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Improved Color For Your 4-Switch Woody: A Public Service Bulletin


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#1 DrVenkman ONLINE  

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Posted Wed Aug 5, 2015 9:46 AM

So in a complete thread-derail last night, I got into a very enlightening discussion with Zylon about the color output of 4-Switch Woody models. He mentioned that Rev 14 and 16 boards typically have very good color. I noted that my Rev 14 actually had rather poor color, at least as compared to my Light Sixer.  Zylon helpfully pointed me to the Atari VCS Field Service Manual; I actually have downloaded this in the past but never paid this particular section much attention. If you have this document, see page 154 , Tech Tip #4: 

 

Tech Tip 4.jpg

 

So I did this little mod this morning and damn, what an improvement! The color now is just about completely on par with my Light Sixer. Fantastic improvement for the level of effort involved. So if you have a 4-Switch Woody with less-than-great color output, a quarter-cent 820 Ω resistor and five minutes of your time can make an incredible difference. 


Edited by DrVenkman, Wed Aug 5, 2015 10:25 AM.


#2 zylon OFFLINE  

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Posted Wed Aug 5, 2015 10:13 AM

I'll add the pictures of a factory one. :)

;) Told ya they have good color.

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  • IMG_6716.JPG

Edited by zylon, Wed Aug 5, 2015 10:14 AM.


#3 BigO OFFLINE  

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Posted Wed Aug 5, 2015 10:40 AM

Now I'm going to have to dig the 4 switchers out of the shed and try this.



#4 DrVenkman ONLINE  

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Posted Wed Aug 5, 2015 9:19 PM

Now I'm going to have to dig the 4 switchers out of the shed and try this.


The Tech Tip says Rev 16 boards have it already installed at the Factory. I would be curious if the Vaders have it as well - come to think of it it, I'm not sure is seen a Vader in person ever even 30+ years ago, let alone outside the case and under the RF shield.

#5 zylon OFFLINE  

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Posted Wed Aug 5, 2015 9:23 PM

The Tech Tip says Rev 16 boards have it already installed at the Factory. I would be curious if the Vaders have it as well - come to think of it it, I'm not sure is seen a Vader in person ever even 30+ years ago, let alone outside the case and under the RF shield.

 

it is built in and just looks like it was always there. it is only an add on to 14's and lower. it helps, but does not work as good on 12's. I took these shots of stock boards in action on the same game with same TV.

As you can see, the 16 and L6er are almost identical. The 12 and 13 do not have the resistor and look more dull.

Attached Thumbnails

  • 4sw Rev 16 video.jpg
  • 4sw Rev 13 video.jpg
  • 4sw Rev 12 video.jpg
  • L6er video.jpg

Edited by zylon, Wed Aug 5, 2015 9:27 PM.


#6 DrVenkman ONLINE  

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Posted Wed Aug 5, 2015 9:34 PM

Interesting comparison. It looks almost as if the 12 and 13 lack a bit of yellow in the output - compare the lack of gold in the invaders, and the tendency toward blue in the Player 1 score display, as compared to the L6er and 16.

#7 zylon OFFLINE  

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Posted Wed Aug 5, 2015 9:39 PM

What I did first was to use kaboom and set them to get the greenest field possible and then switched games to compare.

But major changes easy to see on 12's and 13's. 16 is close but strangely, 13 is worse than 12. 

A few vaders had 14's, but most had 16 through 18 and about half of the 16's were with hard soldered IC's. it makes 14 the best bet for long term use, performance, and ease of repair. Unless you have a socketed IC 16.


Edited by zylon, Wed Aug 5, 2015 9:46 PM.


#8 SoundGammon OFFLINE  

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Posted Wed Aug 5, 2015 10:03 PM

Here's the 2 diagrams of the stella chip, 1st-2600 Sixer, 2nd-4 Switch...

 

4 switch doesn't even show pin 6!

 

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  • Schematic_Atari2600 SIXER.png
  • Schematic_Atari2600 4.png

Edited by SoundGammon, Wed Aug 5, 2015 10:08 PM.


#9 zylon OFFLINE  

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Posted Wed Aug 5, 2015 10:11 PM

Here's the 2 diagrams of the stella chip, 1st-2600 Sixer, 2nd-4 Switch...

 

4 switch doesn't even show pin 6!

 

 

They did add it in for the last few revisions. I wonder if the same diagram is available for 16,17,18



#10 SoundGammon OFFLINE  

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Posted Wed Aug 5, 2015 10:22 PM

Just took a look at the 7800 schematic, same thing, pin 6 UNUSED on the TIA chip!  

 

Hmmmm, makes think about trying something with a 820 ohm resistor!



#11 zylon OFFLINE  

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Posted Wed Aug 5, 2015 11:14 PM

...and 7800's are well known for washed out color in 2600 mode. :ponder:



#12 SoundGammon OFFLINE  

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Posted Wed Aug 5, 2015 11:37 PM

Got to order some resistors!

 

No Radio Shack here anymore... :(



#13 DrVenkman ONLINE  

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Posted Thu Aug 6, 2015 6:41 AM

Got to order some resistors!

