I’m having a rough night. I had gotten my BK to playable and had started handling cosmetic things. But when I went to start it up to play a celebratory round, one of the upper flippers went out again. I adjusted the switches and still no love, so I shorted the coil and got no response. So I shorted the other upper coil to sanity check and got a weak response. Huh. Then I smelled the smoke. I’m still not sure what went wrong.

I seem to have fried my MPU board. Taking out the driver board had no effect. I got the MPU on the bench and confirmed the reset circuit is showing 5V on pin 40 of the MPU and the address bus pins appear to have signal. From what I’ve read it sounds like my next best tool is to put in a test rom, but I don’t have one.

Do I have another alternative? If not, how should I pick a burner? Is eBay my best bet? Any recommendations?

Thank you! I’ve ordered a gq-4x4 and some spare 2532 and 2716. The CPU seems to be running fine, so I hope I just blew out some ROM.

Ok! I was able to run the roms from pincoder and I'm pretty sure I've got a dead PIA. I loaded up the solenoid test, but I'm not sure how to check the whether the flipper relay is energized. The flippers don't do anything at all. And in retrospect, I understand how I fried this thing but not exactly what I fried. I was moving too quickly and attached a test clip to the horizontal metal bar as a ground to test the coil. I'm only now seeing the switch attached. Soooo.

Could someone tell me what it is? Is checking the flipper relay a moot point? Should I just try to track down a new PIA?

IMG_6273 (resized).jpeg

Also, my board's PIAs have the williams logo on them and the id: "SA-8972 8107". Though the schematics says MO 6821. I should replace with the latter, yeah?

Looks like the horizontal bar was the ball-roll-tilt. So, I’m assuming I put way too much voltage (coil level) through the switch matrix via the green-brown wires, I would expect the PIA to be fried, right? Anything else I should check while I’m waiting for replacements to come in?

I think I've been chasing my tail. I'm seeing identical behavior on the board with or without IC17 inserted. I'm not sure why the test rom isn't getting started.

It look like the address busses are cycling and I've got continuity from IC17's pins to the data buffer to the CPU. I've got continuity from the CPU's address pins to ICs 3 and 4 and from those to IC17.

The EPROM burns and does verify ok. I'm not currently using an external power adapter for my burner (gq-4x) but my system claims 500mA are available and the DC power supply people mention only supplies 200mA.

I've checked continuity from the legs of the EPROM when inserted into the socket to the solder pads below the socket.

I have the driver board connected to the MPU, but was seeing the same behavior without it. My test bench setup is an ATX power supply with an adapter board and I've connected ground, 12v, and 5v to IJ2. Two leds light up but no digit.

What am I missing re: requirements for reading and running from the ROM?

Edit: Leon’s guide says only 5V should be needed plus a jumper from C23 to R3, but when I try that the whole thing turns off, including my power supply adapter board, after about 1s. If I add 12v this doesn’t happen.

Here are my more detailed notes per IC incase something stands out:

IC1
* Clock signal on 38 a little high (1.8v vs 1.5. Probably fine?)
* 39 checks out. 40 is showing reset voltage (4.5v)
* Pin 2 and 3 at 5v voltage (4.3 coming from power supply, shows up there)
* Pin 5 showing 3v correctly

IC 4, 3, 8, 9 all look ok, though voltage is coming with a slight bump coming out the buffer
* Consistent bump though

IC 18:
* Pin 2-8 don't show up on the logic probe but show < 2v (1.7-1.9) with dmm
* 9-17 show ~5v

IC 36:
* Pin 2-8 show ~ 2.3v, but show nothing on the logic probe
* Pin 9 is 0.5v
* 10 5v, 11 1v, 12-14 5v, 15-16 0.5v, 17 5v, 18 0.5v, 19-20 5v

I’ve pulled off the driver board to simplify things and see no change. Removing all the non-IC17 ROMs also had no change.

Leon mentions IC13 and 16 need their CS pin (8) to be at 5v on startup. I'm seeing mine at 3.5v. The actual power being supplied by my 5v pin on the power supply is closer to 4.6 and I see that at TP 9. Seems like that might be one of my issues.

Edit: Course, half the PIA pins being at voltages right in the middle, where it's not high or low, seems like an issue too. But I'm not sure if that's because the ROM isn't running or *causing* the ROM not to run. Having bad PIAs sound like they'd keep the digit from displaying though?

