Found this mini CRT inside another JVC GR-M7PRO / JVC GR-M7EG that I seem to have bought without checking I had already bought one.
This post will be shorter, not going into all the details like the initial one – but I still wanted to take it apart just to see if there are at least differences.
Camera overview
As opposed to the initial one, this camera was sold in a bag and had an additional accessory, the video light. And it also seems that the owner was passionate about film photography (unless the seller just added the roll of films just to get rid of them).
A brief camera overview:
Inside the camera
Opening up the JVC GR-M7PRO / JVC GR-M7EG was easy this time because I documented well the first one. I was curious to see if the camera has the same bodges as the first one, and yes it does! Seems exactly the same ones.
The date code is December 1992:
Electronic View Finder Unit
The EVF unit is identical to the initial camera – the same mini CRT (Citizen 2400-38) and same BA7149F Driver IC:
The same label / model MO1KKD70WB is present on this CRT:
After recuperating the connector plug and using Vcc, GND and VIDEO IN on the RED / Brown / White wires accordingly (as identified on the previous camera), the CRT worked, but poorly. The image looked negative, washed out, and with lines across the screen:
Since in the other model I had to swap the capacitors since they were leaky, I decided to have a look on this one too – since … they probably used the same capacitors too. And … indeed. One of the 10μF @ 16V poured its contents out:
Since I already had some spares, I decided to salvage the driver board. I removed all the SMD capacitors (the two standard ones measured fine, I did not touch) by cutting them then lifting each remaining lead. Cleaned up the board and soldered in the new ones:
Results
The image was finally correct and no more diagonal lines. Brightness was very high though, to obtain an acceptable image, I had fiddle with the two pots on the underside of the circuit board.
Temperatures
While having the board up side down (to have access to the potentiometers for Brightness and Contrast), I noticed that the Driver IC was rather hot, the BA7149F was running at almost 60C. I guess a voltage regulator on board was also running hot, at 46C:
I never payed attention if the Driver ICs get hot – since usually they are small and when I do the tests, I do not manipulate the boards due to the high voltages found on them. So it is an interesting find, will keep an eye on other cameras that I will take apart.
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