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Sony (AA-2) KV-27V20

Sony (AA-2) KV-27V20

SuntharMichael LopezAbout 12 minCRT RGB modKV-27S22KV-27V20KV-27V35KV-27S25KV-27S20KV-32S20KV-35V45KV-32V35KV-27V25KV-35V35KV-32S25KV-35V75KV-32V25

Sony (AA-2) KV-27V20 CRT RGB mod

The Sony Trinitron KV-27V20 is a 27-inch CRT TV featuring a Hi Black Trinitron picture tube, built-in 5W stereo speakers with SRS sound, and an automatic light sensor for brightness adjustment. It offers front and rear composite A/V inputs, a rear S-Video input, and both composite and stereo audio outputs. Video inputs accept 1V peak-to-peak signals, and audio inputs have 4.7 kΩ impedance with 500 mV sensitivity. Antenna connections include 75-ohm UHF/VHF terminals. Power consumption is 160 W (on) and 9 W (standby). The set measures about 27" × 23" × 20" and weighs 94 lbs.

Sound on this set really stands out. This set is RGB and component moddable.

Sony KV-27V20 RGB image

View full CRT details and more mod examples →open in new window

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Table of Contents

Contributors

Thank you to everyone who contributed to this guide:

CRT safety

Caution

You can die doing this! So read carefully! CRT TV is not a toy. Do not open a CRT TV. If you don't have any prior knowledge about handling high voltage devices, this guide is not for you. CRT TV contains high enough voltage (20,000+ V) and current to be deadly, even when it is turned off.

READ THIS BEFORE CONTINUING

Plan of attack

READ THIS TO PREPARE

Manuals and Datasheets

Specs

  • Manufactured: USA (1997)
  • Format: NTSC
  • Chassis: AA-2
  • Tube: Sony Trinitron A68KZJ50X
  • Jungle Chip: Sony CXA2025AS
  • OSD Chip: CXP8564D-004S
  • Screen Size: 27"
  • Weight: 89.5 lbs
  • Inputs: Composite, RF

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RGB mux diagram

Prepare the mux diagram. If you are building your own circuit, this diagram should help.

Sony KV-27V20 RGB MUX diagram

Performing the mod

STEP 1: Remove the following components

Remove R1123, R1128 and R133 img

Inject R, G, B at the below locations R1123 (Red) R1128 (Green) R133 (Blue)

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STEP 2: Add a diode to blanking

Blanking diode added. Helps reduce interference. This mod was performed without shielded cables internally and absolutely no interference was noticed.

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STEP 3: Connect RGB and blanking wires

Refer to the image below for the precise soldering points for the red, green, blue, and blanking wires. For the R, G, and B wires, make sure not to solder to the pad connected to the ground.

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STEP 4: Connect audio, ground and sync wires

Now, it's time to turn our attention to the U board. In the image below, you can see where the audio, ground, and sync wires are connected. Since I'm using a separate cable for audio, the wire colors may not match the colors of the ribbon cable. Additionally, make sure to cut the trace as shown in the image.

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  • Red wire is audio right = grey wire on ribbon cable
  • White wire is audio left = white wire on ribbon cable
  • Black = black (common ground)
  • Yellow = yellow (sync using luma input)

To enable the luma input, I chose to use a dummy S-Video plug. Essentially, this means simply plugging an S-Video cable into the S-Video port without connecting it to anything else. You can get creative with this setup—adding a switch to toggle luma on and off, permanently enabling luma, or even using a transistor to activate luma automatically when a SCART cable is connected using the 5V blanking signal. However, I opted for a straightforward and reliable solution with the dummy plug. This approach allows me to seamlessly use both S-Video and Composite input from the back panel whenever needed.

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STEP 5: Build your mux circuit

This mod uses the RGB mux board. This is optional, but will make your mod easier and stable. You can also create the circuit presented in the schematics above without the board. Please also checkout the mux calculatoropen in new window to play with your own values.

On Sony CRT ChassisKV-27V20
CRT RGB inline resistor2.2kΩ
CRT RGB ground resistors removed390Ω
0.1μF caps replacedNo
Add diodes on chassis RGB lines?No
Add blanking diode on chassisYes
RGB mux boardKV-27V20
Mux board RGB termination (R1, R2, R3)75Ω
Mux board RGB inline resistors (R4, R5, R6)330Ω
Mux board Audio LR (R7, R8)1kΩ
Mux board blanking diode (R9)1N4148
Mux board blanking ground resistor (R10)open
Mux board blanking resistor (R11)470Ω
Mux board transistor base resistor (R12)1kΩ
Mux board transistor (Q1)PN2222A

Compatible mux boards:

Buy your RGB mux board kit

It is important to note that the blanking ground resistor (R10) is necessary to prevent strange black backgrounds from appearing on the KV-27S22 OSD text.

