Shop OBEX P1 Docs P2 Docs Learn Events
Fried another SX key — Parallax Forums

Fried another SX key

ElectronegativityElectronegativity Posts: 311
edited 2006-04-04 04:17 in General Discussion
Ugh, burned $80 in as many microseconds last night.

The odd thing was that it was working fine until I tried to debug.
There is no external oscillator on the board, but the SX28 was generating a pulse of ~ 1MHz.
Maybe there is a short between the output pin of the SX and OSC1.

The fried component is a small rectangular chip that is centered between the SX, the copper coil, and a surface-mount capacitor. It glowed bright yellow and burned the plastic sheath.

What is that?
Any chance I might be able to replace it?

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
I wonder if this wire is hot...

Comments

  • Jon WilliamsJon Williams Posts: 6,491
    edited 2006-03-27 16:54
    You'll need to send it to us for evaluation. Sorry for the trouble, but that's best at this point.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Jon Williams
    Applications Engineer, Parallax
  • ElectronegativityElectronegativity Posts: 311
    edited 2006-03-27 17:02
    Hi Jon.

    I was just going to write it off as a loss and pluck what usable components I can from it, but if you think it might be repairable for less than the cost of a new one then I will mail it off.

    Is there any special proceedure for this?

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    I wonder if this wire is hot...
  • Bill FrankeBill Franke Posts: 20
    edited 2006-03-29 00:42
    How many pins does this part have? Six or three?

    Bill
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2006-03-29 02:42
    Don't take any chances -- call Tech Support (888-99-STAMP) for an RMA and send it in. You don't want take any more chances.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Jon Williams
    Applications Engineer, Parallax
  • ElectronegativityElectronegativity Posts: 311
    edited 2006-03-30 17:02
    Hi Bill, there are 3 pins and the number 489.

    Jon:
    Thanks for the advice, but there are no more chances to take.
    This puppy is deader than disco and any conceivable warrantee was voided when I plugged it into the godawful disaster I call a project.

    Right now I am most interested in figuring out what happened so I don't burn another one the same way.
    If I can repair it myself I will, and if not then I will salvage what parts I can from it.

    Thanks again,
    -Alexander

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    I wonder if this wire is hot...
  • Bill FrankeBill Franke Posts: 20
    edited 2006-03-31 03:03
    Alexander,

    I did a some searching and found your part. It looks like it is a FMMT489 medium power transistor made by Zetex. Digikey sells these for 41 cents. You know, Jon is right, don’t mess with it unless your sure they won’t cover it under warranty. If your “mistake” was caused by high voltage, it is very probable that it took out another part. If it was caused by high current, such as a dead short somewhere, it might very well be just this transistor that is bad. I haven’t drawn out the circuit, so it’s a guess on my part (but only a guess) that this transistor is the final driver for the programming voltage since it is a power transistor. Anyway consider this before you pay Digikey’s $25 minimum charge.

    Bill
  • Paul BakerPaul Baker Posts: 6,351
    edited 2006-03-31 13:48
    Actually its a $5 handing fee for orders under $25. I know, I have to pay it everytime I forget to include a part from a BOM.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Current Muppet Terror Level:

    ·· ·terror.php
  • ElectronegativityElectronegativity Posts: 311
    edited 2006-03-31 16:17
    Thanks Bill, it was really nice of you to look that up for me.

    I'm sure there's at least $25 worth of stuff that I want from Digikey... smilewinkgrin.gif

    I am going to try to fix it myself even though it would make more sense to send it to Parallax.
    If I get it working again I will report back.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    I wonder if this wire is hot...
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2006-03-31 17:19
    Thanks for giving us the opportunity to charge you more for the repair later! tongue.gif

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Jon Williams
    Applications Engineer, Parallax
  • ElectronegativityElectronegativity Posts: 311
    edited 2006-03-31 17:23
    You're welcome.

    I just bought another SX key.
    Hopefully for you I will destroy that one as well.


    (Picture of me at my electronics workbench) ----> jumpin.gif

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    I wonder if this wire is hot...
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2006-03-31 18:52
    Actually, we'd really rather you be successful with it so you can order lots of SX chips -- far more fun for both sides!

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Jon Williams
    Applications Engineer, Parallax
  • John R.John R. Posts: 1,376
    edited 2006-03-31 20:50
    Given the reputation that Parallax has for a high level of support, I just can't fathom why someone wouldn't at least send in a device when specifically invited. In addition to getting the device repaired (and having a spare in addition to the extra you purchased), you might even get some useful feedback into the types of things that might have done the damage.

    Given the propencity for going overboard on support and customer satisfaction, you never know what you might gain. I could maybe understand the reluctance if you were talking overseas shipping or customs issues. Also realize that the probably worse case scenario is that they say "this will cost $50.00 to fix, do you want us to do that or not?". Best case is getting a repaired or new key back with no charge.

    How, and why, do you not do this (get the RMA and send it in), especially when specifically asked?????

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    John R.

    8 + 8 = 10
  • ElectronegativityElectronegativity Posts: 311
    edited 2006-03-31 21:13
    Hi John.

    Yes, from a purely economic standpoint it would make sense for me to send it in for repairs.

    But there is more to life than bread!

    I like to try and do things myself, otherwise I would purchase consumer electronic devices instead of manufacturing them in my basement.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    I wonder if this wire is hot...
  • John R.John R. Posts: 1,376
    edited 2006-03-31 21:42
    Electronegativity said...

    Right now I am most interested in figuring out what happened so I don't burn another one the same way.
    Chiphead said...


    In addition to getting the device repaired (and having a spare in addition to the extra you purchased), you might even get some useful feedback into the types of things that might have done the damage.
    Hmmmmmmm

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    John R.

    8 + 8 = 10
  • PJMontyPJMonty Posts: 983
    edited 2006-04-04 04:17
    Electronegativity,

    This is only vaguely related to this thread, but everytime I read this thread (due to new posts), I see your initial message at the top that starts with:

    Ugh, burned $80 in as many microseconds last night.

    For some reason, everytime I read it, I have to do so twice because the first time I always see this:

    Ugh, burned hex 80 in as many microseconds last night.

    And when I do, I'm always baffled what you mean about burning the hex value of 80, until I realize that your dollar sign actually means dollars and does not signify hex values. Too much time spent with embedded programming, I guess.

      Thanks, PeterM
Sign In or Register to comment.