Samsung TXH1973 CRT RGB mod
This tutorial covers the RGB mod for the Samsung TXH1973 CRT TV. Instructions should be similar for the below CRTs. This CRT has some special instructions to improve image contrast and brightness.
- Samsung TXH1370
- Samsung TXH1372
- Samsung TXH1373
- Samsung TXH1386
- Samsung TXH1970
- Samsung TXH1972
- Samsung TXH1973
- Samsung TXH1986
Please also review the RGB mod for TXD1973, as this mod is very similar to it.
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.
Plan of attack
Sometimes it is nice to know the theory behind the mod. I have put this on a separate page. This shows how the various resistor values are calculated.
- Manufactured: 1999 September, SUWON, KOREA
- NTSC, 60 Hz, 65 Watts
- Chassis: K15A
- Tube: Samsung A48KRD82X (This tube was used in swapping K4600 tube)
- TA1286N Jungle Chip
It's hard to find the service manual for this Samsung CRT TV. I had to stitch together this scehmatic diagram from multiple images. Although not perfect, this should be sufficient to perform the RGB mod.
- Samsung TXH Service Manual
- Toshiba TA1282N Jungle Chip Datasheet
- Toshiba TA1286N Jungle Chip Datasheet
Prototyping the mod
I reviewed the schematics and came up with the below plan.
The main board is fairly compact. The main board also comes off the CRT completely, if all the wires are carefully disconnected. This makes it easier to perform the mod. Please make sure to remember or take photos as you disassemble, so that you can reassemble the way it was prior to disassembly.
Simplified circuit diagram that was created to perform this mod. Check the RGB theory page to find more details around how to calculate the resistor values.
Increasing RGB termination resistance
This CRT uses a Toshiba chroma chip that benefits from increased RGB termination resistance. Using 220Ω instead of 75Ω gives the right level of contrast and brightness. This made a significant difference in image quality. Image went from slightly darker, washed out to a vibrant desirable image. This fix applies to the following Toshiba jungle chips. Might also work for other jungle chips, where the RGB signals go through only RGB cutoff block.
- Toshiba TA1286N
- Toshbia TA1242N
I also made an apparatus to sweep through multiple termination values. 220Ω termination seems to hold correct. Not entirely sure why this works, but it works.
Performing the mod
This CRT was fairly straightforward to mod. You can perform the mod on the board itself and make use of the stock SCART port.
Using the stock SCART port
This CRT comes with a stock AV port that has a SCART cutout. I wanted to utilize this to give this CRT a clean look. Here is how it looks when finished.
You will soon realize this is not as easy as it looks. There isn't that much space on the board to accomodate a SCART plug and the necessary wiring.
How was this achieved?
Remove the existing A/V connector.
Move this resistor to the bottom of the board to make some space. Compared to TXD1973, I only had to move this one resistor to the bottom of the board.
Create a flexible pcb that grouned the relevant pins together and allowed for routing of the wires. Flexible pcb was used, because there is not much clearance and you want this to be flexible. I'll let the pictures below explain the process.
Prepare the ribbon cable. Make your own flex ribbon board at OSHPark or buy it here
Flush cut the SCART pins and solder to the flexible pcb.
Solder the SCART connector and cable to it. I used an older printer cable.
Insulate the SCART adapter with some electrical tape
Insulate the main chassis
Now place this entiresetup on the board by carefully sliding the flex cable under the large capacitor. A little finesse and you should have the SCART connector with ribbon cable placed in the existing port.
SCART side view
This is the picture of the board before the mod. Areas of interest are highlighted in green.
Removed resistors R204, R205, R206. Used the existing vias to connect R, G, B, blanking and ground. RGB wires needs a triangle formed between 75Ω and 1.2 kΩ. 75Ω goes to the grounding side. 1.2kΩ faces the 0.1uF capacitors. Below picture is from TXD1973 (idea is the same)
Blanking setup needs a bit more work as we want to make sure 5V only goes in one direction. First remove the below blanking trace. We are going to route this through the diode (see schematics)
Replace resistor R919 (8.2kΩ) with 6.8kΩ resistor. Setup the diode as seen in the below picture. You will have to squeeze one end of the diode and the resistor through the single via. Pay attention to the direction of the diode.
Blanking wire from the SCART connector also needs a diode inline. Again, pay attention to the direction of the diode.
Connect CSYNC to this location. Below picture is from TXD1973 (idea is the same)
Use heat shrink tubes to prevent shorting.
All wired up!
Connector will be a bit wobbly. However, once the back cover is put back in place and closed up with screws, connector should stay strong. Please be mindful not to push the connector in too tightly and break the connector. Understand the limitations of this mod and possibly use an extension not to damage the SCART connector. SCART closeup. Back cover holds connector in place.
Standby mode, using the remote
POWER should bring you to the service menu.
Default settings for this CRT
HS - Horizontal Shift was adjusted to center the RGB image
SNES - Contra III: The Alien Wars
SNES - Super Mario World
SNES - Mega Man X
There is a little shadow that was noticed. You can see it near green/pink transition. As of this writing, there was no cure found.