composite video – Experimental Engineering

Posted on January 1, 2023January 8, 2023 by The Engineer — Leave a comment

JVC CV-F503PAL Viewfinder

It’s time for another CRT-based post! This time it’s a Matsushita 40CB4-based viewfinder from 1980. These came from JVC colour tube cameras, and are physically massive! I’ve already worked out the pinout on the multicore cable here & attached a usable connector.

There’s lots of information on the bottom label of this unit, including a notification in German that the X-Ray emission from the device is shielded, and the maximum CRT acceleration voltage is 8kV. This last point is a bit strange, since the 40CB4 datasheet states a maximum design voltage on the final anode of 6kV. I did measure the voltage at the anode cup, and it’s stable at 7.15kV!

Popping a couple of screws out & removing the enormous eye cup allows the top cover to come off. This unit is very tightly packed inside, with 3 PCBs! The magnifying lens (~45mm diameter) & mirror on the left enlarge & turn the image so the camera operator can see it. The CRT’s at the top, with a copper grounding band around the face.

The CRT face is neatly slotted into the plastic housing, with the tally LEDs to the right of it. The legends on the LEDs are naturally printed in reverse, since they’re intended for viewing through the mirror. The optical section is entirely spray painted black for better contrast & stray light control.

The other 5″ of the casing is packed with electronics to support the CRT. The bottom PCB even “wraps around” to the right, with copper staples connecting the boards together. The CRT tube itself is hiding inside the deflection yoke and under a foam pad at the top of the unit. It’s secured in place with a copper grounding strap wrapped around the face of the tube, and a spring. A single screw secures the strap to the case. This also provides a local earth for the outer Aquadag coating on the tube, which is the negative plate of the final anode smoothing capacitor. The other plate is formed by the coating on the inside of the CRT glass, and the dielectric is of course the glass itself.
The main anode wire snakes off from the flyback at bottom left to the anode cup at the top of the CRT, insulating the 7kV from everything else.

There aren’t many reasons to jack up the final anode voltage on a CRT, past the design voltage of the tube as JVC have done here. The only plausible one I could think of is to increase brightness of the image, but the Sony 4CB4-based units I have only run at around 3kV, and those are plenty bright enough! The downside here of course, is that with higher energy electrons and a brighter image, the phosphor of the CRT will wear out faster.
Increasing voltage also increases X-Ray emission, but even at the 8kV maximum, such X-Rays would be so weak as to not make it through the CRT faceplate glass, which is loaded with lead anyway.

There’s not much sense in yanking the tube out of this unit, it’s identical to the Sony one’s I’ve done in the past:

Slotted into a gap above the CRT is a large TO-220 2SD476 NPN transistor, this is part of the power circuit; it’s the series pass element regulating the input 12v down to 9v for all the remaining circuits. The aluminium sheet on the back provides some heatsinking as this part gets warm! Current draw of this unit with no video input is about 260mA.

Popping the CRT out allows a view of the Vertical & Power Board. This hosts the input linear voltage regulator, and the vertical output control circuitry. Hiding at the back on the right is a NEC µPC1031H2 Vertical Deflection Controller.

Separating the boards reveals the other two PCBs, the Video & Horizontal/HV boards. The bottom board takes care of the Horizontal output, and the lefthand board the video input, sync separation & amplification.

The Horizontal section is controlled by a Matsushita AN294 device. Unfortunately I haven’t been able to locate a datasheet for this one. The flyback transformer (Horizontal Output) is on the right, with another smaller transformer I don’t quite know the purpose of. Oddly, there’s no large switching transistor for the horizontal output stage – as the PCB notes the flyback as being a “HVM” this may in fact be more tightly integrated with some of the drive circuitry in the potting. There aren’t anywhere near as many pins on it as a usual CRT flyback has either.
This section also generates the other voltages required by the CRT – 2.8v for the filament, and ~80v & ~400v for the grids.

A closeup of the video board shows the relative simplicity. Only 4 transistors are doing all the video actions. There is relatively high voltage on here though – an 85v feed from the power supply which is the rail voltage for the video amplifier to the CRT cathode/G1.

