Sylvania stay-lit minis and LOR

[rwertz]

I should have asked this question before we wrapped our bushes. But does anyone have any experience with Sylvania stay-lit minis and LOR?

http://www.kmart.com/shc/s/p_10151_10104_009B685997110001P
“Patented Microchip Technology. A chip in every socket guarantees that sets stay lit if bulbs become burnt out, loose, broken or even missing.”


After wrapping the bushes I ran a long rolling fade sequence to see if things were OK. Two of the bushes did some wild and crazy things. I’m pretty sure the basic problem was related to an old issue which is (hopefully) fixed. But the effect that it had on the lights was a little concerning.

My basic problem was that while certain circuits were fading up or down they would suddenly go on, go off, or flicker. With normal light strings the entire string would behave the same way. But the stay-lit lights went nuts. Parts of the string would be dimming properly while other parts of the string were going nuts.

My thoughts are that my problem was only affecting one direction (alternation) of the AC current. And the current in the other direction was still being properly controlled. This combined with the “Patented Microchip Technology” was selectively affecting parts of the string.

After updating the firmware on the suspect controller everything appears normal. But I’m starting to think that the lights might act pretty strange if a bulb becomes loose and the stay-lit circuitry has to function during a fade.

[-klb-]

Odd. Some other brands do their constant on strings just by using spring contacts to cause the socket to short itself out if a bulb falls out.. So I'm not sure exactly what Sylvania is doing. I can see a range of things that would work... Back to back zener diodes, where the zener voltage plus the forward bias voltage equals a bit more than the bulb voltage would bypass a dead bulb, with the socket empty, or still there. Seems like most anything more sophisticated would cost more....

[rwertz]

You are right, diodes are probably the most cost efficient circuitry. If they used zeners they would need to use two back to back to prevent the forward bias from shorting out the bulb (assuming each bulb sees both alternations).

But if they were configured so that only half the string saw one alternation and rest of the string saw the other alternation that might explain the strange effect I saw. It could have been a direct result of inconsistent control of the two alternations in combination with the zeners (or some other diode configuration).

Now I’m wishing I had taken a video of the problem (to share). Hopefully the problem doesn’t come back, but if it does I’ll have to try to get some footage (after I get a few choice words out of my system).

Thanks

[-klb-]

Hopefully LOR is handling the positive and negative half cycles identically. If not, and the difference is to a great enough extent, it can cause overheating and failure of the utility transformers...

A single diode forward bias voltage is not up to the 2.5V that a standard mini light is nominally rated. Thus my suggestion of back to back zeners...

Just for grins, have you looked to see if they maybe are just doing like the others, and doing something with the socket? Or installed a lamp base with no bulb installed to see what happens?

[rwertz]

I didn’t place a blank socket in. However, there were several bulbs that were inserted but failed to make contact (thanks to shoddy workmanship). The rest of the strings still lit.

We had an issue in the family that is keeping me busy just trying to get set up. But, I’m going to try to find some time to look into how the strings are actually wired and inspect the light bases.

I was suggesting a single zener based on how the lights were acting. Within the same string I had lights that were dimming correctly and lights that were acting erratic. Having different polarities for the two sections of the string seems help to explain how that could even happen. I was thinking that (possibly) they were allowing half the lights to be bypassed while the zener was forward biased. This would not be very energy efficient, but it might be more cost efficient than using two zeners per light.

The difference in power alternations (that I was speculating on) would only have been occurring during my fault condition. After fixing the problem (fingers crossed) the entire string fades consistently.