Hello everyone,

Please allow me another posting of the following message without a lot of
scolding. I initially received two suggestions on possible fixes, but
neither seemed to make sense (at least to me). One Mapugger suggested that I
had fried some sort of encoder, LED, or diode (I think), but as the
description below states, I had this problem before I hooked up the homemade
battery and fried the circuit board. The other suggestion was that I needed
to "tweak" some kind of output on the new circuit board using an
oscilloscope. Again, I had this same problem before I replaced the board, so
are they saying both boards were "untuned?". Also, I have looked all over
the LX50 circuit board and cannot find any kind of potentiometer, adjustable
resistor, etc. What am I supposed to "tweak?"


In a message dated 16-May-99 6:53:12 PM Central Daylight Time, SkySgt writes:

> Dear Mapuggers,
>
> I have been reading the last few posts from people that have been having
> problems with runaway RA drive. I too have been having this problem
recently
> with my 10" LX50. Here is a synopsis of the problem:
>
> When I initially turn on the scope, the electronics go through the
power-up
> sequence OK and when complete, the RA drive kicks-in. It usually starts
with
> continuous drive to the West in a "pulsating" fashion (Be aware that I'm
not
> sure which directions my keypad is setup for, I changed the setting when I
> first got the scope, but have forgotten which I set it to. The continuous
> drive direction could actually be reversed from that which I have stated.
I
> can find out for sure, if it matters).
>
> I can stop the continuous drive by quickly depressing the E button on the
> keypad. From that point on, it seems to work fine until I have to drive
the
> scope in the West direction (by depressing the W button on the keypad), at
> which time the "pulsating" continuous drive starts again. I have played
> around with different scenarios and have found the following to be true
every
> time:
>
> Speed
> 32x - Problem always occurs after depressing the W button on the keypad.
> 16x - Problem is intermittent. Sometimes it happens, sometimes it doesn't.
> 8x - Drive works fine, always.
> 2x - Drive works fine, always.
>
> At present, I have swapped out keypad controllers with a friend. His
keypad
> does not correct the problem, so we can safely say the problem is not in
the
> keypad.
>
> I recently had to swap out the entire circuit board on the scope due to a
> boneheaded error on my part (I hooked up a marine battery to the scope in
> reverse polarity .... fried the circuit board).
>
> *** IMPORTANT SAFETY NOTICE TO ALL ELECTRONIC SCOPE OWNERS ***
>
> Ensure correct polarity when hooking up power to your scope! Reverse
> polarity WILL damage your electronics. The Meade Rep. said it should not
> have damaged the motors though, since almost all motors do not care about
> polarity. If you give them reverse polarity, they'll just run in the
reverse
> direction.
>
> The new circuit board from Meade has the new Rev 6.1 chip on it. However,
> the problem still exists (BTW, the problem existed even before I fried the
> circuit board, so the circuit board is not the culprit).
>
> I have taken the baseplate off the scope and viewed the RA drive motor and
> gears in operation. All seems OK except for the fact that there is an
> assembly at the very end of the RA motor shaft that looks as if it may have
> a problem. The assembly looks like some sort of electronic or magnetic
> encoder. It consists of two thin slotted wheel assemblies spaced micro-
> inches from each other. One is attached to the RA motor shaft and is
> constantly spinning (when power is on). The other is attached to some kind
of metallic arm or
> brace, and is identical to the other wheel, however, it is stationary and
> does not spin (Someone has suggested to me that this is an encoder that
uses
> an LED. The slotted wheels count the drive steps). The abnormality in
this
> assembly is in the stationary slotted wheel. This wheel seems to be warped
> in places and has some sort of flat black coating on it which is chipping
and
> flaking (The coating is not on the side that faces the moving wheel). The
> warping does not interfere with the moving wheel, but is farther from the
> moving wheel in places. The place on this non-moving wheel, where it looks
> as if a diode resides, is quite close to the moving wheel and is not
warped.
> I do not know if this is a problem or not.
>
> If anyone has encountered this before, or has any suggestions on what I
> should do before calling Meade, please reply directly to me at:
>
>
> Or via my website at:
>
> http://members.aol.com/skysgt/index
>
> Thanks in advance!
>
> Pat Lanclos

View index by [date] [author] [subject]
Previous message: [M]: [M] Pictor Values Found!, Greg
Next message: Re: [M]: LX200 software problems!, Email address hidden
Next message in thread: [M]: Still having LX50 RA problems, William Cannistra