power issue

[kevinr]

I'm having an issue during the power-up test 1 for the scope. I get 5v at "+5v" with JP4 open, but when I close JP4, the "+5v" test point voltage shows constantly changing erratic voltages. I'm using USB power.

To troubleshoot, I removed all BOBs except BOB4 and BOB5. I've confirmed that BOB5 output is -5v. Here is the strange thing: if I remove L1 inductor, apply power (via USB), then reinstall L1 and press "reset", it seems to boot up fine (I get 1 flash of the LED, then 2 more) and all test points have the correct voltage. But only if I power up without L1 first, then connect it.

I've resoldered everything and checked for solder bridges and don't see any issues. Any suggestions for further troubleshooting?

[totem12]

Kevin, have you resolved your problem?.... I have a similar problem but I am not sure that I have a good bob 5. will be disconnecting inductor no. 1 ( as you did) and see if I get a similar response.
thanks, Norden N7SOC

[jye1]

AV- could be drag low if there is short or partial short between AV- and GND. AV- powers U1 and U2 so check these chips and associated caps. Do you have C27 and C28 in correct polarity?