DTSS left/right sides intermittent

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DTSS left/right sides intermittent

Postby Oldmate » Sat May 01, 2021 5:07 pm

We pulled the system out for our first race in a while. The tree was acting weird, flashing lights and sometimes nothing! The tree is one of the LED trees, a DTSS model connected to our 2900 timing system. I was hoping there was some troubleshooting I could do to avoid shipping it back for service. When it powers up, sometimes it runs through the normal sequence of flashing each light one at a time on each side. Sometimes it does nothing on one side. When the front fails, so does the rear, that is, the lights seen by the drivers on the front of the tree echoes on the lights seen by the crowd on the same left/right side. Once the tree is finished with the startup sequence, the left side front and rear do nothing except the prestage stays on. No staging, no prestage, no tree start on that side. Any direction would be helpful.
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Re: DTSS left/right sides intermittent

Postby raceamerica » Sat May 01, 2021 5:20 pm

There are a few things you can check on the tree. Probably best to start with a rundown of how the tree is constructed from an electrical standpoint.

There are four sets of stage/prestage/yellow/green/red LED circuit boards in the tree, one set for the driver facing left, one set for the driver facing right, another set for the downtrack facing left and the fourth set for the downtrack facing right. Each of these sets of lights are wired to the tree electronics in the bottom of the tree via interconnect cables. If this was a wireless tree, there is also a coaxial antenna cable connected front the antenna at the top to the tree electronics in the bottom of the tree.

The interconnect cables carry power and signals to each set of LED circuit boards. Some are shared control signal connected to all four boards and some signals are shared data signals between both sets of boards on the left side or both sets of boards on the right side. Power (approximately 15VDC) and ground are connected to all 4 sets. Pulling the tree electronics out of the tree gains access to these interconnect cables.

To remove the tree electronics from the tree, remove three screws holding the bottom plate of the tree in place as shown in Figures 1 and 2.
treeElect1.jpg
Figure 1
treeElect2.jpg
Figure 2


The four cables are grouped as two for the left side and two for the right side and indicated on the tree electronics circuit board between the connectors as LEFT or RIGHT. Unplug each of the connectors and mark them as 1 through 4 so they can be plugged back in where they came from when done troubleshooting.

Plugging in each cable one at a time and powering on the tree will help troubleshoot if one set of lights is failing and causing another set or sets to appear to fail. Of course, only one set of lights will illuminate on the tree dependent on which cable was plugged in. For future troubleshooting, you could note which cable connects to which sets as front left, front right, rear left and rear right.

If this troubleshooting does not resolve the problem, next step would be to check the connection of the other end of each cable. Reaching your arm up into each side of the tree about halfway up, the cable terminates connected to a light set with the same type of connector. The cable is routed through the metal to the circuit board on the other side of the metal. Insure each cable is tight as best you can. If you can isolate down to a single cable or sets of lights, these can be removed or replaced with some additional dissasembly.

The DTSS and the SST are wired the same with the exception of there are only the front driver facing lights are in the SST model of LED tree.
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Re: DTSS left/right sides intermittent

Postby Oldmate » Sat May 01, 2021 6:24 pm

Thank you for the tree insight. I do notice sometimes the tree starts up at power on operating like normal with each light illuminating correctly but when we try to start a race, only one side flashes lights. Why does the tree work at first but not when we start a race?
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Re: DTSS left/right sides intermittent

Postby raceamerica » Sun May 02, 2021 10:33 am

Oldmate wrote:Why does the tree work at first but not when we start a race?

When the tree runs through the startup selftest sequence, it is a visual check of LEDs and a functional test of the connection of signals. The tests are run at a low speed mode communicating to each set of lights one at a time to insure major functions are working. When the tree completes the power on sequence, it switches into a high speed update mode communicating to the sets of lights all at the same time. This would be similar to testing a cable for DC continuity then using it in high speed communications application.

A poor connection or frayed wire or corroded terminals or loose connector would pass the DC continuity test but not the high speed communications due to the effect of a poor connection adding capacitance. Unplugging connectors and plugging them back in a few times or sliding DIP switches on and off tend to clean contact areas and resolve issues and tighten the connection.

Back a few years, RaceAmerica updated the interconnect cable connectors and cable routing inside the tree to add reliability and reduce the long term effect of corrosion and reduce capacitance during the product's life cycle. These were designed in such a way to offer a tree upgrade to older trees by shipping the tree to RaceAmerica or further disassemble the tree, remove the sets of lights and ship those to RaceAmerica with the tree electronics.
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Re: DTSS left/right sides intermittent

Postby Oldmate » Thu May 06, 2021 8:56 am

I found the problem with the tree. Looks like both cables going to the left side were loose. Reaching up into the tree I was able to pop them back in place and all is good. Any idea why these cable would be loose? They seem to seat well when I popped them back in.
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Re: DTSS left/right sides intermittent

Postby raceamerica » Thu May 06, 2021 9:21 am

Oldmate wrote:Any idea why these cable would be loose?


The initial tree design had the cables to the left side sets of lights routed internally up and over the the center of the tree. Assembly and cable lengths became an issue as the tree was updated to faster microprocessors requiring the cables to be shorter in length. The later design routed the cables to the left side of the tree crossing over the lower part of the pipe to get to the sets of lights.

Over the years, we found customers who slide the pipe into the tree after use would usually lay the tree down first. Laying the tree down at certain angles would cause the cables to lay across the pipe inside due to gravity. At the top of the pipe inside is a large nut to prevent the pipe from sliding out of the tree when extending it. This nut would snag a bit on the wires and pull on them time after time until the connector is pulled loose.

The design of the tree continued to evolve and a 3D printed part was added to protect the cables from coming in contact with the pipe. When a customer ships a tree to RaceAmerica for service, we add the 3D part while the tree is completely apart. The easier solution is to not slide the pipe into the tree while laying the tree down.
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