Replaced the Socket (female) and all is well. Turns out is was a 10 pin plug but only 4 pins used. Left the header as is for now, dont want to take out the circuit board and remove all the plugs in case something breaks. Hopefully the resistance is reduced and the new socket wont burn. Otherwise will have to remove board and reflow on back.

Weird, checked the big transistor,and  the pre driver transister as well and it reads same on the DMM using OHM setting as all the others of the same type when powered off. Must be the TTL or the maybe the MPU? Might leave well enough alone and accept that on an 18 year old machine 2 flashers stuck on is a simple fix...remove the bulbs.

Again, thanks for the advice guys.

On the page I linked above, search for "Transistor Testing procedures using a DMM." It uses the diode setting of the DMM (not ohms), and the procedure is slightly different depending on the type of transistor. The 74LS374 chip can also be tested in a similar way, as described.