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LX200 classic won't power up

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#1 aries339

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Posted 19 June 2014 - 12:06 PM

Hi everyone - first post here.

I tried searching the forums already but I didn't seem to find anything specifically like this...

I'm having trouble with my LX200 classic 10". I've had it out for a few days playing with it, going through all the stuff I've had in storage for a few years. Yesterday it was powering on and working perfectly.

Today, I went to test a spare front power panel I had. I had tested it a few days ago: powered-on, keypad and both motors, and it seemed fine, but I wanted to test the reticle and focus today. I took the one I had been using off the telescope, put the spare one on, plugged it in, turned it on, and the ammeter flashed 1-2 bars for a split second, and then nothing. Turned off, unplugged, plugged back in and turned on, NOTHING - no ammeter flash or anything.

I thought maybe the spare had finally gone bad, so I put the original panel back in the telescope and exactly the same thing happened.

I opened the bottom panel to make sure the ribbon cable was connected underneath and it was fine. (not sure if that would be related anyway)

I used my multi-meter on the adapter and I get NO reading at all. But I have no way to be 100% sure that my positive probe is making contact inside the plug. I checked the fuses in the adapter and behind the power panel; both are good. So I don't know what else to try and I have a few questions right off the top of my head:

1) Was the initial ammeter flash just the capacitor discharging? Or did I fry something somehow??

2) Is there anything else to test before I go on eBay for a new power adapter?

3) Any other suggestions from you smart people out there? I'm only basic with my multimeter; I am NOT an expert.

Thank you a TON everyone for your help!

#2 DAVIDG

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Posted 19 June 2014 - 02:55 PM

If the AC/Dc supply is putting out the needed 18 volts then one of the tantalum capacitor most likely fried. There are a couple them in the power panel, hand paddle and also on the main board under the fork. Here is a link to a site that has the schematic that show were they are located. http://www.lx200classic.com/

- Dave

#3 aries339

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Posted 19 June 2014 - 03:39 PM

Hey thanks for the reply. I'm not sure I'm getting a good test on the multimeter. The probe "bottoms out" inside the plug and I touch the other probe to the outside of the plug. I get no reading. The meter fluctuates a little when I move the probes but I'm definitely not seeing anywhere near 18 volts ever. But I'm not certain how/if/where contact is being made with the probe inside the plug.

Is there any other way to make sure it is/is not the power adapter?

Thanks again!

#4 LoveChina61

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Posted 19 June 2014 - 07:12 PM

use an Ohm meter (voltage tester) to test the scope’s power supplier. It should be outputting about 18 volts, so set the Ohm Meter to something like 20 volts so it can test for 18 volts properly. Put the Ohm Meter’s black prong on the outside of the power supplier’s tip-plug, and the Ohm Meter's red prong inside the power supplier’s tip-plug. The red prong should be touching squarely against the inside wall of the tip-plug, not on the bottom of the tip-plug. Is it putting out around 18 volts?

You can read more about how to do it HERE .

#5 aries339

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Posted 19 June 2014 - 08:28 PM

I can't tell if I'm making contact with the inside wall; the probe fills the hole and I can't see inside. I know "how" to test the adapter; I'm just not sure if I'm making contact with the positive probe.

#6 Christopher Erickson

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Posted 19 June 2014 - 09:25 PM

The hole in the middle of the power plug should entirely be the positive connection of the power. Having the red probe anywhere in that hole should give a voltage reading, as long as the black probe is touching the outer-metal sleeve.

And FWIW, Ohmmeters only measure ohms. Multimeters measure ohms, volts, milliamps, etc.

It sounds like your power supply has gone bad.

#7 aries339

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Posted 19 June 2014 - 10:06 PM

Thanks Chris - I'm HOPING it's just the power supply...

#8 LoveChina61

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Posted 20 June 2014 - 01:49 AM

And FWIW, Ohmmeters only measure ohms. Multimeters measure ohms, volts, milliamps, etc.


Thanks for pointing that out :)

#9 aries339

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Posted 20 June 2014 - 08:29 AM

I just checked again - 00.00 DC volts on the multimeter, both before and after the fuse. So I'm gonna go with bad power adapter for now.

Gotta try to find a good replacement now!

#10 jaymcgil19

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Posted 20 June 2014 - 01:14 PM

Try a higher voltage range like 200vdc if you had it set on the 20vdc range it would show as 00.00 since it's probably putting out over 20vdc

John M

#11 Christopher Erickson

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Posted 20 June 2014 - 01:59 PM

Try a higher voltage range like 200vdc if you had it set on the 20vdc range it would show as 00.00 since it's probably putting out over 20vdc

John M


If the range on the multimeter were set too low then it would show pegged, 99.99, OL, ++ or some similar over-range indicator. It would NEVER show something like "00.00" Most modern multimeters are auto-ranging anyway.

