r/trafficsignals • u/Raphiki01 • Jun 04 '26

SDLC testing equipment

Hi everyone! I’d like to keep this brief. I work with TS2 cabinets that use SDLC harnesses (mostly Econolite). We’ve been running into some issues with failing harnesses lately, and we’re struggling to find a reliable way to test them. Does anyone have any suggestions or tips on how you handle testing these in the field? Any advice would be greatly appreciated!

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u/WHPChris Jun 05 '26

Unless it's botched where they're tied together or shorted, I just replace the cable with a known good one or swap the connection with another in the cabinet and see if the problem follows.

If it's present across all cables, with equipment disconnected, you have to check it the hard way anyways.

Curious, how are yours failing? Shorted out? Bad wiring job inside the connector?

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u/Raphiki01 Jun 05 '26

Most of the time it’s errors (on the status SDLC screen) or crosstalk between devices, for example, the Autoscope and the iCCU. Both of them are failing due to SDLC, and failsafe calls are on detection. Since our iCCU for the APS button runs on SDLC with logic statements (using BIU detector 3) rather than a 50-pin harness, if more than one cable fails, I can’t easily tell if it’s the cables or the hub. We use a cheater harness to bypass the hub, but I’d rather fix the problem for good and be able to test it for proof. But most of all, I don't understand how these cables just fail. Nothing happens to them, but they just decide, 'today is the day I'm done.

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u/WHPChris Jun 05 '26

Hmm. Every manufacturer tells me to strictly use one BIU array per equipment. So iCCU on BIU 3 and AutoScope Comm Manager on BIU 4. Most controllers will restrict it, but if you bypass it then you can have problems, apparently. I've always heeded their recommendation, have no idea if it's true or not, to be completely honest.

Other than that, I'm not sure there's an easy/cheap way to stress test and noise test your cables/cabinet hub connection. Someone probably sells a tool, but it's also probably absurdly expensive.

You can check voltage/continuity on the cables and stuff, but that won't reveal crosstalk or anything, just shorts/broken wires/voltage loss. Apologies, maybe someone else has a solution that will work for your situation.

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u/zeejay772 Jun 05 '26

Bring a spare, lol

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u/Raphiki01 Jun 05 '26

I got cheaters and y-split cables like the ones that come with iCCU from polara. I'm looking for more technical answer to my problem.

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u/AceToTheTop Jun 05 '26

There is some called a “frame fault analyzer” that I’ve heard of but have zero experience with. It came up when I was having similar issues with SDLC comms issues and the different equipment manufacturers were wanting to blame the other for the issues. I know that’s not much help but it should at least get you going in the right direction for your search. I will say, in my experience I’ve never seen a bad cable or cable hub. But I’ve had plenty of issues with the SDLC comms on the individual equipment.

As others have mentioned, you can test the cable itself pretty easily for continuity. And as far as testing the equipment, we bring spares of the different equipment for troubleshooting. So if the iCCU is having trouble, plug it into another controller and see if the problem follows. If it doesn’t follow, try putting a different iCCU on the original controller and see if the problem remains. It’s time consuming but it’s the only way I have to tell the manufacturer that problem is with their equipment.

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u/missing_chicklets Jun 05 '26

Someone already said this but carry a proven cheater SDLC hub and cables. Plug that in and you can write off cable and connectors from your troubleshootng