Need help identifying value of this bad SMD cap.

[Spork Schivago]

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

I do believe it's connected to R29 in parallel. It was hard to see with the broken piece there, but I carefully used an exacto knife to move part of the broken piece out of a way and I see two traces going from the resistor and the cap. One trace at each line, like this:

----  ----
| |---| |
|C |  |R |
| |---| |
----  ----

It's hard to see where it goes once it goes through the via to the other side. There's some sort of metal oval can on the other side, I think it's a crystal for timing. The trace seems to go under that piece. I can remove it if you need me to and take a closer look there on the back side. The crystal type thing says on it: CMT-LLAZ(or 7)I(or1)C
On the board next to it, it says Y2. There's another one on the board as well. I believe the Y reference designator generally refers to a crystal or oscillator.

[budm]

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

Thank you Budm! So what does a bypass cap do? What's the point of putting one between Base and GND? Thanks!

OK, I look at the trace at the right side of the cap, it is not connected to the Ground plane but to that round pad which go to the other side of the board, so it can be a coupling cap, you need to see where it goes to.
BTW, is it also connected in parallel with R29?

[Spork Schivago]

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

It looks to be just a small bypass cap between Base and GND, so it can be from .01~.047uF I would guess.

Thank you Budm! So what does a bypass cap do? What's the point of putting one between Base and GND? Thanks!

[budm]

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

It looks to be just a small bypass cap between Base and GND, so it can be from .01~.047uF I would guess.

[Spork Schivago]

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

The other transistor looking SMD component with the same markings, VB sideways P has a resistor that in-circuit measures around 800 ohm. I can't measure the cap because I don't have needle probes for my ESR meter and my DMM says OL when I try measuring it in circuit. The Q5 transistor looking SMD components resistor measures around 400 ohm in circuit. Could these readings be different because I'm measuring in-circuit? If both of the transistor looking components really do use the same resistors and caps, maybe I could pull the good SMD cap and try measuring with my ESR meter out of circuit using those dang alligator clips to find the correct value.

[Spork Schivago]

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

I wonder if the transistor looking component, Q5, is actually a zener diode. It says VB and has a sideways P on it. Could it be a BZB84-B3V0 SMD zener diode? We found another one on the board that appears to have an SMD resistor and an SMD cap on it. Perhaps I could try pulling the cap on that one and checking the value. They're probably the same value, right?

[Spork Schivago]

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

Forgot to say, in the picture, the cap I'm talking about is the tanish / yellow / brownish one that is physically broken in two. Thanks.

[Spork Schivago]

Hello,

We have a broken Microsoft Mobile Wireless Mouse 6000. We have found at least one issue with it, a broken SMD cap. There might be more. I can't seem to find a schematic for this mouse and was hoping someone could help me identify a correct replacement. The board lists it as C38. Here's a picture. Any idea how I can identify what the original value was? Thanks!