Having worked with the DT-V100CG, I stumbled upon this JVC TM-1011G that looked at lot like it, but without the option for the add-on card, thus only two composite inputs. Instead of the add-on, it had a 12V DC option installed, but also integrated audio, which I thought was cool, given I had to add this to the DT-V100CG. Now I thought the RGB mod would be similar to the DT-V100CG, and hey! It was. The board is somewhat different, but still sports the same TA1276AN jungle IC. So with the experiences from the DT-V100CG I started to RGB mod this.
First of all, I didn’t want to lose composite availability, so we need to get a pulldown resistor in between pin 32 (YS2) and GND. On both this and the DT-V100CG pin 32 is connected straight to GND, so this needs to be lifted. Unfortunately it’s connected to a bigass GND plane, so it takes some heat and patience to get up. When it is up, I inserted a 10 KOhm resistor in the original hole and tied it to the pin. Now when 5V is inserted to the pin, it changes to RGB, and when 5V is off, it’s composite.
RGB lines are connected to the RGB pins (35/RED, 34/GREEN, 33/BLUE), through the “normal” circuitry consisting of an attenuating resistor and then a 75 Ohm termination, along with a 100nF capacitor for DC bias (the RGB pins have a DC offset). Some (correctly) mention the ensuring that the attenuation resistor and the termination resistor should amount to 75 Ohm, instead of adding an attenuation resistor to 75 Ohm. Sync is injected at one of the composite BNC pins, so it is routed appropriately into the jungle. Since this monitor also has (mono)audio this is injected directly at the RCA pin for the same channel as the video (I chose input A for both).
Since I’ve modded a few sets, always use SCART, instead of always hacking some wires directly on to the “naked” SCART socket, I made a small PCB to attach to. This is because the circuit mentioned above is needed, and because I also always add some RCAs and a switch to route to audio out from SCART, instead of into the often rather mediocre, at best, speakers inside these monitors, and found it easier to gather all this on a single PCB. The board has space for resistors, capacitors, the SCART, stereo-to-mono mixing circuit, and the audio switch. It then has a row of through holes to add the wires to going into the monitor. The board can be found on OSHPark here.
Now, just as with the DT-V100CG, the monitors’ software kills RGB video by completely darkening RGB registers and so on. To fix this, the I2C communication from the monitors microcontroller to the TA1276AN must be intercepted and “tampered”. I do this with an Arduino board, which in this case ended up being an Arduino Mini Pro (5V version!). Now the deal is to isolate the TA1276ANs from the monitors I2C bus, and add in the Arduino listening on the same address as the TA1276AN, instead, thus getting the Arduino to act as the TA1276AN at least to the monitor MCU. The software library SoftI2CMaster then creates a new I2C bus, which then is routed to the TA1276AN. When the Arduino gets read and write requests, it forwards those to the TA1276AN, except for the ones that kills RGB. Also it will send contrast and brightness settings to appropriate RGB registers so this can be controlled from the panels buttons.
To isolate the TA1276AN, two resistors must be removed, R6612 and R6613. They are small SMD resistors next to the TA1276AN.
The “native” hardware I2C bus (also called TWI for Two Wire Interface) on the Arduino Pro (and Nano 3.0) are on pins A4 (SDA) and A5 (SCL). We need to connect these two pins to the system, either on the pads we removed the resistors from, on the ones away from the jungle, or on any of the other ICs also connected to the same bus. I chose the latter, and connected to IC6101. Pin 9 is SDA and Pin 10 is SCL. I then create the new I2C bus on D4 (SDA) and D5 (SCL), and connect them to the TA1276AN pin 27 (SDA) and pin 28 (SCL). On the Arduino I connect two pull-up resistors of 2.7K Ohm to VCC for pullups, one on D4 and one on D5.
There’s a 100R series termination resistor into the TA1276AN on both SDA and SCL (the two resistors partly covered by the black heat shrink in the picture below). These seem not completely essential, your mileage may vary, they wont hurt 🙂
The Arduino is then glued to the PCB with hotglue. Powering the Arduino is done with by taking 12V from the PCB and connecting that to the “raw” pin. The 12V is taken from the “T” connector pin 7. If I used a 5V from another source as direct VCC, it seemed it didn’t boot fast enough, and the monitor shuts off due to not being able to communicate to what it thinks is the TA1276AN. GND is of course also connected. I simply chose the nearest easily accessible point. The software for the Arduino can be found here.
All the wires are then connected to the SCART breakout board, for which I still need to find a place for, most likely some small 3D printed bracket thing…
With all connected, presto! RGB on this nice little monitor 🙂
Update
So I finished the bracket for the SCART breakout and besides the small mess with the print in one corner, I think it turned out pretty good. Find the 3D model here.
