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Subject: re: LX200's that catch cold
From: Brandon Jones
Reply To: mapug@shore.net
Date: Thu Dec 14 03:32:27 1995

>What's that one-liner? Brandon rushes in where Angels fear to tread? ;-)
>Seriously, that B.J. does have moxy. Now, personally, I'd worry that tweaking
>the pots on the encoder chips (I presume he means the things that are
>on the motor assembly PCs) could seem to fix a problem but really
>
Ok Robert you wanted the boring reply...

Its just the same as mechanics listen to cars and know what the
problem is.This micro- board is excellently designed and simple
mechanically ,the quality is as good as any I have seen in a
microcontroller system such as this.They have also kept the
interaction with connectors down ie as few connections to the
outside world as possible.Microprocessor circuits excluding
software bugs are extremely reliable and the syptoms showed
from simple checks that the board was ok so it had to be an interface
problem.There are only the handcontroller and the motor input
output signals.I unplugged the handcontroller (no Effect)
unplugged the dec drive connections(no effect).Power supply
was stable as I said and I checked by replacing it anyway.
So whats left is the RA encoder interface.Motor works(driver
interface ok) but appears to be
being told wrong information about motion.The infra-red diodes
either work or do not work usually (they must be doing something here)
from symptoms.Ok so whats left a horrible analogue circuit that can
suffer from change in many ways especially temperature.Human
interaction at this point ie did the tech set it up correctly in the
first place(apparently yes).Have the settings drifted or changed.
Problem No shop manual guess from here on or get instrumentation
to check.
This fault comes in the category of post production within
six months of sale and use and is perfectly within any spec that
any manufacturer would have to cope with forthcoming from a piece
of equipment of this complexity.From this list it appears from my
memory only to have been mentioned once before.My previous scope
never suffered from this problem so the conclusion from that would
be that there is no problem with this part of the scope design it was
just my bad luck.However part of the function of this list is to pass
on things like this to others just in case they have the same
problem.None of this information however presented by me
is intended to slag off Meade products in any way only to hopefully
imrove them for others at a later date if Meade take up on a
production level feedback from members of this list.

Interesting isn't it when you think back carefully I have never heard
anybody say anything detrimentral about the optics which is really
what this is all about not electronic crap.Yet when I have shown
my scope to people they have only worried about the optical
quality and did not seem to care two hoots about the electronic
quality or reliability or the problems they might encounter if it
went wrong.This where I fall over because my knowledge here relies
on Meade totally doing their job and supplying a quality within
reason for the price of the optical part of the telescope(there
arn't any trimpots on the mirrors) Other than the collimating screws.

Brandon S. Jones.