Sony Profeel KX-1901/A
In 1980, Sony introduced the "ProFeel" line of prosumer component televisions, consisting of a range of Trinitron monitors that could be connected to various components. Sony KX-1901A is a beautiful set from 1983. It is paired with a tuner component such that a remote can be used to control the power, video input, adjust volume etc.
Sony KX-1901/Sony KX-2501 does not support analog RGB, only digital RGB. However, if you have the later revision Sony KX-1901A or Sony KX-2501A CRT, then you are good. "A" at the end of the model # here apparently stands for "Analog" support. Using the RGB Multi to SCART adapter on non-"A" version will not be that useful for retro gaming purposes.
If you feed analog RGB to digital RGB input you might see colors that are flat, missing or corrputed.
This issue was well-known and problematic for the KX-1901 sets, as it caused the volume to become stuck at a 100% or, in some instances, muted. In my particular case, the volume was stuck at 100%.
To address this problem, I began by referring to the schematics for this specific CRT model. My initial step involved checking the voltage level on the volume pin, which yielded readings ranging from 1V to 4V, depending on whether I adjusted the volume up or down. You can see the pin being probed in the below picture.
As the volume signal appeared to be operating correctly, I focused my attention on the K-board, suspecting that the issue lay there. Reviewed the K-board schematics, and inspected the components that were on the receiving side of the volume signal. Volume singal passed through a potentiometer, RV1201 that was connected to the ground. This potentiometer was designated as
102, indicating it should have a nominal resistance of approximately 1 kohms.
However, it was discovered that this potentiometer was open, rendering the audio to be high at near 100%.
I borrowed a
102 potentiometer from another junk CRT chassis and replaced the faulty one.
The volume function now operated flawlessly. Hopefully, this information proves beneficial to anyone else who might be encountering a similar problem.
34Pin RGB adapter
Adapter on Sony Profeel KX-1901A
There is a dedicated section for the adapter where you can purchase it.
Shifting the RGB image
With every RGB mod, I have always noticed a slight shift in the RGB image. KX1901A was no exception. Without the service manual it was a bit tricky to make this adjustment. Lucikly stabarz was kind enough to make a post on what needed to be adjusted on this particular set. I made the recommended adjustment and it just worked fine. My understanding is that this adjustment only applies to this particular set - KX1901A.
Move H.CENT jumper from the "C" position to the "R" position (circled). Getting to this board is not straight forward, so be prepared to go through several screws and wires.
Another easier method to shift the RGB image, is to use an RGB image shifter. I got one of these
5 in 2 out manual SCART switch for ~$70USD and it worked like a charm! There are probably muliple varieties of these RGB shifters on AliExpress that can get the job done.
This is my current setup