Need help identifying value of this bad SMD cap.

[keeney123]

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

Looks like someone needs a new meter for Christmas.

[Spork Schivago]

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

Omg, there is away! I'm so stupid. For some reason, I was thinking a transistor testing feature. I've own this thing since middle school or early high school (back in the 90's). I was looking at the dial for Ohms and it shows the Ohm symbol, a diode symbol and an auditory bell symbol. When it's switched to Ohm, if I hit the DC / AC button, it switches from resistance mode to diode mode to auditory resistance mode! I am such an idiot!

So how do I understand the results? I put it in Diode test mode and measure
Black on D (C) to Red on G (B) = 0.617 V
Black on D (C) to Red on S (E) = 0.716 V
Black on G (B) to Red on S (E) = Overload

Red on D (C) to Black on S (E) = 0.624V
Red on D (C) to Black on G (B) = Overload
Red on G (B) to Black on S (E) = 0.617V

I'm pretty sure I know what ruined the capacitor there. It was a terrible thing but I had a headache real bad (I'm on medication now for them which is helping) and some website wasn't working correctly and I accidently picked up the mouse and hit it really hard on the table out of anger. I should of never of done that but I don't think something broke and shorted out the capacitor or anything. I think it was me hitting it hard on the table because right after that, it stopped working. I appreciate the help guys.

[Spork Schivago]

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

too bad i cant make out the writing in those foto's
i refuse to believe that a meter with true-rms and a serial interface is lacking a diode test.

I was going to post clear pictures to show you! If you didn't say that, I probably would of never looked at the Ohm dial and would of never of saw the Diode symbol! I'm such a freaking idiot! Thanks!

[stj]

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

diode test shows voltdrop.
one way should show nothing, the other way is usually 400-600mv for a regular diode or 100-200mv for a schottky

[Spork Schivago]

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

So black on D (C) (the collector) to red on S (E) (the emitter) equals 0.624V but should actually say Overload, among a few other pins, right? Does that mean it's not a transistor or does that mean the transistor is bad as well as the cap?

[stj]

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

overoad?????

[Spork Schivago]

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

overoad?????

Yeah, overload. On my multimeter, it just means the reading was too high for my multimeter to read. For example, if there's infinite resistance, it'll show a message OL because the resistance is too high for the multimeter to read. If I have just one probe hooked to a resistor and the other probe floating in the air, I'll get an OL. Or if there's a cut in the trace and I'm trying to measure the continuity on opposites sides of the cut, I'll get an OL.

[keeney123]

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.

[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.

[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?

[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.

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?

[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?

[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.

[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.

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.

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.



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.

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.

'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.