Adapting an old CRT Viewfinder ( 9.3 V DC / 2.7W )

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nickhess

Joined Dec 9, 2018
4
Quarantine project: Adapting a Sony BFV-20W viewfinder

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As a cinematographer, I've always really felt most comfortable shooting with a viewfinder. However modern electronic viewfinders all exist in the "prohibitively expensive" class of filmmaking equipment. But I own a couple of older cameras with black and white CRT viewfinders which have always been more than comfortable and capable. SO I did a little digging and turns out those little CRT's are being adapted here and there to run like little monitors.

There were some doubts at first, some questions needed answers,

"can I find an older viewfinder capable of 16:9?"
"how sharp/pixel-dense could I expect a little monitor to be?"
"can I go for color or is that a stretch?"
Fast forward and I found the sony BFW-20W for a not insignificant sum but enough to justify it. Plus this just seemed like a fun challenge for the time being as well as an excuse to learn some electronics. I've been watching videos like bigclivedotcom and 12voltsvids for a while but I'm a complete beginner, I could use some help.

The Sony BFW - 20W ( manual )
Specs from the listing
listing specs
Specs from original manual
Screen Shot 2020-05-13 at 11.18.17 AM.png
From what I understand so far, converting the right signal wire to a standard RCA type connecter should work fine and shouldn't be too complicated. It's the power requirements that have me looking for help. I noticed a discrepancy between the listing (2.7 W) and the manual's wattage (2.3 W) but the voltage on both remains 9.3 v .

From what I understand, I cannot overshoot or undershoot that 9.3 v number or things get dangerous. I've just had a little trouble finding the information about how to go from a 12v dc source to a 9.3v dc connection.

Because this viewfinder seems to have a higher than the typical power requirement for these littles CRT's, I think I can't reference a lot of the videos out there. Wherein USB is the main power delivery method. Instead, I'm intending to use something like this: Power Tap D Tap to 2.1 DC 12v Screen Shot 2020-05-13 at 11.03.37 AM.png

which will be attached to a battery plate with this description:

Screen Shot 2020-05-13 at 11.03.58 AM.png

so that's where I am so far, let me know if I can provide any more info.

I really appreciate any and all help. Completely new to practical electronic stuff so I invite all feedback and ideas

Thanks in advance!
-Nick
 
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Just clip the pins to the wires red will be 9v+ u can just use a 5v USB cable to power it will be enough. In most viewfinders the orange cable is - and the pink one video in. Could varie. Just put 5v+ to red and touch the minus to the different cables till u get the right connection and it turns on. Than take the video - outer plug and also connect it to the USB cables ground. Take the + from the video cable and touch all other cables till u find the right one and the picture kicks in.
 

MisterBill2

Joined Jan 23, 2018
8,806
Just clip the pins to the wires red will be 9v+ u can just use a 5v USB cable to power it will be enough. In most viewfinders the orange cable is - and the pink one video in. Could varie. Just put 5v+ to red and touch the minus to the different cables till u get the right connection and it turns on. Than take the video - outer plug and also connect it to the USB cables ground. Take the + from the video cable and touch all other cables till u find the right one and the picture kicks in.
The random probing seems likely to convert a functioning viewfinder to a piece of scrap. So the challenge will be to discover the actual connections to the device. That may be possible if you are either able to open and examine either the camera it was intended to work with or the viewfinder itself. But examining a service manual would be best. As for providing the 9.3 volts, a standard 9 volt regulator IC , (LM7809) can handle the task quite well.
There seems to be the presumption that the video format is NTSC video, which may or not be true. And given that the view finder is intended to work with one camera model only, it may be that the vertical and horizontal synch signals arrive separately, in which case it will not serve your purpose.
Can the TS tell us oh many pins there are on that connector?
 
I also just tried different cable connections till I find the right ones. It started smelling so I unplugged it tried another connection and it turned on. But on almost every single viewfinder red is + orange is minus for power cable and - for the video and pink is video in
 
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