Nancy Drew: The Haunted Carousel Hints

How do I use the soldering gun to fix the roller coaster card reader?

  • 1 of 14: You should already know why the card reader doesn't work, and you should already have the soldering gun.
  • 2 of 14: Touch the red tag and open the card reader, then pull out the first circuit and examine it.  What do you see?
  • 3 of 14: You see one of the circuit boards, and a schematic diagram taped nearby.  The circuit board seems to be missing a part.  You need some of Ingrid's knowledge at this time.  Have you read the shop manual that she gave to you?
  • 4 of 14: You may want to read the section of the shop manual about circuits, on soldering, and on red tags, for you will learn information that will enable you to repair the card reader without incident.  You may also want to read the schematic diagram.  Looking at the schematic, do you understand what it is trying to tell you?
  • 5 of 14: First of all, no need to worry too much about whether the wiring needs to be in series or in parallel.  And don't worry too much about the actual diagram either, although you can compare it to the circuits on the circuit board and see that they match.  The main thing to learn from the schematic is: what does the total resistance for the upgrade need to be?
  • 6 of 14: According to the second page of the schematic, the total resistance for the upgrade has to be 15 ohms.  It also says the macro resistor you have in your hand gives 5 ohms of resistance.  That can be verified too: check the manual on circuits.  Learn how to read the stripes on a resistor.  Do you see how the manual says that your macro resistor, which has a green, black, and yellow stripe, is indeed a 5-ohm resistor?  In that case, look at the circuit board, and locate the two resistors already installed there.  Can you read their stripes and determine the number of ohms for each of them?
  • 7 of 14: The resistor on the top of the circuit board has a brown, black, and black stripe.  According to the manual, that's a 10-ohm resistor.  The resistor on the bottom of the circuit board has an orange, black, and black stripe.  According to the manual, that's a 30-ohm resistor.  That confirms what you see in the schematic diagram.  Now, according to the manual, total resistance is determined by simply adding the ohms of each resistor.  You need a total of 15 ohms.  In that case, can you think of a way to combine any of the resistors you have to achieve the needed 15 ohms?
  • 8 of 14: You just need to combine the installed 10-ohm resistor with your new 5-ohm resistor, for a total of 15 ohms.  You would not use the installed 30-ohm resistor, because that would exceed 15 ohms.  So, you must install your macro resistor and solder the board in such a way as to ensure current flows only through the 10 and the 5.  Can you think of a way to solder it in that way?
  • 9 of 14: Since current flows through solder, and doesn't flow where there is no solder, you need to ensure that the wiring at the top of the circuit board is soldered together, and that the wiring at the bottom of the circuit board is not soldered together.  That way, current will flow up through the 10-ohm resistor and then through your new 5 ohm, and will totally bypass the 30-ohm resistor.  Get your soldering gun and solder the circuit board in this way.
  • 10 of 14: Click the switch on the board to "on" when you are done.  The light should glow.
  • 11 of 14: Here is a screen shot of how the circuit board needs to look when correctly soldered.  Note that, when the soldering is done and you click the switch to "on", the red light glows.
  • 12 of 14: Close the card reader.  You're not done yet, for the main power is not turned on.  Consult the section of the manual on red tags.
  • 13 of 14: You must take the tag from the reader and return it to Harlan.  He will restore the power to the reader.
  • 14 of 14: After you leave Harlan, return to the card reader and try it with your access card.  You should see the green light on the card reader.