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Subject: LX200: Fix for Electronically Dead   Top

From: Howard Anderson <> Date: Feb., 2000

After more hours of debug than I should admit to, I have solved and corrected the problem. I'll document it briefly here because if I saw it, the rest of you have a finite probability of seeing it. I'll leave out all the intermediate steps.

Disassembled scope: Disconnected ribbon cable between front panel and main board. Turned power on, blew another fuse. The fuse on the front panel board (Meade calls it the "Power Panel" - Page 85 Meade manual.) did not blow when the initial problem occurred.

That means that the main board did not draw excessive power because that is what this particular fuse is for. So now the problem is isolated to the front panel board. Not much on the front panel board. Lots of connectors. One big capacitor. But wait! There is a 1N5400 diode rectifier on this board and a three pin voltage regulator. Resistance check of the 1N5400 while in-circuit indicated dead short both directions.

Never can tell in circuit containing solid state parts though. Unsoldered 1N5400. (You have unsolder and remove battery holder to get at it properly.) Dead short both directions. Cursory resistance checks of voltage regulator indicates some resistance and sensitivity to direction of current flow. Guess is that it is probably OK. 1N5400 is 3 amp with Peak Inverse Voltage of 50 volts. Maybe I switched power on at exactly the right time to experience a PIV spike of over 50?

Or this thing has been smoldering over the years and just chose last night to go poof? Went down to Radio Shack and bought 1N5402 (3 amps with PIV of 200V). Soldered diode in. Soldered battery holder back in. Fed power just to the front panel board (ribbon connector to main board still disconnected.) Replaced fuse from previous experiment. Threw switch to on. LEDs lit up on the front panel board. Turned power off. Reconnected ribbon connector. Reassembled everything. Powered up. Everything appears to be normal.

More thoughts: Power components such as this diode are always candidates for suspicion. Just the fact that a lot of power goes through them and they heat up. Since I knew something was drawing LOTS of current (enough to blow fuses) I was looking for something capable of drawing lots of current. Only two active components on the board, the diode and the regulator.

Diode was immediately suspect since they are easily damaged by inverse voltages above the rating. Also, with lots of current flowing, there are effects such as "metal migration" where the electrons actually cause the metal to flow slowly over time. Don't know if this happens much in diodes but it does happen to the "wires" of the metal layers of semiconductor devices. I used to work with the guy that did "life testing" and he was studying metal migration in hot circuits with fair amounts of current flow. Of course capacitors could have been the cause. I initially suspected the big one but I got a really good spark when, with power off, I discharged it through a screwdriver. Diode failures are much more common than capacitor failures. Anyway, really relieved that I didn't have to involve Meade, ship boards, etc., etc. Really helps to know exactly which board. Then I lucked out with a fixable problem. If it had been on the main board and one of the special-purpose chips such as the Xilinx ASIC or Gate Array (not sure which, I didn't look that closely at it) it probably would have been impossible for me to fix and I would have had to swap boards with Meade. I understand that they have "kits" available for customer support that will allow one to get the scope back in working order reasonably quickly. They were very responsive and did a great job in the past when I had a problem with the DEC motor.

Sorry, just one more footnote. An EE friend of mine thinks the diode is indeed a "crowbar" diode designed to protect against reversed polarity. He also notes that the 1N5400, with a 50 Volt PIV may be a better choice than the 200 Volt PIV diode I used (1N5402) since it would also protect against 120 Volt AC connection in case that mistake were somehow made. I'm probably going to leave the 1N5402 in there due to the pain of removing it. My theory regarding using a higher PIV was not too sound. I was thinking that it would be less failure prone which is true but that is not a good idea in this case. Bottom line: if that diode goes, replace it with a 1N5400 3 amp 50 Volt PIV diode, i.e., just the same as the one that's in there. Meade engineers got it right. I just had a bad diode I guess - or static charge blew it? - or ???. By the way, the diode is labeled "D1" on the circuit board.


Subject: Dead LX200 -- Things to Check --part 1 of 6   Top

From: Mike McAuley <> Date: Feb., 2000

Well, it finally did it! After owning my for about 3 months now, I turned it on tonight and the thing won't boot up. Here's what it does:

After turning the power switch on, it beeps - the keypad lights flash 4 times - and the display reads "MEADE". That's it. Nothing further. There is no sound of the motors searching for their indexing spot (or whatever it's called) and the display is frozen at "MEADE". The little glass fuse behind the panel is good.


Subject: Dead LX200 -- Things to Check--part 2

From: Larry <> Date: Feb., 2000

I had the same problem and it ended up being the cable between the keypad and control panel, after replacing the guts of the control panel and motors. It still boiled down to the cable from Keypad and scope.


