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Whoops! Reverse polarity to mount!


kerrylewis
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After upgrading the Synscan firmware I got my wires crossed and applied the wrong power polarity to the HEQ5. There was an unpleasant phut noise and now nothing works properly - not surprising! I corrected the polarity and there is power to the mount but the handset doesn't work. Has anyone had any experience of this? Have I blown something in the mount? I don't think the handset was connected when I stupidly got the wires crossed.

I was getting ready for what looks like being a clear night - blown that!

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Phut sounds like a capacitor having blown, however as there will be chips in there one of them could also have been killed and you wouldn't know.

The presumption being that the power goes into a circuit board in the mount. So the mount would have to be stripped enough to get any board out for potential analysis and repair.

Really would be inexpensive to put protection diodes in but to save what I suspect is little more then 20p, they don't in order to make a little more.

I guess you will need to put a post up asking for information from others that have done the same and what they had to do to get the mount operational again. Someone may read this and come along with information.

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like other people have said, it's probably a capacitor that's blown. Cheap to replace if you are handy with a soldering iron.

If it's a bit more than a capacitor and it's some chips dead, I'd suspect that the motors would be OK, just need a replacement motherboard.

i've noticed that ModernAstronomy do replacement boards for the HEQ5 for £108

http://www.modernastronomy.com/mounts.htm#syntaMotors

Rob

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Blimey, that is bad luck. :(

The Astro Engineering PSU I used with my HEQ5 Pro, had one of those reversible polarity tips. I was forever tripping over the blessed thing and pulling it out and must have reconnected it in the dark, the wrong way round a dozen times. All that ever happened was that the mount wouldn't turn on.

Have you tried plugging the power directly into the handset (with the correct polarity ;)) just to see if that works? It'll help narrow down where the fault lies.

Russell

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My lovely new EQ6 GT is up and running. I was paranoid about the polarity - understandably. So I got a psu with a car lighter type socket. I just couldn't risk connecting the wires to my old power supply. I wonder if this mount has protection? It seems incredible that such an expensive bit of kit would not have it.

Now to repair and refurbish the old HEQ5

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There are a couplempf small rectifiers on the circuit board near the power input. These often burn out, they are replaceable. If you do a bit of huntimg you will find a thread on it on here somewhere. It was quite some time ago someone else had the same problem and the kindly put up a few pics of how to fix it.

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My lovely new EQ6 GT is up and running. I was paranoid about the polarity - understandably. So I got a psu with a car lighter type socket. I just couldn't risk connecting the wires to my old power supply. I wonder if this mount has protection? It seems incredible that such an expensive bit of kit would not have it.

Now to repair and refurbish the old HEQ5

Expensive? Takahashi mounts at five times the price don't have it!!! I'm not saying they shouldn't, though...

Olly

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I did a bit of searchingfor you and it wasnt a rectifier that blows, i did think i was probably weong on that , its an inductor and it will be lcated nearbthe power input on the small board under the cin of the mount near the power connector. There should be two or three of them denoted on the board with an 'L' marking.

Ai will have another search romoz for you and see if. Can find the old post.

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Thank you AB, that's very kind. Having got my new one I will now concentrate on getting the blown mount working again and then sell it

Kerry

Oooh! I wouldn't do that. You might not even recover the repair cost!

I'll give you £30, bought as seen :D

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Slightly off topic but those contemplating installing a safety diode to prevent reverse polarity should be aware the diode will drop 0.6 volts from the 12.6 volt input. This may bring on low voltage problems earlier in the battery discharge cycle.

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Slightly off topic but those contemplating installing a safety diode to prevent reverse polarity should be aware the diode will drop 0.6 volts from the 12.6 volt input. This may bring on low voltage problems earlier in the battery discharge cycle.

That should only be a problem if the diode is put in series as a blocking diode.

If it's just put in reverse biase across the incoming supply terminals then it will have no effect until reverse polarity is applied. The the protective diode will then be forward biased and effectively short the supply and hopefully blow an in-line fuse in the supply lead.

Hopefully :)

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I did consider this shunt arrangement but its not considered good engineering practise.

