Dangerous Prototypes Open Source Hardware

getting 3.3V out of 5V vreg (v2go, firmware v2.2)

September 23, 2009, 06:14:51 am

Analog pin and pwr supply
5V(3.3) FAIL
VPU(3.3) FAIL
3.3V(2.2) OK
ADC(2.2) OK

Should I be worried about this?

Re: getting 3.3V out of 5V vreg (v2go, firmware v2.2)

Reply #1 – September 23, 2009, 08:00:07 am

That looks like a problem, but maybe your USB supply is very low (?) - you could measure the voltage at L1.

Do you notice any shorts around VR3/4, C22/24, R18, or R10-16?

Re: getting 3.3V out of 5V vreg (v2go, firmware v2.2)

Reply #2 – September 27, 2009, 07:31:36 pm

Argh.  I just got around to looking at it again.  I've got shorts at R10/R11, R12/R13, R14/R15, and R16/R17.  I confirmed this with a multimeter.  There was a lot of unhappy continuity beeping.  I'm not very experienced with surface mount soldering, but I have done it before.  Should I go ahead and try to fix the shorts myself or would you advise that I send it back?

Re: getting 3.3V out of 5V vreg (v2go, firmware v2.2)

Reply #3 – September 27, 2009, 07:42:34 pm

Nevermind. I didn't look closely at the schematic there. I understand that those are all intentionally connected.  Now I have to figure out what the problem really is.  My L1 voltage is at 5V, so that is not the problem.

Re: getting 3.3V out of 5V vreg (v2go, firmware v2.2)

Reply #4 – October 01, 2009, 01:05:42 pm

silly question time.

have you measured the outputs with a MM, it looks to me like you have just used the internal selftest.

It is allways possible the selftest is faulty.

but as i said it could just be a silly question.