An Experiment: Ultra Video Part 1

[+Larry]

I have several XE and XL computers that can benefit from video upgrades, so here is XE #1. It is stock, except for a 32-in-1 OS module. As you can see from screen shot #1, it really has pretty decent video (as do most XE's, IMO). My only complaint would be that the color lacks saturation, including "wimpy" text contrast. Of course, XE's vary. Displays vary. What we see varies...

 

I've added shots here for most all of FJC's Ultra Video upgrade. Mind you, this is an NTSC machine, and I think some differences vs. PAL were revealed along the way.

 

#2 is "Oops" -- where did the text go? -- when I cut the RF modulator out. As luck would have it, I didn't remove the modulator; I just clipped the 5 leads to the mobo. Restoring the middle lead with a bit of solder restored the text.

 

#3 shows the text restored by the soldering of the middle RF connection.

 

#4 provides the results of R53 and R204 being replaced with 75 Ohm resistors. To my eyes, this helped the saturation, but the text is still lacks "punch."

 

#5 replaces R116 with the 8.2 Ohm resistor. Maybe the text is a bit brighter. Maybe.

 

#6 shows R202 replaced with another 75 Ohm resistor. I can see no difference here.

 

#7 is supposed to be a 220 uf cap in place of the original 10 uf cap. I had to use 100 uf -- all I had on hand. The Super Video for the XE (Atari Classics, Dec. 1993) calls for either 100 or 220 so I went with the 100. I do believe the text looks better.

 

#8 is R205 replaced with a 1N4002 diode. Hmm. Where did that chroma go?

 

#9 shows R205 replaced with a 75 Ohm resistor (as in the Super Video mod).

 

All-in-all, the changes are reasonably subtle. Nothing like when you start with a stock XL with all of those issues. But still, it is improved. The saturation is better and the text is a bit more vibrant.

 

The next XE is completely stock, and it's display is not so good as this one. We'll see how that one fares with the Super Video mod.

 

-Larry

[jmetal88]

I honestly think it looks better in the stock configuration.

[+tf_hh]

Hi,

 

first: Take a shottky diode instead of using a normal silicon diode, for example BAT41, BAT42, BAT43, BAT85 and much more. The normal 1N4xxx series or the well-known 1N4148 cut of voltage by nearly 0,7 volts, the result is a too weak signal for some televisions or monitors.

 

Second: I have built-in this Ultra-Video 1.0 (XE) in many devices and change the value for R116 to 22 or 33 Ohms (in the manual it´s 8,2 ohm). This seems to be the best balance between sharpness and moire-effects.

 

But over all, the picture in the XL series are always better :-)

 

Regards, Juergen

[+Larry]

Hi Juergen-

 

You are saying to try the Schottky diode in place of R205 (where the 1N4002 didn't work as anticipated)?

 

Any particular value you would suggest?

 

What about a 1N34A as a sub?

 

-Larry

[atari8warez]

Stock 130XE.

[+tf_hh]

Hi Larry,

 

You are saying to try the Schottky diode in place of R205 (where the 1N4002 didn't work as anticipated)?

 

Any particular value you would suggest?

 

What about a 1N34A as a sub?

 

The 1N34A is a germanium diode with a forward voltage drop of about 1 volt, this is higher than classical silizium diodes (0.7 volts). The examples above I wrote (BAT41 etc.) are very common and should be can buyed at any electronics store. You don´t need such a high valued one, any shottky diode with 0,1 amps current is enough (forward voltage also).

 

Yes, replace the resistor at R205 with this diode, the cathode (marked with a ring) to the right.

 

Juergen