How to open a GPS anenna

[Arrandir]

I bought a new GPas antenna from M.C Marine for my VHF which I had no time to mount in he proper place before Inset sail. Unfortunately the cable got stretcher and it don't work anymore. Do anyone know how to open so I can solder the connections?
A friend gave me the advice to heat it with a heat gun, it should be some glue which will release if it's heated. I tried that, first careful and later with more heat without being able to open it.

[tkeithlu]

My bet is that it is potted in plastic, and that you will not open it without destroying it, but you could try prying at that seam, or seeing if there is an assembly screw at the bottom of that hole. USB or similar GPS pucks are down to $10 on the internet market now, so do consider simply replacing it.

[Sailmonkey]

Those are typically assembled in such a way that prevents opening.

If you’ve pulled the wire hard enough to pull out of the unit, are you sure the wire hasn’t broken elsewhere?

[Brian.D]

That should be a data cable so you might be able to find where it is "extended". Run your fingers along the cable, with some pressure, and see if you run across a soft or weak spot. That might be where you are losing the connection. Since it is a data cable you may be able to splice into it. I don't think it was pulled out of the unit itself.

Curious, when you say "stretched" how do you mean?

If you have to crack the "egg shell" to fix it, you can put the unit in a tupperware or similar container to maintain moisture proof status.

[Lancerbye]

They are made to be water proof. I tried to open mine once because somehow moisture got in. I ended up having to buy a new one. You will probably have to do the same.

[NorthernMac]

Heatgun and razor on the seem

Some folks put headlights in the oven to help break the glue seal too, tons of YouTube videos on this.

I’d wager that antenna won’t make it through surgery though, or if it does it won’t be close to watertight anymore. If it’s feeding data to any mission critical stuff, autopilot, AIS, chart plotter, Id just get a new one

[thunderhoof]

Most of the time wire breaks occur at the ends. You will probably have poor luck going into the puck but look for damage at the connector. I believe there should be finite resistance between pairs of contacts. You might do a search on the expected resistance values, and what the test voltage limits are. Otherwise cut the cable cover and make enough room to push a pin into each wire; then check for continuity to each connector pin. If a wire is broken cut the connector off and splice on a new one.

[Lake-Effect]

For amusement, I often try to repair what normally isn't repairable. For something like this, usually the case has been glued. You can try probing the seam with a strong knife blade - pushing its edge into the seam, wiggling it to see if you can ease (or break) the case open. If the seam or gap is wide enough, you can also stick a slotted screwdriver in and try twisting it.

If you're unable to get the case open that way, you can use a razor saw or a thin hacksaw blade to cut into the seam a bit, working your way around the case evenly, and doing a test pry occasionally. At some point the case will crack and open at the cut.

When you have access, and can get to the connections, solder in a new cable, TEST THE GPS, and then use something like epoxy or 5200 to glue the case together again.

[Brian.D]

Dremel with a Cutting Wheel is the best option. You can control the depth of the cut.

[Arrandir]

I don't see or feel any damaged part on the cable. The cable is not attached to the glue in the hole where it goes into the antenna and I know the cable were pulled accidentally once.
I will try to use a Dremel to open it. The worst that can happen is some interesting job. Plan B is look for a new antenna which can be connected to NMEA 0183.

[Lake-Effect]

Originally Posted by Arrandir

I don't see or feel any damaged part on the cable. The cable is not attached to the glue in the hole where it goes into the antenna and I know the cable were pulled accidentally once.
I will try to use a Dremel to open it. The worst that can happen is some interesting job. Plan B is look for a new antenna which can be connected to NMEA 0183.

I have a Dremel too, and their cutoff discs do make a nice thin cut, but I tend to break about one a minute .

In terms of Plan B... lots of cheap options. I bought an old Lowrance handheld GPS unit at a flea market for $15, that provides a serial out. There are also many GPS DIY modules. They don't necessarily have to be mounted outside.

[CarinaPDX]

Your main hope is that the break is before the puck, and cutting and splicing will be an adequate solution. Otherwise I would try to carefully cut it open, but wouldn't have a high confidence in the procedure. GPS pucks are pretty cheap these days if you are not in a hurry and know what you want - I order them from China and usually I get what I wanted (but not always). You should have a spare anyway (as I said, they are cheap).

Greg