Subject: LX200 Dead -- Things to Check--part 3   Top

From: Alf Jacob Nilsen <> Date: Feb., 2000

The failure was in the motherboard, which had to be changed. I did also change the keypad, but I doubt that this was necessary. MEADE generously supplied new spare parts...... Good luck


Subject: Dead LX200 -- Things to Check--part 4

From: Rob La Pointe

I had this happen once and it was due to a incomplete plug in on the declination cable. Just a thought, it had the exact same symptoms.


Subject: Dead LX200-- Things to Check--part 5   Top

From: Bob Genung <>

I've been the owner of a number of scopes through the years, most recently the 12" LX200, purchased and running happily since 1997 until 6 April 2000. Image with a SBIG ST-8I/CFW-8/AO-7 combo. I've been a subscriber (member?) of MAPUG since about 1994, I think. Through all these years I've seen dozens of pleas for help such as I submitted a couple of days ago, and yours of the 9th.

As I had never had a failure of the LX200 before, I had hoped there were magical solutions. In your case, there might be -in my case -not so, it seems.

As I had never invaded the innards of the LX200 before (although intended to do so this summer do some of the mods suggested for tracking improvement, etc.), I really didn't know what the possibilities might be. There are really very few. If they are electronic (most likely) forget about solving them yourself unless you know electronics, which, given your plea, I suspect like me, you don't.

In the last several days I've learned the following: (1) There are essentially five electronic components where things can go wrong -the two drives; the motherboard buried behind the plate on the bottom of the telescope; the daughterboard behind the control panel; and finally, the key pad. There are of course, cords, connectors, etc. I'm told by the Meade repair guy in London that it is extremely rare for the key pad or the daughter board to go.

There are really only two things you can check short of an electronic analysis of possible failure points on various boards. These are: The Dec cord. Make certain the connection inside the fork arm is in place, and that connections are solid (this is true of all cables). It is extremely unlikely that it will have come loose on the fork itself behind the Dec lock. That's a multi-pin connector designed to stay put.

The next thing to check is the cord on the keypad, although this is unlikely to be the culprit.

There's no point in checking the fuze behind the control panel. You drive is working, even though in runaway mode. You know there's power. When you pull the control panel, there's really only two serviceable parts. The fuze and the CMOS battery. If your scope is new, it's extremely doubtful the battery has gone, but if you have a test meter, check it out. The battery is easily obtainable/replaceable. The panel daughterboard is, by the way, connected to the motherboard by a ribbon cable. Just ensure it's on tight.

If you feel compelled to open up the bottom, it's easy. Remove the screws around the perimeter of the base, and note where they came from, as in some LX200s there are more holes than screws. Also, one acts as a ground. Towards the middle of the base, there are four small hex screws. Remove the two SMALLEST (they should be on top of the grouping of four). Once you've got the base off, your looking at the motherboard. Aside from checking the ribbon cable and drive cable, there's little more you can do here.

If you find nothing in these checks, it's probable the Dec drive is shot, and if that's the case, I've been told it's also probable the motherboard is shot as well.

Bad news now is that I believe that if your scope is still in warranty (check with your dealer first), I think it all has to go back to Meade. If it's not, you can order the repair kit couple of hundred $ in the US, I think. In it, you get a new MB and two new drives. For some reason, however, Meade does not include lubricant for the worm drives, although it does provide heat sink grease for two large white capacitors (I think they are, anyway).

In the past couple of days, Frank Loch, <> a MAPUG member posted the following when I said I replaced the MB only, not the drives:

Hi Bob -- You may have made a fatal error! The drives "MUST" be replaced at the same time as the MB. If a drive fails, it sometimes fails out the MB. If the MB fails, it sometimes fails a drive. Now if you replace the MB with a failed drive the new MB may be failed out by the failed drive.

I had this very sequence happen to me and since (five years and 3 additional kits later) am always very cautious about this. In my last instance I had an RA failure (probably brought about by unknowingly slewing the camera into the wedge on my remote permanent pier set up for several minutes -- it took two weeks of operation after that incident for the RA drive to progressively fail). Well my Dec drive was performing so nicely, I did not want to return it . At that time Mead was requesting I return " all the electronics" including cables $200 for the swapout).

Well when they returned it to me, I followed their instructions to replace all as a system, and lo and behold the RA drive was now working fine, but the "new Dec drive" was a "runaway". At that point Meade insisted it must be "my fault".

The only way they would let me proceed was if I would purchase a new MB + both drives (same as your kit) for $500, but "NO Warranty" on anything.

