Need help identifying value of this bad SMD cap.

[budm]

Re: Need help identifying value of this bad SMD cap.

"Does that mean the transistor provides a ground connection to the load? I'm specifically asking about the "load sinks current into the NPN transistor" statement."Yes. Sink mean the one end of the load is connected to the VCC, the other end is connected to one end of the switch (Transistor, Relay contacts or MOSFET), the other end of the switch is connected to GND to complete the current flow, this can also be called LOW side switching.
The other way to supply the current to the load is to Source the current (or HIGH side switching), the VCC is connected to the switch (Transistor, MOSFET, Relay contacts), the output side of the switch is connected to the load, the other end of the load is then connected to GND to complete the circuit.

http://electronics.stackexchange.com...high-side-load

http://www.eetimes.com/document.asp?doc_id=1272366

http://www.infineon.com/cms/en/produ...3dfda067250219

[Spork Schivago]

Re: Need help identifying value of this bad SMD cap.

From the last article you linked to, when they say:
"Here, the control signal will turn power on and off to the load. Note that the load sinks current into the NPN transistor when it's made to act as a switch."

Does that mean the transistor provides a ground connection to the load? I'm specifically asking about the "load sinks current into the NPN transistor" statement.

[stj]

Re: Need help identifying value of this bad SMD cap.

what chip is in this mouse?
there is probably an example schematic in the datasheets.

[Spork Schivago]

Re: Need help identifying value of this bad SMD cap.

Thank you Budm! I will give it a shot and see what happens. I will also read the links you have posted once I'm done.

[budm]

Re: Need help identifying value of this bad SMD cap.

Yup, that's mine.

The collector goes to the positive terminal (anode) of the LED. It goes through a diode and possibly a few other things. I think I know what this transistor does. I think it's what makes the LED blink when you move the LED. With the mouse, if you flip it upside down, the LED flashes. It doesn't do that now that the cap is missing.

The NPN Q5 is connected as Common Emitter, so when it is turned on it should sink the LED current to GND to turn on the LED, so the Cathode (-) of the LED should be connected to the Collector, the Anode (+) should be connected to current limiter resistor and then to the Boosted B+ (Probably around 4VDC) or so. The LED should not be always on to save the battery power, there must be some thing that detect the movement of the mouse to turn on the LED. At this point you can try using cap from .01~.047uF in place of the broken cap to see what will happen.

http://www.eecs.tufts.edu/~dsculley/...nsistors1.html

[Spork Schivago]

Re: Need help identifying value of this bad SMD cap.

Yup, that's mine.

The collector goes to the positive terminal (anode) of the LED. It goes through a diode and possibly a few other things. I think I know what this transistor does. I think it's what makes the LED blink when you move the LED. With the mouse, if you flip it upside down, the LED flashes. It doesn't do that now that the cap is missing.

[shortchange]

Re: Need help identifying value of this bad SMD cap.

http://img0051o.psstatic.com/1026616...interface-.jpg

[Spork Schivago]

Re: Need help identifying value of this bad SMD cap.

Okay Budm, I get new results.

When the Blue LED is on, the collector measures 1.45VDC. When I switch it off and measure the collector, I get 0.45VDC but it's counting down. After a few minutes, it reads 0. However, if I switch on the mouse and the blue LED does not light up and then I turn off the mouse, the collector measures 0.004VDC.

[budm]

Re: Need help identifying value of this bad SMD cap.

'I should test the collector with reference to GND when the LED is on and off?' Yes.
As you can see the measured Vbe are < 0.72V, if it is bias on then you should see 0.6~0.7VDC range.

[Spork Schivago]

Re: Need help identifying value of this bad SMD cap.

It's definitely a NPN silicon transistor. Current Gain Hfe = 345, Test Current Ic = 2.50mA, Base-Emitter Voltage Vbe = 0.72v, Test Current Ib = 4.68mA, Leakage Current Ic = 0.00mA. Does any of this information help at all or no?

Once I resolder Q5 back to the board, I should test the collector with reference to GND when the LED is on and off? Like black probe on the negative terminal of the battery, red probe on the collector.

[budm]

Re: Need help identifying value of this bad SMD cap.



https://www.ibiblio.org/kuphaldt/ele...mi/SEMI_4.html

The thing is that you should look at DCV of Q5 D (C) with ref to GND to see what you get when the LED is on and when LED is off, you should see the Voltage on the D (C) change state, right now e do no know what Q5 and Q6 are used for in the circuit. Unless you have another working mouse to do comparison readings, then it will be time consuming to troubleshoot the circuit.

[Spork Schivago]

Re: Need help identifying value of this bad SMD cap.

So when the Blue LED lights up the E-B junction is not being bias ON then per your reading with ref to Negative of the battery/GND plane. So the Collector Voltage rises (Transistor is OFF) to the 1.5V (battery Voltage)
Q5

Post 32: However, when the blue LED is light up, I get:
D (C): 1.55VDC
G (B): 0.146VDC
S (E): 0.007VDC

Q6
D (C): 1.55VDC
G (B): 0.19VDC
S (E): 0.006VDC

I don't understand what you mean when you say it's not being biased ON. It's because I don't fully understand transistors and a few other things yet I believe. I can pull Q5 and use my DCA meter to see what it says if you want. Might make things a bit easier. It's pretty good at identifying unknown components.

