Strange World
Gottlieb, 1978One more question (for now) about this Strange World schematic I've been looking at. Does anyone know what the purpose of the circled capacitor is? It's rated for 100V - is there some sort of kickback voltage occuring here?
Since I'm obviously not smart enough to figure it out myself, I await enlightenment....
Thanks slochar - so where would those voltages be coming from - the score reel coils?
Thanks KenLayton - can you tell what pulse needs to be stretched or timed differently? I just don't see many caps in EM's...when I do, it's usually something to do with a timing circuit, but I don't see where that would apply there. Just trying to learn.
Quoted from leckmeck:The labels on that schematic look unusual. The fonts don’t match anything I’ve seen on another Gottlieb.
... and a feature lamp on the 24V side? Strange World is living up to its name!
leckmeck - That's a re-drawn schematic. Just for fun, I re-draw Gottlieb schematics in Photoshop - well, partly because I enjoy it, partly because it's really nice to have a 2-foot wide schematic laminated so I can draw on it and trace circuits and just erase when I'm done...plus they look cool hanging on the wall. I just chose a font I thought was easy to read....I keep them consistent within my own re-draws. The information on it is correct, though - straight from a legit schematic.
DaMoib - Yeah, you don't see many lamps on the 24V side for sure...but this one was designed by John Osborne, not Ed Krynski. I suppose he had some different ideas....ever seen the inside of Haunted House?
Here's the section of the original schematic....unless I make a mistake, the information is correct.
strange world cap original (resized).jpg
Resistors were often used to prevent arcing across contact points due to EMF. (EMF describes how an inductor or solenoid tends to continue pushing current through a circuit even though a switch on that circuit has opened. If enough current is pushed through, the voltage on the open contact can rise to the level where it will arc across the air gap to the other contact.) Here is an example from Bowling Queen:
Bowling Queen resistor (resized).jpg
Resistors seemed to appear on 0-9 units (or 00-90 units on later games) for reasons that aren't clear to me. It implies that the contacts on these units were more susceptible to arcing than other contacts in the game. On Strange World and other later games these were often AS relays or mini steppers which have smaller contacts which may be more easily damaged by arcing. But even earlier games with regular steppers and snow shoe wipers often used resistors.
In this case the capacitor is unexpected. It's wired in parallel with the Add Replay Unit solenoid which is larger and would draw more current than a relay coil so it makes sense that it's there to suppress arcing. I don't understand though why a capacitor was used instead of a resistor if arc suppression is the reason it's there.
/Mark
Thanks Mark,
Was it just there to protect the bulb from higher than normal voltage transients coming from somewhere down the line? I suppose a capacitor would short a transient more effectively than a resistor? (He asked uncertainly...) I mean, I know caps are typically used to allow AC to pass while blocking DC, but there's nothing but AC in this machine, so it's gotta be passing an unusual AC event, right?
Quoted from paulace:Was it just there to protect the bulb from higher than normal voltage transients coming from somewhere down the line? I suppose a capacitor would short a transient more effectively than a resistor? (He asked uncertainly...) I mean, I know caps are typically used to allow AC to pass while blocking DC, but there's nothing but AC in this machine, so it's gotta be passing an unusual AC event, right?
How a capacitor behaves depends on the topology of the circuit. A capacitor in series would block DC and allow AC to pass (like a coupling capacitor in audio equipment) but a capacitor in parallel wouldn't affect DC and would tend to smooth out the AC. Since the capacitor is essentially in parallel with the solenioid I think it's there to suppress induced voltage spikes. Whether the intended beneficiary is the AS relay contacts or the bulb I don't know.
Quoted from paulace:I don't know, Ken - I don't have the machine in front of me. Might have it to look at on Friday....I'll see then.
20200405_203515 (resized).jpg20200405_203637 (resized).jpg20200405_203651 (resized).jpgQuoted from KenLayton:Ah.... it's a non-polarized (a.k.a. Bi-polar) electrolytic. That means it's being used with AC power.
Somebody should add the designation "B.P." or "Non-polar" to the schematic next to that capacitor.
So with the age of it should it be replaced?
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