I don't think you're supposed to connect that wire. Try it without the wire and see what happens. With that wire connected you're basically replacing the 330 ohm resistor with a 0 ohm resistor.

Check out this Pinwiki section on the flashers
https://www.pinwiki.com/wiki/index.php?title=Williams_System_3_-_7#Flash_Lamp_Problems

I am not smart enough to figure this out lol, this isn't something I've dealt with. To be honest, I leave flashers as incandescent because I don't like how bright the LED ones are, but to each their own.

This depends on your bulbs you got, the circuit from the factory uses solenoid voltage to fire the bulbs, so you're looking at 28vdc nominal. They use #63 flasher bulbs stock in series so the voltage gets cut down. This is likely your issue with them just blinking, depending on your flasher bulbs. They can be wired one of 2 ways, parallel or series.

For parallel:

This makes the circuit wiring a lot easier, since you'll have 2 wires feeding voltage (this is a daisy chain from solenoid to solenoid) and one or two wires for the ground portion (to the driver board). Both grounds and both voltage feed wires get connected together to one lug each on the socket, then put a short jumper from one socket to the other.

The important thing here is to check the voltage on your flashers to make sure they are the 28v version.... IIRC that was supposed to be the 1251 incandescent bulb, so the flasher needs to be that one with this wiring configuration. No resistors needed, the purpose of removing the 330 ohm one is to stop an led flasher from being on all the time. The 330 ohm resistor put just enough voltage to the incandescent flasher to keep the filament "warm" so the sudden flash wouldn't prematurely burn it out (since it's technically overvoltage, even when in series).

For series: (closer to factory wiring)

2 12v flashers in series config would work as well, but again be slightly overvoltage. In this case you'd have the 2 power wires on one lug, a jumper to from the other lug to the next socket, then the ground wires on the final lug. So each flasher should get 1/2 the voltage if they are matched closely, and if they are 12volt flashers (replacements for #89 flashers) this should work, too.

Q25 controls the "Flash" light. Original called for a TIP120. Also, take a close look at the resistor 7th one in from the left above the row of predrivers - it looks burned/broken.

Look at the other resistors around it in the same position. They're all the same value in their respective positions. So in your case, look 3 resistors to the left or right and choose that one.

I get my TIP120's from digikey. They are genuine parts.

It wouldn't hurt to also replace the smaller transistor for that leg of the circuit. It's between the missing TIP120 and the burnt resistor. All of the transistors in that row will be the same.

You can also use these free test ROMs to diagnose your whole game:

https://pincoder.ca

They require either getting a chip programmer and some spare chips, or even better, you can use this adapter:

https://pincoder.ca/index.php/2020/07/10/adapter-2020-06-23-0506/

It comes with every Pincoder test ROM available and allows you to test all Williams system 3 through 7 games.

Go to IPDB.org, look for your game. There’s a link to the pages with the driver board components and schematic.