Save the two new drives that have not been placed in service, and try to get a known working MB to install simultaneously with them. Finally, the main electronic expert (though there are of course others) on MAPUG is Doc G. (Dick Greiner) Both Doc G. and Ed Stewart (see the Topical Archive) maintain extensive archives for just about anything related to the LX200. Doc G. sent me the following private mail:

I am sorry that you have had to face this problem. The reason it is not addressed on my website is that there is no solution that I know of. Since it happened so suddenly, it might well be a connection problem. But that is not certain. I would try checking the Dec cable. There is a connector on the front and the inside of the fork. Check both.

Check all other connections you can find. It would be good to check the battery behind the front control panel on the base, but that is not the problem, I think. That only makes the date and time malfunction, if bad.

If operating the scope on battery power, be sure the battery voltage is at lease 12 volts. This should be at least 14 to 16 volts.

The fuses are OK since the scope partially boots. If none of the above is the problem, I am afraid that something has gone wrong with the main computer or with the keypad. If you use a computer with the scope you might try to run the scope from the computer without the keypad.

I am really sorry, but this is one of the real sudden disasters that happens to the LX scopes. There may not be a simple solution. The scope computer may be dead. Bottom line? Probably your scope needs repair.


Subject: Dead LX200-- Things to Check--part 6 of 6

From: Marc Castel <>

Recently I reported a dead LX200 (Ver 3.30L) where, upon turning on the telescope, the hand control did not get past displaying "Meade". The problem was solved by removing a large buildup of grease around the Hall effect sensor of the RA index marker on the RA worm gear. This fix avoided a costly return to Meade.


Subject: New LX200 - RA Drive Runaway Top

From: Harry Gilday

>Well I just unpacked and setup the new 12" classic for the first time. Turned it on
>and the RA drive continuously goes at a fast (slew?) pace. I turn it off,
>and wait a reasonable time, then on, and the same happens.
>I've found a site which seems to indicate this is "RA Drive Runaway".

I know exactly how you feel. When I got my LX200 12" that is exactly what happened to me. Anyway the fix in my case was the cable had a short in it. I called the place I got the scope from, and they carrier to me a new cable. I think that Meade has problems with their cables. I have had the same problems with other Meade cables.


Subject: Description, Analysis, and Repair of Dec & RA Drives URL

From: Bruce Johnson

I've prepared a detailed description, analysis, and repair procedures for the Dec & RA drives at:

   <> Note: should open a new browser window over this one.


Subject: Runaway in Both RA and DEC

From: John Linse <> Date: Nov 2001

I'll bet the metal plate on the bottom of the scope is touching a few resistors/capicators. Have been there and cured the problem with a piece of Teflon/insolator cut to shape.


Subject: Another Reason for Scope Not Booting-Up    Top

From: Doc G

> doing the reverse operation to setup the magnetic
> sensor, it would go into RA runaway. This is after
> making sure there were NO shorts, even under the
> heatsink (heck board was not even mounted to base). I
> did this for SHORT periods of time, that heatsink is...

The above appeared in a recent post. It is absolutely essential that the circuit board be mounted in the base when doing any testing. It is essential that the tab on the 5 volt regulator be bolted to the base. This bolt provides the ground reference for the entire electronic circuitry.

Gene Chimahusky <>: Understood. All original tests were with the board mounted solid, cover on, and attached to pier. When it did not boot, then went checking with the scope off pier, same results. Then with base cover off but the board mounted to base. Any pressure on the SIP caused a boot stop at "Meade" if pressure is applied at power on or RA runaway if pressure applied during the reverse search for the sensor. It was only then in desperation was the board removed from the base. I tell you, I think this scope is jinxed. Besides alignment issues, I also have a mainboard that glitches, every once and a while it refuses to count or drive correctly slewing west. I got the upgrade kit from Meade, replaced the RA/DEC motor/worm combos, but the new mainboard refused to power up, stopped at Meade. Took base cover off, up it came. Investigating showed that the RA heat sinked SIP chip, if flexed even slightly, would cause the power up issue. I also found that if it were flexed when the startup was doing the reverse operation to setup the magnetic sensor, it would go into RA runaway. This is after making sure there were NO shorts, even under the heatsink (heck board was not even mounted to base). I did this for SHORT periods of time, that heatsink is there for a purpose! Seems there is a stress related fracture of one or more pins on the sip. I check with a 10x magnifier for cold solder, all looked fine.

Doc G: There is, on some boards, a very close tolerance between the heat sink tab on the SIP and some resistors that are mounted under the heat sink. It is possible that you have one of these boards. Check for this problem and possibly solve it by inserting a thin insulating tab between the heat sink and the components below it.

