Looking for a simple Atari 5200 Composite mod

[bradd1978]

I know there is the S-Video board by low budget that outputs composite as well but I've been wondering if there is a simple circuit solution?

 

I've used a basic circuit in Atari 2600's using a 3904 transistor and 2 resistors, tapping the video before it goes to the RF modulator. I'm curious if the same thing might work in the Atari 5200.

I was gonna hopefully look at my 5200 this weekend, but thought I'd check in first and see if anyone had some ideas before I start digging in :-)

[Osgeld]

it should work, just gotta find that magic spot

[bradd1978]

I think it will too. I'm gonna take a shot at it. Surprised I didn't find anything via google on this specific subject.

Ill update with results if anyone is curious

[Osgeld]

best bet is to find the schematic for the 5200, and I would be surprised if its not on this site and just kind of follow it from the RF modulator back to the chip, it should be pretty obvious where the input of the RF meets the final output of the chip via resistors and whatnot

 

or just jab at it with a scope till you find it

Edited February 22, 2014 by Osgeld

[bradd1978]

Yeah I'm gonna look up a schematic in a bit and take a look. I know for a fact it uses the same RF Modulator as the 2600 and it has 4 pins coming out for video, ground, audio and +5 so the circuit should theoretically work

I might put some 1k pots on the circuit to adjust if need be

[Osgeld]

sounds like a plan, good luck

[zylon]

best bet is to find the schematic for the 5200, and I would be surprised if its not on this site and just kind of follow it from the RF modulator back to the chip, it should be pretty obvious where the input of the RF meets the final output of the chip via resistors and whatnot

 

or just jab at it with a scope till you find it

Atari_5200_Field_Service_Manual.pdf

[atariguy1021]

I tried it a while back. I got a picture but there was some weird swirling interference that would come and go. I played with the resistor values but didn't have any luck resolving the issue.

 

The pinout of the RF modulator is the same as the 2600 (Pin 1 - Ground, Pin 3 - +5V, Pin 4 - Video). You can tap audio at the same point as with the low budget mod.

 

Hopefully you'll have better luck than I did.

[R.Cade]

On the similar mod for the 2600 and 7800, you typically have to cut a resistor in the sound circuit so it doesn't interfere with the video. This likely caused the video distortion.

Edited February 22, 2014 by R.Cade

[bradd1978]

Just by looking at the schematics in the service manual, it has a via labeled "comp video" that is just below the heatsink.

I haven't had a chance to dig into this yet (watching my daughter at the moment) but I'm gonna tap this point and see what happens

 

If not, the way I do the 2600 mods is snip the 5 leads from the RF, and use pin 4 for video. This runs through a simple NPN3904 transistor circuit. It looks awesome on 2600's.

Anyways thanks for everyone's input - ill be able to hopefully tackle this tonight. I'm confident I can get a nice picture one way or another :-) Ill keep you all updated

[atariguy1021]

I'm confident I can get a nice picture one way or another :-) Ill keep you all updated

I know one way you're guaranteed to get a beautiful picture out of your 5200....

 

http://electronicsentimentalities.com/Assembled%20Mods.html

 

It looks awesome on 2600's.

If you think the transistor mod looks "awesome" on the 2600, than you'll likely be happy with what you get with it from the 5200 as well. As I recall, the interference that I spoke of was fairly faint and I never went further than putting it through a breadboard, mainly out of curiosity, soldering it up proper may have alleviated the problem (but I doubt it). With the low budget mod readily available, I don't see the point unless you're on a tight budget . In my opinion, the easy transistor mod is only worth performing on the 7800. And that's if you have no interest in using S-video. As far as the 2600 goes, the only reasons to use it are: it's dead simple and it costs less than a $1.00.

[bradd1978]

I've bought and installed the low budget board in a 5200 I used to own and it's awesome, that's for sure :-) But its over $30 shipped....I'd love to go find an alternative that I can do for a couple bucks and a few resistors/transistors

 

With that said I attempted a mod last night with the same circuit I use on the 2600 and it didn't work. No picture at all

 

I'm curious though on the 5200 2-port schematics it shows a point labeled #37 Comp Video. If you follow pin 4 off the RF modulator you'll see it. But I have no clue where this #37 Comp video is?? On an IC somewhere....?

Anyways ill keep chipping away, worst case, ill order a low budget board. Bit thought it might be fun to find an alternative. I mean...it can't be that difficult to get Composite video off the board :-)

[atariguy1021]

With that said I attempted a mod last night with the same circuit I use on the 2600 and it didn't work. No picture at all

 

 

 

Did you attempt on a 2 or a 4 port?

