THS7314 RGB Amp

The Texas Instruments THS 7314 amp is an SDTV video amplifier designed specifically for video signals that's commonly used as an RGB amplifier in retro game consoles.  It has 3 inputs/outputs, plus power and ground.  The power is filtered by a capacitor and the output is regulated by 75 Ohm resistors.  Using 75 Ohm resistors is important, as it provides the exact signal your display is expecting.  Using resistors other than 75 Ohm could cause quality loss in the video output, among other unwanted side-effects.  If you're using one of these amps in your game console, but find the output to be too bright, check the individual mod pages for more info, or simply add resistors to the input side of the amp, instead of changing the output resistance. 

Here's a link to the official datasheet for anyone that wants the full specifications:  http://www.ti.com.cn/cn/lit/ds/symlink/ths7314.pdf

Assembly / Parts Needed
- Soldering skills! 
- Soldering iron / solder (rosin core solder recommended)
- Multimeter
- RGB Amplifier chip, model # THS7314DR
- Circuit board to mount the RGB amp
- Three 75 Ohm resistors, the lowest tolerance possible:
http://www.digikey.com/product-detail/en/MRS25000C7509FRP00/PPC75.0ZCT-ND/595092

- One 0.1uf Capacitor: 
http://www.digikey.com/product-detail/en/C320C104J5R5TA7301/399-9867-1-ND/3726105


First, start by adding solder to both the circuit board and the amp chip itself.  Use your soldering iron to heat the pins/pads, then touch solder to it.  Once the solder points are hot enough, the solder will melt right to it:

Next, solder the THS7314 to the circuit board, but note the alignment of the vertical line on the chip and the square ground pin of the circuit board (see the top pic)!!!  Since you tinned both the pads and pins, you should be able to place the amp on top of the circuit board and just touch the points with the tip of the soldering gun.  If you applied solder correctly, they'll bond perfectly.  This can be very tricky the first time you try it and I recommend using pliers or tweezers to hold the amp and circuit board.  One of those soldering kits with the magnifying glass and alligator clips could come in handy, but I got used to assembling them right on my desk:
 

Next, you'll want to use a multimeter to check your solder points.  When checking, make sure to touch the pin where it enters the chip, not near the bottom where you may accidentally be making contact with the circuit board's pads.  Then, touch the other tester to the pad that matches it's input (ground shown here).  If a connection isn't made, you could try adding more solder to the joint between the pad and pin:

You can use this diagram to test each of the pins and pads to make sure they line up.  You'll want them to match the photo at the top of this page:

Next, add the output resistors.  I bend the resistor so it's close to the board and solder the top.  Then, I snip off the excess as short as possible (so the bottom of the circuit board is smooth) and add a bit more solder to the bottom:

Then, add the capacitor between power and ground.  I realize this might seem strange to a beginner, as you'd normally never touch power and ground together.  In this installation, the capacitor acts as a "power filter", ensuring that the voltage running through doesn't cause interference with the signal. 
It may be easier to add the power and ground wires at the same time you add the capacitor, but it's not necessary:

That's pretty much it.  The inputs on the left will pass directly through to the inputs on the right (numbered as 1-3 in the above picture).  You can use this amp to amplify pretty much any 3-channel SD video signal and even use it to amplify sync if needed (but you'd obviously only use one input/output if you were making a sync amp).

I personally find the output of this amp to look perfect as-is.  In some situations, I may need to turn the brightness down on my monitor a bit, however it never effects the picture quality.  That being said, different people's applications will have different results.  If you use this amp and find the brightness too high, check the individual mod pages for each console, as there are specific mods to tweak each console for the exact brightness that's supposed to be found in each system.

If there isn't a custom fix for your console, but you still find it too bright, try adding resistors to the input side of the amp circuit and make sure to leave the 75 Ohm on the output side.  I'd start with 75 Ohm for the inputs.  If it's still too bright (unlikely), you could try 100, 121, 130, or 150. If 75 Ohm on the input side is too dark, try 33 Ohm:

 

THS7374
As an FYI, there's a newer, 4-channel revision of the chip called the 7374.  The chip also includes an additional noise filter, which softens the image.  I always recommend this filter be turned off (pin 9 to 5v http://www.ti.com/lit/ds/symlink/ths7374.pdf).  Also, please keep in mind that this chip is MUCH smaller and almost impossible to solder by hand.  As a result, it's not a good DIY solution:

 


I hope this page was able to aid with the assembly of the amp and possibly even clear up some confusion about the output resistors/brightness. It's used in many of the mods in my Console Info & Mods page and can be helpful in other applications as well.

If you’re finished, I invite you to go back to the main page to see all the other retro-gaming awesomeness we have on this site... especially the RGB guide!