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Dew Controller problem

Davesellars

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Davesellars

Davesellars

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Not quite sure where to put this so...

Last night while observing I had my Astrozap dual channel controller sat on to of my battery all of that sat on grass (OK, I realise now it was a bad idea...) and at some point the lightweight controller moved on to the grass (which was wet from the dew).   I first noticed when the eyepiece dew strip was cold and looked at the unit - all the lights had gone out.  The battery was fine and have tested this at home connected it to the neq6 and powered up.  The dew controller dried off overnight but still wont power up.   I doubt that's there really that much electronics in the thing.  Surely though these things should be vaguely water resistant to dew?  (for the cost of them, you'd expect so)  Would it be the cigarette lighter connector instead that has just blown through a short? (this was lying in the wet grass...)

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Psychobilly

Psychobilly

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I would try the controller without any dew bands fitted first if there  if you have access to a digital multimeter check the resistance of the dew bands. depending on the length of them they could be anywhere from a few ohms to a low tens of ohms...

Are they the astrozap film type dewbands? I have had issues with them in the past where the insulation on the coax power cable melts where it is attached to the dewband causing a short.

Peter..

 

 

 

 

 

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Davesellars

Davesellars

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Thanks, Peter.

I have three different Astro-zap bands - these ones: http://www.firstlightoptics.com/dew-prevention/astrozap-dew-heater-tapes.html   The 8" and 2" tapes were connected at the time.  I'll change the fuse (any idea what type of fuse goes in the cigarette lighter - are they the same type as ordinary house-hold plugs?)  Don't have a digital multi-meter unfortunately but can test without any tapes and first with the tape that wasn't used that night.

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Psychobilly

Psychobilly

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A cheap DMM is an essential tool ... allows quick and easy checking of voltage supplies, polarity, cables fuses etc...

You don't need anything fancy... if you want something to measure DC current more than a coupel of hundred mA then  it will cost a bit more... but for basic  fault finding Volts and Ohms is all you need...

Peter...

 

 

 

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Davesellars

Davesellars

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Tested the controller replacing the fuse with a 2A from a different cigarette lighter plug (didn't have a 5A will pick on up tomorrow). Lights come on now!  Fuse looked like it had blown. Need to find a way of waterproofing to avoid another incident.  Will test all the dew tapes later.

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Davesellars

Davesellars

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The Astrozap 2" dew strip is causing the issue.  I connected the 4" tape and all good , connected the 2" taking out the 4" and as soon as I put power on to the tape, it blew the fuse again. Looking at the strip it's a bit of a poor job at the join at the tape end as the braided wire is showing, my other tapes the wire is going well inside so it was doomed to fail really at this weakest point where it gets bent instead of being protected by the tape sheath.

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Davesellars

Davesellars

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True, should not be a difficult fix. Open it up (sewn) and cut the cable where it's broken, re-do and re-solder to the joints. It would be a real pain to attempt to re-sewi though so electrical tape should do the job. I just don't have the tools anymore... :p

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