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BS2 OEM with a bad 'Reset Monitor'. What is a good test procedure to find this — Parallax Forums

BS2 OEM with a bad 'Reset Monitor'. What is a good test procedure to find this

Russ FergusonRuss Ferguson Posts: 206
edited 2005-09-01 14:28 in BASIC Stamp
I have parts for several BS2OEM boards and after assembling one I could not get it to work. The 16C57 and the 24LC16 tested ok on another BS2OEM board. While the chips were off I measured the voltage out of the regulator and it was fine. I swapped out the resonator. I tested the transistors with an in-circuit tester and they appeared fine. That only left the MN13811 to swap out. It worked after replacing the MN13811.

Does·anyone·know of·a BS2OEM trouble shooting short cut·which would·identify·a problem·with the MN13811? It took me to long to find the problem this time and I'm hoping that one of you already know how to easily check this.

Thanks
Russ

Comments

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-08-28 04:30
    Russ,

    ·· What were your voltage readings on the RESET line in relation to Vss before the replacement?· My guess is that would be your hint.· The RESET line not being at 5V would be a good indication, but not necessarily the answer.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Russ FergusonRuss Ferguson Posts: 206
    edited 2005-08-29 02:53
    Chris:

    I did not think to measure the voltage on the pin. Could have done it when I looked at the voltage on the Vdd pin, but did not. I will put the bad one on a board and have a look.
  • Philip GamblinPhilip Gamblin Posts: 202
    edited 2005-08-30 05:25
    I both admire and thank you for your effort and for posting. I'm sure that would have been the last component I'd have checked. I have·a few of those myself and that issue is now forever etched in my brain. Again thanks for posting.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-08-30 14:21
    Russ,

    ·· I admire your tenacity.· There aren't many people (Myself included) these days who would be willing to put a bad component back into their device just to narrow down troubelshooting procedures.· =)

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Russ FergusonRuss Ferguson Posts: 206
    edited 2005-09-01 05:15
    Thank you Chris and Philip·for the encouraging words and ideas.

    I had another board that was partially assembled which I put the bad 13811 onto. The voltage on the 'RES' pin was 0.2v, while the voltage on the 'VDD' pin was 5v (both voltages are referenced from the 'VSS' pin. Also note the micro and memory chips were not in the sockets when this was test was performed.

    After replacing the 13811 with a good one, the voltage on the 'RES' pin was 4.9v.

    Some OHM readings on of the 13811 are given in the attached drawing.

    Don't know whether static or heat got to the bad 13811, but my quess is that it was static. Let me know if you have a better idea.

    Sid (NEWZED) gave me another thing to watch for - he said that he has had the resonators fail after being soldered in. Don't know if there is a way to isolate that problem when·the resonator·is on the board. I have not had a bad·resonator (have about 25·BS2OEM's for home school enrichment classes).
    bmp
    bmp
    13811.bmp
    397K
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-09-01 14:28
    Russ,

    ·· I guess you see what I was getting at there?· The RESET line is the clue here.· The 13811 is connected directly to it.· So it's one of·4 possibilities if the RESET line does not read close to +5V.· Is this a new part directly from us (13811)?· If so, drop me an e-mail.


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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
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