Channnel 1 Problems

[max251]

I have a ctb16pc board that fried the 220 ohm resistor next to the channel 1 triac. Talked earlier this morning to someone at LOR, not the tech support person. He said to check for voltage leakage on the left leg of triac, there should be no voltage there. The voltage on the suspected bad triac where as follows left leg 2.4v, center 4.5v and right 2.0v. Does anyone know if these readings are indicator of a defective triac. I checked triac next to the defective channel and voltages where as follows on channel 2 which works fine left leg 200mv, middle 4v and right leg 2.3v. Any info on this would be appreciated.

[Max-Paul]

I would think that one of the outside legs should be 120VAC in reference to the neutral wire. And if the Triac had a load on it and it was turned on, there would be 120VAC on the other leg too. At this time I am not real sure what voltage it takes to run on a Triac. And that would be on the middle leg.

Because you dont have 120VAC on one of the outside legs (look for the copper path that goes to all of the Triacs) I would have to think you are not doing something right. Or the fuse is blown, thus not supplying the triacs with power. I suppose you do not see any solder bridges or any metal debris shorting out something?

[max251]

You are correct max, I mistakenly used the heatsink as ground, but the sink is not connected to ground. Using the neutral I do have 120 volts at the center leg and 7.5 volts on left and right leg. Comparing these voltage to a good channel triac there are 120 volts on middle pin and 15 volts on both outside pins. I have removed the heatsink and checked the traces and for anything possibly shorting across them. I see nothing out of the ordinary on the board, no solder bridges etc.

[Max-Paul]

One of these days I am going to have to reverse engineer one of these boards so I can be of more help. Sorry about the inside and outside legs info I was giving earlier. Forget that Triacs do not mimic transistors for leg assignments.

Ok, good that you are now using the neutral. Ok just off of the top of my head. This resistor is going to the gate of the Triac or is from the hot side going to the optic coupler and then back to the gate. I suspect that the optic coupler might be bad too if my assumption is correct. Anyway you slice it or dice it, I would contact LOR Monday morning and see about repair services before it gets much later. Thus you can get your board back in time for the show.

My suspicion is that the gate might have shorted and thus the excess current draw through the resistor and maybe the opto.

[max251]

Max, I did contact Dan about the problem and he sent the triac, opto and resistor out quickly for me. Installed all three today and tested the unit a few minutes ago, everything is working properly. Thanks for the help Max and can't say enough of the fantastic customer service from Dan at LOR.

[Max-Paul]

Great Max,

Good to hear you are up and running again. Ya, that Dan fellow and his minion are great people. I tell you, if this was the norm in customer care. Only a few fools would be the only people complaining.