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Sony HVF-2000P Viewfinder Teardown & Composite Video Hack

Rating Plate
Rating Plate

Well, it’s time for another viewfinder hack! I’ve been after one of these for a while, this is from an early 1980’s era Sony Trinicon camera, and instead of the tiny ½” round CRT display, these have a 1.5″ square CRT – a Matsushita 40CB4. Luckily I managed to score a pair of these from eBay for very little money. Update: The second camera’s viewfinder module turned out to have a dead flyback transformer, but at least I have a good spare CRT & the rest of the support components. More to come later on the teardown of the camera itself.

Mirror & Eyecup Assembly
Mirror & Eyecup Assembly

The eyecup assembly with the magnifying lens & turning mirror is easy to remove, with clips & a single screw holding it onto the CRT holder sticking out of the side of the main casing.

Top Cover Removed
Top Cover Removed

Removing some screws around the case allows the top cover to be removed, revealing the electronics. There’s certainly more in here than the later camera viewfinders, in this unit there are two boards slotted together with a board-to-board interconnect at the bottom. The CRT is at the top of the photo, hiding inside the plastic housing & deflection yoke assembly.

Bare PCBs & CRT
Bare PCBs & CRT

Here’s the CRT & one of the control boards removed from the case, having been stripped of the heatshrink tube that held the final anode lead in place. Just like on larger CRTs, this viewfinder has the final anode on a cavity connector fused into the bell, instead of being led out to a pin on the base. This is probably due to the much higher anode voltage of 5kV, a big jump from the 2kV on the ½” round tubes.

40CB4 CRT Label
40CB4 CRT Label

Yup, it’s definitely the elusive 40CB4. Apparently these CRTs are still manufactured to this day for professional camera viewfinders, as the resolution of this small vacuum tube is still better than similarly sized modern tech such as LCDs or OLEDs. The phosphor used is type P4 – ZnS:Ag+(Zn,Cd)S:Ag, with an aluminized overcoat.

Bare 40CB4 CRT
Bare 40CB4 CRT

After the base connector & deflection yoke are removed from the tube, the very long neck can be seen, this long glass neck apparently giving better focus & resolution than the stubbier tubes.

Electron Gun
Electron Gun

The electron gun is the usual single unit as usually found in monochrome tubes.

Deflection Board
Deflection Board

The bottom board in the assembly has all the control circuitry for the CRT, including the HA11244 deflection IC, composite sync separator & vertical deflection drive circuit. There are also circuits here to display a video waveform on the CRT, along with iris & white balance markers.

Horizontal Board
Horizontal Board

The other board has the horizontal drive circuitry, along with the video input amplifier. Despite the attempt to miniaturize the entire assembly, these are still well packed boards. Some of the resistors & diodes are bussed together in custom SIL hybrid modules to save PCB space. Like all the other CRT viewfinders, these units are meant for viewing via a mirror – the horizontal deflection coil connections need to be reversed to show a correct image without the mirror. The Red & Blue wires to the yoke need to be swapped here.

Flyback Transformer
Flyback Transformer

The horizontal board on this unit also supports the flyback transformer, which is massive compared to the other viewfinder circuits. Biasing, focus & filament supplies for the CRT are also derived from this transformer, via auxiliary windings.

Boards Connected
Boards Connected

The boards slot together in the centre to form the fully operational circuit.

Video Input
Video Input

Out of the 3 plugs emerging from the cable feeding the viiewfinder, only this one is important, on the horizontal drive board. Black is ground, Brown +8.5v & red is composite video input. There’s also a resistor tied into the positive rail to the video input pin, which pulls it high to 8.5v – this is R1 right next to this connector. Desolder this 22K resistor to help protect anything feeding a signal into the unit, like a RPi, it’s not needed for normal operation.

Fallout!
Fallout!

As usual for a CRT post, the Fallout loading screen on the display. The picture quality isn’t as good as it should be, probably due to the noisy buck-converter I have rigged up for testing. If it doesn’t get better with a linear regulator, I’ll start replacing the 39 year old electrolytic capacitors. Current draw is 130mA at 7.5v. Schematics for this unit & the CRT datasheet are available below:



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Panasonic NV-M5 CRT Viewfinder Hack

Viewfinder Circuits
Viewfinder Circuits

 

The old Panasonic NV-M5 has the standard for the time CRT based viewfinder assembly, which will happily take a composite video signal from an external source.

This viewfinder has many more connections than I would have expected, as it has an input for the iris signal, which places a movable marker on the edge of the display. This unit also has a pair of outputs for the vertical & horizontal deflection signals, I imagine for sync, but I’ve never seen these signals as an output on a viewfinder before.

EVF Schematic
EVF Schematic

Luckily I managed to get a service manual for the camera with a full schematic.
This unit takes a 5v input, as opposed to the 8-12v inputs on previous cameras, so watch out for this! There’s also no reverse polarity protection either.

Pins
Pins

Making the iris marker vanish from the screen is easy, just put a solder bridge between pins 15 & 16 of the drive IC. The important pins on the interface connector are as follows:

Pin 3: GND
Pin 4: Video Input
Pin 5: Video GND
Pins 6: +5v Supply

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17mm µMonitor

I’ve had a couple of viewfinder CRT modules for a while, & haven’t done much with them, so I decided to make a very small B&W monitor.

CRT
CRT

I ordered a small transparent ABS box when I made a large order with Farnell, that turned out to be just about the perfect size for the project! The CRT & PCB barely fit into the space. The face of the CRT itself is about 17mm across.

Module Installed
Module Installed

Here’s the main PCB & tube fully installed into the case. Barely enough room for a regulator left over!
Power is provided by a simple LM7809 IC to take a standard 12v input.

Module Rear
Module Rear

Rear of the case, showing the fit of the control board.

Connections
Connections

Here’s the back of the monitor, with the DC input jack & a 3.5mm 4-pole jack for audio & video. This allows simple connection to many devices, including the one I’ll use the most – the Raspberry Pi.

Completed
Completed

Completed monitor. Audio is handled by a very small 20mm speaker, currently mounted just below the CRT face.
Current draw from a 13.8v supply is 117mA.