Videopac / Odyssey2 forum

Anything not specifically Videopac / Odyssey2 => Other Systems => Topic started by: VideopacBelgium on March 24, 2013, 12:25:35 AM



Title: ODYSSEY AV MOD
Post by: VideopacBelgium on March 24, 2013, 12:25:35 AM
I would like to modify my Odyssey with AV mod.
Can somebody help me?
Thanks


Title: Re: ODYSSEY AV MOD
Post by: Seob on March 24, 2013, 09:39:43 AM
Help as in schematics or building it?


Title: Re: ODYSSEY AV MOD
Post by: VideopacBelgium on March 24, 2013, 01:11:27 PM
Help as in schematics or building it?

Schematics please


Title: Re: ODYSSEY AV MOD
Post by: Seob on March 24, 2013, 01:26:34 PM
Look here: http://solarfox.triluminary.net/hwh_o2avc_p1.php (http://solarfox.triluminary.net/hwh_o2avc_p1.php)


Title: Re: ODYSSEY AV MOD
Post by: VideopacBelgium on March 24, 2013, 01:40:59 PM
Hugh !
I'm looking for the schematics to modify my ODYSSEY. (...not Odyssey²)


Title: Re: ODYSSEY AV MOD
Post by: Seob on March 24, 2013, 08:18:43 PM
Hugh !
I'm looking for the schematics to modify my ODYSSEY. (...not Odyssey²)

Ah, i already tough it was a little strange that you where asking for schematics of the O2.


Title: Re: ODYSSEY AV MOD
Post by: Rene_G7400 on March 25, 2013, 12:49:13 AM
I would like to modify my Odyssey with AV mod.

Since the Odyssey has no A, it will be a V mod only. :)
I've done that, but can't check right now how. Will let you know next weekend. I thought it was pretty simple. Probably just one transistor and a few resistors. Do you have the schematics of the Odyssey console?


Title: Re: ODYSSEY AV MOD
Post by: gertk on March 25, 2013, 10:13:18 AM
On this page: http://www.atariage.com/forums/topic/124552-odyssey-circuitry-diagram/ (http://www.atariage.com/forums/topic/124552-odyssey-circuitry-diagram/) about three quarters down are some schematics.
Not sure if you can really find the complete video signal (My guess the signal is mixed on top of the RF carrier at the modulator test point 'Sweep input')
If you temporarily disable the RF carrier you could check the signal there with an oscilloscope.


Title: Re: ODYSSEY AV MOD
Post by: VideopacBelgium on March 25, 2013, 07:43:11 PM
Right René, ...this is a V mod only  :)
I found the schematics here
http://www.pong-story.com/1tl200blak_sch.pdf (http://www.pong-story.com/1tl200blak_sch.pdf)
The J12 "SUMMER" module seems to mix the WALL, the BALL, the 2 PLAYERS, the V and H sync. to COMPOSITE VIDEO.


Title: Re: ODYSSEY AV MOD
Post by: Rene_G7400 on March 25, 2013, 09:26:17 PM
The J12 "SUMMER" module seems to mix the WALL, the BALL, the 2 PLAYERS, the V and H sync. to COMPOSITE VIDEO.

Yes, it does. You'll need at least one transistor as an emitter-follower for a low output impedance. You might need a few resistors to adjust the levels.


Title: Re: ODYSSEY AV MOD
Post by: Rene_G7400 on March 31, 2013, 06:41:20 PM
Seems I haven't used any resistor. Just one transistor BC547. I've removed the RF oscillator and RF filter boards. (The two PCBs inside the metal boxes.) I've connected the base of the transistor to pin 10 of the summer board (J12), and the collector to the 6.2V power supply (for example pin 9 of the horizontal sync generator). The emitter of the transistor is the video output. If the input of your TV has a capacitor, you'll need to connect a resistor bewteen the emitter and ground. I've adjusted the frequencies of the Vsync and Hsync generators to get a 'PAL' signal.


Title: Re: ODYSSEY AV MOD
Post by: VideopacBelgium on April 01, 2013, 01:04:15 AM
Thanks René, it works
However, the "background" in not black but gray.
I've used the "FILTER" PCB to fix the BC547.
The pin 3 to the base, the pin 7 to the emitter, the collector to the pin 4 of the RF oscillator connector just near (5,6 V)


Title: Re: ODYSSEY AV MOD
Post by: Rene_G7400 on April 01, 2013, 01:55:43 AM
However, the "background" in not black but gray.

