Recently picked up a Lost World (Bally, 1978) that had been sitting around for 25-30 years not working. Overall nice condition after some cleanup. Of course, given the original MPU and battery sitting there for decades, it trashed the MPU perimeter (but nothing else from what I can tell). Testing shows that the MPU might actually be salvageable, but I'll worry about that later. I have a brand new MPU, so that's going in there for the time being. Here's where I am so far:

* Initially, just GI came on, but after some tinkering, I've seen some other signs of life.

* While doing some voltage testing the other day, the game suddenly semi-booted. Not sure why. The displays came on, game took credits, and when I attempted to start a game the scoring/switches worked (but solenoids all dead). I was able to drain 3 balls and go into Game Over/Match, and sounds were working.

* After unplugging the game for a day then plugging it back in, it went back to just GI and display glow, no booting, no Flashes from the MPU, no sounds.

Voltage Testing - Rectifier Board (all I've done is repin the J3 20-pin connector so far)

TP1 5.51 vdc
TP2 244 vdc
TP3 2.51 vdc ***
TP4 6.74 vac
TP5 44.0 vdc

*** Everything is within spec aside from TP3 (should be 11.9 vdc), which from my reading is used to obtain the regulated +5V for the game's logic circuits. When the game was temporarily booting, TP3 showed 14.0 vdc.

Testing at the Transformer on taps 15 & 16 (which feed the voltage for this area) I'm getting around 13.2vac, which is a little high (should be 12vac). Testing at the fuse I'm getting 13.2vac, and testing on the AC connection points of bridge rectifier BR2 I'm getting 13.2vac.

Based on all of this, it seems like the voltage is getting to BR2 (even though it's a little higher coming off the transformer than expected), but not reaching the TP3 with the proper ~11.9vdc expected. Does this mean BR2 is likely bad?

Thank you for the reply! I believe the + and - pins read 2.51 vdc like the TP3 does, but I can double-check. Just so I'm clear what you're asking, you want me to leave J1/J2 connected, and disconnect J3, then test again?

No work done as of yet on the other boards. I removed the corroded MPU for cleaning, etc., and replaced it with a new ultimate MPU I had. I did initial testing on the Rectifier and found that TP1 showed no voltage, and TP3 was incorrect/erratic as well. I noticed that J3 looked a little beat up so I started there and repinned it. This brought TP1 from no reading back to its proper voltage, but didn't fix TP3. I was going to repin J1 and J2 next, since that seemed to make sense as well.

Can I just test (machine off) using the solder points on the front of the board, or would it be best to just pull the whole board and test that way? Guessing I'm just checking to make sure the diodes are properly blocking and not shorted/failed?

EDIT: Found this to answer that question: http://www.pinwiki.com/wiki/index.php?title=General#Testing_a_Bridge_Rectifier will do

LostWorld_BR2 (resized).jpg

Good info, thank you! Going to try it shortly and report back.

Okay, I performed additional testing. Note: I repinned J1 and J2, just in case. No change, but good to have them done.

I disconnected J3 and checked the test points again, here are the results:

TP1 0.00 vdc
TP2 180 vdc
TP3 12.5 vdc
TP4 7.19 vac
TP5 45.3 vdc

As you can see, the TP3 is now within range of where it should be, so I'm guessing that (as you noted) something is screwing it up downstream when J3 is connected.

I also noticed that TP1 had NO reading, and TP2 dropped 60-70vdc, but I assume that's normal with J3 disconnected? When I reconnected J3, TP1 and TP2 went back to normal/within spec, and TP3 dropped back to 2.51vdc again.

BR2 Testing

With the power off and J3 disconnected, I tested BR2. Results: all readings were between .526 and .528, which as I understand it from the instructions on pinwiki are within the .5-.7 range so they're good.

So... it seems like the next question is: What is causing TP3 to drop to 2.51vdc when J3 is connected to the rectifier board?

I woke up this morning and re-did the testing... now TP1 shows zero volts with J3 connected OR disconnected... that's not good, not sure what happened there. The voltage is still appearing on BR1 as it should, so that's odd. I tested the associated TP over on the solenoid driver and it's zero as well. Guess I can deal with that later... the +5vdc regulated on TP3 is probably more important right now anyway.

I pulled J3 off the solenoid driver board as suggested, and sure enough TP3 on the Rectifier is showing 12.26vdc, so it looks like you're correct, something on that driver board is likely the culprit.

F3 is a 4A fast blow (32V) probably original. Pulled it and tested it, looks good.

Adding some pics as requested. Sorry for the angle and dirty look to things, the pic is a few days old.

