Have a question above my understanding. (see attached pic and datasheet). Attempting to repair a pcb with a burnt out Darlington Transistor IC. I have identified all pins except for nos. 11 & 12 (Output 7 &8). I removed what is left of the IC, but could not find any traces as to where these pins might have been connected. Bad choice of words, there is no trace of any circuit trace for either pin. In the surrounding circuits i cannot find any without a verified connection to other components. My question is it possible these two pins are just hanging out there with no connection, nothing to ground etc? or possibly the connections were vaporized in the burn out (severe burning and melting of IC). There are inputs connected to Inputs 7 & 8, though they are shared with a couple of other similar IC's. This is from an 2000's vintage arcade game, 24V voltage, and my reverse engineering seems to indicate these were controlling flashing lamps. Thanks for any help in understanding this IC
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Answer selected by Stefo at 01-12-2024, 07:02 PM.
It is an 8 channel low-side switch. They might have used only 6 of the channels and left pin 11, 12 not connected. If that is true then the input pin 7, 8 for them might also be not connected. Or they are spare outputs if the board was used on other models.
It's OK for there to be nothing connected to the outputs. But. The IC was overloaded so check for shorted loads, a lamp socket must be shorted. There should be pads for the IC pins there unless they melted along with the traces.
I would expect they go to the ribbon cable connector.
The IC looks the same as ULN2803AD if you need to change it, very common. But double check the IC package matches. -
It is an 8 channel low-side switch. They might have used only 6 of the channels and left pin 11, 12 not connected. If that is true then the input pin 7, 8 for them might also be not connected. Or they are spare outputs if the board was used on other models.
It's OK for there to be nothing connected to the outputs. But. The IC was overloaded so check for shorted loads, a lamp socket must be shorted. There should be pads for the IC pins there unless they melted along with the traces.
I would expect they go to the ribbon cable connector.
The IC looks the same as ULN2803AD if you need to change it, very common. But double check the IC package matches.Comment
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what game is it?
those drivers are easy to kill - i buy them in quantity from china i get through so many.
the slot machines use one for each stepper motor
an average game could have atleast 7 drivers in it
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Thanks Redwire, you confirm my suspicion there was not a connection on 11&12. it just seemed odd to me that the inputs were connected. You are correct in that the outs are going to the ribbon cable, for which I have accounted for all the pins. I think the inputs for several of these chips are connected in common to synchronize lights flashing on the machine, this is what threw me off, your explaination helps. Thank you. Ill look at your suggested IC replacement. Oh and the owner of the machine connected a different manufacturers reel cable which instantly shorted the IC. So at least I know the source of the short and it wasnt internal to this board!Comment
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Great Sage, this is from a Bellco Pachislo Japanese slot machine. Thanks for your interest in helping.Comment
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nice, i have no source of manuals for those.
i can tell you that it's rare for those drivers to run lamps - they can only drive 2A
usually the driver feeds a big power transistor that drives the lamps - atleast on european machines
also the 8 elements in these chips can be paralleled to increase the current.
the reel drives are done in pairs for 4A peak so each chip is driving 4 lines with 8pins
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GS you have given me another angle to consider, given the damage source you are on to something there with the reel drive pairs. Thanks for another rabbit hole adventure
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