Renard SS 24 stuck channels

E

error650

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SS24 channels 3, 4, 9, and 10 seem to be stuck "on." Measured with a multimeter while playing a test sequence...4 seconds on, 4 seconds off....repeat. All other channels seem to toggle ok between a low voltage and 120ish VAC.

1. 4 and 10 worked yesterday. 3 and 9 were unused.
2. I swapped all the Triacs from BTA04-700T to BTA08-600 CW today to eliminate LED flickering.
3. Removed optocouplers 3, 4, 9, and 10. No change -- still stuck "on".

Where do I start looking to troubleshoot? I'm looking at schematics and stuck on "optocouplers are removed, so how can the Triacs trigger?"



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That's what I'm thinking... Short between Gate and MT1. Now, just trying to find the datasheet to figure out which pin is which.

Do you think a simple continuity/resistance check with the device powered off would tone/show a short?

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I would think they're bad triacs but..

You can start by cleaning the board and reflowing all the legs of each triac and the resistor that connects to it.
If that doesn't work, I'd replace the triac and the resistor that goes to it. I know most people will think that replacing the resistor isn't necessary but I've had a couple of instances where replacing it fixed the issue. So, for the cost of a couple of cents I find it easier to do both at the same time.
 
Over time, it seems that dirt and condensation on the board contribute to make pathways on the board that can create shorts or other strange behaviors. It's a good idea to clean the controllers and other electronics every couple years or so. It's amazing what you can find inside a CG box when you bring it in after a show season...
 
I slept on it. Had enough "good" channels that I was about to remap in Vixen and get the lights on for the night.

Today, I checked the board and started recording the readings. I noticed gunk, and I think it's flux from the desoldering that didn't get cleaned up good enough.

I cleaned, and cleaned, and cleaned. Front and back. Didn't resolder or replace anything yet. Only presenting the first and last datasets... Even though I have 5.

Start: Ch3@120.4, Ch4@117.1, Ch9@120.5, Ch10@113.0, Ch12@107.0.

After cleaning: Ch3@24.2, Ch4@24.2, Ch9@17.0, Ch10@19.3, Ch12@16.4.

Most other channels are at about 16-18VAC when "off." I'm assuming this is normal range. How much should I keep cleaning and worrying to get the 20+VAC "off" voltages down below 18 or so?

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There is usually some current leakage with Triacs, but I don't know what the acceptable range is. Some Triacs are worse than others, too... Use a cotton swab and alcohol to clean the board. If it's visually clean, additional cleaning likely won't improve things....
 
dirknerkle said:
There is usually some current leakage with Triacs, but I don't know what the acceptable range is. Some Triacs are worse than others, too... Use a cotton swab and alcohol to clean the board. If it's visually clean, additional cleaning likely won't improve things....
Click to expand...

dirknerkle said:
Use a cotton swab and alcohol to clean the board. If it's visually clean, additional cleaning likely won't improve things....
Click to expand...

6 rounds of cleaning so far with q-tips, tooth brush, and toothpicks. Used alcohol followed by a dry wipe. Getting all the nooks and crannies...Around and between solder pads; top and bottom of board. Concentrating on the channels that measured higher voltage.

Funny results between cleanings. Sometimes the voltage would drop 5V, sometimes increase 12V, or finally drop 100V to a tolerable "off" range that I figure isn't high enough to bias the LEDs. After the first round, the whole board was visibly clean. But, additional cleaning definitely changed the behavior.


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error650 said:
6 rounds of cleaning so far with q-tips, tooth brush, and toothpicks. Used alcohol followed by a dry wipe. Getting all the nooks and crannies...Around and between solder pads; top and bottom of board. Concentrating on the channels that measured higher voltage.

Funny results between cleanings. Sometimes the voltage would drop 5V, sometimes increase 12V, or finally drop 100V to a tolerable "off" range that I figure isn't high enough to bias the LEDs. After the first round, the whole board was visibly clean. But, additional cleaning definitely changed the behavior.


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Click to expand...

So in the end, did cleaning fix the issue?
 
I'll also mention that it's a good idea to remove the pic and MOC3023 chips -- one at a time -- and reinsert them back into the sockets a couple times each. Sometimes galvanic corrosion occurs between a chip's pins and the spring sockets and the removal/insertion can scrape enough of it off to allow for a better physical connection. This is especially true for controllers that have been in storage for a while.
 
ctmal said:
So in the end, did cleaning fix the issue?
Click to expand...
It seems to. I remaped the channels in Vixen to the original assignments, and the show went fine. I was watching the area consulted by this box and specifically checking the flakey musical sections I listed in my notes.

Swapping the triacs eliminated the LED flickers.

Super-thouroughly cleaning the board fixed the stuck channels I caused by swapping the triacs.

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dirknerkle said:
I'll also mention that it's a good idea to remove the pic and MOC3023 chips -- one at a time -- and reinsert them back into the sockets a couple times each.
Click to expand...

Didn't deliberately do this, but did remove/reinsert as part of the isolation troubleshooting.



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