I have a meade lx90 8inch 3 years old with autostar 497--when i try to raise the scope up it keeps drifting down also having problems with intermitant slewing on set up-both motors working ok

It depends on which model Meade telescope you own-- you never said?

Yes you can swap a 494 for another 494-- but we need more information to be able to say a 497.

The contrast and brightness can be reset --- here is the manual -- how to do this is listed in the manual. If this does not repair the controller then you will need to buy a new hand controller-- the 497 hand controller is available used on Ebay from time to time.

http://www.meade.com/manuals/TelescopeManuals/ETXtelescopes/ETX-90%20w-autostar%20man.pdf

Manual down load above--

These scopes have many bugs in the firmware and are not a mature technology. Some people have issues and some do not.

About the only thing you can try is to reload the firmware using the SC CARD method. Contact Meade or read the manual to learn how to upgrade the firmware using an SD flash memory card.

Other than that the scopes will need to be returned to Meade for repair.

Many Meade dealers can order you a new hand controller, either Autostar II, or the 497 controller. Contact a large telescope dealer in the UK, or you can order direct from Meade here:
http://www.meade.com/support/index.html

There is a small spring inside that sometimes gets STRUCK DOWN-- this automatically turns off the internal batteries, as the scope things a separate 12volt power pack is plugged in.

Get an external 12 volt power pack and the correct 12 volt cable, and power it up.

If the light comes on and it works the switch is broken. Not really a problem as you should always run a goto scope on a separate power pack.

Did you update the 494 controller improperly with 497 controller firmware. You must use this updater software :

http://www.meade.com/support/auto/Au2ver59.exe

Hold down the ENTER key and the scroll down arrow key at the same time abd power on the scope. This will place the hand controller into the SAFE load function and you will be able to do another update.

If you plugged or unplugged the controller cable with the scope turned on you may have burned out the controller. Contact Meade:
http://www.meade.com/support/index.html

The manuals are all available to download from www.meade.com.

If your scope has the motor drives and a control panel into which a controller could be plugged, then you just need to buy an Autostar 497 - always available on eBay for about £85. However, there are older models of the ETX which only have one motor or as a spotting scope for terrrestrial use with no motors - Autostar cannot be connected to these.

Look at the pictures of scopes on eBay which come with Autostar - if your looks like these, Autostar will fit. Else you are out of luck!

Try doing either a garbage collect or a safe load-- and then reinstall the hand controller firmware--

Instructions-- depending on the type of controller
Autostar 495 or 497: You enter Safe Mode by holding the [enter] and
[scroll down] keys pressed when you power up the telescope. The
Autostar will say "Flash Load Ready"... now go start the ASU.

Autostar II: if you need to use Safe Mode to recover from a disaster,
turn on the telescope, and key 999 before it says "Initializing"
The Autostar will say "Flash Load Ready"... now go start the ASU.

LX200gps: BEFORE proceeding further, click on the OPTIONS item on the Top Bar.
Now click on "Garbage Collect Hbx" ... this will perform data cleanup
within the Autostar which will avoid potential mess-ups.

I assume the small red light on the power panel is ON. ???

If it is the scope is receiving power--- check to make sure the cable from the hand controller is plugged in properly-- jiggle the cable to see if you have a loose BAD cable. Before you panic --- try another cable or reverse the ends ---

Before you buy another hand controller try a new cable-- scopestuff.com sells a nice long flexible one for the 497 hand controller.

When warm and indoors (!) connect Autostar to scope and by serial lead to a PC, allow Meade Autostar suite to update the Autostar Firmware to the latest version (2009!!)
Frome www.meade.com/support/auto.html :
How To Upgrade Your Handbox
To upgrade your Autostar first click on the link below to download the Autostar Update (ASU) Client Application for Windows. If your web browser allows you to open the installation file, you may choose that option when prompted. Otherwise, just save the install file to your local hard disk drive. When downloading is complete, double click on the saved file to start the installation. Follow the instructions provided to install Autostar Update (ASU) on your machine. When installation is complete, start ASU by selecting "Start Menu" -> "Programs" -> "Meade Inst" -> "ASU". If you have an active Internet connection and your telescope with Autostar is connected using the appropriate cable as listed above, ASU will detect and install the correct Autostar code directly from Meade's web site via the "Upgrade Autostar Software Now" button.
Autostar Update
Autostar Update is an application that functions to transfer the event files and software updates from your computer, through the serial port, USB or Connector Cable Set depending on your telescope model. The Autostar Update application is available as a stand-alone client application for Windows. The most recent versions of AutoStar Update automatically check for the newest versions of the AutoStar Updater and download it if necessary. It is critical that you use the most recent AutoStar Updater to ensure that you get the proper software updates for your system.
06/02/09 Autostar Update (ASU) Client Application for Windows, Version 5.6 (1,654 KB). This is the latest Autostar Update. Rev. 5.6 is compatible with the ETX-LS and #497EP Hand Controllers. This version is compatible with all versions of AutoStar II and #497 AutoStar computer controllers. This installation will automatically update the Update Client Application in AutoStar Suite™ Software. If you have previously installed the Autostar Update (ASU) Client Application for Windows, Uninstall the old version before installing this new version. 07/27/09 #497 AutoStar hand controller software update. Version 5BE2 (1,039 KB).
General update. Fixes many known bugs. Real time clock corrections. LXD75 polar alignment. Various LX90 pointing and tracking fixes. Adds new magnetic/true north alignment.
REQUIRES VERSION 5.6 AUTOSTAR UPDATER.