Kelmar dimmer acting up

[Mike Blakesley]

This week with the help of our technician, I got our new replacement server installed to fix the stuttering-playback we were having (see separate thread), and when I fired everything back up, the house lights would not dim. (I know this is unrelated to the server.)

The stage lights work fine, but the house lights do not. When you turn them on, they "fade up" like normal but they don't fade out. the only way to kill them is to just shut them off.

I figured the triac in the dimmer was bad, so I swapped it out, but the problem persists. I tried swapping the wires between the two triacs, but the problem stays with the house lights. Either triac will dim the stage lights, but neither of them will dim the house lights.

The fact that the lights fade up slowly when power is applied made me think that the trouble is NOT in the triac, but what else could it be? It has high, mid and low buttons for the house lights but if I press either of the two bottom buttons, the top one stays lit. I thought maybe it was stuck, but it isn't as far as I can tell, at least externally.

I checked all the wires, everything looks tight, and I re-seated the various connectors between the main board, the terminal strip and the switch panel. Anybody got an idea of anything else I can try?

Our tech is busy with a training class this week so I'm trying not to bug him with this.

[Steve Guttag]

Press ALL of the buttons and listen for the "click" on each one. If one of them just feels mushy but without an audible "click", you have found your culprit. I presume that the LED bargraph meter on the front mimics what you see in the theatre (though with LED lamps, you are normally constrained to the bottom 20-30% of the dimmable range.

Suffice to say, either you have a physical button that is interfering with the change in state or the logic itself has failed and something like the start up pulse (rainy day feature) is locking on instead of giving that 1-shot pulse to bring the state to high.

Depending on your dimmer model, there could be an emergency mode that forces the dimmer to high too (with a relay as well but if that circuit is holding the dimmer in a high state without pulling in the relay, you could get the condition you are experiencing.

A call to Tom at Kelmar could be in order. I don't believe the has ever published the schematics of the dimmers but does offer repair services of the dimmer boards, including loaners and possibly repair-exchange.

[Gordon McLeod]

Check the wireing to the automation and I would disconnect it and see if it works

[Mike Blakesley]

I pressed all the buttons - they all have the 'click' feel and seem normal to me.

We did disconnect the automation last night and that didn't change anything either.

There is no emergency mode that I'm aware of... I was going to post the model number of the dimmer but it doesn't have one anywhere on the outside. It's brown and beige and was installed by John Eickhof in 1995. I took a picture of the inside of it and I think I still have the manual here somewhere, I'll see if the model number is on that but at this moment I have to head out of town for a doctor appointment. Updates later when I get back.

[Brad Miller]

Just post a pic of the dimmer.

When you press a button, does the light on the button illuminate and can you press all 3 buttons and have each button's light illuminate? That would rule out a sticky button (very common) like Steve is talking about.

If the lights on the buttons follow them being pressed, did you disconnect the automation wires on the terminal block INSIDE the dimmer? That's where you should be disconnecting to rule out a short in the cable to whatever you are using as an automation.

[Mike Blakesley]

The LED on the top "house lights" button comes on and stays on no matter what other buttons I press. (The stage lights side works normally.)

By the way, before anyone starts chuckling, the "on" and "off" labels are for occasional members of my teenage crew who, for some reason, have a hard time fathoming what the labels on the dimmer mean.
IMG_8096.jpg IMG_8102.jpg

[Brad Miller]

Either the "house high" button is stuck and won't release or there is a short in the lines from the automation forcing it to stay in the high position. See my previous post.

[Steve Guttag]

Brad, he said he removed the automation connections and that all buttons give an audible "click." It is possible that the up button is still mechanically clicking but electrically behaving as if pressed (contacts stuck). I'm starting to think the control board itself where the start up 1-shot is now a latched signal to the up ("on") mode.

[Ryan Gallagher]

Here is the manual for that deluxe unit:
https://www.kelmarsystems.com/Sectio...ouseDimINS.pdf

The timing after service tech would make me suspect automation too. Disconnecting the automation daughter board via it’s ribbon cable would rule out everything upstream of the control board.

Manual also mentions remotes, if you have any this would segregate them as well for trouble shooting.

[Ryan Gallagher]

Also, it’s a little blurry, but it looks like those resistors (or capacitors?) behind the “high” button have been replaced before, very non-matching package style to the others located near the other buttons? Perhaps that is a clue? Obviously just guessing, could have been factory like that (would need another photo to compare to), but at board level, they do stand out a bit as misfits... maybe.

There is a working pull whole unit on ebay right now, unfortunately no interior photos. Also Kelmar is still around and in business.
https://www.ebay.com/itm/167496388534

Considering Strong wants 1200$ for a replacement 2.4kw toroid, that seems like a good price for a parts unit.

[Mark Gulbrandsen]

I have to chuckle at this post a bit. I have actually repaired them with the customer on the phone before. After they replace the main board, I have them snap a pic and send it to me to be sure the plugs are back in properly. Kelmar(Tom) prefers the entire main PCB be replaced. That way the rebuilt board you get from them has all new capacitors, any bad semiconductors replaced, and all new switches and is tested to meet factory specs, among other things. It's fast and it's easy, and leaves you more time for lunch! Apparently no one posting here has ever done it this way.

[Mike Blakesley]

I did unplug the ribbon cable at some point and it acted the same way with it disconnected. It's gotta be the board, there's nothing else left.

I think this is the first time we've ever had a problem with this dimmer, if memory serves.

[Mark Gulbrandsen]

Usually it's dried up and leaky capacitors. You know it's not the switch on the front because the automation light switch does pretty much the same, even with it disconnected. I never replaced a Triac in a Kelmar dimmer, except in the older models. Yes, you should call Tom, and or who ever your buying from these days and get an exchange PCB. You can probablt swap it out your self, just make sure the AC to it is off.