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Re: [TCML] + 30mA = dead garage door opener

Put some MOVs on the 120 vac feeding the garage door opener.

Do you have MOVs, a good 20 Amp line filter, and some small inductors on the
pri side of your NST?  This will also help.

Dr. Resonance

On Sat, Aug 14, 2010 at 10:15 AM, Joe Mastroianni <joe@xxxxxxxxxxxxxx>wrote:

> Blew up my garage door opener last eve.  I'm still not comfortable with
> rolling the coil out into the driveway.  I put a vent fan in the roof of the
> garage, in fact, to evacuate the O3 & NOx, so I wouldn't have to coil in
> public.   I went as far as unplugging the opener whenever I ran my tests.
> Alas - even unplugged, the opener couldn't take it.
> I had expected the radio would overload or maybe the front end filters
> would fry.  Not a chance.  I am subscribing to the "ain't much RF from a
> coil" theories proffered on this site.
> I am still running the 4.5" x 22" secondary with double toroids - a 3x12 at
> 23 inches and a 4.5x18 at 28 inches as measured from the bottom of the
> secondary.  All of my prior coupling problems were solved on the last go
> around with help from Bart  and JavaTC. (things go infinitely easier when
> you have the expert at hand )   I am now running the secondary with the base
> in the same plane as the primary - no altitude adjustment necessary, now
> that I've carved 2.5 turns out of the inside of the primary.
> The sequence of events is this - I acquired a new 15/60 NST.   Previously I
> had been running a 15/60 in parallel with a 15/30.   I swapped out the 15/30
> for the new 15/60, figuring I'd ramp up the power in increments so I could
> observe the effects with my SRSG based coil.
> Now effectively running 15/120,  I did not increase the primary cap tank.
>  I plan to do that this weekend.  Slowly increasing the variac I noticed two
> effects:
> 1) The SRSG timing was ever so slightly off now.  Where before it was
> running perfectly with no phase adjustment, I had to kick in about 3-5
> degrees (my estimate based on prior measurements with this Freau phaser
> arrangement) to get all electrodes to fire reliably.  Undoubtedly the added
> amperage filled those caps faster,  and possibly inductance of the
> additional NST changed the phase a bit.
> 2) No safety gaps fired until  I got to about 2/3 power, but I had not
> readjusted them with the new NST, so there's no surprise here.
> 3) The streamers were far more "energetic", and what I mean by that is that
> where before a streamer would form and stick around for some fraction of a
> second before evaporating and being replaced by another - they
> stick-around-time of the streamers was shorter.    Overall streamer length
> was about the same at 2/3 power as full power before, and this is a
> qualitative measure, but it seemed within the realm of what might be
> expected with a potential 33% increase in rated input current.  Of course,
> the actual increase in current depends on the loading of the NSTs. Tilbury
> has some curves in his book suggesting a very linear inverse relationship
> between NST output V and I with a dV/dI of somewhere in the neighborhood of
> -0.3, (actual equation:  Vo(kV) = -0.3*Io(mA) + 0.9798 ) suggesting that at
> max rated current the output V would be under 10% of rated output.
> I did take care to unplug the opener, and I had in fact even wrapped the
> power cord around an RF choke.  Alas, this precaution was a completely inept
> attempt. The streamers energized the garage door spring, which is connected
> directly to the gantry holding the garage door opener motor + controller +
> drive belt.   Some currents must have flowed through that gantry into the
> housing of the opener itself.  The effect is that the door will now only
> open.  The opener only closes the door on occasion (during which time it
> appears to functional normally).   The radio control is unaffected, which
> leads me to believe there is no RF-induced damage.  It's strictly a streamer
> hit.
> Oddly, the streamers also hit the wiring for the garage door IR sensor.
>  Those seem to function normally as well during my tests.
> My opener is a Chamberlain model 3280.  It appears from the code it is
> throwing that either the RPM sensor or the logic board itself is fried.  I
> have ordered replacements for both, as the components are significantly
> cheaper than the whole motor (e.g. ~ $80 + shipping).
> When the replacement parts arrive I will dismantle the unit and see if
> there is any obvious spark damage visible.  My greatest fear is that what
> has happened is that one of the limit switches has been somehow compromised
> and that the parts I replace have nothing to do with the failure - and that
> the problem can be solved by simply bending a contact back into place.   But
> I dont have the patience to dismantle the opener in the absence of any
> repair parts.  So that experiment will wait till later this week.
> Cheers,
> Joe_______________________________________________
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