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LX200GPS "no sensor board"

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#26 actionhac

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Posted 10 February 2011 - 01:14 AM

I looked over my sensor board carefully and found a small burn hole in the top of this component.
Texas Instruments LVTH125 printed on the top and a quick look on the internet and I have one being sent to me, cost for this part is 67 cents. I'm not sure what the numbers in the first row are all about, I ordered a LVTH125D which is as close as I could get.
It's very small and I'm not sure how to get the old one off the board. I can't see unsoldering 14 leads at once so I thought I would clip all the leads off the part and unsolder the leads off the board one at a time.
Then I think I'll tin the 14 leads on the new part, place in position then just touch the 14 leads one at a time with my pencil iron to solder it to the board.
I'm hoping the little integrated circuit isn't too heat sensitive.
I also wonder if this part failed by it's self or if something else on the board fried it and will also fry my new part!
Really I shouldn't even attempt this but I just can't help myself.
Here's a picture of the Quadruple Buss Buffer, what ever that is. The burn hole on mine burned one of the legs off the "H" and is actually a small hole through to the inside.

Robert

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#27 neotesla

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Posted 10 February 2011 - 10:24 AM

Use the thinnest tip you have, heat dispersion would be at a minimum...

#28 pgenneken

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Posted 10 February 2011 - 06:40 PM

Radioshack sells these (14 pin retention contact) catalog # 276-1999 $0.99 -
http://www.radioshac...oductId=2062607

might be safer to solder on one of these and then place the chip in it?..

Good Luck and keep us posted.

Pete

#29 actionhac

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Posted 10 February 2011 - 07:53 PM

If that's what I think it is, a socket, yes it would be nice!
I'll go to Radio Shack and take a look at one.
I don't want to forget my magnifier, this stuff is impossibly tiny. My wife is bringing home a dissecting microscope from work for the actual operation.

Robert

#30 George D

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Posted 11 February 2011 - 01:57 AM

While you're at Radio Shack, pick up some solder wick. You may find that you can actually "flood" the chip with solder, and then wick it off, leaving a good contact between the leads and the pins. It's gonna be tough to "tin" those pins without distorting the initial placement on the board.
Clipping the old pins may work out for you but again, solder wick might be a good start and a sharp hobby knife to heat and lift each pin from the board may be a good approach too.
I have found that the quality of the Meade PCB's is horrible. Any force (as in clipping a pin) could also lift the trace. That would not be a fun place to start from.
Good luck!

#31 actionhac

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Posted 11 February 2011 - 12:25 PM

Thanks George.
Heating and lifting each pin does sound safer than clipping the pins.
And solder wick, I've got to try that!

Thanks for the help guy's, I'm starting to feel like I just might be able to do this.

Robert

#32 actionhac

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Posted 14 February 2011 - 02:39 AM

While waiting for the chip I've had a chance to use the scope and everything works fine except GPS.
The optics are very sharp.
Robert

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#33 SimonLowther

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Posted 26 April 2011 - 04:00 AM

Hi,
I have had this problem since I bought my scope 2 years back, and with poor Meade customer service in this bit of the world have just put up with it, as it has little impact on my use, just not what I paid for!

Following through what you have tried, the problem may be either on the aux board itself (I got a new one sent out, but it was the wrong revision and wont work with my scope), or the power management chip on the main board (which I suspect on mine after having an oscilliscope on it looking for communication).

Check what rev the Aux sensor board is in your scope, and if it matches my spare, and you can have it to try so see if it solves your problem.

Si

#34 SimonLowther

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Posted 26 April 2011 - 04:04 AM

Actully I just read your p/n as rev D (same as my original) and my spare is a C.

Sorry cant help, good luck with the chip replacement and I will be interested to see how it goes!

Also, if its not rude to ask, did you buy this scope new? If so for US customers meade have a "first light guarantee" either it works straight out of the box, or they replace it for a new one no charge.

Goodluck

Si

#35 StarGeazer

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Posted 26 April 2011 - 12:53 PM

Nice picture of the beast! I have the classic version, so no GPS for me.

#36 Joe Lalumia

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Posted 28 April 2011 - 09:14 AM

Why not investigate this software--

http://www.stargps.ca/

Rather than taking a chance with replacing the chip-- also consider that GPS is not actually needed at all to acheive a good two star alignment. In fact it might not even save you any time during setup.

As you wait for the gps to get a satellite lock ---- you could have just entered time, date, and site (by Zip Code).

#37 actionhac

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Posted 01 May 2011 - 01:53 AM

Hi Si and Joe.
I received the chip and sort of chickened out. This electronic micro surgery is a little too much for me once it came to doing the job and the size of the chip sitting there on my bench. I use the scope without GPS like you are.
I bought the telescope used and with this problem noted by the seller. He didn't seem to care that it didn't GPS ether.
Someday I'd like to see it working. Too bad rev.C won't work, I wonder what the difference is. Maybe it went to rev.D when the GPS receiver changed to the round shaped unit.

Robert






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