IC identification

Discussion in 'General Electronics Chat' started by tresguey, Dec 8, 2015.

  1. tresguey

    Thread Starter Member

    Apr 22, 2013
    55
    1
    Hi all,

    I have an 8 dip IC I am trying to identify. I am assuming it is a dual op amp. It is in a 12 vdc circuit that fires two relays based on temperature one at a time at two temperatures. From what I have probed I am pretty sure pin 1 = out, 2 = VCC, 3 = out and 4 = ground. I am pretty sure pins 5 and 8 are noninverting inputs. This board does not have transistors to fire the coils of the relays it is just the IC itself which I find strange.

    any help would be appreciated.
     
  2. dl324

    Distinguished Member

    Mar 30, 2015
    3,248
    625
    Did you intend to post a picture, schematic, and/or part number??
     
  3. tresguey

    Thread Starter Member

    Apr 22, 2013
    55
    1
    top.JPG bottom.JPG

    Here are pictures of what I have.

    yellow wire powers the IC, Thicker black is ground, smaller black and purple are for the thermistor and the green over rides or triggers one relay only.
     
  4. dl324

    Distinguished Member

    Mar 30, 2015
    3,248
    625
    Not helpful.
     
  5. SLK001

    Well-Known Member

    Nov 29, 2011
    819
    229
    What does the writing on the top of the IC say? Usually, the part number is there.
     
  6. tresguey

    Thread Starter Member

    Apr 22, 2013
    55
    1
    It was sanded off, they didn't want anyone to know what it is I guess.
     
  7. dl324

    Distinguished Member

    Mar 30, 2015
    3,248
    625
    Treat the unknown IC as a black box and create a schematic of the rest of the circuit, giving part numbers and values for anything with markings.

    The next time you ask for assistance, put yourself in the shoes of anyone who might respond. Do you think you gave anyone sufficient information to help you in your first post?
     
    panic mode likes this.
  8. alfacliff

    Well-Known Member

    Dec 13, 2013
    2,449
    428
    the old "sand the markings off" trick? I have been fighting that since the 70's I found that sometimes they are marked on the bottom too. I havnt found any surface mount ones marked on the bottom yet. somewhere on ePanorama.net is info on identifying chips from the circuit they are in.
     
  9. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    784
    That's something I mentioned on another thread - they do occasionally slip up that way.

    Given the overall nature of the equipment, I'd try an easy way out first - a wild guess that it could be an LM393 dual comparator. Even just starting on tracing out the circuit would give an indication whether it is or not - and by then a fair bit of the circuit is revealed anyway.
     
  10. sailorjoe

    Member

    Jun 4, 2013
    361
    63
    Based on the minimal information available, and from the photo of the circuit, my guess is that you have a dual comparator. The resistor network on the circuit board sets the threshold voltages for one input on each comparator, and the other probably comes from the thermistor. Of course, this is just a guess, but if it was me, that's the premise I would work on until proven differently. Look up an LM393 or LM2903. Good luck.
     
  11. hp1729

    Well-Known Member

    Nov 23, 2015
    1,955
    219
    Look at a data sheet for an LM56 and see if the function makes sense to you. Pinout isn't the same but you may get an idea of what you have. If they sanded off the numbers then it is probably a standard chip.

    Can you identify the chip manufacturer by the body style alone? Seiko (SII) makes dual thermostat devices but not in a DIP package anymore (S-5842 for instance).
     
    Last edited: Dec 8, 2015
  12. tresguey

    Thread Starter Member

    Apr 22, 2013
    55
    1
    Thanks for all the help, I was pretty positive the pinout for 1 - 4 were good and never saw a VCC on 2 and ground on 4 before and figured someone might have some insight. I will work on making a schematic and post. I did give minimal info....sorry
     
  13. tresguey

    Thread Starter Member

    Apr 22, 2013
    55
    1
    I do have the gerbers if that helps.
     
Loading...