rage8885 wrote:
I'm hoping someone can give me some feedback / help on an RGB mod I'm attempting. I've got a Sony Trinitron KV-27V20 (AA-2 chassis) that I was able to pick up for free locally - if I screw it up I won't lose any sleep, but I'd love to get this right the first time. From reading through this post and seeing how others have modded similar TV models, I've put together a diagram of what I "think" I need to do:
The OSD (IC001) RGB and BLK lines need to be cut and redirected into aa 4PDT switch. The lines coming from the Jungle (IC351) RGB and YS also need to be redirected into the 4PDT with the RGB lines having 0.1uF capactiors in line. Finally, I'm adding 3 BNC connectors (RGB) with negative attached to ground, and positive attached to the 4PDT with 75 ohm resistors inline and also attached to ground. I'm also going to feed the 5V standby into the 4PDT switch.
When the switch is "on" the RGB from the BNC connectors and the 5v standby will be hooked up to the Jungle RGB and YS.
When the switch is "off", the OSD RGB and BLK will be hooked up to the Jungle RGB and YS instead.
I took the TV apart and pulled out the A board and tracked down the components:

(front)

(back)
At this point I'm trying to figure out / understand the best place to actually do the mod. My soldering skills are fairly basic and while I can solder small-ish wires without any issues, I've yet to attempt soldering anything surface mount. I've identified two areas where the mod can potentially be done (A and B on the images).
The easier of the two looks like it would be "A" which is nearby the OSD (IC001) chip. There are 4 resistors on the top of the board that are nice and accessible - my thoughts are to remove the resistors and proceed with the mod using the holes on the board in place of the resistors. After removing these resistors I assume I need to keep them in the circuit / reattach them.
With that said, there is an area of the circuit between the OSD and Jungle that I'm not sure of the purpose (the purple question mark on the circuit diagram / back of the circuit board). It looks like there are a number of transistors for each line (RGB) that are attached to the 9V line. Does it matter what side of this area I do the mod?
The harder of the two is "B". I'll be honest, I'm not even sure how to attempt this mod here - the components all appear to be surface mount and possibly even under the Jungle (IC351) itself?
If I can't do "A", is there an easier way of modding this than attempting "B"? I can post the service manual / datasheet for the Jungle IC for this TV as well if that helps. The Jungle IC is a Sony CXA2025S.
https://imgur.com/a/LnylNEG (additional pics from the service manual / board)
This AA-2 chassis TV can also be OSD Mux modded easily. It's already been covered in the thread but here we go again.
This set has an unusual OSD RGB circuit because it converts RGBI to RGB through a series of transistors but that is ok, there is still a simple way to do it.
R1123, R1128 and R133 are the OSD termination resistors that we want to target for the OSD mux. So we remove them.
They are 390 ohm resistors. Instead of using the OSD/External RGB muxing calculator to work out our mux resistors we will just cheat and subtract 75 from 390 to get something close. 390 - 75 = 315. Next standard resistor size is 330 ohms.
So we want to inject our 75 ohm terminated RGB into 330 ohm resistors and then into circuit somewhere between R1121 (Red) , R1126 (Green) , R131 (Blue) and R1355 (Red), R1356 (green) and R1357 (blue). IIRC correctly there are jumpers in there but it's been a while so i may be mistaken. The ungrounded pads left by removing R1123, R1128 and R133 are an obvious spot but may not be suitable.
For a very simple blanking circuit try taking a 5V line to the input of single point switch, then connect the output of the switch to a 470 ohm resistor and solder it onto the leg of L003 that is closest to IC001. Quick and dirty but should work fine.