Component modding CRT TV - EEPROM HACKING

[Zebidee]

Time to talk about hacking the TV's EEPROMs. Here it is, "24C08":





The TV's EEPROM is very much like a computer's BIOS. It stores vital data that is used by the jungle IC to operate the TV, including all the service mode data. TV will not operate without it.

Accessing the service mode can be risky because you might set something that you shouldn't have, and suddenly the TV won't work! Or perhaps you might have a corrupted EEPROM. Both of these things have happened to me! If these things happen the EEPROM may need to be replaced, or at least reprogrammed.

So I bought myself a cheap EEPROM programmer imaginatively called "CH341a", which works with the EEPROMs used in these China TVs (24C08). The unit comes as a kit with some useful accessories, including a clip that can piggyback onto the smaller surface mount SOP-8 ICs. Some pics below so you can see how it attaches.


   



Unfortunately the China TVs use larger DIP-8 chips, the clip cannot be used with them, so the EEPROM must be desoldered from the PCB so that you can slot the legs directly into the programmer. Very inconvenient. I worry about damaging the traces, and after doing this a few times I am now over it.

Working on these latest TVs, I noticed something different about them - a 4-pin connector that wasn't present on the ones I modded 3 years ago. The traces go to the EEPROM pins 5,6,7,8. This corresponds to 5v, GND, and two data pins. the other pins 1,2,3,4 are all connected to GND. Below are some pics, on the left is the earlier TV, note that the connector is missing.


 


I already have the right connectors in that kit I mentioned earlier, So I added a male connector to that vacant spot on the older TV. I also made myself a short cable with two female ends, using red (5v) black (GND) and green/white for the data wires.  Then, carefully considering the correct orientation for the pins and cable, I slotted the 4P connector onto the CH341.


 


Now time to test. Success! Hurrah! Now I don't have to desolder the IC every time I want to reprogram it, or to just make a backup.





For fun, I hacked the vendor name in the EEPROM - now it is a GreenAntz TV!

[delta88]

What else would you do in the menu?

[Zebidee]

What else would you do in the menu?

Thanks for the question.

I'm planning another post soon covering key points of the service menu. This will include getting the colour balance and intensity right, maximising sharpness (largely by setting related values to zero/low) and a few other things. Will be back after this short break 

[nitrogen_widget]

well, this is neat.

[aarkay14]

What else would you do in the menu?

Thanks for the question.

I'm planning another post soon covering key points of the service menu. This will include getting the colour balance and intensity right, maximising sharpness (largely by setting related values to zero/low) and a few other things. Will be back after this short break 

Heyy Zebidee! Please let us know if you have posted more improvement or mods about this China CRT TV board?

[Zebidee]

Hi!

You might check the main China TV thread - There's been some more activity there.

I've done less on EEPROM hacking than I anticipated back in March. What I really need is to learn more about microcontrollers, and stuff like using Arduinos and logic controllers to intercept the I2C and UART communications. Fascinating as all this is by itself, it would be useful for modding certain TVs for which you must enable RGB (or YUV) by flicking a firmware switch, that is factory set only, not accessible via service mode.

I ordered some bits and pieces, they have even arrived, but it'll probably be a little while before I go further into that rabbit hole. I've had other priorities like surgery and recovery related stuff. I've also needed to spend some time on GreenAntz building and development.

In the meantime, I've posted up a couple more TV mod/repair logs for you to enjoy, for a TEAC (component) and a JVC (RGB).