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cowdog360

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Posts posted by cowdog360

  1. Interesting, I like the crowbar diode across C41. Will have to expriment with that one. And yes, Q11/12 is pretty critical. Looks like the older one I was sugesting is gone now. I've starting using AOD514's
    https://www.digikey.com/product-detail/en/alpha-omega-semiconductor-inc/AOD514/785-1357-1-ND/3060919

    The nice thing about this MOSFET is that the RDS(on) is lower, and the on resistance is much lower (about 46X!), meaning less heat, lower battery usage, more efficient!

  2. I just ordered some from Mouser. In order to get free shipping I had to order some extras. I need 4 sets for myself and 6 are up for sale.

     

    There seems to be BZX79C4V3 zener available with 5mA 4.3V.

     

    The MOSFET's were more expensive 757-TK2P60DTE16L1NQ.

     

    I also ordered enough caps for either Lynx I or Lynx II.

     

    With VAT the cost of a caps kit + zener + MOSFET is €7. Shipping envelope + stamp is €3. Total is €10.

     

    Drop me a line if you want some. Supply is limited to the extras I had to get.

     

    Karri, you also need to take into consideration if you're using anything other than a 1N5991b zener, that you need to change the R74 resistor to allow enough current to breakdown the zener to get the 5V regulation. If you don't, you'll find that your Lynx will only be getting like 4.3 - 4.5V instead of 4.7 -5. Some lynxes handle it better than others.

     

    I just have a stash of old 1N5991B's that I'm using (no resistor mod needed), but I've also used the 1N5229 zener and changed R74 from 120Ohms to 30ohms.

  3. That makes sense. If the zener failed (conductive,) no voltage at the rail. Crowbars for everyone, then. My Lynx I got a 5100 mAh flat battery w/ adafruit charge/boost controller, so no worries with that one, but I don't want to butcher all of them that way.

    That's why I'm working on some designs for an improved power system that can be fairly easily installed... soon!

  4. I pulled mine off the board, but I use a Hakko FR-300 desoldering gun, so it just fell out no problems. The glue is innovative though!

     

    You can get a replacement connector here: http://www.digikey.com/product-detail/en/molex-connector-corporation/0039532145/WM2861-ND/2405232

     

    I'll try to get a write-up of everything here shortly. I'm also in the process of designing a PCB that plugs into the PI's GPIO port and has the lynx flex connector soldered on it, audio DAC, safe shutdown circuit, and will utilize the ON/OFF buttons correctly.

    Since the Pi Zero W dropped today, that's what I'll use to test it with.

  5. Some day I need to get around to properly implementing this setup with a LIPO pack and a pushbutton controller IC for the ON/OFF.

     

    A note though, don't run Lithium batteries in series unless you're planning on removing them to properly charge them, or build in a balanced charger circuit. It can be dangerous.

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  6. Yes, they are inserted, twisted and soldered on the corners. I use flux and solder wick to desolder it. For the audio, I've fixed several just reflow in solder on the chips.

     

    Sent from my SAMSUNG-SM-G935A using Tapatalk

    • Like 1
  7. has anyone put a pushbutton switch in the system between the battery line and the 5v switching regulator?

    Would that be a good solution?

    You could do that, or if you were really fancy you could use a 5V regulator with an enable pin and wire it into the stock circuitry to make it work like factory. That all being said, skip the regulator and just get a new zener diode and MOSFET. I can sell you a proper zener.

  8. Hey there, this is really common on the Lynx I. The plastic in the screw holes is very brittle and breaks off. I've had this happen on two Lynx I's. I've tried repairs with plastic epoxy/filler, no luck. In the end I used screws that were a tiny bit longer that could bit into the plastic at the end of the mounting holes, being careful to not have too long of screws to go through the case. At this point, anyone doing mods on the Lynx I should really consider it an open it once, get it done and leave it alone thing (I wouldn't open it for cleanings regularly).

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