Usually the fuse in plug is 5-10 amps and requies 100 amp to blow instantaneously. However if you are using a car battery with a low internal impedance the short circuit current would typically peak at 1000-2000 amps. No doubt the fuse will disconnect but there will be a heafty current flowing for a time. No fuse blows instantaneously. Even worse if you have a slow blo fitted to the plug.

So if you do go down this route consider carefully the type power supply fault current and fuse grading that would be appropriate.

Edited by astrofox
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HUmmmmmmm why not just use a relaible lead and make sure you have the right polarity.

If you have a car ciggy adapter and a correct end on it thes no reason for this to ever be a problem surely. If you run from clip on terminals or a banana plug type outlet surely its simple enough to make sure red goes to red, black to black.

I have always steered people away from ANY lead which has one of the cursed poarity change over elements in it...its just plain dumb to have something like that around a piece of equipment that costs almost a grand which has no polarity protection. Its just asking for trouble.

Get the right gear and this stuff needs never happen but I am always amazed in this hobby that people will happily spend thousands on a scope, mount and eyepieces but ask them to pay for a power supply or lead and they are straight off down to poundland to see if they can get one for 99p and then post asking why things arent working. Seen it to many times and its often tragic to hear about.

Thats not a pop at the OP by the wau, I do understand that the universe is often arbitary and unfair but take reasonable precuations and. A lot of this grief needs never happen.

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Astro Baby

my problem was that the lead to the mount was not black and red but black and black with a white stripe! My ageing brain cells decided that the one with the white stripe was positive - Wrong!

Things happen, people make mistakes - especially as they get older. So no harm in protecting against mistakes. It would cost the manufacturers pence to build in protection

Kerry

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I agree entirely with Astro Baby.

Loads of polarity sensitive electronics out there with non reversible cables and connectors. Made lots of power leads up in my time, I check polarity when commisioning them before use. After that it's use and forget,

Sorry if it seems as a criticism its not intended. Blown up loads of electronic components in my haste to get stuff working. But thats the difference between a component costing pence and one's pride and joy costing mega bucks

Edited by astrofox
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Kerry,

Have you confirmed that the handset is working in Standalong mode (powered directly and disconnected from mount) - Possible you may have blown this so worth a check before forking out of attempting repair of the motor board. Worst case, if you can't repair it, the motorboard is £ 105 and the handset £ 149, painfully over priced for what they are, but probably worth it with a s/h resale price of around £ 500+ on a reasonable/working HEQ5.

Edited by SnakeyJ
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Kerry, you have my sympathies as does anyone who blows stuff up. I have done myself in the long distant past through ignorance, stupidity and haste. Thats why I can advise now having learned better :)

For myself if there was any doubt in m mind I would have either tested the lead out with a multimeter OR taken the lead the lead apart to check OR thrown it away and got one I knew would work.

Many moons ago I blew up something a deal more expensive than an astro mount and also with potentially fatal consequences for a colleague and it was a lesson to me not to gamble on stuff and to be very sure before stuff gets connected and power is applied.

Your right that the manufacturer should but to be far if Sykwatcher implemented everything the astro world says they should do.....

better altitide bolts

pre align the polarsopet

tune the mount to perfection at tha factory

use ceramic bearings

put better chrome on the weight bar

have a higher QC finish for the inside

fi a better saddle plate

put overvoltagae protection onboard via fuses

polatity protection

put a locking fitting on the power lead

...and all of these have been asked for a various times then I rather suspect a few pence here and a few pence the would rapidly translate into a very much more expensive mount.

Honest Kerry that wasnt a pop at you....more of a general caution. You arent the first to blow up a mount but it would be nice if others took heed so you were the last. That wont happen but it would be nice if it did.

Edited by Astro_Baby
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  • 6 years later...

Hello, I was reading about  reverse polarity problem on this thread.  I have done the same thing on my EQ5Pro. My question is did you ever get the electronics repaired?  I replaced the tiny capacitor on the hand controller C55. Once power was plugged in the right way it burnt the capacitor again, I let the smoke out. Dang it. Haste makes waste. Anybody have information that could help me?. Thanks

Edited by RDP
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