However if the input type was set wrong then it could display "00", even though there was 18VDC present on the input. An example would be having it set to AC volts instead of DC volts.

#12 aries339

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Posted 22 June 2014 - 11:38 AM

OK I tried the following ranges, all in DCV:

1000, 200, 20 all show zero. I put the Pos probe in the center and when I touch the negative to the outside the "-" flashes before the zeros for a second and then disappears.

2 and 200m both show minor fluctuations, like .01-.03-ish when the negative probe is touched to or removed from the outside of the plug.

That help determine anything??

#13 aries339

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Posted 22 June 2014 - 12:03 PM

And also... I've found multiple threads and other forums talking about replacement adapters for the LX200 classic in 18v DC. Everyone has a different opinion. Does anyone here know of a replacement adapter that is "definitely" safe and compatible?

#14 JimMo

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Posted 22 June 2014 - 12:47 PM

I had an 8" LX200 and when my power supply went bad I replaced it with a Meade 12v. power supply with no detrimental effect except the normal highest slew speeds were slower. I always slowed the slews down to help check the noise, my observing buddies all would complain I was using a coffee grinder if it was set too high.

#15 Christopher Erickson

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Posted 22 June 2014 - 12:58 PM

This should work well:

http://www.amazon.co...g-Universal/...

#16 aries339

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Posted 22 June 2014 - 01:23 PM

This should work well:

http://www.amazon.co...g-Universal/...


I have read on this and other forums that auto-switching is dangerous for a telescope's electronics... no?

#17 nitegeezer

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Posted 22 June 2014 - 02:05 PM

A switching supply is fine if it is designed right, the problem being that one has no idea of the quality of design.

If you really want to be safe, use a battery. That is the only way you are really guaranteed there will be no unwanted spikes. There is absolutely no failure mode that will allow a battery to overvoltage.

There are a wide range of battery packs out there with a power port built in.

#18 Christopher Erickson

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Posted 22 June 2014 - 06:56 PM

No, 110-220 auto-switching would be just fine.

The big danger with universal adapters is getting the plug polarity backwards or setting too-high of a voltage.

#19 aries339

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Posted 23 June 2014 - 12:28 PM

Would anyone mind telling me if this would be acceptable?

http://www.ebay.com/...c-series-Tel...

#20 nitegeezer

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Posted 23 June 2014 - 01:02 PM

I do not have a classic, so I do not know for sure, but have read where these were part of the problem. The big issue is what kind of voltage spikes can it put out and has your scope been modified with the higher voltage caps. Christopher pointed to one that he was sure was safe and it is only $3 more than the one on ebay, spend the extra $3.

#21 jrcrilly

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Posted 23 June 2014 - 01:08 PM

Would anyone mind telling me if this would be acceptable?

http://www.ebay.com/...c-series-Tel...


It would certainly be both safer and more reliable than anything Meade ever offered for that purpose (don't ask me how many of those "booster" circuits I have repaired over the years). Those brick supplies are true switchers with good regulation and overvoltage protection and do a nice job (I have any number of them around here in various voltages). The only qualm MIGHT be that they forgot to provide the output current spec in that ad - but those units are always somewhere between 2 and 5 amps and anything in that neighborhood would be plenty. You could inquire just to be certain.

#22 aries339

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Posted 23 June 2014 - 08:01 PM

I do not have a classic, so I do not know for sure, but have read where these were part of the problem. The big issue is what kind of voltage spikes can it put out and has your scope been modified with the higher voltage caps. Christopher pointed to one that he was sure was safe and it is only $3 more than the one on ebay, spend the extra $3.


I certainly don't doubt Christopher that the one he recommended will work, but I'm concerned that the additional length of the plug will impact the base of the fork when it's slewing.

#23 niteman1946

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Posted 25 June 2014 - 06:24 AM

I use these two items from Scopestuff. They've been working for over 2 years on my classic.
Mark

http://www.scopestuff.com/ss_rapa.htm

http://www.scopestuff.com/ss_ps16.htm

#24 aries339

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Posted 26 June 2014 - 11:54 AM

Hey thanks for the advice!

Just so everyone knows, I've been in contact with the seller of the eBay listing I had asked about: http://www.ebay.com/itm/351103238710

He says that it is 18vDC, 2 amps, with correct polarity (positive center). So it certainly seems like that's a good option, in case anyone else is looking too.

#25 aries339

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Posted 10 July 2014 - 09:28 PM

Finally got the adapter from that eBay listing. The label says 18vDC but it says 3.5A - not the 2A like the stock adapter (and like what the seller TOLD me).

3.5A should be safe to use, yes? I tested the voltage with a multimeter and it was very consistently right about 18.2.

Thanks!






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