Bad Lamp Socket
After replacing the light bulb it will still not light up.
We have seen with these older light bulb signs some of the newer lamps do not have enough solder on the base of the bulb (base of bulb should be rounded).
The picture below is the correct type of base.
The picture below is the incorrect type of base.
So when you place the bulb in the socket it will cause the contacts in the socket to arc together through the base of the bulb (because the base of bulb is flat). Sometimes the bulb will make contact with the Hot Tab and the Rivet holding the Neutral Tab.
Once that happens ether the socket or the V4 Module Driver Board have to fail. Because the traces on the V4 Module Driver are small, most of the time they will be the first to fail, however the socket could also fail. If the socket failed , then at this point the socket will need to be repaired/replaced. If the V4 Module Driver Board is replace WITHOUT fixing (or replacing) the bad socket first, the V4 Module Board will most likely fail again (that part of the V4 Module Driver board for that bulb location).