HELP! Dead Scope

[pbyrne]

Please help me.

I was observing tonight, I had the scope trained on a beautiful open cluster in Monoceros when I noticed that the cluster began to drift across the field of view, when I looked down at the Autostar I could see that it was dark and the voltage indicator, normally red, was also dark. There was no power getting to the scope. I had it connected to the mains via an extension cord, thinking this might be the trouble I changed the cord, the voltage indicator flashed for a fraction of a second and nothing. Now I was thinking it might be the converter between the extenstion lead and the scopes control panel. I got out my Powertank, connected it up and again the there was a brief flash and nothing.

By this stage I'm panicking, I removed the scope from the tripod, brought it indoors and connected it to a socket, once again a brief flash and nothing.

It seems to be that there is no power getting to the scope.

The scope of a Meade LX200 classic, perhaps 12 years old or so, the chap I bought it off said that there had been an electronic problem before, but he had it fixed.

I'm desperately in need of help as I know exactly nothing about electronics.

Can anyone help bring my scope back to life?

[Merlin66]

Which power adaptor are you using?

It needs to be rated for 12V at 2A minimum; 5A is much better.

[brianb]

Yes, don't give it up until the power supply has been ruled out as a cause of trouble. Low voltage can cause the sort of symptoms you're describing.

[ollypenrice]

A cheap voltage tester would allow you to measure what is coming out of the supply lead.

Olly

[brianb]

A cheap voltage tester would allow you to measure what is coming out of the supply lead.

Except the "open circuit" voltage doesn't tell you much ... if the battery is in a poor state the internal resitance could be high so that the potential at the scope connector might be 13.8V measured with a volt meter at the unplugged connector but drop below 10V when plugged in and supplying current to the scope. (13.8V is typical for a 12V nominal lead acid battery in a good state of charge.)

[pbyrne]

Hi guys

The ac adapter is the one that came with the scope, it had a dc output of +18v /2A, ac input is 115v~/1a or 230v~/0.5A, that's what it says on the back, and I have to confess that means nothing to me.

The powertank is a 12v/10A output unit.

They worked fine up until this, which makes me think that it is an internal problem.

Thanks for the replies.

[Merlin66]

carefully remove the front panel from the base and check the 1A fuse....