Under playfield, left side near the front.

LTG : )

Like Lloyd said.

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Not sure what YOU are seeing.

My photo shows a white wedge base socket with a 555 lamp screwed to the underside of playfield with no insert to light. No expander board in sight. This shot is directly below the left score card position. Those wires go up through the playfield to the outhole kicker solenoid.

The lamp won’t be near an insert. Look for that one.

Post some pics

Another example. Near the expander board, front left. One side of the lamp socket will be attached to the bare wire rail and the other side should have a blue wire striped green.

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Is your game a really low serial number? It's possible your game was not equipped. Early production games did not have a lamp and it was soon discovered that the lamp was needed. Some games were built and shipped out without the lamp and needed to be retrofitted by the dealer. You may have one of the games that was missed.

Wow. That's new news to me. The one I have was a fairly early unit (milky red Special inserts, Red Posts, white pop bumper caps) and its been with me since the mid 80's (and I was with it when first operated). And mine has the lamp socket (my playfield pictured above shot through the coin door) and the wiring looks factory (not an add on). I guess I need to lift the lid and see where the expander is actually located on mine.

What purpose does that lamp serve? I've always wondered about that...

Hey @Mk1Mod0,

Did you retro fit your game with earlier style flipper assemblies (looks like it in the picture) to replace the linear flippers? If so, how do you like the change? I did it to my Centaur and love it but haven't taken the time on EBD since they haven't been sticking for a while. Also, I don't want the added strength it resulted in on Centaur (which actually needed a little extra Ummpf.

It insures that the SCR on the Lamp drive PCB that is used to energize the Opto Coupler (contains an LED) on the SE has sufficient loading to turn off when it should. The same reason why people add a 470 ohm resistor (or similar) to each lamp socket after installing an LED , or use one of the aftermarket load boards that piggyback in line with the lamp harness at the Lamp Driver PCB.

In comparing the two photos, it would appear someone stole the socket thinking it was not needed.

The two wires dangling, appear to both go to the same lug on the lamp socket. Then, you get the other wire for the lamp socket from the ground braid for the Credit Lamp on the score card holder (that nearby socket). You don't use the two larger holes but rather that single small one just next to the ground braid staple (where the old socket used to be soldered).

Photo provided above. Note socket and wire color. This is the solenoid expander bulb.

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I did it two years ago and never looked back. I never had trouble with the linear but it was rare to make the 4X or back to the top by the left lane. Feels right now.

Your picture.

See the 1 hole. That is where the socket for the solenoid expander use to be.
The wire is above marked wire (wire color should be the same as the provided picture). You will see a where the wire is exposed. That is were it is solder to the missing socket.

LS. Is the fing lightsaber above your game blinding me.

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The Sol Exp board Lamp and credit lamp do not run off 43VDC, they run off the feature lamp power. Do any or all of your other feature lamps work (Bonus, Pool Balls DELUXE etc.)?

On a separate historical Bally production early SS notes relevant to this thread, playfield serial numbers are not often the same as cabinet serial numbers on MANY Bally games from 1978-1984. This does not mean playfields were swapped either during their lifetime. Playfield serial numbers are NOT the identifying mark of the serial number of a pinball machine from any era.

Games such as EBD were "mix and match" base playfields based on larger production runs that went into the factory production. Playfields are not always identified in proper numerical order either. This included using playfields from earliest title runs such as original EBD playfields from 1981 (including white pop bumper caps) into the EBD Classic runs from 1984. Bally used what they had available until the run was exhausted, or additional playfields were required to be ordered by Churchill Cabinet Company (CCC). This can be determined from many different game aspects both aesthetically (inserts and ink screen colors), electronically (sockets and boards), and mechanically (assemblies) from parts. All three EBD models for example have many specific differences, even the assemblies are slightly unique based on minor updates.

Hence, the differences including the Solenoid Expander Board (SEB) and even its physical location.

IMPORTANT TECHNICAL NOTE:
DO NOT USE a LED in the SEB lamp, as this will not work in the circuit theory based on necessary voltage unless the circuit has been adjusted with resistance based on a standard Ohm's Law calculation. A lot of new owners do not seem to understand the SEB design technology and why/how it was used. Read the base schematics closely. The SEB lamp is part of lamp matrix, not the SDB, and does not draw power from this part of the game. The proper 6.5v from the SEB lamp is extremely important in order to draw enough current to the MOC3011 opto-isolator on the SEB and activate. I have already seen young technicians not understand these aspects and make this mistake repeatedly on this series of games.

The SEB lamp is not "just another feature lamp".

Recheck every socket you put an led into. You may have grounded a socket into something metal causing a problem.

Pin 1 on the SEB must have feature lamp power of 6.5V as CactusJack mentioned. If you're measuring 43V at pin 1, you need to first find where this short circuit to solenoid 43V power is.

Post a picture under normal lighting conditions showing how you've wired the SEB load lamp.

In terms of the Stern LDA-100 lamp driver board working (presuming it hasn't been modified), the particular SCR at Q54 might have a tolerance with a low "hold current" making it capable enough of running the MOC-3011 optocoupler on the SEB without a load lamp.

You mentioned pin 1 was connect to the bare wire of the shoot again or ball 1 lamp - either is good enough. The bare wire running between the feature lamps is 6.5V DC. Be careful not to make the common mistake of confusing this bare wire as ground.

At this point, since the Stern Lamp driver board works (Solenoid Expander functions correctly), and the Altek driver board does not, it sounds like you just have a bad driver on the Altek board. Nothing wrong with your playfield wiring. If it worked before without a load lamp socket, you are lucky. I have found things to work okay for the most part on my EBD without a lamp installed. But it will certainly cause some flakyness without it.