Simple Expansion port to composite cable

[Almost Rice]

I kept noticing everyone talk about not being able to use the expansion port video signal since it was too weak. So I adapted the 600xl composite out that I had and got a clear signal when there is no sound. It might be the sound like Harry says here. I had to use 68 Ohm instead of a 75 and 3.3K instead of a 3K resistor in the circuit. Also I used a 2N3904 instead of a 2N2222.

 

I was hoping to make an in cable solution. If I have to disconnect the RF, then I would just mount the circuit inside the 7800. I have not connected the sound yet. Also 2600 and 7800 have output.

 

 

										   +5V (Expansion port pin 2)
									---
									 |
									 |
		 		+--------------------------+
		 		|				   |
		 		|				   |
		 		|				   | 
		 		\				   |
		 		/				   |
		 2.2K	\				   |
		 		/				   | Collector
		 		\		   /-------+
		 		|		  /
Signal In			|	Base|/
o--------------------+-------------------|  2N3904
(Expn port pin 3)	|		|\
		 		|		  \				   Signal Out (center RCA cable)
		 		|		   \-------+-------------------->
		 		|		Emitter	|
		 		|				   |
		 		\				   \
		 		/				   /
		3.3K	 \   			   \  68 Ohms
		 		/				   /
		 		\				   \
		 		|				   |
		 		|				   |
		 		|				   |
		 		+-------------------+
									 |
								   -----
									---
									 -(Expansion port pin 1 & outer RCA cable)

Cable shot loose and connected to the 7800.

 

Composite output to the 1702. You can see the diagonal lines.

[PacManPlus]

Nice work, dude! It's too bad we can't get a clearer signal from it - that would be a nice alternative to hacking the system.

[Almost Rice]

I disconnected C9 where it connects to R5 and R6. I then connect a 1uF capacitor to the open spot. The other end to center RCA for the sound. The RF output is untouched though there is no sound. I had to disconnect at R3 to remove all interference to the composite signal.

Edited May 23, 2008 by Almost Rice