Garmin Forerunner 735XT Teardown

Written By: Peter
Published: 29/12/18
  • Comments: 11

Garmin Forerunner 735XT Teardown

Published: 29/12/18

Teardown

Introduction

Garmin's latest forerunner revision provide a good feature set to compete with other fitness watches.

In following other manufacturers, a glued front technique has now been adopted by Garmin.

The unit featured here developed a fault, in under two years of active use.

Support from Garmin quoted a £100 fee to replace the device out of warranty (approximately a third of the cost of the device).

Instead of paying this, let's dive into a teardown and share some information instead.

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    • The strapless 735xt, the straps are secured by two T6 screws on each side.

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    • The front is glued

    • Use an iFixit Spuder to prise around the glue. It's not necessary to use a heat gun here.

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    • Once the screen moves, carefully remove the ribbon connector and the screen.

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    • Two T6 screws hold the mainboard to the body.

    • The main board will move from where the Spuder is inserted.

    • Remove the green protective tape and disconnect the second ribbon cable before proceeding.

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    • The unit will now be disassembled

    • Unplug the battery by lifting up the connector from the bottom.

    • Further disassembly and analysis to follow...

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    • GNSS receiver looks like MediaTek MT3333 with external amplifier+filter+chip antenna. And ARM7 CPU.

    • The watch has at least 3 Cortex-M4 microcontrollers, not counting Ant+ or GNSS chips! Microchip ATSAMG51, ATSAMG53 and MAX32360

    • nRF51422 contains ANT+ and Bluetooth LE functionality. And Cortex-M0 CPU to run these.

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    • Insert wisdom here.

Author

Peter

Member since: 19/07/13

145 Reputation

11 comments

I’ve not attempted to re-assemble yet. The glue was held around the LCD display.

These units are identical to the manufacturing process of more popular units such as the 235. So someone might of given a guide to putting those back together.

The core thing to keep in mind is that a decent seal is going to be required to avoid any water damage.

Peter -

When you have a water damaged Forerunner 735, it is probably not necessary to take the 735 completely apart, to repair it. Just take away the front, and then use a air pressure spray to blow out the water. I did not test it, but here is an instruction, which shows that this worked for the Vivoactive HR:

https://www.youtube.com/watch?v=rAKbZ_Tx...

Peter Gamma

Peter Gamma -

Correction: It was not air pressure spray but CRC electronic cleaner Dean Stucker used in his youtube video which shows how to repair a Vivoactive HR. Difficult to find here in Europe. Alternatives?

Peter Gamma -

I opened up one Garmin 735 watch which I bought on ebay which had a screen which had a kind of a shadow on the screen. I removed the screen, but did not take it away completely. I used air pressure spray to clean the watch. Unfortunately, I was not able to repair the watch by this procedure.

Peter Gamma -

All three damaged Forerunner 735 I own have a fog on the screen, I suppose the screen is damaged. Unfortunately, replacement screens for the 735er are rare to find.

Peter Gamma -

I ve read somewhere Garmin also offers repair of these devices, but they are not water-resistant anymore after the repair. When Garmin is not able to make them water resistant again, who else is able to solve this problem?

Peter Gamma -

Matching switches seem to be Panasonic 4.5mm x 2.2mm Side-operational Edge Mount (EVPAE).

Nicht Albert Einstein -

Yep! Definitely these! Have ordered some to microsolder for repair. Anyone have any reasonable ideas for re-sealing the watch face?

kiwibevanjones -

Peter Gamma:

I’ve not attempted to re-assemble yet.

@peter_gamma and others: I did re-assemble my 735XT after I broke my display, repaired my 735XT, and as it was open, replaced the battery and the display : see YouTube link in pdf. Added a lot of practical stuff:.

NL-pdf : https://workupload.com/file/xTdEDzmPTb2

ENG-pdf : https://workupload.com/file/sFfnQeBDAMR

Remark: Its is now ~ 5 weeks ago I did the job. After full completion I did not encounter problems so far. I even shower with my 735XT on my wrist. The battery-life: It lasts for ~ 1 week with 3 trainings of 1.30-1.45 hrs per GPS-based mid-long distance training with 1 second data collection speed and I wear it nearly day and night (BT off, only on when data needs to be transferred, GPS off, but for the rest I did not disable functions).

I hope it will last stil for several years, it is a very nice, light sport (smart) watch.

@peter_gamma : Thanks for the extra photos.

Route99 -