CleanComp Setup
The CleanComp Universal can be installed in any console that has native RF or composite signals somewhere on the system.
The purpose of the CleanComp is to tune those signals into correct IRE levels, removing the DC offset, cleaning and filtering the signal, and setting the gain correctly.
The CleanComp Universal won't improve or reconstruct the raw video signal like the specific Atari 2600 CleanComp does for example, giving much sharper image than original.
Instead, the Universal is all above removing the DC offset and gaining the voltage level to give the correct brightness and saturation, while also removing any out-of-bound noise using various filters for noise.
You should expect a stable composite signal, but not an improvement over sharpness or detail.
Install the CleanComp into your desired system by soldering it to ground and 5V (or if the voltage is over 5V to the >5V pad).
If you connect a 5V system to the >5V pad, the CleanComp Universal will only receive around 4V and may cut off some of the signal if it is over 4V, but it is the safer option if you are unsure of the system voltage.
Then the IN1 input to your source signal, and the OUT1 to your composite cable.
The IN1 and IN2 are identical channels just doubled if you would like to pass in S-Video Chroma and Luma channels and mix them afterwards.
Every system is different, but the most common use of the CleanComp Universal is to convert RF to Composite.
For this, almost all RF circuits are integrated into a little can, which accept Video, Ground and Audio as inputs. If this is the case, you can send the Video signal into IN1.
If your circuit is different, you must identify at what point in the circuit composite is generated to tap into it. The voltage level and impedance of the signal does not matter, the CleanComp Universal can correct that.
If you have a fully integrated RF circuit, you must disconnect your audio and video signals and modulation from the circuit, to isolate just the composite video. This is rare and most circuits already have a plain old composite signal on the circuit design already.
If you want to do S-Video (you have access to Chroma and Luma channels separately), you can pass in Luma and Chroma into IN1 and IN2 in any order, tune them, and then join OUT1 and OUT2 together via a 470pF capacitor.
The MIX pad on the CleanComp Universal was a test circuit designed to pre-mix S-Video signals together at the input stage so you can have dual outputs of the same signal, however that doesn't work as expected so just mix the outputs together instead.
I will update this circuit design in future so there is already a 470pF capacitor and bridge pad on the output.
Once you have your ground, power and input signals wired up, and the output going to your composite/S-Video cable it is time to tune the signal into the correct IRE voltage levels.
Some signals often have a DC offset so the video signal is sitting on top of say a 2V DC offset.
Notice this signal for example has a 1V DC offset.
The final stage output should not have a DC offset (well, 0.3V but the CleanComp re-adds that for you).
Turning the DC Offset dial Counterclockwise removes more of the DC offset if any is present, and can pull the entire video signal too low if you go to far.
Use an oscilloscope to watch for the DC offset being removed.
If you don't have an oscilloscope, you can turn this blindly until you see some form of video output on your receiver, then alter the divide/gain and come back to this DC Offset once done, tuning it visually on screen.
With the DC Offset tuned to remove any DC offset, you should already see some output on screen.
If you have an oscilloscope, monitor the output voltage at OUT1 or OUT2 pins. You want to turn the gain dial until the maximum output voltage is 1V if connected to a receiver, or 2V if it is floating output.
Sometimes the output signal is already too high. In which case, bridge the DIV1 and/or DIV2 pads (if using IN2), to enable a divider circuit.
Now turn the Divide dial until the voltage is 1V if connected to a receiver, or 2V if it is floating output.
NOTE: On the CleanComp Universal design currently adjusting the divide will have a slight impact on DC offset so you may need to slightly increase the DC offset as the divide removes some DC too.
The CleanComp Universal has several filtering options. These remove potential noise and soften or sharpen edge transitions.
The LPF (low pass filter) pads between the DC Offset and Gain dials can be bridged to slightly soften the image. This can help if you are seeing a lot of sharp edges or color bleeding on contrasting changing edges like black to green or white to red.
NOTE: Composite by nature of how it gets decoded will almost always have chroma bleeding between changes in brightness and hue, causing edges of white text for example to have some color to them.
This is unavoidable but can be reduced using a Low Pass Filter.
The final stage output has a lot of advanced filtering specific to cleaning up composite video:
- 6th-Order 9.5-MHz (–3 dB) Butterworth
- –1dBPassband Bandwidth at 8.2-MHz
- 54-dB Attenuation at 27-MHz
If the image appears too soft, or you want to try and sharpen it a little, you can bridge the Bypass Filter pad to bypass all this filtering.
