Here is the information for the flipper cabinet opto boards.
Quoted from LTG:
No. But they look like after market boards, so something ain't right.
Yes. They are supposed to get hot. The installed resistors are 470 Ohm (YEL/VIO/BRN/GLD - discolored from heat). The +12VU circuit is around 14VDC. This dissipates ~0.4W for a 470 Ohm resistor. This is very close to the 0.5W MAXIMUM rating for the resistor. Ideally, it should be a 1W resistor or a 680 Ohm to dissipate less heat.
Quoted from GILV:
If not, what does it mean that they get so hot, what are the repercussions of them getting hot?
You can't get rid of them as they are the current limiting resistor for the transmitter side of the slotted opto pair.
One major problem with the heat is that it can cause a cracked solder joint at the resistor. I have seen many boards with these current limiting resistors that dissipate heat into the board instead of dissipating the majority of it convectively to the atomosphere.
Quoted from Tranquilize:
You can test the inbound current based on the schematic and fix it or replace the hack with OEM circuitry.
There's nothing to "fix" and this is not a "hack" because it is the OEM circuitry.
Quoted from GILV:
Thanks, those resistors getting hot after a few games did'nt bother me much in the past 2 years, but now they cause the magnet optos to suddenly stop working, but before they stop working, they go crazy at every flipper button press, then, and only then, they go out, I turn the game off for 15 minutes, time to cool down those resistors and everything works great.
Are you sure it is THIS board that is causing the problem? When you turn off the machine, everything cools down. If you want to run a better scientific experiment then just disconnect the connectors at the flipper cabinet opto boards for 15 minutes, plug them back in and see what happens. There are 270 Ohm 2W resistors on the Custom 10-Opto board that get hotter than these 470 Ohm 0.5W resistors. The 10-opto board is responsible for managing the other machine opto pairs.
Note that the board you purchased is pretty much the same as the OEM with respect to the level of heat dissipation. It has 470 Ohm 0.5W resistors installed flush to the board. In the long run, the board will have the same level of heat discoloration.