Meade LX 90 power supply lead broken

[S.A.M]

Hello SGL,

Went out for a viewing session which only lasted about five minutes tonight due to the power lead getting caught around the tripod leg while slewing to first object to view (Uranus) and broke into two pieces.  When I got home and could view everything in reasonable light I noticed the lead broke at the jack plug (this will need replacing), once I had removed all of the bits I tried using internal power (all batteries had a charge of over 1.50 volts dc) and the light would not come on, once I have a replacement cable I will see if the scope works on external power?  I suspect I have damaged the electronics/power with a short circuit,  if this is the case does anybody know who I could send the scope off to see if it can be repaired or not?  I am sure somebody will be able to look at it and hopefully be able to repair it?

Any suggestions would be most grateful.  At least tomorrow morning's viewing session with Mars and Jupiter will only need a scope on a manual mount (Porta Mount II).

Thank you for you time if you are able to answer this question.

Peter

[symmetal]

A short on the power socket is unlikely to do any damage to the scope electronics as the short grounded the input +12V, so effectively just removing power to the scope. The power supply itself may have been damaged but most modern supplies have in built protection so it probably survived too. The only part of the scope that may have been damaged is the power socket on the scope when it was pulled by the cable getting caught. The internal battery supply goes via a set of normally closed contacts on this external power socket, when there is no external power plugged in. Plugging in the external power connector opens this pair of contacts and so disconnects the batteries. This is to prevent the external power supply from effectively trying to recharge the batteries as well as to stop the batteries being used when external power is applied.

It's probably just these contacts on the power socket which have been bent by the force which broke the external plug and no longer connect when the power plug is removed. The socket on the scope may be soldered to a pcb rather than have wires connected to it. It's likely the socket would break before the pcb board itself. If it's anything like the LX200 it appears that removing the four screws holding the panel with the plug and socket connections on will allow the panel to be removed, hopefully enough to inspect the power socket. Any damage may be visible. It's possible it will still work on external power with a new external power plug cable connected. Anyway, good luck. It would be a shame to send the whole scope off for repair just to replace a tiny socket. 

Alan

Edit. On checking, the LX90 connector panel is on the fork arm and not on the base but hopefully it can still be removed fairly easily for inspection.

[symmetal]

This web page shows how to adjust the declination axis on the LX90 which entails getting access to the power panel which is a pcb. Fitting a replacement PCB looks to be fairly straightforward if the pcb itself is damaged.

Alan

[ollypenrice]

If you do need professional help I'd start with Steve Collingwood. http://sctelescopes.com/telescope/

Olly

[symmetal]

It's worth checking the power socket again to see if a piece of the broken plug is not still lodged in the bottom of the socket. The circuit/layout diagram does indeed confirm that the battery negative goes via the power socket. Pins 1 and 2 of the external power socket J1 are normally shorted together when the external power plug is removed to allow the battery to power the scope. Plugging in the power plug breaks this connection and so disconnects the battery. A piece of the plug lodged in the socket could cause this. If you use anything metal to poke around in the socket to inspect it, it's best to remove the batteries first to avoid possibly shorting them.

The power indicator led D1 is connected directly to the power socket and the battery so the fact that the led doesn't light almost certainly indicates the problem is to do with the power socket only.

The front of the power panel looks like it may be strong enough to protect the socket and pcb in the event of the plug being pulled sideways.

Alan

[Longinthetooth]

Yep. Steve Collingwood is the man! Worked wonders for my LX200 when it went belly up. Can't praise his service highly enough!

[S.A.M]

Thank you for all of your replies, will have to look into the problem when I have some free evenings this week?  Getting hold of a 2.5 mm DC power plug has not been sorted yet, just back from Maplins and they have 2.1 or 2.8!  I will try the 2.1 and see if it fits okay or might have to try e Bay to see if I get anywhere.  Failing that I will go to Steve Collingwood as he sorted out a problem for me many years ago BUT I had forgotten his name.

Peter

[S.A.M]

Now got the external power cable sorted out will try it out tonight on my scope and hopefully everything works?  Otherwise it is a trip to the inside working department of the scope!