**** EDIT 08.22.16 ****
It works. Considering selling these as a kit. You would get a sheet of blank PCBs, headers, and 2n4401 transistors.
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**** Original post ****
I pulled off a hack today. Dead transistor inside of the CA3081. I opened my part drawer and found I was out of the CA3081. To get the board going i decided to swap in a single 2n4401 transistor.
All I did was snip off the bad associated CA3081 legs. Desolder the pads clean. Stuff collector and base into the appropriate pins of the CA3081. Emitter is all common together inside the CA3081 and attached to ground. Pin 5 and 15 of the CA3081 are grounded so you can use those, or like i did, just find a nearby ground pad that was most convenient.
Then you don't have to replace the entire obsolete and expensive CA3081. Here is a pic of my hack fixing the q3 (its always q3 knocker circuit it seems) predriver for the CA3081
Works on my test setup to light an LED. I will throw it in a real game tonight.
That led me to also do this PCB layout with discreet NPN transistors.
I couldn't find a different transistor array to sub in, so i figure 2n4401 is probably acceptable commonly used discreet sub. I could make them available as a DIY kit. Any input is appreciated.