(Topic ID: 269241)

What makes 3081 to break?


By Pinballark

13 days ago



Topic Stats

  • 12 posts
  • 7 Pinsiders participating
  • Latest reply 3 days ago by emsrph
  • Topic is favorited by 2 Pinsiders

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    800d793e7b010f1fee2a1c96c704f5b40510761e (resized).jpg
    CA3081_Probably (resized).jpg
    CA3081_Maybe (resized).jpg

    #1 13 days ago

    Hi
    I can understan why the maintransistors (tip102) sometimes breaks due to the high current it has to handle to activate selenoids, but what makes the IC (u3 3081 Fathom) to break?
    My actual q is...is there any thing to think of to avoid these IC's to break?
    They are expensive and hard to find.
    Thanks

    #2 13 days ago

    Sharp spike back up through .
    Electronic fatigue, old components just say "I'm Done"

    #3 13 days ago
    Quoted from Pinballark:

    They are expensive and hard to find.

    You can get them cheap on ebay.

    #4 13 days ago

    But also be aware there are some real winners on ebay such as these counterfeits. My last time buy parts from Intersil had 0049 date codes so I wouldn't trust anything newer than about 2001 or so. CA3081s should have RCA markings up until about 1990 (taken over by Harris in 1988), they should have Harris logos until 1999 when this product was spun off to Intersil, they should have Intersil logo for a brief period of time in 2000 before they were discontinued.
    There are also some signetics SG3081s out there but they're not real common.

    There are some valid ebay parts out there but be aware of parts like these that were supposedly made in 2012 - long after Intersil discontinued them.

    CA3081_Maybe (resized).jpg
    #6 12 days ago

    Unlike the eleleparts, those posted by jj44114 look quite reasonable. Proper date code, proper part number marking (there should not be an "E" suffix shown in the marking on that era of parts), and for those made in 2000 - there is an "MALAY" beneath the intersil logo (for Malasia). Those look almost identical to the leftovers that I have from when Intersil did their last time buy.

    CA3081_Probably (resized).jpg
    #7 12 days ago
    Quoted from G-P-E:

    Unlike the eleleparts, those posted by jj44114 look quite reasonable. Proper date code, proper part number marking (there should not be an "E" suffix shown in the marking on that era of parts), and for those made in 2000 - there is an "MALAY" beneath the intersil logo (for Malasia). Those look almost identical to the leftovers that I have from when Intersil did their last time buy. [quoted image]

    I think these are the last Intersil 3081 parts made. get em now.

    #8 12 days ago

    Bally also used ULN2081 and one other part number I have come across which i can't remember... Maybe it was SK3550? Both of those probably just as obsolete if not more than CA3081. Looks like NTE916 / ECG916 same part as CA3081 too.

    These transistor arrays normally cascade failure when the main driver goes. When just one circuit fails in a CA3081 you can cut the two bad legs off and install a 2n4401 straddling the chip. Bit of a hack job but works fine.
    800d793e7b010f1fee2a1c96c704f5b40510761e (resized).jpg

    Can't remember what brand name is the (2) logo is but they bought or got bought by Allegro at some point. I use TND903 diode arrays in another project and they have that same (2) logo or the Allegro logo depending on the date.

    1 week later
    #9 3 days ago

    Thanks for all replies
    Have my one and only installed now and it works fine...hopefully forever

    #10 3 days ago

    Sorry if this hijacks the thread- I can make a separate?

    Rebuilding a Stern project solenoid driver board now. In one ca-3081 (U4), 5 of 7 of the array transistors are toast. The main driver transistors test ok. Just replace the array along with all the diodes?

    A few other drive transistors related to a different array (U3) show that they were previously replaced. One array transistor there shows Open. Going to use barakandl "piggyback 2N4401 method" on that one. But change all those diodes too?

    Leave all the resistors or change them? They test ok.

    Thanks

    #11 3 days ago
    Quoted from emsrph:

    Sorry if this hijacks the thread- I can make a separate?
    Rebuilding a Stern project solenoid driver board now. In one ca-3081 (U4), 5 of 7 of the array transistors are toast. The main driver transistors test ok. Just replace the array along with all the diodes?
    A few other drive transistors related to a different array (U3) show that they were previously replaced. One array transistor there shows Open. Going to use barakandl "piggyback 2N4401 method" on that one. But change all those diodes too?
    Leave all the resistors or change them? They test ok.
    Thanks

    If you are going to use one the 7x 2n4401 modules to replace a ca3081 no other modifications are needed.

    You should not have to replace any diodes or resistors to install unless they are bad. The 330ohm resistor will burn up if the coil locks on, but it will likely be visibly burnt if there is a problem.

    #12 3 days ago
    Quoted from barakandl:

    If you are going to use one the 7x 2n4401 modules to replace a ca3081 no other modifications are needed.
    You should not have to replace any diodes or resistors to install unless they are bad. The 330ohm resistor will burn up if the coil locks on, but it will likely be visibly burnt if there is a problem.

    Thanks Andrew. Just wanted to make sure I protected the new array. I was surprised so much of it was pooched up without blowing the drivers.

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