RGB shifters
Service Menu adjustments
Before going and getting an RGB shifter, you should first try shifting using the Service Menu. This is the easiest way to shift the RGB image.
Utilize the lever on your set
Some CRTs have a physical switch or a pot that can be adjusted to center the image.
Below is an example from Sony BG-3R. In some cases, especially on larger screens, the picture will not be centered even after adjusting HPOS to 0 or to its maximum value. To get around this, you can try adjusting this lever, which will shift the picture horizontally.
RGB shifters
Sometimes, it is convenient to have an external shifter to quickly shift the image based on your input. You can utilize one of these external shifters.
Tips
None of the below are paid promotion, so you can rely on my honest opinion.
AliExpress RGB shifters
When it comes to RGB modding, a common phenomenon you will notice is that the RGB image gets shifted (horizontal shift) to the left slightly. Therefore, you have to make a minor adjustment via service menu to re-center the image horizontally.
While this can be accomplished through the service menu in most CRTs, there are few reasons why you might want to use an external RGB shifter.
- You don't want to shift the composite, s-video image. Service menu shift is typically universal and will impact other inputs
- You can't get into the service menu for your particular set
- Complex RGB shifting methods that requires opening up the CRT
5 in 2 out RGB shifter from AliExpress. It was around $75 USD, incl. shipping.
If you're planning to use the Mega Drive 2 (MD2) output on your AliExpress purchased RGB switch, the instructions below might be helpful. Avoid using standard MD2 RGB cables, even if they appear compatible. Instead, you'll need a directly wired MD2-to-SCART cable. I purchased a cheap MD2 cable from AliExpress, removed all the unnecessary components, and connected the wires directly.
Direct wired MD2 cable 
Retro Gaming Cable - works well for Mega Drive 2 > SCART output. But, not with this shifter. 
MD2 to SCART cable has components in the RGB and Sync line, which wouldn't help. 
Here’s a diagram that might help with the wiring of this cable. 
Okatu RGB shifter
I have also read some decent reviews about the 6 Port RGB Scart/RCA/Component Switch. I have not tried this switch personally to shift RGB images. Please note that there were some users who complained about a slight wobble. This is apparently due to the VPOS shifting. Several had better experience when they had the option to disable the VPOS shifting. Not sure if that is possible with the Okatu switch.
