Introducing... Dragon!

 No no, not the Gottlieb one from 1978, the InterFlip one from 1977, duh!
I was loaned this machine to take care of it's various issues.  This copy is HUO, I think, and is absolutely beautiful, inside and outside.
The game itself isn't that incredible, but it is fast and furious and would be great in a larger lineup.

The owner was complaining of prolonged squeals from the digital sound card, and scoring that would jump between reels on a single player game.
I went through it as well and came up with a list of issues and tasks:
- sound sometimes pulses on, stays on squealing until a flipper is hit
- bottom right dragon's corresponding rollover lights is always on
- "Ball In Play" reel seems to struggle a bit at times
- add LEDs in backglass
- swap LEDs in playfield
- Top #1 rollover light is off.  Should turn on at start, off when collected.
- Polarity of power probably incorrect, resulting in "live" playfield when turned off.
- Left flipper flutters slightly when compared to right
- lockdown bar is very difficult to move

Apparently this machine was under a blanket in a workshop for 30 or so years.  The counter on it only has 5000 games registered.

you could eat a meal off of it, it's so clean.

OK, new rule, no food on the games.

I went straight to the issue of scoring.  The game had no lights in the head, so tossed in some vital LEDs.  I could then quickly see that in a 1 ball game it was proceeding as:
P1 B1
P3 B1
P1 B2
P3 B2
P1 B3
then over.  I guess that after P1 B3 the game does a scan to check if that was the last ball, and since only 1 player registered, it ends.
My assumption was correct:  J1 to J4 are latch relays that indicate if a player is in.  I tested the latches, and manually unlatched P3.
The game then played through a 1 player game no problem.  My guess is that this is something that was just heavily unused and needs some love.  I heard the biggest problems with EM machines come from disuse, so after sitting for so long, J3 just couldn't unlatch without help.
I plan on having many more 4-player then 1-player games to stress it a bit and see if the issue reoccurs.

There are 5 rollovers on each the left and right side.  100 points each, 1000 points when lit.  Each corresponds to one of the 5 dragons.
The schematic is kind of cute, using this odd symbol to indicate "hey this happens on the dragon".
Checking that bottom right dragon's assembly, it was easy enough to spot the always-closed switch stack and regap them.  Problem solved!

I brought someone in to look at the power issue, since I am actively trying to avoid line voltage in my body.
We quickly found that it wasn't that the polarity was swapped (as was the case in my Out Of Sight,) but that in the plug itself the ground had detached.

yeah that's not quite right.

We also worked on the lockdown bar, which was really binding, but got it to loosen a touch.

Does this photo add anything to this post?  No, not really.

Next up?  I think the top rollover is solved via the P relay assembly, but dang that one is going to be hard to get to.  It is all the way at the back of the cab!
And the sticking sound issue?  I think I've isolated it to physical rollover switches sticking on the playfield.   Will get around to cleaning those eventually.

Note the "& advance" at the standup target...

Oh and I think this machine is also a prototype.  Note the "5000 & Advance" on the far left and far right standups.  There is no bonus add for these in the schematics.  They do not advance bonus.
Checking IPDB, all other machines just have "5000" for them.  I can see the "5000 & Advance" in the advert for this game on IPDB, and it even mentions the advance as a feature.  I am unsure if this is a prototype that was also used as the basis for advertising, or if a bunch of these exist and they then realized they had forgotten the bonus circuit, or something like that, and so changed the playfield.


This game has also been made somewhat notorious for it's hilarious Classic Games Room review...

And this funny gameplay video from PAPA pros where they are probably a bit drunk and the machine basically eats them alive.


More cool shots:

A simple plug allows you to adjust flipper voltage!

The Gottlieb score motor is not here.  We have this really cool motor in the cab, and a similar one in the back.  Very nice designs.