Gene Chimahusky: That was the first thing I checked, heck even removed the heatsinks. It was the flex of the SIP that was causing it. There were no cold solders visible with a 10x loop or cracks visible in the solder on either side of the board, there was nothing but the chips standing on the SIP legs. I do not know how many layers the board is, or if the pin via's were plated thru, but the top layers looked as they should.

Doc G: "This is after making sure there were NO shorts, even under the heatsink"


Subject: RA Initialization Sequence Information   Top

From: Abalos Fernando, Date: Feb 2003

For the last three weeks I been repairing my LX200. It had broken motor drivers and the RA comparator as well. And the processor never passed the *Meade* letters in the display. It was really hard to find the problems one by one. I got some help from list members (special thanks for Brian Bond) and the Topical Archives. As well as the schematics at (see below).

The important info I would like to share is something I have never seen in written and it has been key for me. The initialization sequence can not complete if the system does not receive the "0" level from the Hall-effect sensor in the RA shaft. This shaft moves first thing when turning on the scope, and it is looking for the "0" pulse. If the RA drive or motor or magnet or sensor... is wrong, the processor does not initiate and the display is always telling you "Meade" forever. However the processor or the memories or other digital part is in working conditions. A quick check is connecting to ground the pin #7 ( the one closest to the circular border of the board) of the connector that goes to the RA motor in the main board. It makes to initialize immediately if the processor is good.

I hope this can help to others suffering about an apparently dead LX200.


Subject: LX200 Scope Repair Service-- Telescope Service    Top

From: Doc G, Date: Aug 2002

There is now a company called "Telescope Service."
   <> Contact: Tim Prowten <tima_ttelescopeservice . com>
   Phone: 408-857-2859 or 510-708-3072 (Sacramento, CA)

I have been in contact with Telescope Service and feel they are fully qualified to carry out service on the LX electronics. They are genuine electrical engineers who have reverse engineered the electronics and seem to have found sources for the parts, a number of which are obsolete and hard to find. Note: members have reported that it is best to call as email response has been slow.


Subject: Supercharging (rebuilding) Service   Top

Dr. Clay Sherrod does a "Supercharging" of LX200 (and ETX) could get a major rebuild done.
    Try: <>


Subject: No N, S, E, W Slew --part 1 of 5   Top

From: Bostjan, Date: Oct 2002

I'm having for the ***FOURTH*** time in few years the same problem with my 16" LX200. After turning it on last night I became petrified in realizing that the telescope had stopped working again.

I am really desperate. The repair always lasts almost half a year. The Meade service always replaces the main board with a new one, which works for one year at most and then the problem returns. Unfortunately they are never able to tell me what was the cause of the problem.

The symptoms are virtually the same for the fourth time:

  • when I turn off the telescope after the last "good" observing session, everything seems OK
  • after some time (typically a week or so) I return to the observatory, turn the telescope ON and it doesn't work correctly any more (it seems to break when I am not in the observatory):
        1. the keypad displays [Meade] and the LEDs blink 
                -> the scope passes its startup tests on the DEC/RA motors 
                -> there is a moment of silence 
        2. the keypad displays [16" / Version 8.37L]
                -> the telescope tracks in RA for a second or so 
        3. the keypad displays [Telescope / object library]
                -> the RA motor stops tracking (regardless of mode - polar, land)
                -> (optional - not in all failures)
                the DEC motor starts moving at center(?) speed 
        4. all the menus on the keypad work well (object library, telescope, time,...)
        6. the telescope doesn't respond to the N/S/E/W keys 
        7. but the GoTo command works (scope slew to the object), even if computer-controlled.

I noticed also the following, if I turn on the telescope without the keypad, it:

  • the telescope passes its startup tests on the DEC/RA motors
  • the RA motor starts tracking normally
  • BUT I cannot operate the telescope trough a computer's COM port
  • if I plug in the keypad, the RA motor stops tracking, the DEC motor
    starts moving and the situation is the same as described before.


Subject: No N, S, E, W Slew --part 2    Top

Mark Cearley wrote:

It's been a couple of years but today I went out to the observatory. Took the dessert storm bag off my 12" classic (yes I have been keeping the drying crystals changed), fired it up, no Dec runaway, no dreaded "Meade" message, and unfortunately no N, S, E, W slew either. No movement at any speed. The motors will run if commanded with a "GoTo" command. Apparently the commands are getting from the keypad to the scope, or else I wouldn't be able to give any commands at all (right?) I did try the main board from my other LX200 in the 12", it worked normally. Also put the 12" board in my other scope (10" LX200), no change, still no N,S,E,W slew. Must be the board, but can't understand why motors will run with a "GoTo" command, but not from N,S,E,W keys. Also tried my other keypad.

