Tornado TV TAB DU: wire harness
The TV TAB is equipped wit a very impressive wire harness. The wire quality is very good and every wire is marked with a color coded number. The wire harness connects all the connectors and boards. It's suprising that tie-wraps are used instead of wax wire. Tie-wraps tend to age and degrad in time. Wax coard takes less space, isn't sharp and doesn't age. It seems that high end quality tie-wraps are used and using tie-wraps takes less effort in making the wire harness and probably is 'good anough'. The part number is V22.498.815.
Point to point connections are made directly. Every connector pin has only one wire connected. When a junction of more than two pins is needed, a solder joint is used. The solder joints are protected by shrink tubing. The open end of the tubing is insulated with a plastic 'plug'. All the interconnection joints are secured in the wire harness. The secured joints are shown on the rear part of the wire harness on the image below. The wire harness part in the front shows the joints after removing the tie-wraps. Every wire is clearly marked with a colour coded number.
reverse engineering (raw data)
The engineering of the device is amazing! The quality is great and it's very nice to see that the device is built logical and well thought. See the image below for example. Every wire is marked with a number. Due to the large amount of wires, coloured wires are probably not that practical. So almost every wire is white. To distinguish every wire, every wire is coded with a 0...9 number. This is very convenient for service. The thing I'm surprised by, is that every number ring is also colour coded according to the resistor table! Black = 0, brown = 1, red = 3 and so on. So if the number is unable to read, it's possible to know the number based on the colour code. This is convention since the number is 'always' at the opposite side of the viewing angle. ;-) There are a maximum of four digits used. The digit towards the end of the wire is the least significant number. For example: If red, blue and green is used as marking where red is towards the wire end, the wire number is 265. Every piece of wire had a unique number. The conductor of a coax and the shielding has a different number. But the wire type and colour are relevant! It's possible that a white wire and a green wire can have the same number. For example, the three phase 208 VAC 400 Hz main power input wires are all three marked with  but the colours are red, yellow and blue. Another exception is that a double coax wire can have the same number. The two coax cores are distinguished by a black line on the coax insulator. After finding out the system of coding its 'just' a matter of ours redrawing the wire harness connections. This is relevant for (non destructive) reverse engineering parts of the device. I think green wires are used for power and I think white wires are used for internal communications. But this has to be validated yet...
After a lot of research I found out that the conncetor type is Series II JT.
The wiring goes to seven connectors and one hour counter at the rear panel.
|100 pin circular (m)
|main connector: data/power
|combined video output to EHDD
|TVM video input
|FLR (or SPARE) video input (Forward Looking Radar)
|WFG video input (for digital data like map plots)
|RCN video input (reconnaissance)
|white wire (2x)
pcb bus connections (raw data)
I spent many, many evenings reverse engineering the wire harness. There's no schematic and the wire links are rather inportant for reverse engineering the device. Before retracing all the wires I made a overview drawing of the wire harness. The overview is shown below. The left side of the drawing represents the front side of the device. The right side is the rear end of the display unit. The wire harness is viewed from the bottom. The wire harness is rather self explaining.
The wire harness is shown below. It's likely the resemblance between the dwaring and real word harness is visible.
wiring harness reverse engineering
After documenting the main outline of the harness I retraced all the wires. Yes, every individual wire is followed and documented. It was a tedious job but very important for reverse engineering. It took many ours and many pieces of paper. After making the pencil notes the information is documented isung a computer.
Luckily every wire is coded using the resistor color coding. But it's (occationally) possible that both ends of one wire can have two different numbers. Also there are three wire types: white wires, coloured wires and coax cables. Each wire group can reuse one number! So not only the number has to be documented also the wire type and color has to be documented. The good thing is that only one wire is connected per pin. This makes the process of reverse engineering more conventient. There are several interconnection points, so it's possible that more wires are linked. Every wire is retraced and documented in an Excel spreadsheet.
Not every wire is that intereresting, so I won't bother you with a list of 400+ wires. The most relevant wires are the wires of the main power circuit. The main power circuit is shown below. By clicking the image, the original size is shown if you're interested in the large view.
The drawing needs also more explanation...
main connector A
The left (male) connector of the image below is the main connector A of the device. Pins 65, 66, 76 and 75 are used for powering the device. 115 VAC 400 Hz 3-phase power is needed for powering the device. There is a misconception that the display unit als oneeds 28 VDC. The 28 VDC is used for power button illumination. And remind that the keypad illumination is also still not activated since the keypad illumination have separate contacts to main connector A. Remind that the neutral is mandatory!
|115 VAC 400 Hz phase 1 power input
|115 VAC 400 Hz phase 2 power input
|115 VAC 400 Hz phase 3 power input
|115 VAC 400 Hz neutral power input
Left: Main connector A. Right: Diagnose connector for debugging.
