I guess I know the answer to this..

[Aeolus_IV]

.. but I'll ask anyway.

Our old Shipmate RS5700 GPS is giving me grief, when I turn it on it can take it literally hours to complete startup and work out where we are (until that point in time it thinks it is somewhere in Continental Europe, Holland probably). Once it has sorted it self out, it works perfectly. I believe I've got an error message out of it about not having an almanac, so I guess that its problem is that it hasn't a clue which satelites are above, and so works through them sequentially until its found enough for a fix.

The question is: Is this now a good time to buy a new GPS, or can this be fixed?

I'd love to read the manual on the unit (which I have), but its in Dutch (which I can't read).

Regards, Jeff.

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[WayneS]

Normally this only happens if it has been turned off for more than 6 months or you have moved more than 500miles since your last fix.

Otherwise it knows roughly where your are etc.....

Possibly the little internal battery which allows this info to be remembered has died. In which case, it is prob easier and cheaper to buy new.

Cheers

Wayne

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[LORDNELSON]

Try having the internal battery replaced. It should not cost more than £20 if you have it done for you or about £4 if you solder it in yourself.

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[AndrewB]

Is this an old fault?

Many older GPS's went this way following the Rollover on 21st August 1999. Some are fixable, some always have to go through a full autostart thereafter, some stopped working.

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[jfkal]

Re: Is this an old fault?

Correct that is the problem. Go for a new one.

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[Aeolus_IV]

Re: Is this an old fault?

This is what I feel, but it seems strange that the unit was working quite acceptably until the last few weeks, so may be there is an old battery in there some where. I'll try taking it apart before spending hard earned cash on a new GPS ('coz then I'd be forced to buy one of those cleaver chart-plottery thingies /forums/images/icons/smile.gif, and I haven't got the money at the moment /forums/images/icons/frown.gif).

Thanks everyone,
Jeff.

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[jfkal]

Re: Is this an old fault?

What I understand is that the units have built in Flash Memory for the Almanac data. This somehow gets used up (apparently worse for pre-rollover units). Therefore once the memory is used up it has to acquire the information through the satellites on each new power up. Try getting a used one (post-rollover) from Ebay.

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[MainlySteam]

Re: Is this an old fault?

Sounds like it is doing a cold start, having "lost" both its ephemeris and almanac data (don't panic, it can regain them from the satellites). It either has a time related algorithm error in its firmware (unlikely I would have thought seeing it is just a startup problem and everyone with the same software version would be having the same problem) or the backup battery is dead . Am not familiar with the unit, but you may find that there is short term retention of the volatile data maintained by a charge on a capacitor in it, in which case if you can start it, let it establish a fix, turn it off, then turn it on again after a few minutes and it reestablishes the fix again much more quickly (minutes or less) then I would say it is the battery for sure.

The rollover has been and gone 4 years ago and is nothing to do with your problem at all. Go for the battery, if it is not that, then start worrying.

John

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[Aeolus_IV]

Re: Is this an old fault?

Had the unit apart yesterday, nicely put togther - tough, but comes apart in a simple logical manner. Sure enough, soldered onto the middle board (of three) is a penny battery (looks like a cr20xx - can read last two digits, they are under one of tags spot welded onto the battery). In reflection, if this is all thats been keeping the memory live, its lasted rather well, so this weekend its out with the clippers to cut out the old battery and see if I can't rig another in its place. Got to be cheaper than getting a new unit - but with the SBS just around the corner....

Thanks for everyones suggestions - I'll let you know what happens.

Regards, Jeff.

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[MainlySteam]

Re: Is this an old fault?

You will probably find it is a Lithium battery (CR20xx is in fact Lithium). Manufacturers commonly say 5 years in back up situations - but commonly last a lot longer. My own GPS is 7 yrs same battery (probably die today now I've said that!) and I have a transmitter with a memory backup battery now 11 years old.

Hope that is the problem solved, John

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[Aeolus_IV]

Re: Is this an old fault?

Yup, a CR2032. Was giving 0.2v, so its no suprise the GPS was forgetting everthing. Bought new one (£1.95) and managed to attach it using some short leads rather than trying to attach where the original was. So now I get 3.2v across the terminals. First time the unit was powered up, it (as expected) took several hours to sort itself out. Once working, I turned it off, then on again. Came up in 3 or 4 minutes. Certainly not quick off the blocks, but a huge improvement. However the time after that (the next day) it still took quite some time locate itself - not a couple of hours, but probably between 15 and 30 minutes or so. Is it going to take some time to rebuild its internal tables, will the startup time improve with time? If its going to be consistently less that 30 mins then this is OK for the time being (it takes that long to get out of the marina), but I'll be looking at a replacement over the winter.

Thanks again for your help.

Regards, Jeff.

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[MainlySteam]

Re: Is this an old fault?

Glad it worked, so far. Regarding the time to reinitialize, I am not familiar with the actual receiver at all and not sure how long they took to reinitialize after losing all data. But it takes around 12.5 minutes to build an almanac from nothing. On top of this it has to follow some algorithm to do a world wide search and find 3 satellites before it can give a fix, but the several hours to start seems long but it may be so for an older unit (I do not know how old the unit is).

When you turned it off and on again, it looks as if it had an almanac but not the ephemeris which is not unexpected.

Not sure why it took so long the second time (the next day) but it may be that there is something in the manual that you have to do as part of the reinitialization process. Some, for example, you could put in an approximate fix to get them started quicker. But given that it seems to be sorting itself out it may be worthwhile just trying it again and seeing if any improvement next couple of times before rushing out and learning Dutch. Be aware that the ephemeris data will have aged and it will have some tidying up to do next time you start it, which in an old receiver may add to its confusion if it is still sorting itself out. I would be inclined to leave it on as long as possible when next turned on - it may be that leaving it in one position might help too.

At the time of the week rollover in 1999 there was some talk about GPS's which would fail between the week rollovers (the next is in 2019) but how true that was I do not know, however, some manufacturers talk of "user intervention" being required after some intermediate date between the rollovers if all data is lost eg flat battery. Given the unit is starting up again and giving a fix seems against that, but it could be that there is a date related fault in the firmware which will cause slow warm starts. Unlikely, but perhaps possible, but running it a few times will tell. If it turns out to be the problem then it will just have to be put up with until you renew the unit (assuming the probability that a firmware upgrade is not available for an old unit).

I would be interested to know what happens next time.

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[Aeolus_IV]

Re: Is this an old fault?

Ahh... "12.5 minutes to build an almanac from nothing" - well, it all ought to be sorted out by now then. It was on for 5 hours or so on Sunday (while we drifted around and clinched last place and sun stroke in the club race - luckily only 4 in the race /forums/images/icons/smile.gif). I had left it on (after completing startup) for far less than this on Saturday as I was out of time and needed to get on. Shall be out again soon, so I'll let you know (unusually for me I'm optimistic that this is sorted - now only need to put those waypoints back in).

Thanks again, Jeff.

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[MainlySteam]

Re: Is this an old fault?

It cannot download the almanac until it finds a satellite it likes, then after it has downloaded the almanac and then the ephemeris (much quicker) it then has to work out where in the world it is too. So these other things are extra to the 12-13 minutes. New ones do this pretty (very) quickly, but the old were slower. I had a look through a few old manuals (mid 90's vintage), but none gave definitive times for a start from ziltch after battery replacement. For the pound or two for the new battery, worth seeing if it settles down. Especially as you are looking forward to a Christmas present rather than a mid summer expense.

John

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