Same results. Just to clarify, scope seems to track at normal speed ok, and will move in RA and Dec if commanded with a GoTo command, but will not respond from keypad N,S,E,W commands. Any ideas would be greatly appreciated.


Subject: No N, S, E, W Slew --part 3

From: Rick Sheve <>

I also had the same symptoms you describe in my 2-year old Classic LX200 10". I replaced the mainboard last year, and it has work fine since then.

If I had this problem again, I would probably talk to this place to see what they think and maybe even let them do the repair. <> Note: see part 4 following.

I think in my case, the problem may have been cause by doing a slew through the fork arms and my CCD and Flip mirror stopped the OTA. It was after this that I saw the problem with no slew in N,S,E,W, but would slew fine from PC control.


Subject: No N, S, E, W Slew --part 4    Top

From: Tim Prowten <>

To those of you with no N, S, E, W slew, but able to GOTO on your LX200 Classic I have just fixed a main board with these symptoms. The problem turned out to be one of the CCD Guider inputs (East in this case) was shorted to ground in the U11 74LS14 chip on the main board. You can check this on your board if you have a Digital Volt Meter (DVM) or some other way to detect a short circuit. If you want to check your board let me know and I will give you exact details, or if you feel adventurous go to my website and download the main board schematics from the technical page (sheet 1 has the CCD inputs).


Subject: No N, S, E, W Slew --part 5 of 5

From: Keith Graham

I occasionally have the same problem. I rectify the situation by pressing the GUIDE key, then momentarily pressing any direction, then pressing the SLEW key, and finally any direction key. I have heard of others having a similar problem and rectifying it in the same manner. I have no idea why this extra step should be necessary, but I have been using it for quite some time.


Subject: LX200 Inconsistant Boot-Up Problem    Top

From: Peter Millet, Date: Nov 2002

Roland wrote:
I have a problem with my LX200 when I turned it on, yesterday and today. The keypad lights, flash and stay frozen with meade written on the LCD display, and there is no motor noise. I tried to verify the connectors (Dec motor and keypad) and I switched on/off 15 times, after 15 times it was ok. Today I had the same problem and after 15 switch on/off, it switched on correctly. Then I switched it off/on several times and everything was ok.

I tried with the AC 220V and 12V power supply but there is no difference. The thing strange on my LX200 is that after several on/off, it switch on correctly.

What can be the cause of this problem ? Why this is not a permanent problem ?
---------------End of Quote-----------------

We have also had a boot problem. In our case there is an initialization of the RA motor but not of the dec motor and the boot process hangs at that point.

Interestingly, the problem does not occur when the scope is brought inside for closer examination or when we were looking for the source of the problem on very warm days. So, it is easy to see that Meade could have checked out the scope indoors and concluded it was OK.

We have removed the covers from the base and from the dec motor electronics searching for poor connections. We found that the connectors used are not of the most reliable kind and have done some minor repair to an unreliable connection. We also noticed that booting would continue when we brushed the circuit board with our fingers incidental to looking for loose connectors.

We have found that by putting a finger in a certain position on the Dec motor electronics board and then turning the power switch on, we can get a normal boot. After we take our finger away, the telescope continues to function. However, we have not attempted to train the drive (PEC) so we are not certain that getting through the boot process in this way leaves us with a telescope that is meets its specifications.

Our local electronics expert suggests that there could be a cold (i.e., faulty) solder joint at the point where we must press on the circuit board. Such a "touchy" connection could also be affected by temperature, so this is consistent with our experience: that is, it boots when it's warm but not when it gets to normal outdoor operating temperature in our northern climate. This may be easily fixed but will require us to remove the circuit board. At this moment we will not do that since we have a project under way and have apparently mastered the finger technique.

That your scope boots after 15 power cycles is the sort of strange, unreliable behavior I would associate with loose connectors and/or weak soldering in the circuit board. Of course a bad power switch (you could check with a voltmeter) could give you the same problems. and is easily fixed. An easy way to check that is to unplug your scope once you've got it working (or throw the switch on a power strip into which the scope is plugged) instead of using its power switch. Then plug in the scope to apply power. If it starts reliably this way, you might have a bad power switch.


Subject: Stopped LX200 clocks --part 1 of 4   Top

From: Greg Bolt <> Date: Nov 2003

I have had my wedge mounted 10" LX200 for over 6 years now and until recently had only ever had one problem with it, which was the main power supply failing. Last week a very strange problem has appeared. I have searched the Archives but cannot find anything like this.