 

 

I'm curious though on the 5200 2-port schematics it shows a point labeled #37 Comp Video. If you follow pin 4 off the RF modulator you'll see it. But I have no clue where this #37 Comp video is?? On an IC somewhere....?

Maybe it goes to the expansion slot? I don't know how many pins that is off the top of my head... Follow the trace off pin 4 and see where it leads.

 

 

Anyways ill keep chipping away, worst case, ill order a low budget board. Bit thought it might be fun to find an alternative. I mean...it can't be that difficult to get Composite video off the board :-)

Tinkering is fun!

[bradd1978]

It was on 2 port system. The expansion has 18 pins I believe.

Ill trace out pin 4 again and see what happens

[bradd1978]

Here is the page I was referring to earlier from the service manual. It shows the "Comp Video" point near the bottom with the #37. I'm at work right now but I've snapshot and attached it

I was looking at some of the schematics but can't find an answer

[bradd1978]

Quick update - I had an hour of free time yesterday and pulled my breadboard out and played with some resistor values in the 3904 transistor amp. I'm no expert, my theory stinks when it comes to building circuits. I can follow instruction, and that's about it

So I used 1K pots and 5k pots. I managed to get a dark image with alot of interference. And stupid me didn't take a picture :-(

I was testing on a 15" LCD TV by the way.... I got out the multimeter to see what the resistance was on my pots so I could replace them with resistors. But when replaced, I had no image. The TV was having an issue with the signal I guess, it was strong enough

So I'm back again where I started. Any experts have any suggestions? I'm getting close, I know it can be done I just don't know what resistor/cap values to use. I'm gonna try again this week....keep grinding at it :-)

[Jess Ragan]

Here's my suggestion... get a mod kit from 8-Bit Domain! It's incredibly easy, until you realize all the wires are three inches too short and you have to solder in extensions.

 

(I shouldn't speak ill of the dead, but fuck those guys.)

[jum]

Just removed the RF modulator from my 2-port 5200 and wired in a simple composite connection using 1 transistor (2N2222?) and one resistor between video out and ground.

 

Also cut the one leg of the resistor (R33?) that connects the audio to the video output. Have yet to connect the audio output.

 

Very surprised at how good it looks (way better than 2600 and 7800 composite mods I have done). Will post pictures later.

 

Tweaked the big pot on the lower right side of the board to get the colours correct. Video output may be a bit "hot", need to check that and maybe add voltage divider to the circuit.

 

[jum]

Here are the pictures, although in person the images on the screen is not so bright and the ghosting is much less noticeable.

 

Hopefully putting the mod onto a proto board and a bit of tweaking will give a slightly better image.

 

 

Note:

- RF modulator removed completely

- Resistor R33 leg (audio) lifted off the board

- Video signal taken from left side of L12 (green clip)

- +5V taken from top of L13 (red clip)

- Ground taken from top side of C40

- Transistor used in mod circuit is KSP2222N    (2N2222?)

- Resistor used in mod circuit is 100 Ohms

 

These are just the first points I saw on the schematics that looked like they have the right signals, possibly there are better points to take the signal off.

 

 

Edited January 14, 2020 by jum

[+DrVenkman]

I'm going to just install a UAV into my 2-port 5200 in a week or two. I've got them in a 7800, a 2600, and several Atari computers - excellent output with minimal fuss.

[+-^CrossBow^-]

On 1/14/2020 at 6:35 PM, DrVenkman said:

I'm going to just install a UAV into my 2-port 5200 in a week or two. I've got them in a 7800, a 2600, and several Atari computers - excellent output with minimal fuss.

Hopefully you are able to get away with not having to put the 4050 back in circuit as I've had to do. Then again, I've only done the UAV on 4-ports so the 4050 being required might be a 4-port thing..?

[+DrVenkman]

22 minutes ago, -^CrossBow^- said:

Hopefully you are able to get away with not having to put the 4050 back in circuit as I've had to do. Then again, I've only done the UAV on 4-ports so the 4050 being required might be a 4-port thing..?

My friend has done several 2-ports and always had to leave the 4050 in. I expect to have to solder a socket over it for the UAV. 

[jum]

Final install of the composite mod, with screenshots from a small LCD monitor:

 

 

[+DrVenkman]

UAV installed and working great.

 

 

 

 

 

 

[Adam Mace]

On 1/21/2020 at 9:53 AM, jum said:

Final install of the composite mod, with screenshots from a small LCD monitor:

 

 

Do you happen to have a schematic of this circuit you've made?  I'm working on a 5200 and getting real bad RF interference.   I'd rather bypass it entirely without buying a UAV board, but my theoretical knowledge isn't that great.