 

No Radio Shack here anymore... :(

 

I bought about 1280 bulk 2% resistors in a few dozen different values on eBay for <$8 shipped ... I spot checked a few and got pretty accurate values, said "Good enough for my ham-fisted hobbies ..." and stopped worrying about it. One of those quarter-cent resistors works great to bring back color on the Rev 14 board, and another dozen or so have been used in some 8-bit mods that have turned out fine. :)

 

If I don't lose my motivation through the day, I'll try the mod on my 7800 today - my model is an AT-84 serial number version, complete with the never-used Expansion Interface and fully socketed. Should be fun. :)



#14 DrVenkman ONLINE  

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Posted Thu Aug 6, 2015 9:51 AM

Okay, did the 7800 today - I can't see much if any noticeable improvements with my Rev A 7800 board. Not worth even showing pics, to be honest. The weather here has turned storming and rainy since the "Before" pics and the overall change in room lighting might be enough to throw any minimal comparisons anyway. It would be interesting to know if later variants of the 7800 show improvement from this little mod.



#15 DrVenkman ONLINE  

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Posted Fri Aug 7, 2015 3:04 PM

Just a little follow-up after two days and half days or so with this mod in place ... I noticed last night and confirmed this morning with the Test Pattern Generator rom that my colors have drifted a bit. A couple minutes to take the case off again and then boot up the test patterns with a small screwdriver to adjust the color pot and things are back where they need to be again. 



#16 atari-dna OFFLINE  

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Posted Fri Aug 21, 2015 2:40 PM

Very informative thread gentlemen, thank you

#17 Kosmic Stardust OFFLINE  

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Posted Fri Aug 21, 2015 2:49 PM

You guys have me curious. I'm gonna go take another crack at my morning woody. :P



#18 Kosmic Stardust OFFLINE  

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Posted Fri Aug 21, 2015 4:53 PM

Nope. Mine is a revision 12. No resistor underneath the TIA. Picture is good enough. I'm just gonna leave it stock for now.



#19 spawnshop OFFLINE  

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Posted Sun Sep 6, 2015 10:48 AM

I'm gonna try this with my current mod.   I have a REV12, no resistor.  But I gotta buy them.   Anyone recommend a good place to get them cheap?

I don't have this one in my bag of goodies at home.



#20 zylon OFFLINE  

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Posted Sun Sep 6, 2015 10:55 PM

I'm gonna try this with my current mod.   I have a REV12, no resistor.  But I gotta buy them.   Anyone recommend a good place to get them cheap?

I don't have this one in my bag of goodies at home.

 

I found mine from old Soviet surplus being sold on ebay.



#21 DrVenkman ONLINE  

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Posted Mon Sep 7, 2015 7:51 AM

I'm gonna try this with my current mod.   I have a REV12, no resistor.  But I gotta buy them.   Anyone recommend a good place to get them cheap?

I don't have this one in my bag of goodies at home.

 

I bought a 1280 count assortment of resistors from eBay for under $8, shipped. Took about ten days to arrive but they've been great. I've used them in a bunch of mods and repairs for classic computers and they've worked just fine. 



#22 spawnshop OFFLINE  

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Posted Mon Sep 7, 2015 7:59 AM

 

I found mine from old Soviet surplus being sold on ebay.

 

 

I bought a 1280 count assortment of resistors from eBay for under $8, shipped. Took about ten days to arrive but they've been great. I've used them in a bunch of mods and repairs for classic computers and they've worked just fine. 

 

 

Well, I guess ebay it is then......Thanks guys


Edited by spawnshop, Mon Sep 7, 2015 7:59 AM.


#23 rednakes1 OFFLINE  

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Posted Fri Oct 14, 2016 9:45 AM

What I did first was to use kaboom and set them to get the greenest field possible and then switched games to compare.
But major changes easy to see on 12's and 13's. 16 is close but strangely, 13 is worse than 12. 
A few vaders had 14's, but most had 16 through 18 and about half of the 16's were with hard soldered IC's. it makes 14 the best bet for long term use, performance, and ease of repair. Unless you have a socketed IC 16.

Hi guys,

I came upon this thread after recently purchasing a 4-switch woody with Rev 13. Are you saying that the resistor will not make a big difference to a Rev 13 board?

Also, I am still using the RF video output, so will a future composite mod require this resistor as well for improved color?

I'm about to buy the resistor but want to be sure it's worth my time or not.

In regards to the soldering, I haven't opened up the metal shielding on mine to inspect the board, but is it easier to melt the existing solder under the IC pins to stick the resistor into them, or shall I use extra solder? I'm just worried about shorting the IC joints as I don't have the steadiest of hands.

Thanks!

Edited by rednakes1, Fri Oct 14, 2016 9:51 AM.


#24 zylon OFFLINE  

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Posted Sat Oct 15, 2016 3:36 PM

Rev 13 boards will show much improvement. In my testing, it had the most improvement because it had the worst color saturation of the 4 revisions tested to start.

I just put the resistor on the bottom side. Atari techs put it there if doing a repair or refurb. Some had it up top, presumably when being built.



#25 rednakes1 OFFLINE  

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Posted Sat Oct 15, 2016 3:46 PM

Rev 13 boards will show much improvement. In my testing, it had the most improvement because it had the worst color saturation of the 4 revisions tested to start.
I just put the resistor on the bottom side. Atari techs put it there if doing a repair or refurb. Some had it up top, presumably when being built.

Thanks. I'm thinking that the best approach would be to solder from the bottom side instead of directly solder onto the TIA. So I guess I'll have to remove the TIA from the socket before soldering, so that the solder doesn't accidentally attach to the TIA.

Edited by rednakes1, Sat Oct 15, 2016 3:47 PM.





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