Some people should NOT handle schematics, soldering irons etc.

Now that I got THAT out of the way, seeing as how I should have posted this BEFORE I thought I could find my own problem...

Please stick with me, this one has a little lengthy explanation.

I'm trying to trouble shoot the very list issue on my Laser Ball, the lady's hand flashing lamps (type 89 bulbs) remain lit and they have since I acquired the machine, I noticed early on the two large resistors on the back of the light board were toast so I replaced them long ago, didn't worry much at the time as the machine was undergoing my scalpel.

So fast forward, and fearing the logic probe (God knows why, I've read the @terryb guide many times) I started off replacing Q42 and Q43 as I interpret the schematic to indicate it is this solenoid drive that controls these (schematics pgs 4 & 17.) I DID check these with my DMM prior to replacement and while they did test GOOD, I've seen anomalies before where a transistor or SCR tested fine but in operation they fail. SO, I replaced Q42 and Q43, no change, the type 89 lights stay lit constantly (LEDs I did not think to try incandescent).
This is where I made an ass out of me and the umption... I examined the schematic a little better (page 5, sheet 1 of 2), looked like perhaps the blanking circuit was a possible culprit. After all it has a signal line into IC4? I Found Q76 and Q77 might be to blame, and the other part of the umption, not having the EXACT required components (2N6427 - 40V/0.5A nor a TIP42 - 40V/6A, again BOTH originals TESTED FINE) I dropped in an BC32740BU - 45V/0.8A and TIP102G - 100V/8A respectfully, and FAILING to notice the BC32740BU was an E B C configuration, and not an C B E, turned machine on and while there was no change to the type 89 bulbs that SHOULD be controlled by Q43 I took note that now ALL player lamps are illuminated, the SAME PLAYER SHOOTS AGAIN lamp is illuminated, TILT was on and maybe others, just can't recall, it was now 0000 hours and I would get up this morning at 0400 and try again.
While "technically" there was no smoke, no faint smell of ozone (sorry if my title mislead you), as my pappy used to say, the dog don't hunt. It turn on, but won't operate. It had been able to start a game an launch the ball but now won't do even that. I had traced with my DMM continuity as best as I could determine and found all traces intact that I tested.

Schematics at the ready, order pending for silicone components, half way decent pictures of I'm just at work and not home to test / report results.
Pictures now show a missing IC13, as I intended to removed IC14 but on less than 4 hours sleep, I do have sockets and replacement 7408 chips to replace BOTH these today after work. Damn work getting in the way of a hobby.

As the prosecuting attorney now says, is there a question anywhere in the future,
I beg the jury, what could I have fouled up, suggestions for remedy?

And with that I throw myself to the mercy of Pinside...

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Thanks Grumpy!

I'll replace missing components, install incandescent bulbs and try again.
Thoughts on what I might have cooked?

OK, I've taken a little nap, dropped in new 7408s (SN74S08N) in locations (after socketing) IC13 and IC14, installed new SCR (sorry, NPN Darlington Transistor 100V, 500mA, 625mW ) spot Q76 and transistor (100V 5A) into Q77, put machine back into service and at first thought all was well, the BG lamps that had been on were now off BUT after about 10 seconds they started to light until the ones mentioned in post 1 above were back on. DAMN. I don't have bayonet 89s so wasn't worried about that circuit just yet, just getting game back playable. Question, would removing the warming resistors allow that circuit to support LED 89s?

I cycled the machine power a few times and the results were same, it would first power up fine then about 10 seconds later, FUBAR.
Again, I did not have EXACT matched components from original but they were rated higher than the OEM parts, too much higher? Got more parts on order from Digi-key with values closer to or exactly the same as original parts so will try again later in the week.

Thanks for your input GRUMPY !!

Dandy, thanks again!

