Video circiut design help

[Kurt.A]

Hi Guy's, I am wanting to create a video out port on my fish finder so that I can hook the video to a larger screen that will be viewable from a further distance in the boat. I have a 15 inch led monitor that runs on 12 volt with a variety of ports on the back that can be used to input the video to. (HDMI, USB, VGA, RGB, and AV). I have the Fish finder apart and found that the existing screen is being run by a flat ribbon cable with 44 conductors. The majority of the components on the board are surface mount. I do not have a schematic for it and the manufacturer is not interested in helping to supply a schematic or are willing to perform the task for me. I have a bit of experience soldering on boards and have built a few gadgets in the past with success. I would really appreciate some help in designing a circuit and tapping into the video signal so that both screens are displaying video at the same time.

Kurt

 

[ronsimpson]

Welcome

flat ribbon cable with 44 conductors

I need to know what screen is in the fish finder. Each type of screen has a different format and timing. It is very likely the timing is not compatible with a external monitor.
Example: VGA: There is one wire for the green signal, one wire for red and one for blue plus H and V each have a wire. In you 44 pin conductor there are likely 8 wires for green. VGA wants a horizontal sync (new line) at a rate of 32,000 times a second while your screen likely has a much much slow line update rate.

 

[crutschow]

You would have to determine the signal format of those 44 signals and then convert that to a standard video format. Without know that the task would be quite complex. You would likely need a digital logic analyzer to determine the signal format and then design the circuit from that result.

 

[Kurt.A]

Ok Guy's
I found a removable steel plate on the back side of the screen. Under the plate was another circuit board which I took a photo of, see attached. All but one of the boards have the manufacture as Techsonic. I did some research on the net but have gotten stonewalled. The Techsonic web site wants $250.00 a year to view there service manuals. Hopefully the pic will help sort out what screen we are looking at. The backwards facing RU in the bottom left corner is also on the other boards that have Techsonic on them as well. I lifted the board up but there is nothing of value that would help ID the screen.

 

[KeepItSimpleStupid]

The 44 pin interface may be standard. See https://www.google.com/url?sa=t&rct...ja16P9jyLg73Ib5VMZxV94Q&bvm=bv.53537100,d.dmg

There is an interesting blurb here: https://www.afiata.com/circuit-diagram-laptop-lcd-display-to-vga-interface-project/#.UlHgqpH0Fok

So, you could have a standard LCD 44 pin interface and if you needed a larger monitor, then just replacing the monitor could possibly work.

The first pic seems to have a long cable in the picture, possibly for connecting a 44 pin interface further away.

 

[ronsimpson]

There is a not populated connector in the bottom center of the PCB. What is it? I can see the pins are (from left to right) gnd, signal, signal, gnd, gnd, 4-signals, gnd.
Could it be video? gnd, H, V, gnd, gnd, R, G, B, ?, gnd??????

Above the connector there are resistors missing. The left two signals (that I call H &V) need to be looked at with a scope. If the signals have 60hz and 15k to 32khz then I know what to do. There is a small chance that the IC is out putting standard broadcast video (something like CGA) on those pins.

 

[Kurt.A]

There is a not populated connector in the bottom center of the PCB. What is it? I can see the pins are (from left to right) gnd, signal, signal, gnd, gnd, 4-signals, gnd.
Could it be video? gnd, H, V, gnd, gnd, R, G, B, ?, gnd??????

Above the connector there are resistors missing. The left two signals (that I call H &V) need to be looked at with a scope. If the signals have 60hz and 15k to 32khz then I know what to do. There is a small chance that the IC is out putting standard broadcast video (something like CGA) on those pins.

I checked the non populated connector in question with a multimeter and have confirmed the gnd circuits that you see. They would need something to bridge the non populated resistors to actually ground the IC legs. The meter I have is a Fluke 87 which will measure hertz. Unfortunately with the boards assembled so that I can put power to the assembled unit the pads in question are completely covered. Can I supply power to just the board by itself to perform the test? If so how? Do the other 2 screen ribbon connectors need to be removed for this test?

 

[Kurt.A]

The 44 pin interface may be standard. See https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&cad=rja&ved=0CD4QFjAG&url=https://www.esis.com.au/LCD-Monitors/LCD_Kits.pdf&ei=DuBRUs2_G6-r4APt34HIBw&usg=AFQjCNE-NGPja16P9jyLg73Ib5VMZxV94Q&bvm=bv.53537100,d.dmg

There is an interesting blurb here: https://www.afiata.com/circuit-diagram-laptop-lcd-display-to-vga-interface-project/#.UlHgqpH0Fok

So, you could have a standard LCD 44 pin interface and if you needed a larger monitor, then just replacing the monitor could possibly work.

The first pic seems to have a long cable in the picture, possibly for connecting a 44 pin interface further away.

Good info in the links! Looks as if I have a couple choices here now. I will follow both suggestions to see where we get. The ribbon cable that you reference I believe is the one with the blue band on it. It does go to another 44 pin interface on another board that stacks on top of this board. The way the assembled unit goes through batteries I think it would be safe to assume that the screen is LCD.