Electronic help, ID this component.

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I'm trying to repair a non-functioning playmobil RC motorblock. The motor is good, but the circuit board has a problem. I think I may have narrowed down the problem to a specific component pictured below, by comparing voltages with a good motorblock. The input voltage from the battery was about 5.3 volts on the left side of the component in the picture. It says 'L6' on the component. Can anyone ID this component for me so I can find one to try to replace it with(I'm guessing some sort of transistor?)? Also, if you think the component is good and there may be a different problem causing this anomaly feel free to chime in.
pcb.png
 
It is (or was!) a transistor..
From your meter readings, it would appear the junction form left to lower-right, has gone short-circuit. There still being 0.6V across the other junction, that would appear OK. - Unfortunately, you can't just swap the faulty junction! :rofl:

There *should* be a part number on the device, but good-luck in reading it!
 
actually I just checked and I measure the same resistances across each connection as on the good one, no shorts. weird. The 221 component below it is not shorted either. Now I'm wondering if a transistor can still be the problem while measuring the correct resistance across each leg.
 
Measuring resistance is not the same as what happens when power is applied, this is an active device.

Hint: the voltage from your meter is not usually enough the bias the transistor to turn on, and then there is the polarity issue when you are measuring resistance.

Pretty much an ohms measurement on a transistor is a meaningless exercise.

Greg
 
I'm guessing there's an internal problem, allowing the full voltage to pass through, and the resistance I measure is coming from another component in parallel.
Now If I could just figure out how to ID the part to find a replacement... There seem to be a variety of L6 transistors... :-(

I wonder if this would be appropriate:
50PCS 2SC1623 L6 0.1A/50V NPN SOT-23 SMD transistor | eBay
 
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If you want to test a transistor use the diode test on your DVM. An NPN transistor is two diodes cathode of one diode = C. cathode of the other diode + E. and the two anode of the diodes + B. If a PNP transistor the two diodes are reversed. The transistor maybe a FET so is not the same.
 
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The previous picture I posted was of the good board.
Here are two images of the bad one:

my_photo-376.jpg
my_photo-378.jpg
That fact that the bad board looks less clean helped create some suspicion over that transistor. But I've heard that transistors can have incorrect voltages if the problem is elsewhere on the board. Any ideas on what else might have caused those voltages?

From what I understand, the collector is on the left, Emitter on the top-right and Base on the bottom-right in my pictures.
I have the older style playmobil RC block, without the lighting circuit.

There is a newer version of the board with lighting on ebay here:
RC Motor & Control Module 4010 4011 4016 4017 Playmobil Train Spares #1 | eBay
pcbe.jpg
I can see similar components there and they seem to have marked the C, E, and B on some of the pins of those components. Directly left of the crystal socket you can see one with E and B marked. Towards the bottom-left there is one with the C marked... Another near the top-left with all 3 pins marked. So it is clearly a SMD sot 23 transistor. But is there a way to test it without removing it from the circuit? Is there a good way to determine if it's NPN or PNP without removing it? If I can't be certain I may have to gamble and try one of these: 50PCS 2SC1623 L6 0.1A/50V NPN SOT-23 SMD transistor | eBay Does that seem like an appropriate replacement component for this? It looks the same, but I'm not sure if the voltage ratings are appropriate for this board.
 
I'm not getting results expected from the tutorials I've seen, I'm using the diode setting in the ohm section of the DMM and an unpowered board:

Positive on Base, negative on Emitter:
my_photo-380.jpg
Negative on Base, positive on Emitter:
my_photo-382.jpg
Positive on Collector, negative on Base(I think this reading could be from the parallel resistor below it):
my_photo-383.jpg
Negative on Collector, positive on Base(I think this reading could be from the parallel resistor below it again):
my_photo-384.jpg
Negative on Collector, positive on Emitter:
my_photo-385.jpg
Positive on Collector, negative on Emitter:
my_photo-386.jpg

Can anyone make sense of this?
 
I am a very armature dabbler, but have found false readings when a component is still fitted due to the interaction of other components on the board!
 
You are pretty much on a hiding to nothing, trying to test in-circuit.. - To many other components, and current-paths, unless you really know what to look for.

Even then, you can be deceived.. :(
 
As already discussed there is no point in trying to determine the state of a component whilst in circuit. If you do not have a circuit diagram measuring voltages is a pointless exercise! If the transistor shows signs of damage remove it from the circuit and try to determine whether NPN or PNP and then replace it as the board at present is faulty and therefore you have nothing to lose. Personally if I could not measure the transistor I would fit an NPN and see what happens. Hope this helps, best of luck!
 
Thanks guys. I think I know what I have to do. It would be a pain to replace it only to find that the problem may have been elsewhere on the board. But it's probably a risk I need to take.
 
