Blown Electronics

Hi all

Still having trouble with the scope. I have the Autostar uprgrade installed, when the cigar charger was attached to the 13.8v regulator or the Powertank the 2A fuse kept blowing. I installed an 8A fuse, hoping this would prevent it from blowing.

When I turned on the power, there was a pop, followed by a burning smell and finally smoke. I removed the bottom plate and the images show what I found.

I have no knowledge of electronics whatsoever. Was the 8A too much? Can the unit be easily replaced? Where can I find a similar unit? And finally, is there anyone out there who can show me how to replace it.

I am at the hair pulling stage now and want this trouble ended.

Any help gratefully recieved.

Yikes, that looks nasty . I think there was a 2A fuse already there for a reason. Is the board from the handcontroller, the scope or the power supply?
It sounds like a short somewhere.

Yikes, that looks very nasty Paul.

If the original 2A fuse keeps blowing it’s a sure sign of something wrong somewhere else in the circuit, for example there could be a short. The fuse is a first line of defence so that expensive circuitry is protected; it’s usually easier and cheaper to replace just a fuse (always best to locate the original fault and rectify as soon as possible).
The fact that you replaced the original 2A fuse with an 8A fuse (x4 times nominal rating) means that the fuse could not blow straight away and therefore the problem was transferred after a delay into the delicate circuitry, so something else had to give.
Looking at some of the pictures I think a repair job would be quite costly unless you know what you are doing regarding debugging, de-soldering damaged components, re-soldering new components, testing / calibration to manufacturer’s recommendations etc. Is the equipment under guarantee?
It might be a cheaper route to purchase guaranteed/tested second hand PCBs or even new PCBs from the manufacturer and self install or have a friend that is competent in doing this work for you. Sure like to see up and running again Paul, its unfortunate that this has happened to a dedicated amateur astronomer.

Clear skies
Mike

Hi Paul

Sorry to hear of your problems.

It looks like you have blown one or more of the pcb boards in your scope. I had a dec pcb board blow on me on my Lx90 a few months ago so I feel your pain.

One thing that will cause immediate frying of your scope in this way is feeding it reverse polarity charge. There is no reverse polarity charge protection in Meade scopes.

You will need to get a replacement board as they are very hard to repair. If you wish to try, you will need to assertain the chips that have blown and get the replacements from radionics etc. or if they aren't available, find out their specification and order the equivalent chips. You will then have to de-solder out the blown chip(s) and put in the new ones. If the traces themselves have burned off also (very likely), then you will need to figure out which part of the chip goes where etc and repair the traces as well. Even though there was only one chip blown on mine it proved just impossible to repair the old board and I had to get a new one in the end.

The big problem is Meade are just not helpful in sending repalcement boards out. Your only choice is therefore to send it over to telescope House in UK who repair scopes. They quoted me £50 to fix my scope and replace the board with a new one. Only problem was getting it over there and back was going to cost me nearly €500 via DHL.

Luckily I was able to beg Andy Mccrey of North Down Telescopes to ask them to send me a replacement board. He was able to talk Telescope House round into sending me a new one. I think he is definately worth an email in your case.

Replacing the board itself is not too difficult for someone who knows about these sort of things but I think you do need to know a bit about electronics. The replacement board that I got was actually different to the one I had taken out as Meade had upgraded it in the meantime. So it was lucky that I had the help of someone who knew what he was doing.

Kind Regards



David Branigan

Thanks David

I believe that the capacitor needs to be replaced and the board traces repaired, a simple enough procedure I'm told.

Does anyone know of an electronics repair firm in or around Dublin that might take on the job.

I have had quotes from Telescopehouse for the purchase of equipment and the shipping quotes have been horrendous, I was asked for £30 to post an eyepiece, I cancelled the order.

The dec motor runs fine, the trouble is in the RA motor.

As my ignorance of electronics is complete, what exactly is a pcb board, printed circuit board?

I take it that what I am holding in images 2 and 3 is not the pcb board.

From what I can see, again I am an electronic ignorant, the only damage that I can see is in that particular part.

Dave, I'll contact Andy and see where we get from there.