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Built, but not working

Knob_ProblemKnob_Problem
edited July 2014 in Troubleshooting
I've emailed Julian, who is being very helpful, but I'll post here in case anyone can help.
Here are the pertinent details:
-Machine does not appear to power on, and the LCD remains black (I attached it after these photos were taken)
-The unit is receiving voltage at the points marked +5v and GND next to the ATMEGA, and on the voice board
-LEDs are functional, and "run" when pins PD4 and PD% are bridged (or something in that vicinity--effect discovered by accident)
-22pf capacitor replaced with one of equivalent value at C6, also due to butterfingers
-I attempted to update the firmware but since the unit doesn't power on, nothing seems to have happened
-The unit is not recognized by a host over USB
-The power supply is a bit strong; we read 8v across P1 instead of 3.3v

The photos show some uncut LED legs; those are all trimmed off now.  It also shows some resistor networks connected backwards; those are now fixed.  All of these continuities ring good
  • pin 11 of each 595 IC should be connected to pin 19 of the AVR
  • pin 12 of each 595 IC should be connected to pin 18 of the AVR
  • pin 14 of U3 should be connected to pin 20 of the AVR (DOUT_DATA)
  • pin 9 of U3 is connected to pin 14 of U7
  • pin 9 of U7 is connected to pin 14 of U9
  • pin 9 of U9 is connected to pin 14 of U13
  • pin 9 of U13 is connected to pin 14 of U11

Any help is much appreciated!

Comments

  • julianjulian
    so you read 8V between the 3.3V and GND pin on P1?!
    Thats not good at all. I would advise to remove the mainboard temporary until the UI is working to reduce the risk of frying the mainboard if there is a short somewhere (menues and LEDs will work without the mainboard)

    could you make sure that there is no short between the pins 18,19 and 20 of the AVR (and their neighbour pins)
  • Knob_ProblemKnob_Problem
    Oops -- we tested across the 5v in to ground, not the 3.3v out and ground. I'm afraid to plug the main board back in to do that test.
    We do have continuity between those pins on the AVR, although the solder joints are clean there.  Is that a fault of the AVR or ???  

    Thanks
  • julianjulian
    aha... seems we are getting closer ;)
    which pins exactly have continuity to each other on the AVR?
  • Knob_ProblemKnob_Problem
    That's a bit tricky -- 40 down 2 is a big number of combinations.  We get about 7k ohms on 18,19, 20 (upper right in my image -- I'm not sure what the correct numbering is!) and the same on each of these to most every other pin.  Except pin 1 (upper left in my image), which seems connected to all other pins (0 resistance) and pin 30, which has about 500 ohms and pin 29 which has about 3000 ohms.  Do these seem strange?  What should we be reading?  Sorry to be so dense about all this!

    thanks again
  • julianjulian
    edited July 2014
    the numbering for the pins is like this
    image

    so pin 18,19 and 20 are in the lower right.
    You don't have to measure ALL pins on the IC.
    just check for continuity between 17+18, 18+19, 19 + 20.
    the others have nothing to do with the LEDs.

    If you measure a few hundred ohms or more you don't have a short. that is normal.
  • julianjulian
    do you have a multimeter that has a 'beep' mode to measure continuity? much easier than using the resistance measure method (multimeter makes a beep if the 2 probes touch each other)
  • julianjulian
    are you sure the 22pF replacement has the right value? if not the AVR won't run as this generates the clock frequency. what is written on it? I can't read it in the picture.
  • julianjulian
    also check the soldering on all the 595 ICs.
    I just had another customer with the same problem who found some pins he forgot to solder.
    maybe re-solder them (just touch them with the iron so the solder melts to reflow the joint). could be a cold solder joint
  • Knob_ProblemKnob_Problem
    1) We only have a non-ringing meter; the pins 17-20 don't have <500 ohms.
    2) The cap says "222".  Also, we reversed it in case it was polarized, but saw no difference.
    3) The power is still reading very hot (9v) across the 5v; without the mainboard attached we're having trouble reading across the 3.3v out to ground.  Should we plug it back in?
    4) We tried reflowing the 595 joints.  No difference in performance.


    The LEDs do light when 18, 19 & 20 are jumpered.  I don't know if that means anything.

    thanks!
  • cj55cj55
    A cap wich is labeld 222 means 2200 pF. That can not work.
  • Knob_ProblemKnob_Problem
    <blush>  oops.  
    We will dig up the right part and install it...

  • Knob_ProblemKnob_Problem
    Problem resolved.  Thanks for all the help; the world is filled with robot fart noises :-)
  • julianjulian
    :) glad it works now!
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