When you say "It appears to test proper" can you elborate on how you came to this conclusion? Did you scope it?

IBJ

No.

You need to test diodes D-8 and D-9 and resistor R-119 on the CPU board.

It could just be that the wire for that row has wiggled out of it's connector as well. HS is when Williams exclusively used IDC style connectors and they are really bad for wires coming out.

I'm curious if this got resolved. I have a similar issue but for me it's row 5. All lights in that row are out, test mode or gameplay. They were flickering a couple days ago and now they are completely out.

Power down, then open the backbox. Wiggle the two connectors in the lower-right corner of the main board (groups of red wires and groups of yellow wires), these control the lamp matrix. See if this helps. If not we'll need to dig deeper.

Hi thanks for responding to this thread! I would appreciate all the help I can get!

I have tried wiggling both connectors and I even disconnected the J6 connector to see if anything looked suspicious and reseated it and still the row won't light.

I've looked at wires underneath the playfield following the red/green wire to all of the sockets and nothing looked broken.

I took Grumpy's advice earlier in the thread and tried to figure out which diodes/resistors/transistors went to row 5. I know Q84 is connected and I it looked to me like D12 and D13 were also. I did some DMM testing on those parts in circuit (which I am still learning and didn't test anything yet out of circuit because I have never soldered anything before) and D12 was the only part that produced suspicious readings. With the black lead on the stripe side all of the diodes were testing 0.596, but D12 was testing 2.4. I understand from doing a lot of reading, you tube videos and other threads that testing in circuit isn't reliable, but they were all (diodes, resistors, transistors) producing similar results except that diode so I figured I would start there unless you have some other advice or things to test.

This is something to look at further. Disconnect j-6 from the cpu board. Then compare like components in different circuits such as compare D-12 to D-10. If D-12 reads a lot different then D-10, then lift one lead of D-12 and retest D-12. It is essentially out of circuit now and should test correctly, if not replace it.

Test a dead string of lamps/temporally turn them on :
Remove the ROW plug take the key out and shift the plug one pin over to inject any of the working 7 signals into the dead string to rule out a broken wire on playfield .

That's a good idea, thank you so much!

This is all great information, I really appreciate it.

I will have time tomorrow to shift j6 over a pin and then do further tests on D-12 if need be.

Seriously, you guys rock!

So I shifted j6 over and row 5 lit up! So no broken wire.

Then I unplugged j6 and tested D12 against similar diodes (D10, D8, etc) and got the same readings as before. Other diodes tested at 0.587-0.596 and D12 tested at 2.4 with black lead on stripe.

D12 sure seems suspicious so I clipped one of its leads and tested it... and it tested the way it should. Ugh.

So where should I look next? I would imagine Q84 transistor (TIP 122)? I've read that a faulty transistor can cause a circuit to fail, but I've tested Q84 against the rest of the transistors and they were all producing similar readings (assuming that I was testing correctly). Black lead on the middle leg and red lead on the outer legs (in diode mode), they would read 0.5 and 0.6.

Im not an expert but start off simple. Unplugging wires and moving them generally is not the first course of action. If something was wrong that blew something now you move wire and blow another row up and have 2x as much to fix. First do you even have power at the pins on mobo? Could be something as simple as a cold solder joint. My course of action would be pull connector and check for power at pinson motherboard. If power at the pins swap multimeter to continuity. One lead goes into plug/wire that we think is bad other end goes to end of string. Do we have continuity? If no/low power at pins we first check for cold sodler joints. If these couple things dont work I would try to figure out what controls that row and replace it. Also have you looked up the system 11 repair bible? I was new to all this about 6 months ago and with some help from here and https://hansbalk.home.xs4all.nl/rep/sys11/index.html I "shopped/minrestored" a F-14 Tomcat

If you check the solder pads where the diode was connected it will still read 2.4 ohms. Find the bad component that is dragging this circuit down by lifting some more leads.

Took this handy dandy screenshot for reference as I do some more testing.

Screenshot_20190817-085405 (resized).png

I did check pinwiki and it seems to point to Q84 as the culprit if the row of lights are out. It mentions a test for the column driver which involves using alligator clips on the j7 column pin 1 and the j6 row pins, with a test bulb and socket. I haven't run that test yet because I don't have any extra sockets. I need to get extra sockets anyways, but is that test worth running?
Would this test rule out the j6-6 pin? Since it's bypassing all of the components that I'm testing for faults?

Is there a better place to start than others?

You're right, it does still read 2.4 ohms. So I take it that it's really not worth testing anything without lifting a lead, or removing the component altogether?

