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The A/V Board

Photos by @dwbrite

Step 1: Before we begin
  • This page will walk you through building the A/V Board, which generates the signals that go out to the TV.

  • In general we'll be placing the shorter components first.

  • It will help to have a flat board handy, about the same size as the PCB. This can be used to keep parts from falling out as you flip the whole board to solder components.

Step 2: Bypass Capacitors
  • The bypass capacitors smooth out the power supply to each chip.

  • Every IC gets a 0.1uF capacitor next to it.

  • There should be 35 of these

Step 3: Filter Capacitors
  • A few more capacitors are used for audio and video filtering

  • Leave C1 vacant

  • Use 100pF in C2

  • Place the respective capacitors on the slots labeled 680pF, 820pF, and 82pF

  • (82pF is missing from the photo due to a shipping error, and will appear in later step photos)

Step 4: 1K Resistors
  • There are 14 1kOhm resistors to install

  • The resistors inside the rectangle are meant to be installed vertically, as in the picture.

  • Cut the resistor leads after soldering

  • Bending the legs of horizontal resistors inward can help them stay in place for soldering.

Step 5: Other Resistors
  • Install the rest of the resistors according to their labeled value.

  • 3 x 150 Ohms

  • 4 x 3.3kOhm resistors

  • One each of 470, 16k, 68k, 10k

  • R26 can be just a wire, such as one clipped from another resistor after soldering.

Step 6: Big Capacitors
  • One filter capacitor for video and the two bypass capacitors for inter-board connectors are big 220uF electrolytic caps

  • The symbol for these capacitors has a small "+" plus sign indicating the positive lead

  • The capacitor has a stripe indicating the negative lead, which should go in the opposite hole of the plus sign.

Step 7: DIP Sockets (Prelude)
  • The next several steps will insert sockets for chips.

  • The "wood board" method will still help if the sockets are still the tallest thing on the board.

  • Otherwise, you can bend the socket pins outward to help them stay in the holes before soldering.

  • BE SURE TO match the divot on the socket to the divot on the printed socket outline!

Step 8: DIP16 Sockets
  • Next insert the DIP16 sockets, which have two rows of eight pins.

  • There should be 11 of these on the A/V board.

Step 9: DIP14 Sockets
  • Now insert the DIP14 sockets, which have two rows of seven pins.

  • There are places for 15 of these.

Step 10: DIP20 Sockets
  • Install the DIP20 sockets, with two rows of ten pins.

  • You'll be placing 3 of them.

Step 11: DIP40 Socket
  • The next socket is the DIP40 that will hold one of the GameTank's two 6502 CPUs

  • There is only one place for a DIP40 socket on the A/V board

  • This CPU will be the Audio Coprocessor

Step 12: PLCC Sockets (The square ones)
  • There are two square sockets to install, which will hold the Video RAM and Audio RAM chips.

  • Be sure to match the direction of the arrows on the sockets to the arrows printed on the board.

  • "Protip rest it on something and get the corners first." - dwbrite

Step 13: Inter-board connectors
  • Next, install the two inter-board connectors on the BOTTOM of the board.

  • You'll need one "receptacle" and one "plug" connector

  • IMPORTANT: Each of the connectors has a single corner flattened on a diagonal. These diagonals should be oriented INWARD towards the cartridge hole for consistency.

Step 14: DIP8 Connector
  • Install the single DIP8 connector that has two rows of four pins.

Step 15: A/V Output Jacks
  • Install the two RCA-style conectors on the corner of the PCB

  • The yellow connector should go on VIDJACK

  • The white connector should go on AUDJACK

Step 16: 6-pin Header
  • Install the 6-pin female header

  • This will be for the video buffer amp module

Step 17: All sockets have been installed
  • Pat yourself on the back!

Step 18: Assemble the Video Buffer Amp
  • If you didn't request a pre-soldered module, this will be one of the two surface-mount soldering tasks in the console.

  • This will use the small PCB with THS7374 printed on it, as well as the chip with the same name.

  • Flux and low-temperature solder paste are recommended

  • Align the THS7374 to the outline, matching the divot on the chip to the printed dot on the board.

  • This can be soldered with an iron, hot air gun, oven, or hot plate.

  • If any pins are bridged, add flux and use copper braid to remove excess solder.

  • C1 and the resistor outline on this module can be left vacant with no issues.

  • Then solder on the 6-pin male header to the BOTTOM of the board.

Step 19: Install the Video Buffer Amp
  • Insert the video buffer amp module into the 6-pin female header, with the arrow pointing towards the front of the console.

  • It will hang over the electrolytic capacitor next to it, but there should be enough clearance.

Step 20: Inserting Chips (Prelude)
  • Next you'll be inserting chips into all these sockets you just soldered

  • The chip names are printed on the the PCB, but they are now obscured by sockets.

  • A layout diagram will come in handy for finding where chips live.

  • It will also help greatly to have a Lead Forming Tool to straighten the chip pins, as they ship with their legs slightly bowed outward.