There’s a few adjustments available on this unit, here are the Focus & Horizontal Frequency (Hold) pots. Amazingly, even though this unit is about 43 years old at the time of writing, the unit fired straight up when I applied power & a composite video signal, with no adjustments required at all!

Unfortunately there’s no service manual or schematics that I could find on the web for this or the camera it came from, but connections to make this unit work are very simple:

Wire Colour	Signal Name
YELLOW	+12V DC
BLACK	GND
Coax - Core	Composite Video 1v p-p
Coax - Shield	Composite Video GND

There’s another blogger who’s done this particular viewfinder, but they didn’t dig into the unit anywhere near as far as I usually do:

https://hex.ro/wp/blog/matsushita-40cb4-mini-crt/

This blog has a lot of CRT-based viewfinder teardowns, mainly from newer cameras. It’s an interesting read.

Datasheets for the important parts (the ones I could find!) below:

µPC1031H2 Vertical Deflection Controller Datasheet

1 file(s) 261.96 KB

Download

40CB4 CRT Datasheet

1 file(s) 1.42 MB

Download

2SD476 NPN Power Transistor Datasheet

1 file(s) 35.86 KB

Download

Posted on July 1, 2018October 16, 2019 by The Engineer — 2 Comments

Goodmans Quadro 902 Composite Video Mod

Here’s the CRT & it’s drive board removed from the main chassis. Nicely modular this unit, all the individual modules (radio, tape, TV), are separate. This is effectively a TV itself, all the tuner & IF section are onboard, unlike in other vintage units I’ve modified, where the tuner & IF has been on a separate board. There’s a 3-pin header bottom centre for the tuning potentiometer, and external antenna input jack. The internal coax for the built in antenna has been desoldered from the board here. here a the usual controls on the back for adjusting brightness, contrast & V Hold, all the other adjustments are trimmers on the PCB.
Unfortunately after 30+ years of storage, this didn’t work on first power up, neither of the oscillators for vertical or horizontal deflection would lock onto the incoming signal, but a couple of hours running seemed to improve things greatly. The numerous electrolytic capacitors in this unit were probably in need of some reforming after all this time, although out of all of them, only 21 are anything to do with the CRT itself.

Here’s the anode side of the unit, with the small flyback transformer. The rubber anode cap has become very hard with age, so I’ll replace this with a decent silicone one from another dead TV. The Horizontal Output Transistor (a 2SC2233 NPN type) & linearity coil are visible at the bottom right corner of the board. Unfortunately, the disgusting yellow glue has been used to secure some of the wiring & large electrolytics, this stuff tends to turn brown with age & become conductive, so it has to be removed. Doing this is a bit of a pain though. It’s still a little bit flexible in places, and rock hard in others. Soaking in acetone softens it up a little & makes it easier to detach from the components.

There’s little on the neck board apart from a few resistors, forming the limiting components for the video signal, and the focus divider of 1MΩ & 470KΩ feeding G3. No adjustable focus on this unit. There’s also a spark gap between the cathode line & ground, to limit the filament to cathode voltage. The flyback transformer is nestled into the heatsink used by the horizontal output transistor & a voltage regulator transistor.

The CRT is a Samsung Electron Devices 4ADC4, with a really wide deflection angle. It’s a fair bit shorter than the Chinese CRT I have which is just a little larger, with a neck tube very thin indeed for the overall tube size.
Unusually, while the filament voltage is derived from the flyback transformer as usual, it’s rectified into DC in this unit, passing through a 1Ω resistor before the filament connection. I measured 5.3v here. The glow from the filament is barely visible even in the dark.

The electron gun is the usual for a monochrome tube, with 7 pins on the seal end.

The electrodes here from left are Final Anode, G3 (Focus Grid), Accelerating Anode, G2 (Screen Grid), G1 (Control Grid). The cathode & filament are hidden inside G1. In operation there’s about 250v on G2, and about 80v on G3.

