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1. Do you have a closer picture? (you can try putting it under a microscope, then putting your digital camera up the eyepiece; works in a pinch)
2. Do you have a circuit schematic?
3. Can you pull it out of the circuit and check it's resistance with an ohmmeter/multimeter?
4. What kind of system is this used in, and what circuit is it located in?
1. Do you have a closer picture? (you can try putting it under a microscope, then putting your digital camera up the eyepiece; works in a pinch)
2. Do you have a circuit schematic?
3. Can you pull it out of the circuit and check it's resistance with an ohmmeter/multimeter?
4. What kind of system is this used in, and what circuit is it located in?
On the schematics i cannot find it. It is a car diagnostics multiplexer the analogue side. on board when i measured it it was 205 Ohms.Schematics attached.
I have looked thoroughly but no use.
Probing the device in-circuit will give you messed up results, because you are also measuring all of the circuits it's connected to, in parallel with it. If it's a capacitor, it could read 10 ohms, when it should really read open-circuit. To do it correctly, you'll have to pop it off the board (if you are handy with a soldering iron).
What is the reference designator of the 3-pin SOT-223 device in the box you drew (U1, Q7, L3, C2, etc)? And, can you find the RefDes of the capacitor beside it? I have no clue where to begin to look on the schematics without some point of reference. If you can find the SOT-223 part on the schematic, the cap and unknown part should be connected to pin 3 (the small pins, from left-to-right are 1, 2, and 3... the big tab is pin 4).
I have found it on the schematics. On the relay PDF called VT2 on the second page type ON Semiconductor BCP 56. And the part must be the resistor with the value 180E. What the hell is 180E?Does it makes sense?
I think you may have a bad part, if that is indeed a 180 ohm resistor. If you put a resistor in parallel with any other circuit (like being wired to a bunch of stuff on a PCB), you should always measure some resistance less than or equal to the nominal R value (in a non-energized, passive circuit).
Example:
1. Start with a 180 ohm resistor all by itself, a multimeter will read 180 ohms (+/- the tolerance of the part, but we'll disregard that for this exercise).
2. Add a large (but not infinite, like "circuit" 1) resistance in parallel with the 180. Say, 100K.... then then 180 will look like (180*100k)/(180+100k) = 179.68 ohms
3. Add a smaller resistance in parallel with the 180, say 1000 ohms. Now the 180 looks like (180*1000)/(180+1000) = 152.54 ohms
Case in point, if you have any additional conduction path in parallel with a known value resistor, then the measured resistance should always be less than the original resistor's value. Note: this works when your circuit is unpowered... if you have power applied and active circuits, then all bets are off.
Long story short, I think your resistor may be dead. 1) you said it ohm'ed out to 205 ohms, and 2) the traces near it look dark, like something got overheated and started to burn the nearby soldermask.
I'd still remove the part from the board and ohm it while not in-circuit.
Done, mesures infinite. Means dead. When i removed it carefully tha side contact come off and i can see 3 little wire ends in the package under the microscope. I have see the burn marks and measuring contacts no damage to leads.How can i overpaint the burned off lacquer to make proper insulation before placing new on?
Done, mesures infinite. Means dead. When i removed it carefully tha side contact come off and i can see 3 little wire ends in the package under the microscope. I have see the burn marks and measuring contacts no damage to leads.How can i overpaint the burned off lacquer to make proper insulation before placing new on?
Does the trace going under the part connect to one of the pads for that resistor? If so, I wouldn't worry about covering it back up. If you are careful with your placement, and don't overload the pads with solder, you shouldn't run a risk of shorting the trace to one of the pads.
If the circuits are separate, I'd check the resistance between each solder pad and the trace under the part before and after, to make sure you don't create a short after you solder the new part down. On prototype boards we made in college, we'd use PCBs that were just etched copper, no silkscreen. As long as you made the pads the right size, and set the part on the pads, you would avoid shorting out to the signal running under the part. Instances like this is why running traces under parts in other circuits is highly frowned upon in my industry... for reasons like this, I understand why they have the rule.
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