Dew heater controller woes

[jonathan]

Just wanted to share my experience with this.

I used a dual-channel controller successfully for a couple of seasons, however one of the channels decided to stop working for some reason.  A dual channel controller reduced to one channel wasn't much use to me when I have two heater tapes going so had to eventually replace it (I chose the Hi-Tech Astro model which also does powered outputs for the mount - a better module all-round); the cost of posting the faulty unit back to the USA and price to repair made it uneconomical to bother.

So the now single channel dew heater controller sat in my box of astro gear annoying me, until I eventually decided to try to fix it myself.  I took the lid off and saw two main driver ICs and two POTs, a controller IC and not much else.  Testing the voltage out of the dead channel driver IC I concluded that it could be the driver IC at fault, so I purchased some new from an online electronics website, fitted it, still nothing.  I moved to the POT and noticed that it had an odd feeling to it when turned, like something was broken inside; it was very subtle but definitely not smooth like the other one, so I went about purchasing a replacement for that component as well, except it seems the only place that sold them is based in the USA - they were not cheap components and the shipping plus VAT made the repair bill almost half the cost of the unit.  I bit the bullet and did the repair, however even after replacing two components I'm left with a unit that still doesn't seem to work properly - both channels do not appear to vary the output voltage, it is fairly constant at 13v, even though the LED dims when the POT is turned down.  There is nothing more I can do with this unit as the only parts left are small surface mount and I don't want to put any more money into it (half of which seems to have been postage costs so far).

It's frustrating that I don't know if this is how it always was from new, it could have been a faulty unit to start off with (although both channels worked, maybe they didn't vary the voltage as they were supposed to?  I never bothered to test), disappointed that one of the supposedly tough and rugged POTs completely failed after only a couple of season's use, and to have spent so much attempting to repair only to find it still doesn't fully work as I expected it ought to.  The unit is little more than an adaptor now as all it does is take 13v in and put 13v out, as far as I can tell - I may as well just use some cabling instead.

Lesson for the day: Just buy a replacement unit!  Use the old one for parts or make something else out of it.

Thought: I wonder if it was actually dew inside the unit that caused it to become faulty in the first place?  That would be ironic.

PS Sorry, may have posted in the wrong forum.

[MarsG76]

What brand was the one that died on you?

[The Stoat]

If the controller uses PWM the output voltage may not appear to change much, so it could be working just fine.

Cheers, Mark.

[jonathan]

I never thought of that, PWM.  I don't have an oscilloscope to check though.

It was AstroZap Dual Channel Control unit that half-died on me.

If it is actually working properly then great, it was a successful repair!

[The Stoat]

A quick Google shows that unit does use PWM, so I would hook it back up and check if the bands are heating. Could well be a successful repair!

[focaldepth]

I hope you are up and running by now but to test it, you could connect a small light bulb, say 12V 6w to the output and use it as a lamp dimmer.

[faulksy]

as the stoat says, if its a pwm which it is. it works on the principle of a timer, and switchs the power on and off in quick succession,you vary the time by adjusting the pot thats why the voltage doesnt drop much