The chipset used here is all NEC, starting with a µPC1366C Video IF Processor, which receives the IF signal from the tuner module to the left. This IC outputs the standard composite signal, and a modulated sound signal.
This then splits off to a µPC1382C Sound IF Processor & Attenuator IC, which feeds the resulting sound through the two pin header at the right bottom edge of the board to the audio amplifier in the chassis.
The composite video signal is fed through a discrete video amplifier with a single 2SC2229 transistor before going to the CRT cathode.
The remaining IC is a µPC1379C Sync Signal Processor, containing the sync separator, this is generating the required waveforms to drive the CRT deflection systems from another tap off the composite video line.
From this chip I can assume the unit was built around 1986, since this is the only date code on any of the semiconductors. Besides these 3 ICs, the rest of the circuit is all discrete components, which are well-crammed into the small board space.
There are 5 trimmer potentiometers on the board here, I’ve managed to work out the functions of nearly all of them:

SVR1: IF Gain Adjust
SVR2: H. Hold
SVR3: V. Size
SVR4: B+ Voltage Adjust
SVR5: Tuner Frequency Alignment? It’s in series with the tuning potentiometer in the chassis.

The PCB bottom shows the curved track layout typical of a hand taped out board. The soldermask is starting to flake off in places due to age, and there a couple of bodge wires completing a few ground traces. Respinning a board in those days was an expensive deal! Surprisingly, after all this time I’ve found no significant drift in the fixed resistors, but the carbon track potentiometers are drifiting significantly – 10KΩ pots are measuring as low as 8KΩ out of circuit. These will have to be replaced with modern versions, since there are a couple in timing-sensitive places, like the vertical & horizontal oscillator circuits.

Here the anode cap has been replaced with a better silicone one from another TV. This should help keep the 6kV on the CRT from making an escape. This was an easy fix – pulling the contact fork out of the cap with it’s HT lead, desoldering the fork & refitting with the new cap in place.

Here I’ve replaced the important trimmers with new ones. Should help stabilize things a little.

Injecting a video signal is as easy as the other units. Pin 3 of the µPC1366C Video IF Processor is it’s output, so the track to Pin 3 is cut and a coax is soldered into place to feed in an external signal.

After hooking up a Raspberry Pi, we have display! Not bad after having stood idle for 30+ years.

Datasheets for the important ICs are available below:
[download id=”5690″]
[download id=”5693″]
[download id=”5696″]

Posted on November 22, 2016October 16, 2019 by The Engineer — 1 Comment

Panasonic NV-M5 CRT Viewfinder Hack

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.

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.

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

Posted on August 27, 2016August 17, 2016 by The Engineer — 2 Comments

Sony Watchman FD-280 Composite Video Hack

As with the previous Sony Watchman hack, injecting a composite video signal into this one is just as easy. I desoldered both the VIF/SIF IC & the digital tuner control (the tuner controller was still injecting it’s indicator into the video circuitry with the IF IC disconnected).

Composite video is on pin 18 of the Video IF IC, with the audio on Pin 13.

Posted on August 23, 2016August 15, 2016 by The Engineer — 1 Comment

Sony Watchman FD-20 Composite Video Hack

Hacking the Sony FD-20 to accept a composite input is easy – the tuner receives the RF transmission, produces an IF, this is then fed into IC201, a Mitsubishi M51364P Video IF Processor. The VIF IC then separates out the composite video signal, which is output on Pin 13 (in photo above, left side, 3rd pin from the top). The audio is separated out & sent via Pin 11 to the Audio IF processor.

In the above photo, the VIF IC has been removed from the board with hot air, as it was interfering with the signal if left in place. The RF tuner was also desoldered & removed. Unfortunately I managed to mangle a pad, which is the ground pin for the VIF IC. This isn’t much of an issue though, as an identical signal ground is available, just to the left of the IC.

The audio can be tapped into in a similar way, the circled pad in the centre of the photo marked SIF is the place, this is the output of the Audio IF processor to the audio amplifier. The Audio IF processor didn’t interfere with the injected signal, so it was left in place.

