Hi, i am just about to do the Composite Video Mod.

As the transistor used in the project (BC182) is hard to get hold of now could anyone advise on a replacement e.g. 2N3904.

Has anyone done this mod? could someone give me the jist of the instructions, which is written in Hungarian, on the page above. Are the any pitfalls that i should watch out for?

thanks

Jack

thanks, i will try this.

What is the value of the resistor you have added?

110 ohm

I tried to make a colour composite modification, but it didn't seem to work in my case.
I used 2N3904 instead of BC182.
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But there’s only a messy picture on the screen.
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(this is IS-Basic start screen)

https://www.dropbox.com/s/7do91aypyvpsm1e/tc4k_load_Telegr.mp4?dl=0

Where could I have gone wrong?

The composite video needs a 75ohm impedance cable.
In my opinion from transistor output to the TV. On the other side the cable lenght at transistor must be as short as possible. Keep the transistor close to the IC output.
 At 1MHz (where the composite signal bandwith has), long wire acts as inductivity.
 Next to your transistor i am not sure that a big electrolit capacior is a good idea. A small 10uF tantal cap would be better.

I'll try to shorten the wires.

I suspected that this might only cause slight image interference. Because standard B/W picture is very good.

The BC182 is a general purpose transistor with the following spec:
BC182 TO92 NPN 60V 0,1A 0,35W
 The circuit has a ca. 75ohm resistor on the emmiter, which is a negative coupling, thus the frequency response of tha amplidifier circuit is better.
 As I remember, the circuit needs the 12V supply of the EP board, that way the transisor amplifier circuit responds faster.

 The video signal has level from 0,5V to 2V with max 5MHz.

Another option would be to remove the resistor (marked in the attachment) and replace it to a 75ohm, connect to a capacitor in series, and then connect to the output B1 (or a 75ohm bnc connector)

I removed the R101 resistor and changed to a 75ohm (in my case it was easier to find an SMD resistor in my drawer) and then i connected to the RF output (see picture).
 I do not need the capacitor, because yesterday I placed a capacitor in the old CRT TV, and I am going to use the enterprise only  with that TV.
 Of course the external connection of the RF modulator has to revoved. To avoid interference.
 Result beautiful color picture.