Intellivision Composite mod - Anybody try it?

[FABombjoy]

Well, I did, and the results are only so-so. I'm using an Intv 2 + the schematic here:

http://www94.pair.com/jsoper/intv_vmod.html

Picture is pretty dark & a little noisy. I got rid of most of the noise by using the modulator power feed instead of the board +5v. Still looks dark... like the signal needs a little more amplification. Has anyone here tried this, and what were your results?

[omnedon]

I was going to try it, but on an Inty 1.

John sent me this alternate schematic he hasn't tried yet:

dammit- I can't get the formatting to not mess it up. Pm me, and I can e-mail what John sent me, to you.


It's not his, but belongs to someone he's corresponding with. PM John for more details.

I'd certainly like to ry it with the best circuit first. Troubleshooting these circuits is not for the newbie.

[FABombjoy]

Hmm... Well, I tried the new schem that Omne provided and it looks very good... except the image has light streaks running towards the right from where the lighter colors appear. I'll keep tinkering. Copy and paste this into a text editor that supports monospaced fonts.



* +
* Input 10--|(--+ ^ +5V
* CC1 | |
* | |
* RB1 | RA1 |
* 0------/\/\/------3------/\/\/------1
* | | |
* | |b |
* | ____|____ |
* | / \ |
* | e V \ c |
* 0---/\/\/-----4 +--2--/\/\/---1
* | RE1 | RC1 |
* | + | |
* | +--|(--+ |
* | | CC2 |
* | RB2 | RA2 |
* 0------/\/\/------6------/\/\/------1
* | | |
* | |b |
* | ____|____ |
* | / \ |
* | e V \ c |
* 0---/\/\/-----7 +---5-/\/\/---1
* | RE2 | RC2
* | |
* __|__ | +
* - +----)|----8---
* GND CC3
*

* stage 1
CC1 10 3 100uF
RA1 1 3 50K (I used a 51K)
RB1 3 0 30K (I used a 33K)
RC1 1 2 660
RE1 4 0 330
Q1 2 3 4 Q2N3904

* stage 2
CC2 2 6 100uF
RA2 1 6 15K
RB2 6 0 20K (I used a 22K)
RC2 1 5 75
RE2 7 0 22
Q2 5 6 7 Q2N3904

[FABombjoy]

Oh yeah, I should note that all of the caps seem to be listed backwards... or the + indicators are on the wrong sides. I tried reversing the caps but it made no improvement.

[FABombjoy]

Ok, streaks gone. Added 1000uF cap across +5 and ground on circuit. I guess it just needed a little help. There is still a faint shadow to the left of bright objects, but it looks much better now.

[omnedon]

Wow! Cool!

I finmd that schematic hard to follow, but I'm still learning to read them. There is a transistor in it isn't there? How can I tell what rating transistor?

[FABombjoy]

There are 2 transistors, both 3904 type. Pretty generic part, easy to find, cheap. It's the same part used in the 2600/5200/7800 composite/svid mods.

[john_soper]

BTW, that two-transistor circuit comes courtesy of Joe Zibiciak and Tim Lindner. I'm not taking any credit or blame on that one :)

[FABombjoy]

Hey, it's way better than the previous 2 mods that I tried. All I added was the cap across the +5 and ground, and a 100ohm pot on the output to tone down the slightly-too-hot video signal. I'm not sure why the circuit that I built had the streaks appear, but it's gone after the added cap.

I also tapped +5 from the power feed to the modulator. That clears up a lot (but not all) of the interference present in the screenshot that I saw (in the original forwarded email from Omne).

[leonk]

can you post screen shots?

I'm interested in doing such a mod on my INTV1.

[leonk]

The scematics don't seem to be complete.

What is the value for CC3?

[FABombjoy]

I used another 100mF cap.

I'll try and post a screenshot when I get the chance

[FABombjoy]

Pictures (click for bigger versions):

(sorry, lost the pictures)