After powering up I now have the following symptoms:

  1. The local time clock constantly displays 00:00:00 - and my attempts to set the local time are ignored.
  2. The sidereal clock constantly displays 00:00:00
  3. The RA display runs 'backwards' (i.e., Westerly motion) at what appears to be clock rate. And the RA display can be held constant by slewing East at the slowest slew speed.
  4. The telescope is actually tracking in RA at the correct rate, and the slow motion controls work correctly in all directions and axes.
  5. My Lat/Long settings are intact and correct.

So it seems there is a problem causing the sidereal clock to be stopped, and the scope is updating the RA in a westerly direction to compensate for the normal tracking motion. It is as if the world has stopped rotating, but the scope is still moving West, so the RA is updated accordingly!

End result: the scope's stored position is moving further and further away from where it is actually pointing, and this makes slewing almost useless.

So, does this mean I have to get a new main board etc., or is there a known solution for this problem? Or have I just missed something totally obvious?


Subject: Stopped LX200 clocks --part 2   Top

From: Greg Bolt

-----Original Message-----
From: Roger Hamlett
Interesting. I'd say 'change the battery'. This is inside the front panel, and is a 'button' cell, like those used to power the clock on PC motherboards. If it hasn't been changed in 6 years, it is due to fail, and may well have done so. So I'd try changing this, before looking for anything worse. Sometimes when this type of battery fails, the behavior can be very 'odd', with some parts of the chip keeping working to lower voltages than others. The Lat/Long, is often held, even when the voltage is too low to run the clock. The LX200, actually contains two clock chips (DS1202, replace with DS1302), so the odd behavior, might be explained if one had stopped, rather than both. These are reasonably cheap chips, and if you are electrically competent, or know somebody who is, replacement of these alone, is probably the next stage, as is a check of the two diodes, that power the chips (if the one from the 5V rail had failed, the chips would only be running entirely off the battery - if this had then failed as well, the behavior might make sense). If you look through the posts here, you will also find that there is a repair company, who might well be able to service your board, and given that the main logic still seems to all be working, this would be cheaper than replacing the board.
-----End of Original Message-----

I have replaced the backup battery with a new one, but unfortunately the problem still exists. The old battery still measures 3.0 volts, the new battery is 3.3 V. I also checked to make sure the voltage was present on the front panel board, just in case the battery contacts were bad. So now it seems I do have to move onto more serious things. Checking the clock chips, and surrounding electronics will be my next step. I am in Australia, so getting the main board off for repairs etc. is a bit more of a hassle for me... Given that the scope is still essentially operational, that seems to narrow down the likely problem area (hopefully!).


Subject: Stopped LX200 clocks --part 3 of 4

From: Roger Hamlett <>

----- Original Message -----
From: Greg Bolt
I have replaced the backup battery with a new one, but unfortunately the problem still exists.
----- End of Original Message -----

Rats. It was worth checking. 3V, was getting very low. I'd next try verifying that the chips are receiving power themselves (a failure on the supply diodes, would stop this). If you have not already got them, pull the circuit diagrams from the Archives. These are not 'perfect', but cover the majority of the design quite well. The two diodes are D1/D2, while the clock chips are U7/U8. Personally, I'd probably just replace all four parts. The chips are cheap (about 3 each in one off quantities). If you have problems sourcing them, they are easily available in the UK, and I could send you a couple.

There isn't much 'surrounding electronics' at all. Two crystals, the chips, the supply diodes, and then these connect directly to the programmable logic array that forms the heart of the scope logic.


Subject: Stopped LX200 clocks -- Solution Found! --part 4 of 4   Top

From: Greg Bolt <>

Right now I have to eat a bit of humble pie. After I spent time studying the schematics, and finding a supplier for the clock chips here in Oz, I took the cover off to get at the main board and immediately noticed the likely problem -- the main ribbon cable connector was almost off at one end. I pushed it back on properly, booted the scope and the clocks now work perfectly!

I believe the connector was partly dislodged when I removed the front panel about 12 months ago while I was diagnosing another problem (which turned out to be the power supply, and which later totally failed in a puff of smoke). In the process of unplugging the front panel connector I must have pulled too hard on the cable... It apparently took 12 months for one of the pins to actually lose its connection, maybe after I bumped the scope recently or something. The funny thing is that when I replaced the backup battery last week I was very careful not to pull on the cable, because I had remembered reading a comment somewhere about being careful with it.