Posted on August 22, 2016October 16, 2019 by The Engineer — 6 Comments

Sony Watchman FD-20 Flat CRT TV Teardown

Here’s an oddity from the 1980’s – a CRT-based portable TV, with a very strangely shaped tube. Sony produced many types of flat CRTs back in the 80’s, with the electron gun at 90° to the curved phosphor screen.

The front panel has the display window, along with the tuning & volume indicators. Unfortunately since analogue TV transmissions have long been switched off, this unit no longer picks up any transmissions off the air, but it can be modified to accept a composite video input.

The back panel has the battery compartment & the tilt stand.

The certification label reveals this unit was manufactured in May 1984, 32 years ago!

Rated at 6v, ~2.1W this device uses surprisingly little power for something CRT based.

The battery holder is a little unique, this plastic frame holds 4 AA cells, for a 6v pack.

The battery holder slots into the back of the TV, there’s also an extra contact that the service manual mentions is for charging, so I assume a rechargeable 6v battery pack was also available.

Removing a pair of pin-spanner type screws allows the front glass & screen printed CRT surround to be removed. Not much more under here other than the pair of screws that retain the CRT in the front frame.

Here’s the back cover removed, after unscrewing some very small screws. As per usual with Sony gear, the electronics is extremely compacted, using many flat flex cables between the various PCBs. The main PCB is visible at the back, this has all the deflection circuitry, RF tuner, Video IF, Audio IF, video amplifier & composite circuitry.

Lifting up the main board reveals more PCBs – the high voltage section for the CRT with the flyback transformer, focus & brightness controls is on the left. The loudspeaker PCB is below this. The CRT electron gun is tucked in behind the flyback transformer, it’s socket being connected to the rest of the circuitry with a flat flex cable.

Here’s the back of the CRT, the phosphor screen is on the other side of the curved glass back. These tubes must require some additional deflection complexity, as the geometry will change as the beam scans across the screen. There’s a dynamic focus circuit on the schematics, along with extensive keystone adjustments.

Here’s the tube entirely extracted from the chassis. The EHT connection to the final anode is on the side of the tube bell, the curved phosphor screen is clearly visible. The one thing I can’t find in this CRT is a getter spot, so Sony may have a way of getting a pure enough vacuum that one isn’t required.

I’d expect the vertical deflection waveforms to be vastly different on this kind of CRT, due to the strange screen setup. Not much of a beam movement is required to move the spot from the top to the bottom of the screen.

No doubt to keep the isolation gaps large, all the high voltages are kept on a separate small PCB with the flyback transformer. This board generates the voltages for the electron gun filament, focus grid & the bias to set the beam current (brightness) as well.

Here the deflection yoke has been removed from the CRT, showing the very odd shape better. These tubes are constructed of 3 pieces of glass, the bell with electron gun, back glass with phosphor screen & front viewing window glass. All these components are joined with glass frit.

The electron gun in the neck looks to be pretty much standard, with all the usual electrodes.

Here’s a view from the very top of the CRT, the curve in the screen is very obvious here. The electron beam emerges from the bell at the back.

Here’s the full schematic of the entire TV, I extracted this from a service manual I managed to find online.

More to come on hacking this unit to accept a standard composite video input, from something such as a Raspberry Pi!

Posted on August 1, 2016July 21, 2016 by The Engineer — 1 Comment

Sky+ HD Set Top Box

Time for another teardown! I managed to fish this Sky+ box out of a skip, but to protect the guilty, all serial numbers have been removed.
These are pretty smart devices, with DVR capability on board.

There’s a lot of ports on these units, from RS-232 serial, POTS modem, eSATA, HDMI, USB, Ethernet, SCART, Optical, digital outputs & even composite video.

Removing the top plastic cover reveals the operation buttons & the built in WiFi adaptor, which is USB connected to the main logic board.

The PCB on the front of the chassis has all the indicators, and the IR Receiver for the remote.

Removing the top shield of the chassis reveals the innards. The PSU is on the top right, 500GB SATA disk drive in the bottom centre. The main logic PCB is top centre.

Here’s the main logic PCB. The massive heatsink in the middle is cooling the main SoC, below.

