload a clear picture of each side of the main board. I want to try to follow the track that comes from the white wire.

 

[pharaon]

the plug board been damaged when I tried to remove the transistor but I think I can make some bridges to fix it later..
hope those pic can help you to determine what is cause of that issue

 

[KrisBlueNZ]

Oh dear, that's not looking too healthy. You could start by cleaning the board by rubbing it firmly using cotton swabs dipped in solvent - isopropyl alcohol is best, but methylated spirit will do. Also, can you clean up the solder on the remaining transistor lead, so I can see what that pad does (and doesn't) connect to. Then upload a clear, in-focus picture of the copper side of the board.

I suspect you're going to have to remake that board on a piece of stripboard, using a cigarette lighter plug for the connection to the car. But let's figure out what's on that board first. Most importantly I want to figure out what the white wire does.