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Trying to find information on two Texas Instruments IC's, may be obsolete. — Parallax Forums

Trying to find information on two Texas Instruments IC's, may be obsolete.

ihmechihmech Posts: 179
edited 2011-08-14 10:58 in General Discussion
I need help in finding information on two IC's on a garage door opener circuit board. I am including all of the information found on both chips.

1.) Texas Instruments CX8918DN 65616 125C66

2.) Texas Instruments RX8918 N 68837 125C49 *

*This one is my main suspect. It drives three transistors that drive relays for: Up, Down, and Light

The opener light and up circuits function correctly. The down function does not work. I do not get an audible click from the down relay. I have tested the transistor and relay. Both are fine.

I appreciate any help with this. Thanks!

Comments

  • $WMc%$WMc% Posts: 1,884
    edited 2011-08-06 18:54
    This is an obsolete part. But you might find one at the link below.
    '
    I have used these guys to find some old RF tubes.
    '
    Good luck
    '
    http://www.obsoletepartfinder.com/125C3AN_125C51_125C601H01_stock.html
    '
    125C49 looked like a simple resistor array in an IC package.
    I couldn't find a data-sheet on this chip, Only a reference to resistor array.
  • $WMc%$WMc% Posts: 1,884
    edited 2011-08-06 19:06
    Is that a IH in your Avatar?
  • ihmechihmech Posts: 179
    edited 2011-08-06 19:11
    Thanks, I put in a quote request for both parts. I have been searching for data sheets on them and can't find anything. I'm not sure what they even do, that's my biggest curiosity. The 125C49 is connected directly to a dip switch with 9 switches with three positions.

    It's most likely a fools errand, but I thought if it was an easy fix I could save my brother in law some money. Besides, I have a bad habit of not leaving something broke alone. If I can't fix it, I at least want to learn from it. :-)
  • ihmechihmech Posts: 179
    edited 2011-08-06 19:17
    $WMc% wrote: »
    Is that a IH in your Avatar?

    Yes it is, it happens to be a 9300 series Steiger Quadtrac, most likely a 9370. Here's a link if your interested in the specs.

    http://www.tractordata.com/farm-tractors/001/2/2/1223-caseih-9370qt.html
  • kwinnkwinn Posts: 8,697
    edited 2011-08-06 20:47
    ihmech wrote: »
    Thanks, I put in a quote request for both parts. I have been searching for data sheets on them and can't find anything. I'm not sure what they even do, that's my biggest curiosity. The 125C49 is connected directly to a dip switch with 9 switches with three positions.

    It's most likely a fools errand, but I thought if it was an easy fix I could save my brother in law some money. Besides, I have a bad habit of not leaving something broke alone. If I can't fix it, I at least want to learn from it. :-)

    If the 125C49 is connected to a dip switch it is possibly an array of pullup resistors, and unlikely to be the problem. You can verify this by measuring the voltage on the switches. The voltage should go low in at least one of the three positions, and high in at least one. If the other chip is the problem it may be simpler and cheaper to go to your friendly neighborhood Home Depot/Lowes/etc. and get a new opener.
  • tobdectobdec Posts: 267
    edited 2011-08-06 20:52
    Theres a place here in town called fair radio sales. they may have the exact part u need just laying around. This place is like a time capsule for electronics.....this guy has an ungodly amount of tubes just laying around new in boxes
  • ihmechihmech Posts: 179
    edited 2011-08-06 20:55
    kwinn wrote: »
    If the other chip is the problem it may be simpler and cheaper to go to your friendly neighborhood Home Depot/Lowes/etc. and get a new opener.

    I agree, like I said it's probably a fools errand. I just like to know how stuff works and wanted a datasheet more than the part itself. I didn't have a meter to do any testing while the circuit board was live. I could have probably had better results in my troubleshooting. :-)

    I'm going to study the circuits around the 125C66 and see what it interacts with. I wanted to see if I could sub something in its place, if I can't then I can't. I'm going to at least try my best and do some learning in the process.
  • $WMc%$WMc% Posts: 1,884
    edited 2011-08-07 09:21
    ihmech
    '
    How did you test the transistor and relay with out a meter?
    '
    What manufacture/model is it?
    '
    I too like to tinker with stuff like this.You have my curiosity up now!
  • ihmechihmech Posts: 179
    edited 2011-08-07 09:53
    @ $WMc%

    It's an old Craftsman/Liftmaster opener. I removed the cover on the opener and had my father in law operate the button on the wall.

    All I did with the opener was do a visual test and I removed the limit switch drive shaft and made sure the motor would run. It will only run for open and does nothing for down.

    I did manage to track down a guy on ebay that has several of those old circuit boards and I may have one bought.

    I brought the circuit board home and did some bench testing with my meter, that's how I checked the suspect transistors and relays. Next up stream was the 125C66 and I wanted to know what function it did.

    I thank you all for your interest and help. I had a lot of fun tracking down parts. I do still want to find a datasheet on the 125C66 though. It looks like I should have a cost effective solution this afternoon. Thanks! :-)
  • ihmechihmech Posts: 179
    edited 2011-08-13 19:46
    Garage door opener is fixed. I did some looking on ebay and found a guy with a used circuit board.

    For $33.44 with shipping it was an easy decision. I was able to go to my brother in law's today and install the circuit board. He's pretty happy, he has not been able to close the door for 2 years.

    Thanks for the help everyone!
  • GadgetmanGadgetman Posts: 2,436
    edited 2011-08-14 09:49
    Just thinking ut loud...

    Could it be that the unknown IC is some sort of Diode network?
    (Chip stuffed with diodes)
    After all, where you have relays you also want to have a diode to protect the system against the current pulses.

    Yeah, I know it doesn't matter any more, but if the replacement board breaks in a year or three...
    (It's old after all. )
  • $WMc%$WMc% Posts: 1,884
    edited 2011-08-14 10:58
    ihmech...
    '
    Glad to see you got it going!
    '
    Like Gadgetman said above,repairing the board would give you a spare.
    '
    I found this http://www.liftmaster.com/consumerweb/service/manuals But I don't have enough info to start a search.
    Model # ?
    Serial # ?
    date of manufacture?
    '
    This might help in finding the data sheet for the 125C66
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