I'd check each lamp on that row and make sure the wiring is firmly attached and that the diode on each socket is also firmly attached and oriented correctly. Make sure nothing is shorting to nearby metal etc. If everything checks out, you can try testing from the driver board. Here's a snippet from Clay's guide for Williams system 3-7 games that covers the procedure:

*Testing a Lamp Row/Colums with the Game On*

Another way to test the lamp rows (and indirectly the columns) is to do this:

Turn the game on.
Press the manual-down/auto-up coin door button to manual-down.
Press the advance coin door button once. The score displays should go blank.
Press the advance coin door button again. The score displays should all show zeros.
Using a alligator test lead, attach one end to ground (the grounding braid in the bottom of the backbox or pin 40 of the interboard connector).
Touch the other end of the alligator test lead to any one of the driver board transistors Q47, Q49, Q51, Q53, Q55, Q57, Q59 or Q61 (these are all in a vertical row in about the center of the driver board).
All the corresponding playfield lamp matrix row lights should all turn on (eight lamps in all). If less than eight light, refer to the operator's guide and see which lamps in the particular row are not turning on, and make a note of it.
Move the alligator test lead to the next lamp matrix row transistor to test the next eight row lamps.
If several lamps did not turn on, check the operator's manual and see if all eight lamps are in the same column or row. Note this does not test the row or column transistors themselves. It just tests everything from the driver board to the playfield. Also do NOT repeat this test for the *column* transistors! Doing that will blow the lamp matrix fuse.

If the transistors are good (we'll presume they are since you just replaced them), the next stop in the circuit looks to be the 7406 at IC12, which can be tested with a multimeter (though a logic probe would probably be more conclusive). Here's what Clay's guide instructs for testing with your meter (set to diode test!):

The 7408 Lamp Column & 7406 Lamp Row Chips.
If a row or column is still locked on or not working, next look at the 7408 chips that drive the lamp columns. These are at IC13 and IC14. Also there 7406 lamp row chips at IC12 and IC19. The IC12/IC19 lamp row 7406 buffer chips actually fail quite often, compared to the lamp column chips.

These chips can be tested with a DMM set to the diode function and the game off. For the 7408 at IC13/IC14, put the red lead on ground (pin 7), and put the black lead on pins 1,2,3, 4,5,6, 8,9,10, 11,12,13. A reading of of .4 to .6 should be seen for each pin (a reading lower than .2 is a big sign of a bad chip).

(**Below is the part to follow**)

Likewise the 7406 at IC12/IC19 can be tested in the same manner. With the game off, put the DMM's red lead on ground (pin 7) and put the black lead on pins 1,2, 5,6, 8,9, 10,11, 12,13. Again a reading of of .5 to .7 should be seen for each pin (a reading lower than .2 is a big sign of a bad chip).

Remember though, testing TTL chip mounted in a circuit board using a DMM's diode test can give false readings. If the chip is socketed, it's better to use the DMM diode test with the chip removed from the circuit. An even better test (with the board powered on) is to use a logic probe and to compare similar TTL chips. That is, compare two (or more) similar 7408 or 7406 TTL chips which both control lamps (see the schematics).

Nice!! Any time I suspect a bad diode, I'll usually replace it (and test it with my meter afterwards). If it's not a bad diode, I'd bet it's a faulty socket.