[budm]

Re: Need help identifying value of this bad SMD cap.

This mouse does use just 1 double A battery. It's a Microsoft Mobile 6000 Mouse or something like that. The GND plane does appear to be directly connected to the negative side of the battery. When I made the measurements, I had the black probe on the negative side of the battery (unless I clearly stated otherwise).

So when the Blue LED lights up the E-B junction is not being bias ON then per your reading with ref to Negative of the battery/GND plane. So the Collector Voltage rises (Transistor is OFF) to the 1.5V (battery Voltage)
Q5

Post 32: However, when the blue LED is light up, I get:
D (C): 1.55VDC
G (B): 0.146VDC
S (E): 0.007VDC

Q6
D (C): 1.55VDC
G (B): 0.19VDC
S (E): 0.006VDC

[Spork Schivago]

Re: Need help identifying value of this bad SMD cap.

This mouse does use just 1 double A battery. It's a Microsoft Mobile 6000 Mouse or something like that. The GND plane does appear to be directly connected to the negative side of the battery. When I made the measurements, I had the black probe on the negative side of the battery (unless I clearly stated otherwise).

[budm]

Re: Need help identifying value of this bad SMD cap.

Q5 S (E) is connected to GND plane, so you should check and see if the GND plane is connected directly to the Negative of the batteries or not, then your reading may make sense.
Does this mouse use just one AA battery? my 3500 uses just one AA to run so I am sure it has dc Voltage booster circuit to run the Blue LED.

[keeney123]

Re: Need help identifying value of this bad SMD cap.

What ever it is it does not appear to have the conditions to turning on at least not DC wise. With common base a transistor need 0.7 volts to turn on base to emitter. With the FET the gate voltage/current would turn on the FET that would be conditional on the design and could be a switching condition that may not be able to be measured in a DC mode. So BudM what do you think?

[Spork Schivago]

Re: Need help identifying value of this bad SMD cap.

1.55VDC seem to go into D (C) on both Q5 and Q6. Don't seem to get any readings coming out of either really, when the LED isn't lit up. On Q5, G (B) reads 0V, Q6, G (B) reads something like 0.005VDC or 0.006VDC. However, when the blue LED is light up, I get:

Q5
D (C): 1.55VDC
G (B): 0.146VDC
S (E): 0.007VDC

Q6
D (C): 1.55VDC
G (B): 0.19VDC
S (E): 0.006VDC


When I put the black probe on D (C) instead of on the battery's negative terminal, I get these readings:
D (C) - S (E): -1.474VDC
D (C) - G (B): -1.303VDC
G (B) - S (E): -0.141VDC

I get the same values but positive if I switch the probes around. Red probe on D (C), black probe on S (E), +1.474VDC, etc. Does this mean it's a MOSFET and not a transistor or do these measurements imply it's a PNP transistor?

[Spork Schivago]

Re: Need help identifying value of this bad SMD cap.

If it is MOSFET, then you will read Body Diode between Source and Drain pin.
BTW, did you do any DCV checking on all 3 pins to see what you get? or in other sections also.

When the battery was plugged in and the blue LED lit up, we measured voltages to see if places where getting them. I can't remember what the voltages where but I'd be more than willing to try it again. When we try to turn it on, most of the times the blue LED doesn't light up. But if we switch the on / off switch a bunch of times, sometimes the LED light will light up and stay lit. When it's not lit up at all, I want to say there wasn't much voltage on anything. When it was lit up, we did get a bunch of voltage readings. I'll try to take some measurements now for Q5 and Q6.

[Spork Schivago]

Re: Need help identifying value of this bad SMD cap.

So is this a transistor with a NPN or PNP or is is a FET with S,D,G? it would seem to be a NPN but are you measuring in circuit because the Collector to emitter should be open either way.

I'm measuring in circuit but with the busted cap (completely removed now), wouldn't it be equivalent to measuring out of circuit because now one of the pins aren't hooked to anything, just a pad that goes nowhere?

I'm not sure how to tell if it's a transistor or a FET. Perhaps that's what Budm was trying to figure out by having me measuring the various pins? The chip itself has the letters VB with a sideways P on it. We found this site:
http://www.s-manuals.com/smd/vb

The only ones it would fit on that site is a zener diode. I highly doubt that site has every SMD component markings on it though. The collector to emitter is not open either way I measure it, if it is a transistor. There's another one on the board though (Q6), same markings and it has a resistor and capacitor hooked in parallel as well.

I was wondering if I could use that one as a test reference. Do the same Diode test and see how the numbers compare and possibly even pull the cap and measure it's value to find a correct replacement for the bad cap. If I pull the resistor that's hooked up to Q6 and it's the same value of the resistor hooked to Q5, wouldn't it make sense that the capacitor on Q6 would be the same value as the bad cap that was hooked up to Q5?

[budm]

Re: Need help identifying value of this bad SMD cap.

If it is MOSFET, then you will read Body Diode between Source and Drain pin.
BTW, did you do any DCV checking on all 3 pins to see what you get? or in other sections also.