Lost_World_Rec1 (resized).jpg

Lost_World_Rec2 (resized).jpg

Lost_World_Sol_Drive (resized).jpg

I'll try this today and report back. Sadly, I don't have that capacitor on hand (closest I have is an 18,000uf one, which is too far off from what I need it seems). But I can at least try the test you suggested and see what happens. Everything is original in this thing, more or less, so it needs some upgrading for sure.

Will do, thanks. I only pulled it off to take a peek (and clean it up some). I have plenty of thermal paste from various computer and electronics stuff, so I'll put some fresh stuff on before reassembling. Though for a short voltage test, I guess I could leave it off temporarily. Just got home, I'll go take a look at all of this now.

Just performed the suggested test (Disconnect one side of C23, remove J4 MPU, connect J3 on SD/Rectifier boards). No change... TP3 on rectifier still reading low (2.60vdc). Does that mean it's likely the 5V regulator to the right of C23 on the board?

J3 disconnected from SDB, measured resistance from metal casing of regulator to TP5 = 1.359 on 2M setting after it settled and held.

I can change the batteries in my meter, but all the other readings look good and test fine, so that would be an odd reason. I'll check themf though just in case.

I've used a couple of different ground spots just in case, and the readings are always the same. The most common ground I've been using lately is the leg of the big resistor on the rectifier, as suggested in the repair guides. All the other readings work fine with that so I'm guessing that's ok.

I'll check the ground resistance and continuity, but there's actually no ground prong on the plug, it's original I believe. There's a little ground wire hanging loose off the end. Wouldn't it be strange though if grounding was an issue for just the one vdc reading and okay for the others?

Hi Steve - I replaced all the connector pins, but not the headers as of yet. I don't have the proper size headers handy, but it wouldn't hurt to reflow/test them. On mine, the only pin/connector that appeared discolored was one of the GI related ones, but that doesn't mean the others don't need love too. That being said, since unplugging the connector on the SDB J3 corrects the TP3 voltage on the regulator as Quench noted, I'm guessing my issue is downstream. This is the kind of troubleshooting I struggle with sometimes. Much better when the fixes are clear cut!

Open to suggestions on what to try next

What voltage do you read between the ground leg of the big resistor on the rectifier board and the "GND" test point on the SDB? zero volts
What voltage do you read at test point TP5 on the SDB? 2.59 vdc
What voltage do you read at test point TP2 on the SDB? 199.8 vdc
J4 on MPU disconnect Measure the voltage at TP3 on the rectifier board 4.37 vdc (up from the 2.5 vdc with J4 connected)

Note this is a brand new ultimate MPU... but I have not repinned any of the connectors for the MPU yet. Not sure if that might be related.

Okay, so I just went back to test the SDB test points again (J4 on MPU still disconnected) and some strange things just happened:

I plugged the game in and tested TP1 on SDB

TP1 = 5.0vdc so that's good. It has stayed that way each time I've tested, but...

I tested TP5 again:

TP5 = 7.0vdc (also showing this on TP3 of Rectifier too)

I turned OFF the game, then turned it back on

TP5 = 9.6vdc (both SDB and Rectifier)

I turned the game off and on a few times (sometimes right away, sometimes waiting a minute or two), and the voltage on those test points was bouncing in the 7.1-9.7vdc range. I decided to turn off the game and try plugging J4 back into the MPU. Turned it on, and the LED on the board lit briefly, but then slowly faded and went out. I checked TP5 (SDB) and TP3 (rectifier) and they're back down around 2.5vdc again.

Definitely strange.

Sidenote TP3 SDB still zero volts.

I have some 912 bulbs, 12V but like 12.8W I think. I can dig in my parts, or try those I guess.

Quench I just tried something interesting, not sure if this matters but here's what I did:

I turned the game on (J4 still disconnected from MPU, everything else still connected) and I connected the black lead of my meter to the " - " solder point of BR2. I then put my red lead on TP3 of the Rectifier and got 11.47vdc. I checked TP5 of the SDB and got the same reading. But if I connect my black lead to a known ground (like the leg of the resistor on the rectifier, the ground on the SDB, the ground on the MPU, etc.) it shows a lower voltage as indicated in the other tests.

Why would using the negative BR2 connection show all the proper voltages at the test points, but testing from actual "ground" locations show lower voltages?

EDIT #1 - I just checked for continuity from the other Ground points. I have Ground continuity to the " - " connections of BR1 and BR3, but NOT to BR2

EDIT #2 - I decided to jumper the ground side of one of the other bridges to BR2 ground and test TP3 (Rectifier) and TP (SDB). Readings were 16.49vdc... a little high. Not sure if jumpering was a valid idea, but given the lack of ground continuity to BR2, figured worth a shot. Thoughts?

Of the game in general, like the playfield and such?

Here are a couple, before I started taking it apart to clean it, etc. The backglass is in amazing shape, playfield pretty good as well.