Subject: LX200 Water Damage Repair Suggestions --part 1 of 7    Top

From: Bob Shultz, Date: March 2003

Being in medical electronic service for too many years, I have worked on systems that have had water damage, coke damage, coffee, etc. Usually, you can just remove the circuit boards, go to a good electronic store and buy a good spray cleaner/solvent. Make sure it is the kind that is safe for plastics. These cans usually cost around $15 each. With the boards removed, hold the boards over a catch basin and spray and spray and spray, when the boards are still wet, scrub them with a stiff bristle nylon brush, also available from the electronic store, lastly spray again and let dry. This should take care of the problem.

----- Original Message -----
Recently had water leakage in my observatory - water has gotten into
the base of the LX200 causing erratic electronic malfunction.
I imagine it will be shipped to Meade for repair.
----- End of Original Message -----


Subject: LX200 Water Damage Repair Suggestions --part 2

From: Radu Corlan <>

In low-voltage circuits, shorts aren't that bad - they don't mean immediate destruction. Also, water doesn't usually create 'hard' shorts.

IMO, the best strategy to use when you have some piece of electronics wet is to: first remove power from it; then take it apart, clean up (my recipe would be distilled water + alcohol + a few drops of dishwasher soap). To make sure the cleanup is complete, remove parts from sockets (and of course any batteries), then rinse in several changes of water.

Then, dry the thing thoroughly with a hair drier (on cold air, or with care). Make sure the board is well-dried even in inaccessible spots (under parts etc.). It helps to leave it for a day or two in a warm place to make sure it's dried.

If the telescope was still working, even erratically, there's a 99% chance that a good clean and dry will completely restore it.


Subject: LX200 Water Damage Repair Suggestions --part 3

From: Richard Shell

While the solution suggested might sound pretty simple, I have found that if a circuit is properly protected, just drying the unit out, removing gunk, and replacing the fuse may do the trick. Before manufacturing focusers, I used to manufacture audio equalizers in the 70' and 80's and went through this experience with customers several times. It's always worth a try!


Subject: LX200 Water Damage Repair Suggestions --part 4 Top

From: Roger Hamlett <>

As a reference point, I used to work for a company, where the test equipment was _all_ cleaned by water immersion annually. This included kit like oscilloscopes!... The units were cleaned in _pure_ water, and then dried in a special dehumidified chamber, before recalibration. It prevented problems from dust build up etc.

Now the key thing is that water on it's own does no damage to electronics, provided it is pure (in fact the best thing you can do if coffee, or something more corrosive is spilt over electronic equipment, is to get a gallon of distilled water, and rinse the kit off with this!). However two things will cause damage. The first is if the equipment is not completely dry when you attempt to restart it. The second is having power available inside the equipment when it is immersed. In this context, the part most likely to be harmed in an LX200, is the circuitry round the real-time clock, where the battery will cause corrosion. Water is actually quite a good insulator >19Mohms/cm^3, but if any acids are present, the whole game changes. Rain water will be fairly clean, but have a slight acid content (depending on the rain, and local pollution levels - thunderstorms are normally more acidic).


Subject: LX200 Water Damage Repair Suggestions --part 5

From: Jim Henson <>

We assemble circuit boards here and have experience in washing them. Almost all circuit board manufacturing now uses water soluble flux in the soldering process, and are washed with water. (as odd as it seems)

There are a few things to watch for. Socketed components can be removed and washed separately, but it is not necessary. Remove any batteries, and tape over PC mounted speakers to keep water out. Paper labels, like on socketed chips and ROMs, will likely get messed up.

Use only water, with no additives like soap or alcohol. You can do the bulk wash with hot tap water, but finish with hot distilled water. Tap water has minerals and often chlorine and other goodies, so the board must be rinsed thoroughly with DI or distilled water. Don't use hot and then cold water, as the temperature shock might be a problem.

The board will start to dry due to the hot water used, but air dry with clean compressed air before the water dries. Be sure to blow out any components like switches and connectors, and blow the water out from under ICs. Follow with hot air, a hair drier will work fine. The board can be heated up to the point where it is almost too hot to hold, but not much more. Be easy on plastic components that can melt. Heating the board drives out moisture that the air didn't get. The board can be put into service as soon as it cools down.


Subject: LX200 Water Damage Repair Suggestions --part 6

From: Tim Long <>

You might be surprised by the water cleaning. Besides, what have you got to lose? Worst case, its still broken and you ship it to Meade. Best case, it could fix the problem and you save a big wedge of cash and lots of hassle. Has to be worth a try.

Sometimes moisture can get drawn into the spaces between and underneath components. A good cleaning with something like Isopropyl alcohol, followed by a thorough drying out might just solve the problem.


Subject: LX200 Water Damage Repair Suggestions --part 7 of 7 Top

From: Turgut Kalfaoglu

I recently dissected a cell phone that had fallen into a tub of water (!) I found that the ribbon wires going into connectors had been corroded. I used an oily-contacts cleaner spray to clean them out, the phone is as good as new.


