Losmandy Titan mount problems.

[Lester]

Hi all, long time since I have been here with my life taking a different direction. I tried to fire up the Titan mount last night after about 2 years and the dec motor stalled. I checked the worm and it is free and easy to turn with my finger. I also tried to fire up the mount again with the motors disconnected from the worm drive, so there is no drag at all on the motors. Still the Dec motor stalled. I changed the motors over and still the Dec motor stalled. So I think the problem is in the Titan computer.

Is there anyone on here that can service these electronic components? I would be happy to post, motors and Gemini system.

Thank you.

[wasyoungonce]

Lester ...is this your Gemini 1? You have the Titian with Maxon motors.

I repaired this back in Apr 2013, RA motor lags, stalls, replaced RA "H" bridge.

If you have not used it since and it is not working return it and I will certainly consider that this is an issue that I should look at for free.

But first, have you changed the battery and re-installed your Titian settings?

[pmrid]

As a matter of interest perhaps, I run my Titan at 18 volts instead of the usual 12. It overcame a tendency to stall that I had encountered at the lower setting.
Peter

[wasyoungonce]

Peter, you could be on to something.

Last time the RA "H" bridge was definitely dead and the input power, 12~18VDC goes to very few places, the PSU and RA/DEC "H" bridges.

There may be an issue with input power damaging these Bridges. That said the "H" bridge input Vmax is ~55 Volts and the PSU IC ~ 25V. They are both well spec'd above the input voltage.

Well in any case the only commone thing is the +12V rail.

Lester, also your mount is a Titian 50 not a std Titian, for Gemini settings.

[tlgerdes]

Were the gearboxes disconnected from motors for your testing?

[Lester]

Thanks for all your replies. Yes I had the motors disconnected from the gearboxes for testing. I could try upping the voltage perhaps if you recommend it Brendan. Otherwise I am happy to return it for your expert knowledge for testing, but I want to pay you as like I said it has been a long time with them sitting idle and that alone is not good sometimes.

[Lester]

No I have not changed the battery. I will look into this.

[wasyoungonce]

Hi Lester...no...I think if the fault was staying in DEC when swapping cables and motors then it's a DEC issue. I was really musing as to the cause, speaking out loud when I shouldn't have.

I'm concerned i fixed it returned it to you and I remember you had trouble with the system settings...the mount is a Titian 50 then obviously you have stored it for a few years, re-started and it's dead in DEC.

This shouldn't be so. Yes, do change the internal battery.
Barring that....yeah no problem I'd look at it again for free as I'd be embarrassed about this failing you for no reason when it was last in my hands.

[Lester]

Thanks Brendan, I will look at replacing the battery tomorrow and see how it performs then.

[Lester]

Just spent 2 hours trying all the possible battery places in Port Lincoln without any luck. So just ordered the battery on the internet. I have been informed that batteries cannot go by air any more, but by road. That is a bit strange as whenever people take cameras on the plane there are batteries included.

I will inform you Brendan, when I get the battery and try the Gemini system.

[wasyoungonce]

Hi Lester.

I'm guessing it's not a battery issue, but, i have seen strange voodoo things happen when the battery goes bad, so you never know.

[Lester]

It could take a week for the battery to turn up, but best to check that. Look at the simple first is best.

[Lester]

Hi Brendan, I received the new battery today and installed it into the Gemini without any change. The Dec motor still does not go. I changed over the motors and still the Dec output does not power a motor, but this time the RA motor revved at high speed without me touching any controls, just turning on the power to the Gemini.

Is your address still the same as it was a few years ago for me to post the unit and motors to you?

Thanks.

[wasyoungonce]

Hi Lester, same address. We spoke on phone. Looks as if the gremlins are playing havoc. It'll be sorted.

Brendan

[Lester]

Hi Brendan, I posted it yesterday afternoon from Port Lincoln, Monday. You should have it by the end of the week. Thanks mate.

[wasyoungonce]

Cheers...I'll be he waiting for it.

[wasyoungonce]

Hi Lester, email sent to your gmail account.

System fixed, sadly the DEC motor caused DEC H bridge burn out (this is why it was dead in DEC) and when this IC replaced this motor slews un-commanded on either RA or DEC position, you have a bad motor.

Happy to fix this for free but we need to discuss the motor. More than likely this motor was on RA and caused the original RA H bridge burn out. The email explains it all.

Brendan

[wasyoungonce]

Ok the system is fixed, took a few hrs but testing takes days!

Turns out the DEC H bridge was dead and when I replaced this the DEC motor did un-commanded slews. Swapping the DEC to RA etc the fault followed the motor. Replacing with my motor, all was good.

I did some fiddling and found the DEC motor had a bad encoder, as compared to a good unit (some funny ohm meter measurements, though I have no cct diagram of what's in the encoder). I had a 2nd hand encoder so I replaced this and the motor is fixed. No more un-commanded slews or uncontrolled runaways.

Now the original fault, a few years back, was a dead RA H bridge. I replaced this and all was good. But it looks as if the motor (or one motor) had intermittent fail in the encoder and years later when re-assembled, it burnt out the DEC H bridge (the motor was assembled to the DEC channel this time).

Obviously this was the original fault years back but was intermittent as it passed all my tests (a few days of testing), Lester tested it ok and packed it away. Reassembling it a years or so later it killed the DEC channel as this intermittent fault came back but this time the motor was on DEC. At least this time it had a hard fault so I could go hunting for it. Well that's my story and I'm sticking with it!;)

Lester is lucky as a replacement motor would have cost ...a lot. Lester has the Maxon motors.:thumbsup: I love these motors.

I'm also thankful Lester sent it back to me as I had the history of this unit and was more critical in approaching it.:D Tickets anyone!:lol:

[Lester]

Thanks a heap Brendan. I am very grateful that we have you in Australia with the expertise to fix these units. I have replied to your email. All the best.

[wasyoungonce]

No problems Lester, just glad to get to the bottom of it all.

System booted and ran fine this morning, did a couple of boots and tests, all is good. I'll hang on to it for a day or 2 to test it, thoroughly, and send it back.

[wasyoungonce]

And just when it's all going swimmingly...tapping the CPU causes system re-sets, garbled display and system shutdown. I rebooted and repeated, same thing.:shrug:

Pulled CPU found quite a lot of oxidisation on the CPU pins, the socket was fine. This is an OEM CPU. So, I cleaned the pins as best as I could, re-seat, all now good. Tapping, no issue now.

The system had passed multiple boot and slew tests before this showed up.

Glad to have found this before sending back but I am a little surprised. Gremlins at every corner. Final testing, RS232; ST4; system slews RA/DEC now all good, DEC motor behaving as it should. Oh and it also passes the tapping test!:lol: