Williams Solved Black Knight (Williams, 1980) light row 8 not working

[ganastas]

Hi, new to the forums. First time poster.. Hehe

My BK works fine and I have repaired it myself for years. But now I'm a little stumped.

All the lights in row 8 will not work at any time. I have replaced S7, Q58, Q59 twice, Q77 twice and Q76. All no joy. I also notice that Q59 gets REALLY HOT when pin is turned on. I also switched row 7 with 8 to see if its a playing field issues. All the lights in row 8 worked then. Just not when hooked up properly. Any help would be appreciated because I don't know where to go next. HELP... Or I'm I looking at a IC issue now?

Thanks,

Ganastas...

 

[pinballdaveh]

Row 8 lamp matrix ptoblem

the Q76 and Q77 that you changed are for column or strobe 8 and should not be part of the problem. the other 3 semiconductors that you changed are part of row 8. resistors R129-R134, diode D8, and cap C22 need to be checked also. to properly test them 1 leg of each part needs to be unsoldered and lifted from the board. otherwise false readings from other parts of the circuit may happen. i have found resistors to be bad and still look good example the resistors in williams high voltage section. diodes will have a resistance in one polarity direction only. and caps are usually checked on a higher resistance range on a dmm or vom. resistance values of parts can also be compared to known values of other parts example the row 7 section. if all part readings are good and within tolerance IC12 7406 or might be called SN7406 is the next part to be changed.

 

[ganastas]

Sorry for the late reply.

After looking very closely at the transistors I changed I notice one was a PNP and should have been a NPN.. My bad.. Put the correct one in and BOOM all's well. Thanks for your help!! Got another issue with the sound. But I'll search it out first, before I make a post.