And I've verified the data bus looks like it's getting real signals. But nothing is coming out of the PIA I outputs and going to the digit. So it sure seems like it's at least one major issue. I've got PIAs coming in and I'll put in a socket and swap it out and see what happens unless someone has a better idea for a next step.

I’ve replaced PIA I on the MPU and now I’m getting flashing lights from the test ROM. Still no Diagnostic Segment Display.

I *do* get the bottom right segment of the diagnostic display lighting up during the memory test portion of leon's rom. Going to try pinside next now that programs are atleast loading.

Ok, pincoder tests 1-4 all run fine except that the 7 segment diagnostic led doesn't light all the way.

@pincoder Got a tip on what I need to run down to figure out what part of that is busted?

If I check IC 34's pins based on this doc: http://www.blackknightpinball.com/sys7-mpu-leds-info.htm

It looks like I'm getting an 8 when I hit the diagnostic button. Seeing as it's on the bench with no driver board, that sounds good? Seems like I just need to replace the display itself?

Progress report: while I have the board on the table I swapped out IC19 with nvram. I’m now getting 0 on the diagnostic if I’m reading the output from the 7447 correctly. The display doesn’t show anything anymore, though before it was only showing segment G (the cross on the 8), so it’d make sense that it shows nothing for 0.

On the assumption the display (MAN72A) is bad, I pulled it out in prep for a new one. But I was curious about why some segments failed so I hooked it up on my 3.3V with a 150ohm resistor and I’m getting every segment lighting up just fine. That makes me wonder if the voltage or resistance is off on the connections.

Welp. It's my 7447. Inputs look good but no outputs.

I took the 7447 out in prep for a new one, but I was seeing high on all the inputs (previously was seeing inputs corresponding to 8 according to that doc - inverse binary was a weird choice). Outputs don’t show up either way in my logic probe. If I’m recalling correctly they were in no man’s land for a signal and not enough Vf to light the LEDs.

Replaced the 7447 and now @pincoder’s test rom #1 counts up on the display just fine and the black knight flipper rom shows 0 on the diagnostic display.

Main displays are still blank. I checked the voltage and it’s about 90 at 4J6 which is expected since I replaced the Zener diodes when I rebuilt the power supply. Next I’m going to check the BCD inputs by using the pincoder display test (rom 5) unless someone has a better idea. That rom showed nothing when I used it before the 7447 replacement, but I didn’t poke around very long and it looked like the program might not be running. I wasn’t seeing signal changes on IC18’s PB pins which afaict go to bcd outputs, and I’m not sure how the rom could be running without that happening.

pincoder Thank you! That's extremely helpful. I was having trouble finding a write up on how the display signaling worked.

I'm seeing signals on the PIA and on IC 6 with my logic probe. No oscilloscope, so I can't check details but I'm seeing movement. The cycling is very clear in IJ5, so I'm going to double check the blanking test rom and the move to the display board.

Confirming that blanking checks out at TP4.

I reinstalled my mpu and driver board and put test rom 5 back in. It came up with a flash of the leds and the diagnostic display which then went blank. But I wasn't able to see any cyling on IJ5. I touched the chips lightly to see if something was loose and when I got to IC 18 the leds and diagnostic came up. Now IJ5 is showing high across the board. TP4 shows low. I'm not seeing pulses from PIA's 2,3,4. Behavior persists across restarts. IC 1 shows pulsing on the address and data bus.

Huh.

I took off the driver board and now I'm getting a response from the rom that's in (which at this point is Leon's). I guess I'll leave it out and debug the displays before figuring out what's wrong with the driver.

And with the displays test rom I'm getting digits cycling! Player 4 display is flakier than I remember, but seems to be doing better as it warms up.

Progress!

I've established that without a driver board, Leon's test rom runs correctly. When I add the driver though, I get no blinking (just lights on and 0 on display). Leon's guide (http://pinwiki.com/wiki/index.php?title=Leon_Borre_WMS_System_7_Repair) seems to indicate that the good PIAs should show signal while the bad PIAs shouldn't, but when the driver board is added I'm seeing no signal on even the MPU PIA outputs. They're locked high on IC 18 and vary, but don't pulse, on IC 36.

