Escape from the Lost World
Bally, 1987Hi guys,
I am working on an escape from the lost world.
I have solved most issues, but I am left with one which I don't understand.
On the top bumper (Q12) the associated 330 Ohms resistor (R140) is burning when activating the coil.
I've changed the coil, the transistor, and the resistor itself.
Should I put a bigger (more watts) resistor there? Or the issue lies somewhere else?
Any hint appreciated !
Bigger resistor will only result in a bigger fire! (After all - it's worked perfectly for 40 years without needing a bigger resistor).
Does your new coil have a diode fitted to it's lugs? Correct way around?
The driver IC, which is a bunch of transistors in one package, is possibly shorted on that driver (internally) - you might be able to do a comparison measurement from the 330R resistor with other drivers and look for a difference to ground (power OFF).
schematic (resized).png
Hello,
Many thanks for your answer.
Yep, I have fitted a diod in the new coil, correct way.
Don't know where your schematics are from though, here is the ones from the game 
So U19 could be the culprit? I checked and there is no continuity through its legs 11,12,15
Resistance values between legs 11 and 15, and 12 and 15 are the sames as between 9 and 15 and 10 and 15.
also, important info:
when I am grounding the transistor tab to ground, the coil is activating as it should
Quoted from Nihonmasa:also, important info:
when I am grounding the transistor tab to ground, the coil is activating as it should
This only tells you there's continuity from the transistor to the coil and nothing else. It does not test the transistor.
The only way R140 (330ohm resistor) can burn is by seeing too much voltage/current and the path to high voltage/current is through a shorted Q12 transistor (collector to base) or shorted C74 capacitor that's causing R140 to see 43 volts.
More likely transistor Q12 is failing.
The banded side of the diode on the coil is to the 43V solenoid power wire (yellow wire, not the yellow-blue wire)?
What model new coil did you use?
What model transistor did you install at Q12?
The playfield solenoid fuse is the correct rating of 1 amp slow-blow? i.e. has someone previous overfused it?
Quoted from Nihonmasa:So U19 could be the culprit? I checked and there is no continuity through its legs 11,12,15
With the game OFF, in diode mode on your meter at U19 you should measure 0.6 - 0.7 between pins 11 and 12 and between pins 11 and 15. Swap the meter leads around if you get no reading.
With the game ON in attract mode, in DC voltage mode on your meter at U19 you should measure 0.85V on pin 11 and 0.3V on pin 12. Pin 15 is ground.
Quoted from Quench:This only tells you there's continuity from the transistor to the coil and nothing else. It does not test the transistor.
The only way R140 (330ohm resistor) can burn is by seeing too much voltage/current and the path to high voltage/current is through a shorted Q12 transistor (collector to base) or shorted C74 capacitor that's causing R140 to see 43 volts.
More likely transistor Q12 is failing.
The banded side of the diode on the coil is to the 43V solenoid power wire (yellow wire, not the yellow-blue wire)?
What model new coil did you use?
What model transistor did you install at Q12?
The playfield solenoid fuse is the correct rating of 1 amp slow-blow? i.e. has someone previous overfused it?With the game OFF, in diode mode on your meter at U19 you should measure 0.6 - 0.7 between pins 11 and 12 and between pins 11 and 15. Swap the meter leads around if you get no reading.
With the game ON in attract mode, in DC voltage mode on your meter at U19 you should measure 0.85V on pin 11 and 0.3V on pin 12. Pin 15 is ground.
Hi Quench many thanks for all this info!
I used a WMS AE-26-1200
Q12 has been changed twice already, issue is elsewhere. I used a TIP102; which I also used on the same board for other dead transistors, which are now solved. Diod band is towards the yellow/blue wire
I tried as you instruct:
between pin 11 and 12: 0,7 and no reading the other way around
between pin 11 and 15: 0.7 and 0.888 the other way around
No continuity on C74
under pf: it was obivously blown, so until I've finished solving it I installed one I made of 3 amp which goes off without killing the fuse, and that I can rearm afterwards. Usefull for testing
But probably need to make one of 1A as well 
Quoted from Nihonmasa:Diod band is towards the yellow/blue wire
This is the problem. On the coil, the banded side of the diode must be on the *yellow* wire. You have it backwards which is causing transistor Q12 to see a short circuit and blow.
You need to replace the coil diode this time oriented properly since it's been overloaded with current and also replace the Q12 transistor again and the 330ohm resistor.
Also put the proper playfield fuse in before something really gets damaged
Good luck!
Quoted from Quench:This is the problem. On the coil, the banded side of the diode must be on the *yellow* wire. You have it backwards which is causing transistor Q12 to see a short circuit and blow.
You need to replace the coil diode this time oriented properly since it's been overloaded with current and also replace the Q12 transistor again and the 330ohm resistor.
Also put the proper playfield fuse in before something really gets damaged
Good luck!
Sorry I miswrote! The diod is correctly installed, that is not the cause unfortunately 
20220117_153436 (resized).jpgQuoted from Roamin:Either your eyes, or mine have issues. But on your picture, the banded (silver band/ring) of the diode is on the red wire side..
[quoted image]
Yep, but Calice, it's the right way:p
It was my previous answer saying it was towards the yellow/bluie which was wrong.
All other coils have the band in the same direction and are working fine.
Quoted from Nihonmasa:Yep, but Calice, it's the right way:p
It was my previous answer saying it was towards the yellow/bluie which was wrong.
All other coils have the band in the same direction and are working fine.
And solved by replacing C74 which was the issue.
Many thanks Quench and all others who replied!
Quoted from Nihonmasa:And solved by replacing C74 which was the issue.
Great to hear!
Thanks for the solenoid picture, the schematics don't list the playfield solenoid bus wire color and it's listed as yellow in another 6803 game which is why I said yellow.
Cheers.
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Chénens
Gaborone
Saint-hyacinthe, QC
Wichita, KS