This mini CRT came from a JVC GR-AX7EG (GY) JVC Video Movie camera that I got at a flea market. It does power on and shows an image 🙂
The blog post will contain mostly images, with few comments here and there.
It was very fast to reach the CRT holder piece without having to dismantle the whole camera first. Refreshingly, the whole camera can be taken apart using only a 1.2x40mm Philips head screwdriver.
It seemed the CRT will easy to control as there are only 5 wires that are coming out of the EV unit, and they are colored. I guessed correctly for Red/Black (8V/GND) but not for the yellow for Video Composite input. The Video In (Composite) is the White cable.
Although the goal was to get inside the EV unit to see the CRT, I decided to continue dismantling the camera just out of curiosity. Found no less than 7 boards connected at 90 degrees, with copious amounts of connectors to keep the whole thing together! I have even taken a 3D Image – an animated GIF:
While taking the camera apart, I could not help noticing few bodged capacitors. Nothing is perfect.
One of the reasons for taking the camera apart was to also recuperate one of the connectors (or more) so that it would be easier to power up the CRT unit without having to cut any wires.
Thus, I had to bring out the Heat Gun to desolder some of these connectors. I needed at least a 5 pin ones. I also found a nice 4433619 Hz quartz that I decided to keep. To try to not deform the connectors, I heated mostly the back of the board, only switching to heat the connectors directly just to nudge them away.
The outcome of the whole procedure:
Finally, it was the time to open the Electronic Viewfinder and see what is inside.
When having a closer look at the CRT, I noticed a little spec, but I didn’t know if is permanent or if it can be removed. It was very easily removed with some Isopropyl alcohol.
I discovered a CRT model called Citizen 2400-36 and that the board is powered by AN2512S, an Electronic Viewfinder Driver. I went for the Red/Black as VCC/GND and by trial and error, discovered that the Video IN signal is the White cable (the middle one on the connector):
Time to put it to test. Initially, I’ve tried powering it with 5V, but the image was rolling badly. Since I don’t have 8V available, I decided to then power it with 7.5V. This stabilized the things as you can see on the left image below. Powering it with 9V created a sharper image but with stronger ghosting, as you can see on the right.
I should try powering it with 8V in the future, however, lack of space made me reluctant to go fetch and install the bigger power supply, so maybe I should create a small power supply with a 12V wall wart with a ready made buck converter.
I decided to try to record a small video of Raspberry PI 3B+ booting + me playing Manic Miner (in Fuse Emulator) over VNC – as it was impossible to discern / play directly by looking at the CRT.
So the CRT is functional and no overscan settings are needed. This little CRT flickers too using
sdtv_mode=2, but flicker goes away with
sdtv_mode=18 (progressive PAL).
One interesting thing I found was an RGB sensor with 10 pins – but I have no clue what part it is. I did find the camera service manual online, and there is a schematic on how the CPU interacts with the sensor, but I had no time to play with it:
I have however preserved it for when I have more time.
Update (4 Sept 2021)
I decided to go back and test this mini CRT once I had the adjustable power supply installed, and I can’t believe how sharp it became once fed the correct voltage. In fact, adjusting the input voltage is like tuning the focus! The sharpest I was able to get it was at 8.24V. The text is discernible using a macro lens (Canon 100mm Macro) even with
sdtv_mode = 18:
I had to reply Manic Miner to enjoy the sharpness and not only 🙂 the difference is amazing compared to the previous video. Again, shot with the macro lens at its minimum working distance (1:1 true macro) and with a 1.6x crop factor camera (Canon M50):
Another fun mini CRT!