Question for Meade owners

[LateLifeCrisis]

Good day, all.  New to the forum here, and have a question for those more knowledgeable than I (that would include virtually everybody on the planet, I think!).

Many years ago (early 2000's), I purchased a Meade ETX 90 primarily for using outside urban areas when camping - using the 'scope from a very dark isolated campsite was tremendous and my young kids loved it.  However, life moved on with a new job which required me to travel extensively, so I packed the Meade away for a lot of years.  I recently got the bug again now that the kids have flown from home, and was considering getting something a bit larger, a bit like whatever the current version is of the ETX200.  Before I do that, I'd like to once again get the '90 back in action for the grandkids.  Before I turn it over to them, I want to get a power adapter so they (a) don't run down batteries halfway through using it, and (b) don't have to remember to take the batteries out before storing it, in case it doesn't get set up for quite some time later.

Meade apparently discontinued offering their own branded adapter, so I managed to pick up an aftermarket one.  But before connecting, I want to verify/confirm whether the center post at the inlet port of the telescope body is positive or negative.  My adapter can be configured for center positive or center negative, but the body of the telescope doesn't indicate what polarity the center post is.  And the original owner's manual (which I still had!) doesn't specify that either.  I don't want to burn out the electronics by just plugging in the adapter and hoping for the best.

Anybody here have a Meade telescope with a power adapter?  If so, could you have a peek on the adapter body label and see whether the center post is indicated "+" or "-".

Thanks, All.

L.L.C.

Edited January 16, 2021 by LateLifeCrisis
spelling correction

[wulfrun]

In the absence of any postive answers (sorry!) - you could find out easily enough. Assuming there's an on/off switch (not just buttons but an actual switch), make sure it's "off" before the test. Remove any batteries. Connect a multimeter from the battery negative terminal to the outer terminal of the power socket. Set the meter to ohms/continuity and see if it shows zero ohms or close to it. If not, swap to battery-positive in the holder and centre-post of the socket. Between the two tests, you should get a definitive answer*. Chances are it's centre-positive but you're wise not to assume. One terminal of the battery holder will be permanently connected to one socket terminal.

EDIT1: *If neither test above gives a zero/close, swap the tests to the opposite battery holder terminals and same socket ones - and then it's negative-centre - I almost forgot!

EDIT2: when you've established which and set your adapter, tape up/glue the switch or whatever to prevent accidental swaps from small fingers.

EDIT3: I've re-read it and realised it's written confusingly. The last sentence of the first paragraph is the important bit. One terminal of the socket will be permanently connected to one of the battery holder terminals and finding which will give you your answer. Not sure why I made it so compicated! Easier to do that to describe is my excuse.

Edited January 16, 2021 by wulfrun
clarity

[michael8554]

Most telescopes require 12 volts, but the ETX90 only requires 9V.

The plug should be centre positive.

The  correct plug size is 5.5mm with a 2.5mm centre pin, not 2.1mm

Make sure the unit is a Regulated Power Supply.

Cheaper Unregulated Power Supplies do not supply a steady 9 Volts under load.

Michael

 

[michael8554]

LLC has advised me that only early ETX90's are 9 Volts.

Newer ones like his are 12V.

All the other details are correct.

Google Is Your Friend - NOT !

Michael