LW_bg1 (resized).jpg

LW_pf1 (resized).jpg

I'm so tempted to try plugging in J4 to the MPU and trying it with my jumper idea above on... but that 16+ vdc is way above the 11.9vdc it should be now. Waiting for someone to chime in before I blow things up ha.

You're right, thank you! I disconnected J3 from SDB and sure enough the Rectifier TP3 shows 12.5vdc now. I reconnected everything (J3 / J4) and the game booted up again!

I haven't done further testing, but I'll do so and report back. I'll try reflowing that " - " on BR2, and just permanently jumper if that doesn't work like you said.

As a precursor, the next trouble spots I know existed were:

* TP1 (rectifier) showing zero volts for "feature lamps" (it's shown 5.0 before so I bet it's likely something flaky)

* Flippers/Solenoids dead

I'll be back soon with an update. Quench thanks so much for sticking with me on this, I appreciate it, we're almost there. More to come...

Update: Okay, so with BR2 properly grounded, the game boots with sound and the displays come on.

* Adding a credit for some reason will add more like 10 credits, but I'll worry about that later.
* I can press start and a game will begin (music plays, ball 1 displays, score goes to zero).
* The ball does not kick out, none of the solenoids will fire, and flippers are dead.
* Manually triggering various switches will score points (and sounds are emitted properly)
* At least one switch somewhere is stuck closed, or intermittent, because sometimes the game will just start scoring non-stop

TP1 on the rectifier is still zero volts
TP5 is showing 44.5 vdc so that solenoid power is present there. Haven't found any blown fuses so far, but the fuse under the playfield near the flippers has a semi-broken clip, so that could be an issue despite seeing continuity there. I'll replace it, but I am not sure that's the problem with the solenoids.

I did jumper from ground to the metal "tabs" on the solenoid board transistors, and the coils did fire for things like the pops and slings.

Thoughts?

The relay doesn't click at all from what I can tell, not during boot up and not when a game is started, so nothing is happening there from what I see.

"Feature lamps" are the inserts? Right now all I have is GI from what I can tell.

zero voltage on the + / - pins of BR1

transformer taps 13 & 14 showing 8.42vac, and so are the AC/AC pins of BR1... so the AC voltage looks like it's getting to the bridge. I know TP1 showed 5.0vdc earlier in my testing, but now nothing.

Solenoid power is also used on the sound board as a power source for the amplifier so the 43V supply is working.
What happens when you go to solenoid test mode and the game cycles through activating the solenoids?
As CanadianPinball mentioned, do you hear the flipper enable relay clicking on the SDB when you start a game and during solenoid test mode at solenoid test #11?

Not 100% sure how to get to solenoid test mode... I used the self test button, and cycled through displays and then other things... nothing ever fired though solenoid-wise that I saw.

I did check for voltage right before that relay on the SDB. I tested at CR20, which is immediately before the relay, and I am getting 44.1vdc , so it looks like the voltage is getting that far.

BTW before I forget, you have a couple of incorrect fuses on your rectifier board. The only slow blow fuse that should be on there is the one at F6 for mains power. Make sure your mains wall power cable is disconnected before touching that fuse and even the others for your safety..

Okay, I'll check out all the fuses and see what's going on there.

timab2000 I have only changed a few pins on the MPU connectors. I was going to re-pin everything, but wanted to sort out the voltage issues back over on the rectifier first, since I still don't technically have all the correct power coming off of there. I guess I could start repinning, since the only incorrect/missing voltage now is the feature lamp.

Follow-up ... Checked for voltage at the fuse under the playfield near the flippers. It's sitting at 44.4vdc on both sides, so no issue there either. So it looks like the power is getting there it needs to so far... just nothing actually working when a game is started, no relay click on, nothing. Only time I can get them to fire is when I manually ground the transistors associated with them.

Should I just start re-pinning all the connectors, or is something else going on I should look at first?

EDIT: Also checked the solenoids themselves, and they are showing 43vdc as well.

Yep, mentioned that above a while back, but there are lots of posts so it's mixed in there. Grounding the transistor tabs fires the coils. I've seen the pops, slings and other fire just fine that way.

Good call! Jumpering TP1 to TP3 on the SDB fixed the dead solenoids!

That being said, I have some bugs there to work out. When I start a game, the ball kicks out, but a pop bumper is rapid-firing, so I'll check the switch then dig into it if that's not the issue. That would explain my non-stop scoring mentioned earlier though, so I'm guessing it's just a stuck/bent pop switch.

I will do some further testing, and also start checking into the BR1 issue. Yes, I did power the game with the rectifier removed from the backing plate. I didn't leave it on long when I did, but is that something that would blow BR1?

Okay, I'll check that out. If it is failed, I can disconnect the pop for now and work on that. Looking at it currently, so I'll report back in a bit.

