LED Project #2 - MKIV VW Cluster UpgradeDIY IS NOW COMPLETE - DIY AWAY!!!!
After many months of R&D and buying different parts, I believe I can call LED Project #2 finished. I have entailed all the details below, and if there are any questions please feel free to PM me (FaelinGL) or Wes (SPKNGRMN) or email me at contact@fallastarmedia.com.
Before you do, *please* read everything in this document, as your question may have been previously answered. I would like to thank SPKNGRMN, Rob'sVR6, staggered MK4, VgRt6, and everyone who contributed to this project.
Functionality added
This DIY will install LEDs that dynamically track engine speed and vehicle speed. When completed, the install basically looks stock. Click on the pictures/links below to check out the movies(MPEG format). You can download the MPEG codec HERE if you don't have it installed.


LED Project #2 - Shift Light Enabled
LED Project #2 - Shift Light Disabled
COLOR SELECTOR
By popular demand, people want to know what their cluster will look like before they choose to do this. If you do, please click on the COLOR SELECTOR and figure it out.
Preface
If you are using the DIY method, you really do need some experience with soldering, wiring, and understanding circuit diagrams. A couple of legalities:
1)You WILL void your warranty, at least for the instrument cluster.
2)You WILL be taking parts of your car apart, prying them open, and putting them back.
3)The circuit diagram is Patent Pending. I give you permission to make your own circuit, but please do not attempt to sell or otherwise promote it. I'm really not a fan of long, drawn out legal battles 
Theory
Rather then fill up this document, if you're going to do this I highly recommend you read THIS PAGE. It will give you some valuable insight as to what exactly you're trying to accomplish.
All right, let's get started. Please be careful. Do this procedure at your own risk, I can't be held responsible if I have made a mistake in the steps. There are MANY steps, so be sure you understand what you are doing instead of following the procedure blindly.
Needed Parts
Kit Method
-Super Glue (not Gel! I recommend "Loctite" Precision Max Superglue)
-Electrician's tape
-2 AA Batteries (optional)
-Thin wire (optional)
-All remaining parts are included in the kit
DIY Method
-Super Glue (not Gel! I recommend "Loctite" Precision Max Superglue
-Electrician's tape
-Thin Wire for jumpers/splices - 30 gauge, single strand, Kynar insulated wire works best
-Applicable parts to build the circuit (see the diagram below)
-2.5mm by 7mm rectangular LEDs of your color choice (you can get these from http://www.digikey.com)
Needed Tools
Kit Method
-10 mm socket
-ratchet
-ratchet extension
-small blade screwdriver
-medium blade screwdriver
-Torx-20 screwdriver
-Torx-10 screwdriver
-Voltmeter (optional)
-Small round file (a Dremel tool works MUCH better)
-Small pliers
-Air source (for cleaning the dust out, a computer dust can works too)
DIY Method
-10 mm socket
-ratchet
-ratchet extension
-small blade screwdriver
-medium blade screwdriver
-Torx-20 screwdriver
-Torx-10 screwdriver
-Voltmeter (optional)
-Small round file (a Dremel tool works MUCH better)
-Small pliers
-Air source (for cleaning the dust out, a computer dust can works too)
-Soldering Iron
-Solder Remover
-Solder
-Applicable tools to build the circuit
-Lots of Time
-Black Spray Paint
-Blue Painter's tape
-Lacquer Thinner
-Small side cutters
Initial conditions - DIY Method only
-You will need a LOT of time to invest for testing and wiring with the DIY method, whereas the Kit method requires only about 3 hours to do the installation. 
-You can complete wiring up and testing the circuit board prior to pulling out the instrument cluster.
-You can reinstall the instrument cluster with the gauge faces removed so you can complete installing the LEDs.
The Circuit Board
For the DIY Method, this is the hardest part. You will need to figure out how to wire up the circuit to a breadboard. I really can't explain how to solder, how to read circuit diagrams, or how to understand a manufacturer Datasheet. So if you do not know how to do that then you may want to opt for the Kit method. That being said, if you still want to proceed you may go through many, many circuit changes before the circuit works. As an example, here is a picture of the my original DIY board compared to the Kit Board.
Front

Back

What I have below is a simplified circuit diagram for one side of the circuit (ie, the tachometer). You will need to wire two of these together to power both the Tachometer and Speedometer LEDs. Use this in conjunction with the manufacturer data sheets listed below to design your circuit. Two words of advice - Work Small. Do one piece of the circuit at a time. Test it, make sure it's working, then solder it to the breadboard. It took me the better part of a week to get the circuit to do what I want reliably.

Frequency to Voltage Converter - LM2907 Datasheet
LED Display Driver - LM3914 Datasheet
For the circuit diagram, the pots labeled R1 through R5 control the circuit in the following manner:
R1 - Controls the slope of the Voltage Response
R2 - Controls the initial DC offset of the Voltage Response
R3 through R5 - Fine tune the circuit response per the LM3914 Datasheet, page 16/17.
If you pull the RPM signal from the ECU, you will need to use the 561 pF capacitor. If you get it from the blue connector in the cluster, use the .01 uF capacitor.
Don't get frustrated!! I'll do my best to help you fix your circuit, but I can't really see your breadboard so I can only offer my own experience. Once you are satisfied with your circuit, continue on to perform the installation.
Disconnecting the Battery
Note:You may need the radio code to reset your radio after disconnecting the battery (OEM Radios only)
1.Pull the hood release latch to unlock the hood.

2.Raise the hood by pulling out on the locking tab and lifting the hood.

3.Remove the battery cover by lifting up on the front and pulling it out.

4.Remove the battery clamp for the red, positive terminal cable by loosening the nut with a 10 mm socket.

Removing Interior Parts
5.Open the interior fuse cover with a medium blade screwdriver.

6.Remove the side dash cover by pulling it out and away.

7.Remove all three Torx-20 screws located under the dash. You can see the middle one here.

8.Remove the lower kicker panel by pulling out on the left side. Then, pull out and up on the right side.

9.Remove the flat plastic piece under the dash by pulling the front out and down.

10.Remove the two Philips head screws under the steering wheel on the lower steering column cover.

11.Remove the upper steering column cover by lifting it straight up. Pull directly out on the plastic trim connector to remove it.

12.Remove the two instrument cluster screws with a Torx-20 screwdriver.

13.Work the cluster out of its place by tilting it back and forth.

14.Lift up on the pink tab of the blue connector. You can use a screwdriver to help, but be careful not to snap the plastic lever.

15.Remove the blue connector by sliding it out of the cluster.

16.Repeat step 14 and 15 for the green connector.

17.Slide the instrument cluster out of the dash and set it to the side.

Modified by FaelinGL at 11:17 PM 10-26-2006
Modified by FaelinGL at 6:46 PM 11-10-2006
Modified by FaelinGL at 7:54 AM 11-11-2006