According to the manual, the background should be gray, not black (otherwise you won't see the graphics of the overlays).
http://www.magnavox-odyssey.com/Manual/US%20manual/6.jpg (http://www.magnavox-odyssey.com/Manual/US%20manual/6.jpg)


Title: Re: ODYSSEY AV MOD
Post by: VideopacBelgium on April 04, 2013, 04:31:34 PM
On some TV, the wall, the ball and the players are black instead of white!
I can turn them to white with a resistor 27 ohms between the video out and the GND.
Is this correct?


Title: Re: ODYSSEY AV MOD
Post by: Rene_G7400 on April 04, 2013, 04:41:52 PM
On some TV, the wall, the ball and the players are black instead of white!
I can turn them to white with a resistor 27 ohms between the video out and the GND.
Is this correct?

27 Ohm is a bit low. Does it work with 82 Ohm too?


Title: Re: ODYSSEY AV MOD
Post by: gertk on April 04, 2013, 07:08:42 PM
On some TV, the wall, the ball and the players are black instead of white!
I can turn them to white with a resistor 27 ohms between the video out and the GND.
Is this correct?

27 Ohm is a bit low. Does it work with 82 Ohm too?


Or put a trim pot of 100 ohm in series with that 27 ohm and see what happens when adjusting it.
My guess is that there is no black level defined in the signal aka 'no back porch' (a thing which a lot of older ZX81 have also on modern TV sets) messing up the automatic black level adjustment.


Title: Re: ODYSSEY AV MOD
Post by: Rene_G7400 on April 05, 2013, 10:58:55 AM
My guess is that the TV has a capacitor on it's input, so no DC current can flow through the transistor without emitter resistor.


Title: Re: ODYSSEY AV MOD
Post by: VideopacBelgium on April 10, 2013, 11:36:40 PM
Finally I put a trim pot of 100 ohm.
On this tv (pic) I have to adjust the trim pot at 27 ohm to get this screen.
On another TV (LCD or other) adjusted to 80 ohm.


Title: Re: ODYSSEY AV MOD
Post by: gertk on April 11, 2013, 06:57:58 PM
Finally I put a trim pot of 100 ohm.
On this tv (pic) I have to adjust the trim pot at 27 ohm to get this screen.
On another TV (LCD or other) adjusted to 80 ohm.

At least you used a trimpot from the same era  :D

With an emitter follower you need a resistor to ground from the emitter, maybe a series resistor of 75 ohms to the TV input might help too, some TV also react strange to DC voltages so a relatively large series capacitor (220 uF) resolves this.


Title: Re: ODYSSEY AV MOD
Post by: VideopacBelgium on April 11, 2013, 10:37:04 PM
At least you used a trimpot from the same era  :D

Yes, I use the Q2 142N4 from the RF oscillator board as the emitter-follower transistor and a trim pot from the shop near my work, as I said in another topic, they have a lot of components from the seventies and eighties (now for sale at -50% till 30 april)


Title: Re: ODYSSEY AV MOD
Post by: Rene_G7400 on April 12, 2013, 09:33:26 AM
The TV's I'm using have a 75 Ohm resistor on the video input to ground, therefore I didn't need an extra resistor in the Odyssey1 video output.


Title: Re: ODYSSEY AV MOD
Post by: gertk on April 12, 2013, 08:36:04 PM
The TV's I'm using have a 75 Ohm resistor on the video input to ground, therefore I didn't need an extra resistor in the Odyssey1 video output.


Normally you would have a series resistor to match the (coax) cable impedance but then you also need to have your input signal at about double the required level on you load impedance.. An oscilloscope can give you some clues what is going on.. 


Title: Original Magnavox Odyssey AV Mod
Post by: KylJoy on June 20, 2017, 04:12:27 AM
Reviving this topic!  :)

I am interested in a composite output modification (or s-video or RGB for that matter) but I want to keep the original RF, too.  How would I go about doing that, please?

Thanks in advance!


Title: Re: ODYSSEY AV MOD
Post by: Rene_G7400 on September 25, 2017, 09:35:17 AM
More info about AV mods can be found in the hardware section of this forum:
http://videopac.nl/forum/index.php?board=7.0 (http://videopac.nl/forum/index.php?board=7.0)


Title: Re: ODYSSEY AV MOD
Post by: grips03 on October 26, 2017, 10:43:04 PM
I have a O2 composite PCB design at oshpark.com.  Search for grips03 under shared projects.