Last weekend my Taxi fried Q75 for the left bumper. So I replaced it with a new TIP122 and the pre-driver only to find that the coil had melted in the down position. So I replaced the coil only to find now that as soon as the game is turned on it fires.
So I pulled out the logic probe and looked at U45 (SN7402) for driving Q75 and the output 13 is low and 11 and 12 are high. All the other NOR gates are high on the chip. So I can order either a SN7204 or DM7204. Does it matter which one I use?
Either is the same, just different manufacturer. Can also use a 74F02, and IIRC 74HCT02 or 74LS02. My preference is the 74F02's
-Hans
Use a 74F02 as a replacement. You can have problems with 74LSXX ICs in the solenoid driver section on system 3-7, i assume 11 is the same way.
Quoted from vectordreams:Thanks that helps as I have some 74LS02 chips.
Use your 74LS02 for now as a temp, but you probably want to replace it with the higher amperage part: 7402 or 47F02 (sooner rather than latter).
There are times where neither 74LS02 nor 74HCT02 will work as a sub for a 7402:
74HCT02 - high = 400uA, low = 4mA
74LS02 - high = 400uA, low = 8mA
7402 - high = 400uA, low = 16mA
Well the 74LS02 has me back up and working. I guess at some point I will order some 7402 chips and replace it if I have issues.
7402 is obsolete so you will have trouble finding those. 74F02 are still available inexpensively.
I would say it is pretty important to use the right part here. When these solenoid ICs fail they typically lock on a solenoid(s) and if it happens when your back is turned major damage can happen if the fuse does not blow.
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Colorado Springs, CO
Sana'a