Gemini 1 misbehaving. handpiece, cable or the Gemini?

[mithrandir]

While I was observing tonight - about 15 images into a run, the handpiece display suddenly started rotating through the function list you get when you press and hold the Menu key. PHD could still guide so I let it finish the run before fiddling.

The Gemini would respond to commands through the RS232 from the computer, but nothing short of powering off would break the handpiece out of the loop. I got the computer to park the mount at CWD, powered it off, powered on said I wanted a warm start, chose Achenar to align (almost dead centre) and before I could use the menu to tell it to synch it went back into the loop.

I took the Gemini inside, pulled the backup battery (just over 3V) and replaced it with a new one (about 3.2V). After putting it back on the mount, connecting the GPS, resetting the mount type in SRAM and restarting, a few minutes later it went back into the loop.

Any guesses which bit is most likely at fault?

It was VERY humid - the whole rig was dripping wet - so I wonder if that had anything to do with it, but last night was just as wet and I had no problems.

[Octane]

Hrm, could be the cable going dodgy, or something in the RS-232 port on the Gemini itself?

H

[wasyoungonce]

Even though the handset membrane switches are well sealed from moisture it sounds like moisture in the menu switch. A good old dry out may help.

You can probably measure this switch via the flex on the back of the membrane or at it's header plug.

Another possibility is that the membrane switch tracks can degrade over time (EDIT: right at the point where the membrane is flexing), at the actual area where you depress the switch. Again you can measure this.

[Barrykgerdes]

Hi Andrew

My first guess would be based on just this effect, moisture on the menu key. I am sure you have seen similar effects on the computer (when you spill coffee on the keyboard?)

A complete dry out of the controller may fix the problem. Particularly as the guider input had no problem with the actual control of the scope. If not I should expect the problem to be more likely in the Gemini (ugh). Look for evidence of water here also.

I would discount the cable at the moment because the problem is relative to specific problem and I am sure you have already tried tests associated with the cable.

Barry

[mithrandir]

Thanks B&B.

Moisture seems to be likely. I dismantled the handpiece and left it out in the sun to dry. It is now showing about 20 ohm with the Menu key pressed and open circuit with it not pressed.

I have reassembled it and will leave it running for a few hours in the garage to see what happens.

Now I think I've managed to destroy my NX-01 GPS by feeding it reverse voltage so I'm not having a good weekend.

[Barrykgerdes]

My condolences Andrew.

You might be lucky enough to find the problem. I have found from past experience that IC's will often withstand reverse voltages but tanatalum capacitors usually fail instantly.

Barry

[mithrandir]

It's a sealed unit (http://www.stargps.ca/GPS.htm) Barry, so repair seems unlikely, but I've emailed StarGPS to see what they have to say. If the answer is return to Canada for repair, I think I'll buy another one since it is out of warranty. They quote no more than 10 days delivery to Oz.

Depending on their answer, I'll probably put a protection diode in the power lead. The voltage drop is not a problem - even 9V would be fine.

[Waxing_Gibbous]

My condolences.
Its the Gemini.
Its rubbish.
Worst $4K I ever spent.
Mine did the same as yours after six months of not going-to, slewing, tracking or in any way being a useful bit of kit.

All one need do is look on the Losmandy Yahoo group to see the cascade of lamentations relating to Gemini misbehaviour.
The Bible is shorter.
The mounts themselves are luurverly pieces of engineering, but the electrics are complete kludge.
Usually contacting Losmandy bears little fruit but it's worth a try.
Failing that, try the Yahoo group; its full of never-say-die types who generally have an answer.
Good luck!

[mithrandir]

Peter, you have a G2. I have a G1. After drying out the handpiece it behaved itself for several hours until I turned it off and sat down to watch the GP. It had never had an issue with dew before and think I'll seal it in a plastic bag to keep it dry in humid conditions.



I follow several of the Yahoo groups including both the G1 and G2 ones. Were you testing the latest G2 firmware? I thought your name had cropped up when they were looking for southern hemisphere testers.

The G1 has been around for many years and has gone through four generations of firmware adding various functions, and version 4 has had at least five patch levels. Mine has 1.04 since 1.05 doesn't have anything I need and I don't have an EPROM burner to write a new one.

Scott and Rene probably should have started on the G2 earlier, say as soon as they were told some of the chips needed for spare parts would be discontinued, so they would have had more time for development and testing.

You might have an easier time coming to grips with the whole Gemini thing if you can find a G1 to use until the G2 firmware is finished. Stuart has his G11 and G1 listed for sale, and he's down in the deep south too.

[Waxing_Gibbous]

Andrew,
Mine was a G1!
Possibly even a G.01
I bought it new in 2004 (or 5 maybe). One of the factors that induced me was that I had read either on the Losmandy site or OPT, that the firmware was based on the Meade Autostar suite (I might be completely mis-remembering this).
If so, whatever they did with it in no way enhanced it's capabilities!

Perhaps personal pride is involved, but I suspect the makers would be far better-off commisioning AP or Argo-Navis (the two best IMO) to work up a package for them.
Even my humble HEQ6 out-guns a G1 in terms of accuracy.
Again, a real pity, as I think they are beautifully made and when used without Gemini, will work virtually problem free.