So I sourced a rottendog mpu327 while waiting for parts to attempt original repair.
It worked great until...
Finally got my new parts in for old board, swapped out a few components that I thought could be the issues to no avail.
I decided I would just send it out to an expert, hey I got a new board so I can at least play the game.
I replaced the mpu327 into to the game.
In my haste I installed the IJ2 connector onto the IJ6 pins and now have no displays.
I went through the install instructions for the 327 again, no go, I've now cooked something else, hopefully NOT the new mpu, hopefully just the old master display as the mpu327 diag LEDs seem to indicate its functioning properly.
Any suggestions where to start over?
Damn I'm kicking my self!!

Would that be this guy, they call IC6?
Do I even bother testing it or just acquire a new IC?

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DOH

I have this logic probe...

What should be my findings be for each pin?

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20-23 pulse
1-10 NO pulse, they were all HI

LOL

I will source a new U6 IC and try again!
Thanks for your help!!

Alright, back to the issue with the original board. See below image of the lamps that illuminate when they should NOT, they all come on gradually then remain lit. I did some troubleshooting last night and this ONLY occurs when 2J4 is plugged in, and strangely enough, if this plug is left open and I turn off the machine and then plug it in, they illuminate!
Attached are the schematics in question for these circuits, signs point to bad PIA III, IC10 ?

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1 of 2 (resized).jpg

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Driver board (resized).jpg

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The plan for this evenings affairs are to double check Q76 & Q77, Q62 & Q63. I have the following replacement items in lieu of originals.
I MAY have an MC6820 to drop in if you guru's think it may be blown out?

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TIP42 (resized).jpg

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Yes, seems to be simultaneous

Recent developments:
I replaced the components in post 19 above (minus the 6820) the good news is the lamp issue seems fixed, the bad news is no all solenoids fire simultaneously at machine start. I immediately turn it off upon that occurrence.
If I remove connectors 2J9, 2J10, 2J11 and 2J12, it simply does not fire those solonoids.
Also, if those are left unplugged, I can start a game (minus the ball of course) and it seems to score each switch properly and the lights respond accordingly although i do think I smell overly excited electrons.

Belay my last.
Certain pf lites now misbehaving by not being lit during game over mode nor lamp test mode and as above, only items unplugged are solenoid connections.

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2J-10 plugged in, all solenoids banged once upon turning on game, the no noise.
Lamps out above remain out.
All pf lamps that light seem to flicker now where they did not prior to yesterday.

For feck sake, I had plugged in j11 onto 2j10!
I've correctly placed plugs onto proper terminals, replaced the 2.5 slo blo fuse that popped, solenoids now function as they should again but some lamp issues remain.
Eg player 1 lamp no workie.
Lamp flicker is now gone during game play but flicker in game over mode.

Time to see what all the non lit lamps have in common.

Also upon turning machine off then on again, all solenoids fire once then function normally.
I don't recall them doing that before yesterday.

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Interesting, let me check this evening and I'll advise. Thanks Andrew.

You were correct in the blanking signal being pin 37.

I've finally done extensive continuity testing at the following locations:
Between CPU IC23 9 - Driver board IC14 12 - continuous
Q77 to 2J52 - continuous
CPU IC7 5 to IC18 4 to IC6 21 - continuous
CPU Q5 to C32, C32 to IC7 6 - continuous

I feel like I can eliminate the blanking signal from being the problem on old boards?

New 7415 due tomorrow finally, will see if I can return the R-dog mpu to working order.

Schematic images of test points I checked to follow from mobile device.

Thanks
I'll check it out!

Dave's not here man!

Driver board IC4 5, starts low then goes Hi
IC14 12, 9, 2 & 4, start low then go hi
IC13 12, 9, 2 & 4, start low, go hi

As a result of the above testing, found bent pin on IC14

Straightened that, displays now work!
Game still fires all solenoids upon start and still having lamp issues.
See image taken during lamp test

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After a SNAFU in shipping, my original replacement CD74 chip for the R-Dog board went to Amarillo, I finally got another one (ten actually, any one need one?) and popped her in, displays are now 100%. Alas the issues with the original board persist so looks like the lucky buyer of this Laser Ball will get a brand new R-dog combo board! Going to mark this solved even though it kinda isn't. I'll play with the original board again if I ever get another Williams machine of this era to trouble shoot in.

Thanks to all who participated and provided the much needed support and guidance!!

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