BR1 will die from overheating if not thermally cooled, but actually in your case with it not screwed to the metal backing plate it probably wasn't a cause of failure since the game hasn't been booting so none of the feature lamps were on anyway and there was no current draw through the feature lamp BR1 bridge.

Makes sense. Okay, I'll see about doing all those tests you suggest and go from there.

* Okay, I remove one leg of the capacitor on the switch for the machine-gunning pop bumper (right bumper for reference). It stopped firing non-stop.

When I trigger it manually now, it only fires if I hold the switch down a little longer, which I assume makes sense since I think the capacitor was designed to help with it triggering properly? I remember reading that, but could be wrong. I assume if I replace that capacitor, I should be good to go for that issue, right?

EDIT - looks like the schematics refer to the capacitor as .002, so I'm guessing a .0022uf 1000v ceramic disc replacement would work? I see those for cheap over at GPE.

EDIT 2 - glancing at the actual capacitor it looks like it says .05 12V... but I'm wondering, could I just steal the one off the tilt bob if I wanted? It's .05 50V

* Feature lamps definitely all out, which makes sense with no voltage on TP1 of the rectifier. Still haven't take it all apart/out in order to test, I guess that's next.

Good news is that with the pop bumper switch capacitor disconnected, the game seems to be playing aside from a few items. Flippers work, scoring works, most switches good. Right slingshot is scoring, but not firing... probably minor, but I'll look into that next. Displays a little flickery aside from P1, but they're all on. Reflowing solder or repinning at the displays is likely going to help I believe.

Great, thanks Quench, will do.

* I reflowed all the header pins on the displays, and they're all bright and clear now, no flicker or dimness. Only issue I see is P4 display has the final digit completely out. The rest are perfect. I'll look closer at that later.

* Thinking I'll order a new bridge rectifier for BR1 (maybe others and just rebuild that rectifier board a little while I'm at it). I'll get caps for the SDB as well, and do the suggested mods/upgrades as well where needed.

* Have to figure out why the right sling is dead too... little mysteries, but nothing too crazy I hope.

Thanks for all the help so far, it's been great as always! I'll be back soon with updates as I go. Awesome to see this game that sat for so long coming back.

Quench Update on the Right Slight Shot - checked resistance vs. the left slingshot, they match. Also checked wire continuity from J5 on SDB to the lug on the coil, as well as the wiring to the other side of the coil, all good. Grounding the Transistor metal tab does NOT fire the coil. Normally when that happens I assume a wiring issue, but continuity is there so I'm not certain now.

EDIT - meant to also mention that I checked voltage at the right sling coil and it's 44.4vdc, so the power is getting to the coil just fine. Also, the switches for the sling score points as they should.

EDIT #2 - I used a jumper to quickly jump from the ground braid to the non-banded side lug of the Right Sling Coil and it fired, so I know that works now.

So in Summary:

* Solenoid does not fire when switches are closed, but scoring occurs
* Solenoid fires when non-banded lug jumped to ground
* Solenoid does NOT fire when transistor tab is grounded
* Continuity exists from black-yellow wire on solenoid back to A3J5-14 as expected

Wondering if I should be checking either the transistor, or the path/trace from the transistor to the connection at J5-14?

No continuity from Q11 to J5 pin 14 (or the adjacent pins). Q10 was a little iffy as well, intermittent, but did get contact. The rest of the associated transistors to that chain of connection all show good continuity, so it looks like something between Q11 (maybe a little of Q10 too) needs checking. Maybe it's as simple as reflowing some solder to the headers, I'll pull the board and check some things this morning, then report back on progress.

Update

* Several pins on the J5 header were definitely cracked cold solder and in need of reflow.
* I reflowed all the headers on the board, and added the suggested mods/updates to the SDB via jumpers on the solder side

* Reconnected the SDB and all coils work great now!

** Next up: Order the replacement caps, BR1 bridge rectifier, and a few other odds and ends

Looks like I'm on the home stretch on this one!

Update:

* Reflowed solder to BR1 again, realized I missed the "+" leg of the bridge. Sure enough, that fixed the issue, so my feature (insert) lights are back up and running. I've got about a dozen or so insert lights not working, but given the "loose" feel to the sockets and such, that's not a surprise. I'll tweak, clean and replace/fix the ones that are out.

* Coin lockout is buzzing like crazy, but I think I can just disconnect that and leave it be, if tightening things down doesn't help

* I cleaned and adjusted all the switches that were iffy, and that sorted them all out

So overall, this project is basically running and "finished" from a technical standpoint. I'll work out the last minor bugs, but assuming no other issues, I think we can call this game revived! I'll report back again when I have it in completely good shape.

Thank you to all, especially Quench, for all the responses, effort and assistance. Couldn't have done it without you!