RAF Nimrod cockpit LCD / MFD reverse engineering

[adriansmith31]

Hi all, first time posting and I was pointed here to ask a question about a LCD display unit which was purchased along with other avionics some time back for the purpose of teardown videos and eventual component salvage.

I posted in the tech log but was advised to post here as well. If its in the wrong place admins please delete.

So to begin I have acquired a MFD from a RAF Nimrod MRA4 which is a LCD unit 9" square with believed resolution of 768x768. It runs off 28V DC and I have successfully managed to power this thing on but at startup it displays a large "T" and then after a period of time displays a green diagonal line which I was told in avionics speak means no input signal or data.

I've done a video of the power up sequence and teardown but I'm wondering if there's any avionics engineers that are familiar with similar units or could give any sort of idea what video input this needs. There are three coax connectors on the back which eventually go to the video processing board where they are fed into a triple channel video amplifier and then into a ADC. It looks like the unit takes 3 video inputs (9 coax connectors in total) but only three are fitted.

There's an absence of MILSTD and ARINC transceivers which after doing the teardown I believe this is purely an analog display and it doesn't generate any symbology within the unit itself like the MFD's used in commercial aircraft. It's been suggested I try component video or 768x768 @ 50Hz sync on green but I don't have any way to generate this signal.

I can't post links but if you google for LCD66N teardown it will bring up my videos so you can see the display I'm talking about.

Thanks in advance for any help.

[Sim25]

Hi,
I can't help you out, but are you sure that the unit doesn't get any digital data signal via the other (not coax) pins? I have a Airbus CRT Display Unit together with a DMC here and there is a digital connection Airbus called DSDL between them.
Don't ask me what DSDL exactly is, I didn't find the time getting my setup working (Plus I don't have a 115V 400Hz AC source, yet). Apart from that the DUs receive a sort of digital component video from the DMC for weather radar display. Maybe your coax connectors have the same purpose?
I have the same problem... Getting information is really hard, CMMs would help, but honestly, I don't know where a private person should get those...

Simon

[adriansmith31]

Originally Posted by Sim25

Hi,
I can't help you out, but are you sure that the unit doesn't get any digital data signal via the other (not coax) pins? I have a Airbus CRT Display Unit together with a DMC here and there is a digital connection Airbus called DSDL between them.
Don't ask me what DSDL exactly is, I didn't find the time getting my setup working (Plus I don't have a 115V 400Hz AC source, yet). Apart from that the DUs receive a sort of digital component video from the DMC for weather radar display. Maybe your coax connectors have the same purpose?
I have the same problem... Getting information is really hard, CMMs would help, but honestly, I don't know where a private person should get those...

Simon

Hi thanks for the info. It definitely does take analog video input as the three coax cables eventually find their way to three analog video amplifiers which are then fed into an analog to digital converter. That then goes on to one of the ASCI chips. It may well take digital inputs too but I'm not aware of any. At least 16 pins are taken up by RS485 serial interfaces (which I cannot get anything out of) and the others appear to be control lines. It's very difficult to reverse engineer with the design of the unit and no information on the application specific chips that are used.

With the airbus displays the analog input is an option. I have a service & installation manual for one of the LCD's used in the A330/A340 but it is completely different to my unit.

Thanks,

Adrian

[Sim25]

Hi Adrian,
do you mind sharing the manual? My unit is a crt, but it would be interesting to have a look at it. How is the LCD-DU connected with the DMC? Regarding DSDL I suppose it might be something like A429 but with a higher clock frequency => higher data rate.
BTW. the VDO chip in your unit: In my DMC there are a plenty of VDO chips with VGAxx labeling and they do not process video data, instead I think that these might be ASICs for DSDL, maybe glue logic and other custom peripherals.

​​​​Simon

[adriansmith31]

Hmm,
I thought the VGA on the chips had something to do with video processing but I was wrong about that. Not sure about anything else with this display or how / if it does process digital signals. I can't see any MIL-STD1553 transceivers inside it nor ARINC interfaces. I can share the manual but I don't have enough posts to be able to post URL's (I have it on dropbox) but I can't seem to send you a private message either. If you have enough posts could you send me a PM or have somewhere I can send you the file?

[NutLoose]

Try asking in the military forum.