Tag: PCB

Following on from the viewfinder teardown, here’s the rest of the camera. This unit dates back to 1980, and is made almost exclusively of cast aluminium. Very little plastic has been used here & only for the bits that the user comes into contact with. This camera is based around the Sony Trinicon camera tube system, technology dating back before CCDs. There aren’t many controls on this side of the camera, only the record button, which is hidden behind the camera handgrip.

The other side of the camera has most of the controls for the picture.

The image controls inclue auto / manual iris, white balance & colour balance.

Sharpness & fader controls are on the back of the camera, along with the umbilical cable which would have connected to a Betamax recorder.

The lens on this camera is massive, at least a kilo of optical glass. Focus control is manual, with both auto & manual zoom control.

The Zoom controls are on top of the grip, with a button to the rear of the control which I have no idea about. The internal belts are a bit rotted with age so the zoom function doesn’t work great.

After removing the side covers, the two large PCBs become visible. These units are absolutely packed with electronics. On this side is the Trinicon tube control board, generating all the high voltages for electron beam acceleration, focus & electrostatic deflection of the beam. There’s around 500 volts knocking around on this board, with some rather specialised hybrid modules doing all the high voltage magic.

The other side of the camera has the video process board, which performs all the colour separation of the video signal from the tube, processes the resulting signals into a composite video signal, and finally sends it down the umbilical.

Removing some of the remaining covers exposes the bare video controls, and a small PCB just underneath covered in trimpots to set factory levels.

The white balance is partially electronic & partially mechanical. This lever actuates a filter inside the lens assrembly.

A DIN connector offers remote control ability. The large loom of wires disappearing off to the right is dealing with the zoom mechanism & the onboard microphone amplifier. Just under the DIN connector hides the system power supply, inside a soldered can. The can under the white tape is the head end amplifier for the Trinicon video tube.

Hiding in the centre of the camera inside the casting is the Trinicon tube assembly itself. The label can just be seen here.

As is typical of 1980’s electronic design, the main boards swing down & are designed to slot into the base casting folded out for repairs. Internally the unit is a rat’s nest of wiring loom. There’s also another shielding can in here nestled between the boards – this is the video sync generator circuit.

The other side gives a better view of the video sync generator can. I’ll dive into the individual modules later on.

Under the remaining side cover is the zoom assembly & microphone amplifier board. More massive wiring loom hides within.

The video sync generator is pretty sparse inside, just a large Sony CX773 Sync Generator IC, with a pair of crystals. There are a couple of adjustments in here for video sync frequencies.

Removed from it’s shielding can, here is the head end amplifier for the Trinicon tube. This very sensitive JFET input amplifier feeds into the main video process board.

The Trinicon tube target connects to this input transformer on the front of the amplifier board.

The internal white balance controls are on this small PCB, mounted under the user-accessible controls.

Here’s the main control board responsible for the Trinicon tube & exposure control. Down near the front is the auto-iris circuit, nearer the centre is timing control & at the top is the high voltage power supply & deflection generator ICs.

Here’s the high voltage section, the main transformer at right generating the voltages required to drive the video tube. The large orange hybrids here are a pair of BX369 high-voltage sawtooth generators that create the deflection waveforms for the tube. The other large hybrid is a BX382 Fader Control.

The other large board contains all the video process circuitry, all analogue of course. There are a lot of manual adjustment pots on this board.

After removing the lens assembly, the tube assembly is visible inside the barrel casting. Not much to see yet, just the IR filter assembly.

Here’s the unit removed from the camera. Unfortunately this tube is dead – it shows a lot of target burn on the resulting image, and very bad ghosting on what poor image there is. The Trinicon tube itself is encased in the focus coil assembly, the windings of which are hidden under the shielding.

The IR filter is locked into the front of the tube, on a bayonet fitting. The twin target wires are running off to the left, where they would connect to the head end amplifier.

After removing the IR filter glass, the Trinicon tube itself is removed from the focus coil assembly. There’s an electron gun at the rear of the tube, like all CRTs, although this one works in reverse – sensing an image projected on the front instead of generating one.

It’s a little difficult to see, but the electrostatic deflection electrodes in this tube are created from the aluminium flashing on the inside of the glass, in a zig-zag pattern. The interleaving electrodes are connected to base pins by spring contacts at the electron gun end of the tube.

The electron gun is mostly hidden by the getter flash & the deflection electrodes, but the cathode can is visible through the glass, along with the spring contacts that make a connection to the deflection electrodes. This is also a very short gun – it doesn’t extend more than about 5mm into the deflection zone. The rest of the tube up to the target is empty space.

Finally, here’s the target end of the tube. I’m not sure how the wires are attached to the terminals – it certainly isn’t solder, maybe conductive adhesive?
It uses a vertically striped RGB colour filter over the faceplate of an otherwise standard Vidicon imaging tube to segment the scan into corresponding red, green and blue segments. It is used mostly in low-end consumer cameras, though Sony also used it in some moderate cost professional cameras in the 1980s.
Although the idea of using colour stripe filters over the target was not new, the Trinicon was the only tube to use the primary RGB colours. This necessitated an additional electrode buried in the target to detect where the scanning electron beam was relative to the stripe filter. Previous colour stripe systems had used colours where the colour circuitry was able to separate the colours purely from the relative amplitudes of the signals. As a result, the Trinicon featured a larger dynamic range of operation.