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10" LX200 time capsule

classic equipment Meade optics SCT catadioptric
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#1 Piggyback

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Posted 10 August 2018 - 02:07 AM

I am the custodian for a Meade 10" LX200 f/10 catadioptric. It belonged to a late doctor who had never found time to use it. For 17 years the entire shebang was stored in what the widow says is a dry place in the basement of the house. Before I proceed to open the sealed cartons of this time capsule I am asking the experts in this forum for advice. I assume the grease in all the bearings of the drive train may have hardened. If that is the case what can I do to prevent motor burn on first start up. I am curious if there is other measures I should take. The sales slip lists a #1812 D.C. converter so I should be fine to run it from our local 220 volt power grid. 


Edited by Piggyback, 10 August 2018 - 02:11 AM.


#2 rferrante

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Posted 10 August 2018 - 10:40 AM

Hi Stefan,

 

It seems like the latest this scope could have been built is around 2001, but maybe earlier. Do you know if this is an LX200GPS, or an LX200? Definitely don't power it up yet, if it is an LX200 "Classic" (marked simply "LX200"), you will want to replace some capacitors.

 

If you can't tell, you can post a photo of the front panel.

 

--Rob



#3 Piggyback

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Posted 10 August 2018 - 03:34 PM

Thanks, Rob. I believe it is a LX200 classic. So if I blow the capacitors on first start up, what am I gonna do?

 



#4 rferrante

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Posted 10 August 2018 - 04:13 PM

In the extreme case, you'll find yourself with a broken handset that will be hard to fix/replace. So you at the very least need to replace the one in the handset before powering up. It's unlikely it will fail on first power-up, but, it is old and the kind of capacitors used back then have a higher probability of failing the older they get, apart from usage issues, which they also have. And yours are 17+ years old.

 

There are lots of great threads here on Cloudy Nights with detailed procedures, pictures, etc. But as a quick guide, you want to clip out the yellow, pea-sized, kind-of-droplet-shaped one near the bottom of the PC board. I think it may be the only yellow-colored thing in there.

 

You will need to replace that with a minimum 35V, 6.8 uF electrolytic capacitor. The 35V rating is important. They need to be soldered onto the leads left after you clipped off the old one, and importantly, the two leads are not interchangeable, so you need to know which is the positive lead, and which is the negative. Again, you can get help here doing that.

 

--Rob


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#5 NearVision

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Posted 10 August 2018 - 04:15 PM

From what I know (which ain't a lot of the history), the earliest lx200's had round DIN connectors and ran on 12 volts DC. At some point they changed to the modular plugs that we see now (think phone and network type wired connectors) and changed to 18 volts DC. Later they changed back to 12 but I think those are not classics.

In any case it's the models that say 18VDC by the power connector that you have to be concerned about the capacitors mostly. What happens is that the Meade power supplies are not well regulated and can send the voltage spiking higher than the caps are rated for. When a cap gets over-voltage it blows up. The problem is that the early tantalum caps that were used when these were built tended to blowup like a small incendiary bomb and burn anything nearby. Don't be too alarmed by that description. Think the size of the cap guns we played with in the 60's, not a firecracker or larger. It will take out something close but would be very unlikely to get outside the case. Newer tantalum caps don't do this as often so they are safer. And most people replace then with electrolytic's which only smoke and stink.

 

Something else to keep in mind... Any components can just decide to quit working at any time, so don't always blame the power supply if it quits.

 

If it's been sitting in a box for years the electronics should behave, at least for initial testing. I would be more concerned with the mechanicals. Think grease, dust, rust, corrosion, fogging of the glass/mirrors.

 

What I would do is a very complete visual inspection inside and out. Not taking apart the scope itself but the drive assembly. Take the covers off of the bottom and sides and look closely. Then if you have 1, put a volt meter on the power supply before you connect it to the scope to check that it's putting out close to the right voltage. If I remember the caps are rated at 24 or 30 volts so anything near 24 or higher may next looking at. If everything looks good then pray and plug it in. Before you turn it on check the base and power supply (PS for short) for heat. The PS will be warm just being plugged in to AC but not HOT. Then turn it on and again check for heat, smoke, unusual noise. They do make some noise at startup but not a lot. Also look at the AMP meter on the base, if it stays with all bars lit up there's probably something sticking and drawing excess power.

 

If it passes all this put it through it's paces and see how it does.

 

Good Luck!

Let us know how it goes.

Tom


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#6 Piggyback

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Posted 11 August 2018 - 01:17 AM

https://m.youtube.co...eature=youtu.be

 

Just hope my LX200 time capsule stayed dry. Will start opening cartons over the weekend.



#7 rutherfordt

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Posted 11 August 2018 - 08:07 AM

 It's unlikely it will fail on first power-up . . .

I think that's incorrect-- many of these old scopes that have been stored for a long time without power will have something blow the first time they are powered on-- I can't provide a specific reference, but have seen mention of this happening several times here on CN over the years so I really think that its a mistake to power it up without changing the capacitors-- especially that one in the handset.  If you must power it up, use a 12-volt battery-- not the 18-volt converter that came with it-- a battery will not send an over-voltage into it-- the converter might.

 

Tom


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#8 NearVision

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Posted 11 August 2018 - 10:36 AM

Tom,

Thanks for the clarification. I was going mostly on generic experience with electronics not specific experience with these scopes. I know that caps will 'dry out' with age whether they are used or not, that's why I suggested the staged approach and watch closely for any signs of a problem. I do like your mention of using a 12v battery first. The lower voltage will cause less stress to the system if anything is weak and nearly ready to go. If I remember correctly the reason Meade went from 12 to 18 volts was because the motors were sluggish and they wanted to speed things up. Unfortunately they didn't increase the ratings on the rest of the circuit and we now have to replace caps. I've been running my classic on battery with a 12 to 18 step-up converter that is regulated so I'm not concerned about spikes just old age.



#9 Piggyback

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Posted 14 August 2018 - 12:49 AM

Thanks, guys. I have decided to let your info sink in. No rush. Will report when I feel confident for that first power-up. This thing is too precious for me to ruin it out of the box.



#10 Mike7Mak

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Posted 14 August 2018 - 06:03 AM

The Meade #1812 power supply is a DC to DC, 12v to 18v step up converter and is not the unregulated AC to DC one that fried the caps. But I would still do the cap replacement if this scope turns out to be 'new in box' before powering it up. At the very least the one in the handbox because as mentioned if that one goes the handbox is toast.


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#11 E Sully

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Posted 19 August 2018 - 12:50 PM

I have a couple of threads on the LX200 Classic which may be of help to you. 

Regarding the power supply, you will need a good 12v power supply with probably a minimum of 3.5 amps.  As for using the Meade #1812 D.C. 12 to 18V converter it will depend on whether it has the current limiting resistor pack installed in late versions of the LX200 Classic.  Post 20 in this thread shows the white resistor pack on the right side of the picture.  My scope is about the same age, so yours should have them.

https://www.cloudyni...12-or-18-volts/

I highly recommend that before you power it up for the first time you replace at least the capacitor in the handset.  It is shown in this thread.

https://www.cloudyni...-classic-lx200/

 


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#12 Piggyback

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Posted 21 August 2018 - 01:44 AM

Wow, thanks a lot for your advice E Sully.

As I am in no way prepared to do electronics work, I will try find me someone to perform the cap job. Your detailed advice and photography will be of invaluable help.




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