Since D-12 is removed from the circuit, you can check from the cathode of D-12 to the intersection of R-124/R-125. Then check from the anode of D-12 to the same intersection. Which one reads 2.4 ohms?

pasted_image (resized).png

Playfield row 5 wiring tested working:

In lamp test go to PIA 54 where Row 5 signal begins, check for a moving signal at output Pin 6 then at IC U56 Pin 1 and 2 using a logic probe.
if signals present replace Q 84 If no signal is present then the signal must be confirmed before moving to D12 and R13 as Signal must be present at U56 Pin 2 for the Row to operate.
williams-system-11a-cpu-mpu-pcb-board_1_204f12f98cb5a3377b8c7931ae400ed2 (resized).jpg

I just realized that I have been in diode mode this whole time, not resistance. So the 2.4 reading was 2.4v in diode mode while the diode was in circuit. When I removed the diode completely and tested the pads, I was still in diode mode and got 2.4v. Should I be testing resistance?

Yep.

I have a logic probe arriving on Monday. I've never used a logic probe before, can you instruct me as to where's the best place to put the negative and positive leads?

I checked the solder pads again where D12 used to be with the black lead on cathode/red lead on anode side I get a reading of 0.652ohms in resistance mode.

Is the intersection of R-124/R-125 the emitting leg of Q84?

Connect a logic probe to these locations.

Awesome, thank you!

Sorry, I should clarify again, my multimeter reads 0.652 M ohms. (Actually I just took another reading and it is 0.739 M ohms)

That's normal.

Where is the intersection of R124/R125? I see on the schematic where they converge, but where does that happen on the board?
Screenshot_20190817-085405 (resized).png

If this would have been a resistance test, then there would have been a shorted component. A shorted component is very easy to find with an ohm meter. Now since this is not the case you will need to use a logic probe and follow the pulse train to each component.

I received my logic probe today so I am ready to start testing.

I have some questions before I start:

What logic family should I use to test both PIA U54 and IC U56? CMOS OR TTL?

Should I be in ALL lamp test, or attract mode?

Will there be any problems since D12 has already been removed from the circuit?

This era of electronics is TTL.
Attract mode is fine for testing.
D-12 either needs to be patched or replaced to finish testing.

Check Signals in Lamp Test:
In lamp flash test go to PIA 54 where Row 5 signal begins, check for a moving signal at output Pin 6 then at IC U56 Pin 1 and 2

download (resized).png

williams-system-11a-cpu-mpu-pcb-board_1_204f12f98cb5a3377b8c7931ae400ed2 (resized).jpg

Since I need to replace D12 to finish testing, I better brush up on my solder skills. I have some practice kits I'm going to use, and I'm still chugging through Terryb's solder guide, (and logic probe guide).

Grumpy and Pintec, I appreciate your help and especially your patience as I make my way to the end of this particular problem. I'll get back to you guys once I get D12 replaced.

Aside from the diode testing/soldering which will not affect the signal test, now if there isn't any problems found with Diodes Resistors,Transistors,Scr's, without the vital signal coming out of pin 2 of u56 the row will not function.
Suggest checking and confirm if needed signals are present by placing the tip of the logic probe on pins 1 and 2 on U56 in while lamp flash test is running.

You may verify what working signals will look like on pins 3 and 4 known functioning input/output on u56 in lamp flash test mode because that's what can be used for a reference to what 1 and 2 must look like.

While in attract mode, with probe set to TTL and also set to pulse, I checked PIA 54 pin 6 and there was a signal. (I should note that after watching videos of most probes clearly displaying an arrow or light reading of low or high and making a sound that is either low or high, my probe looked and sounded like it was doing both, making a screeching sound.) Whether or not it was reading the right signal, there was definitely a signal.

I moved on to IC U56 pin 1 and 2, and there was a signal at both of those pins, similar in look and sound to PIA 54. Just to make sure I tested IC U56 3 and 4 and they produced similar results.

The signal will be high and it will be pulled low momentarily switching back to high.

Signal good:

Change Q84

Thought I would take a photo of the CPU board while I had it out.

I'm going to replace D12 and Q84 here shortly.

Is there anything else that looks suspicious?

@GRUMPY, you mentioned finish testing once I get those components soldered in. Are there any tests I should try while I've got the CPU board out?
IMG_20190901_095815 (resized).jpg

I couldn't wait to get the board back in and play. So I plugged everything back in and lamp row 5 is back up and running!

Thanks again @GRUMPY and @PINTEC for all your help.

Playball!!