Subject: The Dreaded "MEADE" Only Display on Hand Controller --part 1 of 2 Top

From: Gene "lynol1000" <>

Alan Sickling wrote:
>My 12" is off its pier at the moment (have a GPS model on that
> temporarily). Last night looked a good night for conditions, so I
> put the Classic on a tripod to try to do a precision collimation on
> the OTA. Had to use ALT/AZ (which I had never used before with this
> scope) and ran straight into a problem with the alignment. Wouldn't
> pass the "1 or 2 star" alignment option step. I quickly found this
> was another of Meade's wonderful Instruction Manual boobs and got
> past this. Then found that the seeing wasn't as good as I expected
> and couldn't make much improvement to the tube collimation. I waited
> a couple of hours for thermal equilibrium and tried for an hour or
> so but couldn't get an Airey disc.
> However, on two occasions during this session, I heard some
> unexplained beeps from the scope and on looking at the handbox (controller)
> display found it illuminated with only the "Meade" line displayed.
> The scope was disabled from this point on. I switched off and
> attempted a restart. To my surprise, the scope started normally, re-
> aligned and worked perfectly for an hour or so, then repeated the
> event. Again, it restarted normally and continued to work until I
> decided I'd had enough and switched off.
> Now I have read about this problem and my understanding is that -
> - it usually occurs on initial switch-on
> - the scope is always "dead" after it has occurred
> - the condition is permanent and requires a mainboard repair.
> - I vaguely remember reading that it is due to failure of the
> mainboard to handbox transmission ICs.
> Only other info is that I have added some protection diodes around
> this area of circuitry (very similar to what others have done). It
> was also an exceptionally cold night for this neck of the woods -
> got down to about -6C.

Alan, I have had three mainboards in my LX200

-First one went kinda crazy, would 'work' for a while then all of a sudden forget what it was doing, no reset beeps or such but would just start tracking as if it were pointing someplace else (Al/Atz)

-Second board had the symptoms of the 'Meade' only display, I tracked it down to the ra/dev driver sips on the mainboard having broken pins at the sip case, I could get Meade only, run-away RA and run-away dec by applying pressure to the sips (last picture on this page:

<> the rectangular aluminium plate partially covered by the wires near center is the heatsink for the sips.

-Third one has just worked...

For your 12", was it perm mounted EQ or did you place and remove? Reason I ask is now with the 12 on the tripod, you have different stresses placed on the bottom plate. The board I had that showed the 'Meade' would 'work' as long as it was not on the tripod.


Subject: The Dreaded "MEADE" Only Display on Hand Controller --part 2 of 2 Top

From: Alan Sickling <>

Gene, once again, thanks for your input. To reply to your points in turn:

I modified my mainboard soon after I got the scope. I inspected it minutely at that time and it looked in excellent condition with no signs of any dry joints. (I have 45 years experience of electronics, including maintenance, design and construction.)

Don't know how old the instrument is but its serial no. is 115657 - mid-1998, perhaps?

I use a 15v supply from a linear PSU (I don't care for SMPSs much) so no, I don't use the Meade unit.

The mains power here in the UK is probably the only thing we have which is superior to your services. Highly reliable, stable voltage levels, free from large spikes and noise and no problems at the time in question. (Don't know how long it will remain in this state with what the Government wants to do with it, though.)

I think the Meade mainboard electronics are not badly made, although they are not up to the best standards. However, I do agree with you about the arrangements for the heatsinking around the L2724 power ICs, which is a bit pathetic. Meade's heatsink is inadequate, which is why they bolt it to the baseplate to supplement its capacity. Unfortunately this causes the problems you mention. In my instrument I have replaced the ali plate with a larger, copper heatsink which is mechanically braced to the PCB platter. It can't eradicate all the stresses at this point, but it's very much stronger than the original mickey mouse arrangement.

I'll still open the base up to have a look, when I have a moment. Your info about your board working on a wedge but not a tripod is interesting. I'll think about that.

Meanwhile, I've had the scope in the house all day, on the tripod, and have left it on to see what it does. No repeat of the problem yet. That might signal a temperature effect, perhaps?


Subject: Canadian LX200 Repair Service

From: Ed Stewart Date: Feb 2005

In recent issues of S&T there has been an ad in the Market Place section for a Canadian firm, Norteck, that offers a repair service for LX200s: <>


Subject: U.K. based LX200 Repair Service?

From: John Mahony, Date: March 2005

You can try Brian Bond at: <> He's repaired a number of LX200 classics.


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