Did the tutorial tell you to use the diode setting? If so, please post that link so I can give that guy a piece of my mind.

You need to be doing this with a high-impedence measuring device, normally ohmmeter set for ohms.

Again, there are no guarantees when in circuit, but you can usually extract more information comparing resistance with both polarity than a simple continuity test.

Also, there is no use trying to measure the damaged transistor, I thought you were trying to determine NPN vs PNP... take the good board, remove the transistor, test it.

Greg
 
Greg Elmassian said:
Did the tutorial tell you to use the diode setting? If so, please post that link so I can give that guy a piece of my mind.

You need to be doing this with a high-impedence measuring device, normally ohmmeter set for ohms.

Again, there are no guarantees when in circuit, but you can usually extract more information comparing resistance with both polarity than a simple continuity test.

Also, there is no use trying to measure the damaged transistor, I thought you were trying to determine NPN vs PNP... take the good board, remove the transistor, test it.

Greg
Click to expand...
The collector of an NPN transistor goes to the positive supply line (usually via a resistor)
The collector of a PNP transistor goes to the negative supply rail (usually via a resistor)
 
My45G said:
The collector of an NPN transistor goes to the positive supply line (usually via a resistor)
The collector of a PNP transistor goes to the negative supply rail (usually via a resistor)
Click to expand...

I guess that tell's me it's an NPN, thanks My45G.

Greg, I looked at a few tutorials which all said to use the diode setting, but I think they all had the components removed from the circuit, so that might explain the problem.
 
Umm... I read those 2 sentences. Neither of them answers my question... did the tutorial indicate to use the diode/continuity setting on the meter as opposed to actually reading resistance.

The point I tried to make is my second and third sentences.

Also, hopefully the 4th sentence registered, more for the person that commented about measuring the damaged transistor, a waste of time.

Greg
 
I replaced the transistor in the RC motorblock and it had the same problem. so the original transistor was good. ......

But I discovered why the voltages were wrong at the transistor. There was an open circuit I had not noticed before, so I added a jumper to fix the open ( I know the wire is a bit large for the job, but it's what I had available. And perhaps only one connection needed resoldering instead of a jumper):
jumper.JPG

The jumper returned the transistor voltages back to normal. Now the remote control works. And the ESC works, but it will only drive in reverse. I can easily make it drive forwards (without reverse) instead by changing which wires attach to the motor. But Now I need to figure out why forward is not working. Time to re-check everything.
 
Greg Elmassian said:
Are you telling us that the board in post #9 is the same board as in post #18.... sure looks like a different board...

whatever caused the burned/open trace could have wiped out the reverse transistors/part of an H bridge.

Greg
Click to expand...
Thanks for the suggestion Greg.

It's the same motorblock as in post #1 and #9 but the motorblock has 2 boards sort of sandwiched together and connected to each other in multiple places. Both boards are green on the outer sides and brown on the inner sides. In post # 18 you can see the bottom of the other board from post #1&#9 underneath with the brown color from it's underside and the yellow antenna wire attached to it. One of the connections between the two boards is where I added the jumper. I'm not convinced it was a burnt trace. I think it might have been a cold solder joint, and adding the jumper merely reflowed it with the additional heat when I added more solder there for the jumper. The copper battery connectors look pristine as if the train was never used, and I think I found another cold solder joint causing an open elsewhere which I also fixed. I think I went through all of the connections and couldn't find any other similar continuity problems with the solder joints. There may be another anomaly. At the blue arrow in the following image, this component does not match the component at the same location in my identical working motorblock:
jumper.JPG

Since there seemed to be at least a couple of cold solder joints, and battery connectors which look like they were never used, I wonder if this motorblock was defective from the factory. If that's the case, then I wouldn't be surprised if the wrong(but somewhat similar looking) component was used by mistake at the blue arrow. The working motorblock has a teal component at the location of the blue arrow, much like the teal component directly beneath the orange arrow( peeking out above the other green component). Both motorblocks have the similar looking teal and green components, but the defective one has one fewer teal component, and one extra green component in it's place.

I feel like I'm at a stand still in the troubleshooting since I don't now what those components are. But now that I've restored RC control for variable speed in at least one direction, I might just add a manual toggle switch to the loco to allow the RC control for forward or reverse at the flip of the switch. I already have the toggle switch and know how to wire it. I just need to find a good place to mount the switch.... I was thinking it could be inside the cabin or chimney to hide it.

Edit: I'll try to look into the H bridge a bit since your suggestion makes a lot of sense. There are 4 decent sized transistors there on the other side of the board in the middle of the sandwich(you can see the 3 leads of each of the 4 transistors just above where the red wire connects to the board). The desired voltage doesn't show up somewhere around there with forward control. I wouldn't be surprised if they mixed up one of the NPN or PNP transistors there.
 
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