  • Lead Forming Tools can be purchased commercially, or produced on a 3D printer.

  • Simply place the chip on top of the middle bar and squeeze. The chip will now fit a socket perfectly.

Step 21: Gather your chips
  • 1x 74HC164N/E

  • 1x HC151E (74LS151N)

  • 2x HC08E (74LS08N)

  • 2x HC257N

  • 1x HC564N/E

  • 2x HC573N

  • 1x 7524CN/JN (AD7524JN)

  • 3x HCT74N (74S74N/74LS74N/)

  • 1x AC32N (74LS32N)

  • 5x HC00E (7400N)

  • 1x HC40103E (CD40103)

  • 1x HC86E (7486N)

  • 1x HCT30E (74AS30N)

  • 4x HC4040E (4040N)

  • 1x HC04E(7404N)

  • 2x HC161N (74HC161)

  • 1x LM358

Step 22: 1 x 74HC151
  • Depending on the market, the HCT or AHC versions might be easier to get. These will work fine.

  • The text on the chip might end in an N or an E. This denotes what factory they came from and doesn't matter here.

Step 23: 1 x 74HC30
  • Depending on the market, the HCT or AHC versions might be easier to get. These will work fine.

  • The text on the chip might end in an N or an E. This denotes what factory they came from and doesn't matter here.

Step 24: 5 x 74HC00
  • Depending on the market, the HCT or AHC versions might be easier to get. These will work fine.

  • The text on the chip might end in an N or an E. This denotes what factory they came from and doesn't matter here.

Step 25: 1 x 74HC04
  • Depending on the market, the HCT or AHC versions might be easier to get. These will work fine.

  • The text on the chip might end in an N or an E. This denotes what factory they came from and doesn't matter here.

Step 26: 3 x 74HC74
  • Depending on the market, the HCT or AHC versions might be easier to get. These will work fine.

  • The text on the chip might end in an N or an E. This denotes what factory they came from and doesn't matter here.

Step 27: 2 x 74HC161
  • Depending on the market, the HCT or AHC versions might be easier to get. These will work fine.

  • The text on the chip might end in an N or an E. This denotes what factory they came from and doesn't matter here.

  • In your overall parts order is at least one 74AC161, but don't use it here! Save it for slot U$6 on the main board!

Step 28: 1 x 74HC32
  • Depending on the market, the HCT or AHC versions might be easier to get. These will work fine.

  • The text on the chip might end in an N or an E. This denotes what factory they came from and doesn't matter here.

Step 29: 2 x 74HC08
  • Depending on the market, the HCT or AHC versions might be easier to get. These will work fine.

  • The text on the chip might end in an N or an E. This denotes what factory they came from and doesn't matter here.

Step 30: 1 x 74HC86
  • Depending on the market, the HCT or AHC versions might be easier to get. These will work fine.

  • The text on the chip might end in an N or an E. This denotes what factory they came from and doesn't matter here.

Step 31: 1 x 74HC164
  • Depending on the market, the HCT or AHC versions might be easier to get. These will work fine.

  • The text on the chip might end in an N or an E. This denotes what factory they came from and doesn't matter here.

Step 32: 4 x 74HC4040
  • Depending on the market, the HCT or AHC versions might be easier to get. These will work fine.

  • The text on the chip might end in an N or an E. This denotes what factory they came from and doesn't matter here.

Step 33: 1 x 74HC40103
  • Depending on the market, the HCT or AHC versions might be easier to get. These will work fine.

  • The text on the chip might end in an N or an E. This denotes what factory they came from and doesn't matter here.

Step 34: 2 x 74HC573
  • Depending on the market, the HCT or AHC versions might be easier to get. These will work fine.

  • The text on the chip might end in an N or an E. This denotes what factory they came from and doesn't matter here.

Step 35: 1 x TLC7524
  • Might also be called AD7524

Step 36: 1 x 74HC564
  • Depending on the market, the HCT or AHC versions might be easier to get. These will work fine.

  • The text on the chip might end in an N or an E. This denotes what factory they came from and doesn't matter here.

Step 37: 2 x 74HC257
  • Depending on the market, the HCT or AHC versions might be easier to get. These will work fine.

  • The text on the chip might end in an N or an E. This denotes what factory they came from and doesn't matter here.

Step 38: 1 x LM358
  • Audio buffer op-amp

Step 39: IDT7007 (Video RAM)
  • Larger of the two square chips

  • BE SURE TO align the dot on one edge of the chip to the direction of the arrow on the socket

  • If inserted wrong you will need a special PLCC Removal Tool to extract it.

  • To insert, just make sure the dot and the pins are lined up and press down firmly.

Step 40: IDT7137 (Audio RAM)
  • Smaller of the two square chips

  • Same warnings and advice for IDT7007 apply

  • Double check the direction of the arrow, it isn't the same as the other socket!

Step 41: 6502 (Audio Coprocessor)
  • One of the two 6502 chips in your parts order

  • Not the 6522 VIA which is also a 40 pin DIP chip

  • With this installed your A/V Board is complete! Well done!

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