Dead LX200--Things to Check
Subject: LX200: Fix for Electronically
Dead 
From: Howard Anderson <handy primenet.com> 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
From: Mike McAuley <mikemcaflash.net> 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 <Wld714aol.com> 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
From: Alf Jacob Nilsen <ajnilsenonline.no> 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
From: Bob Genung <rgenungrgenung.free-online.co.uk>
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, <flochearly.com>
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 <castelrobosky.com>
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
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:
<http://www.mapug-astronomy.net/ccdastro/decfix.htm> Note: should open a new browser window over this one.
Subject: Runaway in Both RA and DEC
From: John Linse <HeadleyObsaol.com> 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
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 <lynol1000yahoo.com>: 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
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 telescopeservice.com
(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
From: Doc G, Date: Aug 2002
There is now a company called "Telescope Service."
<http://www.telescopeservice.com/>
Contact: Tim Prowten <timtelescopeservice
. 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
Dr. Clay Sherrod does a "Supercharging" of LX200 (and ETX) scopes...you could get a major rebuild done.
Try: <http://www.arksky.org/supercharge.htm>
Subject: No N, S, E, W Slew --part 1 of 5
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
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 <sheveswbell.net>
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. <http://www.telescopeservice.com/services.htm>
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
From: Tim Prowten <timtelescopeservice.com>
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).
<http://www.TelescopeService.com/>
----------------------------------
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
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
From: Greg Bolt <gboltiinet.net.au> 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:
- The local time clock constantly displays 00:00:00 - and my attempts
to set the local time are ignored.
- The sidereal clock constantly displays 00:00:00
- 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.
- The telescope is actually tracking in RA at the correct rate, and
the slow motion controls work correctly in all directions and axes.
- 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
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 <ttelmahntlworld.com>
----- 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
From: Greg Bolt <gboltiinet.net.au>
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
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 <rcorlanpcnet.ro>
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
From: Roger Hamlett <ttelmahntlworld.com>
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 <jimhbga.com>
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 <Timlong-family.com>
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
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
From: Gene "lynol1000" <lynol1000yahoo.com>
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:
<
http://www.geocities.com/lynol1000/lx200_internals/index.html> 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
From: Alan Sickling <alanthesicklings.force9.co.uk>
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: <http://www.nortek.on.ca/meade_repair.html>
Subject: U.K. based LX200 Repair Service?
From: John Mahony, Date: March 2005
You can try Brian Bond at: <www.bbcl03736.pwp.blueyonder.co.uk> He's repaired a number of LX200 classics.
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