The main SoC in this unit is a Broadcom BCM7335 HD PVR Satellite System-On-Chip. It’s surrounded by it’s boot flash, a Spansion GL512P10FFCR1 512Mbit NOR device. It’s also got some DRAM around the left edge.

The smart card reader is on the PSU PCB, the controller here is an NXP TDA8024

The PSU itself is a pretty standard SMPS, so I won’t go too far into that particular bit. The logic PCB attaches to the large pin header on the left of the PSU, some of the analogue video outputs are also on this board.
There’s also a Microchip PIC16F726 microcontroller on this PCB, next to the pin header. Judging by the PCB traces, this handles everything on the user control panel.

Some local supplies are provided on the logic board for the main SoC, the IC in the centre here is an Allegro A92 DC-DC converter. I didn’t manage to find a datasheet for this one.

The RF front end for the satellite input is a Broadcom BCM3445 Low Noise Amplifier & Splitter, again not much info on this one.

The standard MAX232 is used for the serial interface. I imagine this is for diagnostics.

The POTS modem section is handled by a Si2457 System-Side device & Si3018 Line-Side device pair.

Posted on March 16, 2013April 22, 2013 by The Engineer — 3 Comments

Wearable Raspberry Pi Part 1

Here is the project I’m currently working on. A completely wearable computing platform based on the Raspberry Pi & the WiFi Pineapple.

Above can be seen the general overview of the current unit.

On the left:

Alfa AWUS036NHA USB High Power WiFi Network Interface
512MB Model B Raspberry Pi, 16GB SD card, running Raspbian & LXDE Desktop. Overclocked to 1GHz.

On the right:

WiFi Pineapple router board
USB 3G card.

The WiFi, Pineapple & 3G all have external antenna connections for a better signal & the whole unit locks onto the belt with a pair of clips.
The Raspberry Pi is using the composite video output to the 7″ LCD I am using, running at a resolution of 640×480. This gives a decent amount of desktop space while retaining readability of the display.

The case itself is a Pelican 1050 hard case, with it’s rubber lining removed. The belt clips are also a custom addition.

Here are the connections to the main unit, on the left is the main power connector, supplying +5v & +12v DC. The plug on the right is an 8-pin connection that carries two channels of video, mono audio & +12v power to the display.
Currently the only antenna fitted is the 3G.

Closeup of the connections for power, audio & video. The toggle switch is redundant & will soon be replaced with a 3.5mm stereo jack for headphones, as an alternative to the mono audio built into the display.

Current state of test. Here the unit is running, provided with an internet connection through the Pineapple’s 3G radio, funneled into the Pi via it’s ethernet connection.

Running on a car reversing camera monitor at 640×480 resolution. This works fairly well for the size of the monitor & the text is still large enough to be readable.

Stay tuned for Part 2 where I will build the power supply unit.

Posted on September 14, 2011October 16, 2019 by The Engineer — 10 Comments

Camcorder CRT Viewfinder

Here are the viewfinder electronics from a 1984 Hitachi VHS Movie VM-1200E Camcorder. These small CRT based displays accept composite video as input, plus 5-12v DC for power.

Here is the front face of the CRT, diameter is 0.5″.

Closeup view of the PCB, there are several adjustments & a pair of connectors. Socket in the upper left corner is the power/video input. Pinout is as follows:

Brown – GND
Red – Video Input
Orange – +12v DC
Yellow – Record LED

The potentiometers on the PCB from left:

H. ADJ
V. ADJ
BRIGHT
FOCUS

PCB Part Number reads: EM6-PCB

This unit utilises the BA7125L deflection IC.

Reverse side of the PCB, very few SMT components on this board.

Here is an overall view of the CRT assembly with scan coils. Tube model is NEC C1M52P45.

Closeup view of the CRT neck, showing the electron gun assembly.

The old CCTV camera used to feed a composite signal to the CRT board. Sanyo VCC-ZM300P.

Connections at the back of the camera. Red & Black pair of wires lead to 12v power supply, Green & Black pair lead to the CRT board’s power pins. Seperate green wire is pushed into the BNC video connector for the video feed. video ground is provided by the PSU’s ground connection.