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Polar T61 HRM transmitter dissection!

skatey-mark's picture

Well, after a couple years of faithful service, my HRM strap finally stopped transmitting. Unfortunately, it happened about halfway through A2A... Anyway, I know others have tried to replace the battery themselves without luck, but I started thinking of trying it anyway. After seeing the price to have Polar replace it ($30 plus shipping), I decided to give it a try. The first thing I found was Blake's blog entry suggesting to go in from the front. I also found forum entry on another site with a picture, so I knew what I was getting into:

 

http://www.timetriallingforum.co.uk/lofiversion/index.php/t10082.html

 

That forum entry also confirmed that Polar does replace the battery and return the original transmitter, so there must be a non-destructive way to get at the battery. So I puzzled over that for a while, then I got my heat gun... :)

 

Now, some of this way trial and error, so I think I could do a better job next time. But I think I have a pretty good idea now of how this is put together. Or, rather, how to take it apart in such a way that it has a good chance of being put back together. I saw what appeared to be a seam along the back of the monitor. I thought perhaps that the entire front might pop off, so I heated that up. A couple trim pieces at the top & bottom didn't really like that. Also, the front did not come off, but the back did quite easily...

 


 

After that, I tried many things to get the front to come off -- nothing worked. I heated various bits with the heat gun, tried slicing what I thought were important parts with a utility knife, still no luck. Finally, I had heated up one side (I thought I could get a screwdriver in there and pry it apart)... That's when the strap started to come apart from the center of the transmitter. I pulled harder and it came apart completely...

 


 

Now, I tried prying the circuit board out without luck (more on that later.) So I figured, okay, lets rip off the other half of the strap...

 


 

Now, surely the board would come out! I got my little screwdriver in there and the darn thing was being really stubborn. I could see the battery... I kept prying and suddenly the board came loose from the plastic!

 

In retrospect, I think all I needed to do was unscrew those 2 tiny screws in there! Ooops! It took me about 5 minutes to find one of them, but I did manage to get all the parts eventually...

 


 

After having done that, I'm not sure if it was even necessary to remove the straps from the center...

 

I do think a good way to get at the innards would be this:

 

1. Heat up one side of the center where the strap connects. Pull hard to disconnect it. Looking at the transmitter from the back, I think I would disconnect the strap from the left side.

2. With the strap disconnected from one side, it should be easy to pop the back of the transmiiter off. Just put a small screwdriver in the side and twist. It's possible that you might have to heat it up with a heat gun, but I don't believe at this point that it was necessary.

3. With a very small screwdriver, remove the 2 little screws.

4. Pry up on the little tab and separate the pcb from the plastic housing. Be careful not to damage the coil.

 

Sometime this week, I'll be heading to Batteries Plus to get a replacement battery. I'll post a follow-up and let everyone know if the transmitter lives through the operation!

 

- SM -

 

Comments

roadskater's picture

Thanks for the Polar T-61 Heart Rate Monitor Strap Repair Info

Thanks for this info. I dug into mine from the front and fully intended to show my photos from that operation, but haven't gotten to it yet. I never completed my attempts as I got a replacement strap for my birthday...one of the Wear-Link style, which are both good and bad, in my view. I have had some trouble with the snaps on the Wear-Link. In any case I may look for my photos and see about posting. I dug in from the front but didn't have any idea what was in there so I may have damaged something, or it may have already been damaged. When it didn't work right off, I just gave up for the time being. Thanks again for this useful info for the world to have!
eebee's picture

Eagerly Awaiting the Outcome of your Polar T61 Surgery!

A very interesting post, Skatey-Mark (in a car-wreck rubbernecking kind of way!). Did the side-straps actually rip, or do they slot back in to the other bits that stick out of the main, um, bit? After doing all of that, do you have any idea how they must get the thing open at Polar? I love the step-by-step pictures! Looking forward to hearing the outcome...
skatey-mark's picture

T61 strap disassembly

I haven't made it out to Batteries Plus yet, but hopefully will this week...

 

As for the straps, I believe they will go back in.  They didn't break, and there appears to be a little tab to lock them in place.

 

It's possible that the straps don't even need to be removed...  I'd obviously have to start with another strap to know for sure...  :)  If I were to try again, I'd get the back off first, unscrew the 2 little screws, and see if the innards came out.  If that didn't work, I'd take one strap off, which should definitely be sufficient to coerce the little board out of the plastic housing.

 

- SM - 

roadskater's picture

T61 Back on My To Do List, Ha!

OK the T61 heart rate strap monitor is back on my to do list, though way down. I have photos I can share of the step by step, which I never posted. Also, I tried the strap afterward but gave up quickly since I had a new one. I should give it another test if I can find that battery. Let us know what you find and thanks for sharing. I think going in from the front was not such great advice but at the time that's all I could find online. Hopefully with your photos from the back of the strap and mine hacking in from the front, we'll have it. I became convinced I had ruined the strap but now that I see more of it, I doubt it. It was either ruined already, perhaps in the electrodes area, or it should still be OK. Interesting stuff. while I like some things about the WearLink strap, especially the replaceable battery, the snaps are not great and sometimes I can't get my heartrate, especially early on. I think the WearLink needs more specific and frequent care.

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