Picture of RGB mux rev B board img

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OSD mux overlay

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One thing to note about the OSD overlay on top of the RGB image is that it appears sharp on darker screens, but on lighter screens, some streaking is noticeable. This issue only affects the OSD. By adjusting the inline resistors, I managed to reduce the streaking slightly, but I suspect the best solution might involve using diodes in the OSD path. However, this would add complexity to the mod without providing significant benefits. It's also possible that this issue is specific to this particular set.

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Games & Pattern

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Set

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Pictures

Photos by Suntharopen in new window

After years of assuming the circular jailbar issue was a CRT design flaw, finally discovered it was actually caused by the standard 28 AWG IDC ribbon cable. Switching to a thicker 26 AWG cable completely eliminated the interference.

KV-27V20 - This picture pretty much sums up the issue, you can clearly see the annoying circular jailbar on the left side.
This picture pretty much sums up the issue, you can clearly see the annoying circular jailbar on the left side.
KV-27V20 - I decided to compare a standard IDC ribbon cable, which typically uses 28 AWG wire, with a custom IDC ribbon ca...
I decided to compare a standard IDC ribbon cable, which typically uses 28 AWG wire, with a custom IDC ribbon cable I built using 26 AWG, 6-core wires. AWG refers to the thickness of the wire — a lower number indicates a thicker conductor. This measurement applies to the internal copper or metal core, not the outer insulation layer. Both types of IDC ribbon cables use 7-strand wires, but each strand in the 26 AWG cable is thicker than those in the 28 AWG version. I think this background detail is important to understand the comparison.
KV-27V20 - In this picture, you can see how I connected the R, G, B, and blanking wires to perform the comparison test. Tw...
In this picture, you can see how I connected the R, G, B, and blanking wires to perform the comparison test. Two sets of wires are shown — one from my custom cable and the other from the standard IDC ribbon cable.
KV-27V20 - I ran several tests, but this screen captured the issue most clearly. With the standard ribbon cable (28 AWG),...
I ran several tests, but this screen captured the issue most clearly. With the standard ribbon cable (28 AWG), the circular bar is especially noticeable on the above color shade.
KV-27V20 - When I switched to my custom 26 AWG cable, the circular bar completely disappeared.
When I switched to my custom 26 AWG cable, the circular bar completely disappeared.
KV-27V20 - I didn’t immediately conclude that the 28 AWG cable was the problem. I tested several mux adapters (1.3B, 1.3C,...
I didn’t immediately conclude that the 28 AWG cable was the problem. I tested several mux adapters (1.3B, 1.3C, 1.4B, 1.4C) and even tried adjusting using a custom RGB tuner with different resistance values, but none of these changes made any difference. This ruled out the mux board as the source of the issue. I then examined the ribbon cables more closely, paying attention to how they were crimped, but found no obvious overlaps or faults.
KV-27V20 - You can see the zigzag pattern in which the cables are crimped, ensuring that each metal contact grips only a s...
You can see the zigzag pattern in which the cables are crimped, ensuring that each metal contact grips only a single wire and maintains sufficient clearance from the neighboring wires.
KV-27V20 - I found a 3M-made ribbon cable with 26 AWG wires from Digi-Key. It wasn’t as flexible as my standard ribbon cab...
I found a 3M-made ribbon cable with 26 AWG wires from Digi-Key. It wasn’t as flexible as my standard ribbon cable and was noticeably more expensive — but I had a feeling it would get the job done!
KV-27V20 - R, G, B, blanking, ground wired using the 3M ribbon cable.
R, G, B, blanking, ground wired using the 3M ribbon cable.
KV-27V20 - Another picture of R, G, B, blanking and ground wire.
Another picture of R, G, B, blanking and ground wire.
KV-27V20 - Sync (yellow), s-video detect (organge) and audio left (white) and audio right (grey) wires.
Sync (yellow), s-video detect (organge) and audio left (white) and audio right (grey) wires.
KV-27V20 - After wiring everything up, the circular band was completely gone.
After wiring everything up, the circular band was completely gone.
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Photos by Michael Lopezopen in new window

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Reference Photos

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See more photos and contributions →open in new window

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