eTrex Vista Cx won't turn on - Repair ideas?

Discussion in 'Garmin GPS' started by jsl87, Oct 14, 2018.

  1. jsl87

    jsl87

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    Seems like my eTrex Vista Cx kicked the bucket, but I thought I might see if anyone has ideas on maybe getting it running again.

    I used it about a month ago with no issues, then went to use it yesterday and found that it wouldn't turn on. Multiple sets of batteries and multiple USB power cables with no luck. Dead. Would not respond to master reset button combination either.

    I thought it might be a bad power micro switch, so I pulled the unit apart and probed the micro switch. It appears to be functioning fine. I also checked the voltage of the button cell battery and it was 1.5V so it seems to be fine...I'm not sure a dead button cell would cause this issue or not.

    Any other ideas?
     
    jsl87, Oct 14, 2018
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  2. jsl87

    Nuvi-Nebie Moderator

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    What type of button cell is in your eTrex Vista ?, the 'backup cells' are quite often 3 Volts so this may be your problem, as a low internal battery voltage can cause a 'turn on' failure
     
    Nuvi-Nebie, Oct 22, 2018
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  3. jsl87

    jsl87

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    You may be on to something! I had just assumed it was a 1.5V cell because that's exactly what I measured, but after some digging I think you're right! I found several mentions of it being 3V, with one website in particular giving a part number ML621-TZ1-D which is a 3V lithium battery.

    http://www.jpf.de/jpf/garmin_fix/page_01.htm

    This looks promising! I'm going to do some testing to see if the battery is the culprit...seems like there is a very good chance it is. Thanks again!
     
    jsl87, Oct 22, 2018
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  4. jsl87

    Nuvi-Nebie Moderator

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    Nuvi-Nebie, Oct 22, 2018
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  5. jsl87

    jsl87

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    Well, good news! Though I'm a little puzzled, too.

    I took a look at the battery and on the side that was visible it only had markings "68 f+" which I couldn't find any info on. I decided to de-solder the battery hoping there was a marking on the other side but unfortunately there wasn't. I soldered on a couple leads to the battery terminal with plans to do some testing with an external 3V battery to see if I could get it to boot up.

    I did measure the battery voltage again after I removed it and ended up with 0.5V. I'm not sure how I was seeing 1.5V before, perhaps it was a residual charge because the last time I took a measurement it wasn't too long after removing the main batteries. Anyways, the 0.5V reading gives me more confidence that the battery is the culprit.

    I put the unit back together with the leads coming out. Inserted the AA batteries and for fun tried to turn the unit on before applying 3V to the leads. And what do you know, it booted up! Without the 3V! I wasn't expecting that at all. What's the purpose of the 3V button cell? There is a reason it is there so I'm definitely replacing it (with an ML621 I guess) but I'm definitely curious what is going on.

    Thanks for helping revive her!

    On a side note, do you have any suggestions for a double-sided tape to use for installing the rubber when I get back to that point? I'll have to see what I can find for a thin tape...may have to order something.
     
    jsl87, Oct 23, 2018
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  6. jsl87

    Nuvi-Nebie Moderator

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    The 3 Volt button cell powers memory in the GPS when the main batteries are flat / removed, this memory maintains time /date, waypoints etc and almanac data, e.g. what satellites should be visible. When this memory is cleared the GPS will take a lot longer to get a satellite 'fix', if the GPS can't get a fix place it somewhere it has a completely uninterrupted view of the sky away from trees / buildings etc. and leave it stationary for half an hour or so.

    The dimensions of the ML621 are 6.8mm dia x 2.1mm, so if the size if your 68f+ is the same, I think it will be OK.

    The rubber is sometimes glued into place, so you could try that
     
    Nuvi-Nebie, Oct 23, 2018
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  7. jsl87

    jsl87

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    I thought that might be the case after I looked through the page I linked to earlier, where they mention it was a fix for the GPS not receiving satellites.

    I did a little more digging on the battery. The battery I removed has a diameter of 6.75mm and an overall thickness of 1.74mm. These dimensions line up more with a ML614 battery, rather than a ML621 which has a overall thickness of around 2.65mm. Either one will work though since there is plenty of room for the battery on the PCB. The only difference is the battery capacity: the ML614 is 3.4mAh where the ML621 is 5.8mAh.

    I'm guessing the '68' on my battery is referring to the standard 6.8mm diameter.
     
    jsl87, Oct 23, 2018
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