Does anyone know what expected behavior should be in this situation?

frunch I haven’t, but it looks like whoever worked on it last did. I’m seeing extra long mating pins and the coloring doesn’t look old enough to be original. I’ve got parts on hand to replace it if I need, but I suspect, given how I zapped it, I have chip issues on the driver board. Possible connection too though.

pincoder I’ll give those a shot. Other theory I ran into is that a bad PIA can muck with the reset voltage and keep things from moving.

Pulled the idea from here: http://pinwiki.com/wiki/index.php?title=Williams_System_3_-_7#CPU_will_not_start

Kind of just fishing in the dark for ideas to test though.

pincoder 01a-leds doesn't appear to start when the driver board is connected to the mpu. The lights and segment display flash once and then stay off. I've seen it turn on after I've had it on in that state a little while, but I haven't yet figured out what changes. Just happened again actually. I wasn't touching the machine, it was sitting on (with the MPU completely connected and the driver board with only the 40 pin connected) with my logic probe connected to TPs 10 and 9. I heard a click and now the leds and diagnostic display are on. If I turn it off and back on the display and leds are on immediately, as if I'd filled up a cap that hasn't had time to discharge. I haven't figured out how long it takes to get out of that state, but if I let it sit long enough I've seen it go back to the other behavior (flash and then blank). This kind of behavior is what makes me wonder about a voltage issue.

I'm going to take it back to my bench and poke around with the other roms and my logic probe. Starting to wonder if I should get an oscilloscope so it's easier for me to log and see what's going on.

Two minutes appears to be enough time to get it to go back to LEDs off after the initial flash.

Here's a quick investigation of 01a-leds with and without the driver board. Will run 01b-bus asap. Notable is that the voltage drops pretty significantly once I plug the driver board in. Unclear if that's because of my PSU (a mini ATX with an adapter board) or indicative of something else:

TP voltages with logic probe attached but no driver board, LED diagnostics running:

Input from PSU: 12V nominal 12.9V actual, 5V nominal 4.4V actual
TP2: 3.3V
TP3: 0.08
TP4: 0.01V
TP5: 4.3V
TP6: 2.2V
TP7: 4.4V
TP8: 4.4V
TP9: 4.4V
TP10: 0

2P1 1,2: 4.4V

Address and Data buffers on 2P1 pulse. Reset pin (19) at 4.3V. Blanking pin (37) at 0.01V.

With driver board connected and program apparently not running and LEDs locked on and 0 on diag display:

Input from PSU: 12V nominal 13V actual, 5V nominal 3.9V actual

TP2: 2.7V
TP3: 0.08
TP4: 0.14V
TP5: 3.7V
TP6: 1.9V
TP7: 3.8V
TP8: 3.7V
TP9: 3.8V
TP10: 0

2P1 1,2: 3.7V

Address and data buffers pulse. Reset pin (19) at 3.7V. Blanking pin (37) at 0.14V

@pincoder Here's results of 01b-bus with driver board connected. Will collect without connection when I next have time. Looks like the driver board might be keeping it from finding the rom?

Differences from stated system 6 6808 results (though I've got a system 7):

5 VMA: HIGH
7 NC: low - 0.01V
9-20 A0-A11: pulses
22-33 A12-15, D7-0: pulses
34: HIGH
36: low
38: pulses
39: pulses
40: HIGH

pincoder That's correct.

I don't have an option to pulse or not pulse, but the pulse light is on and while I'm seeing pulsing on other pins (address and data bus for example) I'm not seeing it on reset (either IC 1 pin 40 or TP 8).

My ATX supply might be a special case - I pulled it out of a NAS and it's made specifically for it but has an ATX connector and seems to give normal voltages (though I'm missing -12V). I've got power applied to 2J8 similarly and I see no change. I'm seeing about 4V actual today from 5V nominal with the driver board connected. Counter argument to the power issue is that I see the same behavior when connected with the actual power board in the backbox and since I just replaced the caps and I've seen it give proper voltages, I can't imagine it would be insufficient power. I'm going to call 1 not very likely for now.

If I flip power on while my logic probe is on reset I see it start low and almost immediately jump high.

I've got 3 additional PIAs on hand and two of the chips on the driver board are already socketed, so I'm going to swap a couple out and see if that makes a difference.