Rear view of the partially dismanteled display unit.
The power from connectoe A fed into the device is wired to the filter board as shown below. The aluminum mounting plate has four 'CLC' filter units. This units acts are low pass filters to reject high frequency noise. One 'large' filter for each line and one smaller filter for the neutral line. The mounting plate is connected to the chassis and there are also two other white ground wires numers 309 and 310.
Since only one wire is connected to each pin, some wire links are installed. Several wire ends can be soldered together and each link is isolated using thick shrink shroud. These wire links are embedded in the wire harness. For reverse enginering purposes I marked each link with a ('random' and unique) letter. Normally these links are not marked and the letters are just for my reference. Filtered 115 VAC 400 Hz L1 is for example fed from the filter board via wire [white 26] to interconnection [R]. A real word example of a wire link is shown below. The wire links in the main power drawing are: R, U, V, W, E, S, T and D.
One of the interconnection points.
One of the interconnection points. Each connections is shielded with thick shrink shroud.
There is an (115 VAC 400 Hz) relay that acts as the main power switch of the display unit. The input power is fed from the interconnectipon points R, U, V and W to the power relay. In off position the input power stops at the relay. By powering the relay coil, the contacts are switched. The neutral wire is connected via inteconnection point W to contact X2 of the power relay coil. The other contact (X1) is connected via interconnaction E to the keypad. The [ON] toggle switch on the frontpanel switches 115 VAC 400 Hz L1 from interconnaction R to the relay coil contact X1. By pressing the ON button, the power relay is energised and the contacts are switched. The three phases are switches on/off by the relay so the low voltage power supply is (de)energised by switching the power relay. Very intersting is that normally closed contact D is also wired to the low voltage power supply. This is a safety feature. By switching off the relay, the high voltage capacitors in the low voltage power supply are short circuited to bleed the capacitors. This prevents lethal voltages present at the capacitors when the power is turned off. By activating the power relay (switching on the display unit) the contact is opened and high voltages can be present. By switching off the power, the capacitors are therefore directly bleeded. So if the display unit is turned off, there's no dangerous residual voltages present. This is a very nice design feature! The power relay is shown below. The 'shiny metal box' is the power relay. On the second image is the power relay with gold plated contacts and it's socket visible.
The heavy duty power relay in the middle of the wire harness wiring.
The heavy duty power relay.
There's a capacitor board installed that is used to suppress high frequency components on the power signals after the power relay. There are three 1 uF caps connected to the neutral and each of the 115 VAC lines. The board is marked with code V22.498.753-11 where V22.498 is used for the display unit identification and 753-11 is the identification of the capacitor board espacially. Below are images shown of the capacitor board.
Bottom view of the capacitor board.
Top view of the capacitor board.
There's also a hour counter installed at the rear panel. The counter operates on 115 VAC 400 Hz one phase. The neutral side (wire white 84) is connected to the neutral interconnection point W. The 115 VAC 400 Hz side is connected to phase L2 at interconnection point T. In my case the hour counter shows 9.126 hours. That's more than one year os permanent operaton! (No wonder that the display became dim due to wear...) Note: I've got also three (broken) successor TV TAB's with a digital display. The hour count is 4.728, 1.493 and 3.402 hours. The original CRT ones wear dute to the phosphor ageing, but the digital ones fail even more often. The three broken digital ones have barely more operation hours than the CRT one. The CRT ones wear, but are much more stable and reliable! The hour counter is shown on the image below.
Hour counter at the rear panel of the display unit.
The right connector is a debugging/diagnose connector. Usually this connector is not used for normal operation. Strategic test signals are fed to the diagnose connector for repair/debugging purposes. Pins A, B and C have the 115 VAC 400 Hz three phase output signals. This is conventient to test if the expected signal is present. If the relay fails, it's possible to determine which contact failed. It's also possible to measure the noise on the signal to see is the filtering is still working as desired. Note: Don't use the diagnose conector for powering the device! When the power relay isn't energised, the high voltage capacitors are short circuited. Thus powering the device via pins A, B and C, the low votlage powersupply is powered, but the input signal is also short circuited. If you want to bypass the power switching circuit, be sure to remove the power relay to remove the capacitor bleeding 'bridge'. And remind that the filtering is bypassed also. So, my advice is to use only the diagnose connetor for diagnose purposes and not as a power input.
Left: Main connector A. Right: Diagnose connector for debugging.