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tbzep 05-01-2019 09:29 PM

Retired Launch Controller
 
1 Attachment(s)
I've tried, but I can't get my classic controller working anymore. It has been flaky and had some dead digits on the 8 segment LED displays. I touched up the soldering on them and got all the segments to work, but the system was still flaky, sometimes turning on with odd number segments lit up, and occasionally firing on power up if the leads had continuity. I could usually cycle the power and get it to work correctly. It counted down and fired correctly on several test runs. Then for some reason it started hitting the relay as soon as I hit the start button. I've looked for any contamination on the components and the runs on the board. I've re-seated all the chips. It got wonky about 20 years ago and I replaced all the socketed parts like the 555 IC's and such. I may try that one more time. I'm no electrician, much less an electrical engineer. I can read simple schematics, so I can slowly verify everything is wired correctly on the I/O board, but that's about it.

It was designed and built for me by my cousin. He needed a project in one of his electrical engineering classes so I was only out the cost of surplus Radio Shack parts (his dad owned one for a while). He went on to work on EF-111's and who knows what else at Warner Robbins AFB. Sadly, I haven't seen him in nearly 40 years. He and his brother introduced me to model rocketry.

Shreadvector 05-02-2019 10:05 AM

Have you tried talking to it?


https://www.youtube.com/watch?v=h73PsFKtIck




Quote:
Originally Posted by tbzep
I've tried, but I can't get my classic controller working anymore. It has been flaky and had some dead digits on the 8 segment LED displays. I touched up the soldering on them and got all the segments to work, but the system was still flaky, sometimes turning on with odd number segments lit up, and occasionally firing on power up if the leads had continuity. I could usually cycle the power and get it to work correctly. It counted down and fired correctly on several test runs. Then for some reason it started hitting the relay as soon as I hit the start button. I've looked for any contamination on the components and the runs on the board. I've re-seated all the chips. It got wonky about 20 years ago and I replaced all the socketed parts like the 555 IC's and such. I may try that one more time. I'm no electrician, much less an electrical engineer. I can read simple schematics, so I can slowly verify everything is wired correctly on the I/O board, but that's about it.

It was designed and built for me by my cousin. He needed a project in one of his electrical engineering classes so I was only out the cost of surplus Radio Shack parts (his dad owned one for a while). He went on to work on EF-111's and who knows what else at Warner Robbins AFB. Sadly, I haven't seen him in nearly 40 years. He and his brother introduced me to model rocketry.

tbzep 05-02-2019 10:18 AM

Quote:
Originally Posted by Shreadvector
Have you tried talking to it?


https://www.youtube.com/watch?v=h73PsFKtIck

Yes, but it was more like this:
https://www.youtube.com/watch?v=xaVgRj2e5_s


.

matthew 05-02-2019 04:14 PM

If there are any electrolytic capacitors in there, I'd replace them as a first step.

teflonrocketry1 05-02-2019 08:27 PM

Quote:
Originally Posted by matthew
If there are any electrolytic capacitors in there, I'd replace them as a first step.


I second that motion! Electrolytic capacitors are prone to degrade over time. I once got an email from an electrolytic capacitor manufacturer stating that they had neglected put a stabilizer in the paste they use inside the capacitors they were manufacturing for years; visit the capacitor plague at: https://en.wikipedia.org/wiki/Capacitor_plague . On the computer mother boards I have repaired when the electrolytic capacitors around the RAM chips start to fail the computer starts to behave oddly, similar as described.

tbzep 05-02-2019 09:08 PM

None are leaking or swelled like I used to see with bad motherboard capacitors. I may try to resurrect it when I finally get some time off to fool with it. I'll see about replacing caps at that point.

I put a straight 2.2v to the old LED's and they were much brighter than with the board supplied power. I will need to look into the onboard voltages if I end up trying to get it going again. I could see them in bright indirect light when it was new. They are very dim now.

ghrocketman 05-02-2019 09:55 PM

+1 more to replacing all the electrolytic caps whether they "look" bad or not.

kapton 05-03-2019 11:54 AM

Quote:
Originally Posted by tbzep
I put a straight 2.2v to the old LED's and they were much brighter than with the board supplied power.


LED's are current driven devices, not voltage driven. You need to drive them from a constant current (or pseudo-CC) source. Typically that means using a resistor in series with the LED.

Driving directly from a voltage source can easily result in excessive current draw and destruction of the LED.

ghrocketman 05-03-2019 01:04 PM

Absolutely. Directly driving an LED w/o a series resistor will result in blown said LED quickly.

tbzep 05-03-2019 06:58 PM

I used a power supply that I can dial in current and voltage. Current was turned down, but I don't recall what it was reading.


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