Reset looks fine on pin 40 of the solenoid matrix PIA but low on the switch and lamp matrix PIAs, so I went to swap those out. I pulled out IC 11 on the driver board and decided to test it by plugging it into the known working MPU (without driver board) in place of the good PIA in IC 18. MPU no longer booted. I swapped in the good PIA just to make sure things were still working and get no lights. TP 9 and 10 were measuring half a volt. My 12V contact on the power supply was only measuring ~7V. I turned it off and reseated the good IC 18. Still no lights. I'm seeing 5V on pin 1 of MPU IC 1.

Did the bad PIA short something?

Huh. Moved my ground connection from 1J2-1 to 1J2-2 and now it’s booting again.

Edit: Looks like those headers need to be replaced. I'm seeing cracks underneath.

pincoder IC11 is swapped and 01a-leds is now running with the driver board attached.

Dunno if it was the reset getting pulled low, but the PIA on the driver board was keeping the CPU in a restart loop.

Plugged my boards back in and I'm able to get to audit mode! Digits test runs fine. That's the good.

The bad is:

* The big resistors on the bottom right of the driver board are running crazy hot and seem to have burnt the board. I can smell it when they turn on. I've got IRF9Z34Ns on hand and am going to replace the TIP42s and resistors, but seems like there might be an underlying issue there.

* Sound test has no response, though sound diagnostic button works fine.

* Solenoid test has no response. Test 25 or coming back to 1 makes a clicking sound like a relay flipped. Maybe IC 5 PIA bad too.

* Switch test replies with 38 37 35 34 33. So column 5 seems like it's having some issues, but not across the board.

* Lamp test has no response. Thinking IC 10 PIA is bad.

Disconnected the driver board and now I'm not getting a boot again (*facepalm*). Reset was low. I jumpered it against 5V and then it boots and runs 01a-led.

Today, after replacing the TIP42s, reset seems to be fine.

Oh, and IC10 PIA tested fine in the IC18 spot last night (after I jumpered reset), so that theory for the lamps is out. But it seems possible the transistors I just swapped out had fried and were the issue. Could explain the resistor issue too. Will test later.

Schwaggs pincoder I very much appreciate the advice! I wouldn't have gotten this far without your help. Virtually everything was working before I shorted it out, so it's a little sad I'm going back to basics but not that unexpected.

Just to review, here's what's been done so far:

* Power board has had caps and resistors replaced per Vid's bulletproofing guide. This happened before the short.
* On MPU: 7447 replaced (IC 34), PIA I replaced (IC 18), CMOS RAM replaced with NVRAM, IJ2 reflowed as a stopgap until header replaced.
* On Driver: PIA II (IC 11) replaced, TIP 42s replaced with IRF9Z34Ns and resistors replaced with jumpers in the lamp column drive section.
* PIA IV tests good when placed in MPU's IC 18 socket. PIA II is not socketed and hasn't been removed for testing yet.

The headers appear to have all been replaced whoever cleaned it up before it wound up at my parents' house. Use since then was very very light, likely in the low 10s of hours. But the solder job doesn't look great. Downright ugly in some places. I'm wondering if desoldering and re-soldering would be as useful as replacing the headers. I've got a hakko 301, so it's easy to do and the hardware doesn't appear worn or burnt. Though it isn't the square pins. If anyone has a strong opinion that I should replace the hardware entirely, I'd appreciate hearing it. If it was original I'd definitely do it, but my gut says this is mostly fine except for the solder job.

If I'm replacing headers, these are all .156"?

The *connectors* all appear to be original IDC. I wouldn't be surprised if they've gotten a bit banged up in this shuffle and expect I might have to replace them. pinrepair.com has a list of tools for handling connectors but it seems a little bloated and I can't figure out which things are actually needed and which are best bang for the buck. I don't mind spending a little more to get a good crimp that I don't have to find a re-work later. GPE's site seems to advise away from grabbing tools for ejecting pins which makes me question the pinrepair recs entirely. Would very much appreciate advice here.

pincoder I'm going to spend some time working through the ROMs and will make sure to take a look at 11b and the beta release. Thank you thank you! I'm a coder by trade and have done a fair amount of low level stuff. Let me know if there's anything I can do to help in addition to testing out releases. At this point I've used so many of your ROMs that I'm considering swapping out IC 17's socket with a ZIF so I stop mangling pins. I'm really ready for that adapter board to exist so I can put it all on one chip.