Fix bad video on II Plus caused by RAM card?

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Fix bad video on II Plus caused by RAM card?

I recently got an Apple II+ with a clone of the Saturn 128 memory card installed. I have it connected via composite video out to a modern LCD TV. With the memory card installed, there is a lot of red and blue color bleed around text on the screen, and a bunch of vertical blue dashed lines that are continually pulsating. Without the memory card, the text is crystal clear. Interestingly, whenever I load a program on disk, the bad text and vertical lines clear up while the disk drive is running, then come back.


Bad:

 

Good (while disk is loading):

 

Is there any way to fix this? Should I find an official Apple 64k upgrade card and use it to replace the clone Saturn card? Do I even need a 128k memory upgrade? :)

 

 

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Electronizer wrote:Is there

Electronizer wrote:

Is there any way to fix this? Should I find an official Apple 64k upgrade card and use it to replace the clone Saturn card? Do I even need a 128k memory upgrade? :)

I think there isn't the one and only solution because this seems to be a timing issue. Sorry but I don't know the schematics of the saturn boards but I see some pics of that card. Every TTL chip (the 74LSxx) is a candidate to replace but also the MC3242AP (a DRAM multiplexer).

 

Regards

Ralf

 

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Maybe your problem is not

Maybe your problem is not related to the RAM card at all.  Somehow a 3.58MHz color burst frequency level that passes in a text mode despite the color killer circuit in your Apple ][+ to your modern TV is sufficient for the TV to switch in an NTSC color mode.  You can lower to the minimum the color saturation via the TV set's controls. You could use a different TV set...

 

 

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Curious to see the RAM Card you are using...

Curious to see the RAM Card you are using...

Can you post a pic of the card?

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Could be partially RFI also. 

Could be partially RFI also.  Is this a later model ][+ with the rear shielding?  Are the floppy drive cables the grey shielded ones or the early style rainbow ribbon ones?

 

 

 

 

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same problem but reversed

I have a similar problem, with the screen with either the 128k board or the language card

the screen is nice when the floppy is stopped

and I have color patterns when the floppy is working

 

when the memory board are removed the screen is ok with the disk either on or off

 

I reduced the effect by changing the value of the resistor in the color killer circuit

(before the problem occured when I had any board inserted in any slot)

 

 

 

 

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Thanks everyone for the insights!

Thanks everyone for the insights!

I played around with it some more. Apparently I wasn't remembering the symptoms correctly. It's not just the memory card that causes video noise, it's similar to what dvador mentioned: if any card is present, then the video noise appears. Without any cards, it's a nice, clean text display.

Where is this color killer resistor, and what value should I change it to?

 

Here is a picture of the RAM card:

And here is one of the internals (not sure whether the late model shielding is just supposed to be the metallic paint on the inside of the case or something more substantial):

As I received it, this machine also had a Viewmax 80 card, an Alaska card, a Disk II card, a clone CP/M card, and an RF modulator. Every single cable coming out the back had been cut off :( The printer card is for a Trendcom 100 40-column thermal printer. I had the printer, and as luck would have it, a friend had the card. The printer is a neat little device, and brings back memories of the Silentype my dad had in his work setup.

Are there any other video mods that are typically done on these machines to improve the video output?

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I wrote  you it was not

I wrote  you it was not related to the RAM card just wanted to be more polite to the other poster that had directed you to dig into the schematics and chips of the Saturn card ;) . Try to rotate gently the COLOR TRIM capacitor.

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Electronizer wrote:It's not

Electronizer wrote:

It's not just the memory card that causes video noise

Some additions to my first post that directs you to timing issues: if the problem exists also with other cards there is probably a timing issue with the mainboard.

 

The signals Phi0 and Phi1 are a bit suspicios, IMHO. These are generated by the 74S175 on position B1. It seems to be important that this chip is a 74S and not a 74LS type. Try to replace this one. My next step would be replacing the three 74LS138 on the positions F12, F13 and H12. These chips are also responsible for the right timing of the cards.

Regards

Ralf

 

 

 

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Good ideas

Thanks Casablanca and RalfK—I’ll try playing with the color adjustment cap first since that’s easy.

Would there be any benefit to using AS or ALS instead of S series parts to reduce the power dissipation? I’m guessing it probably won’t make a difference if it’s just a few chips, though maybe fanout is an issue too?

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Electronizer wrote:Would

Electronizer wrote:

Would there be any benefit to using AS or ALS instead of S series parts to reduce the power dissipation? I’m guessing it probably won’t make a difference if it’s just a few chips, though maybe fanout is an issue too?

Fanout is one thing, the other is the timing. Exactly that seems (for me) your problem. In 1977 when the Apple II was created AS and ALS were not available, AFAIR. They came 10years later.

Regards

Ralf

 

 

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The computer is running as

The computer is running as designed, I wouldn't have wasted time with changing TTL ICs unless they are definitely burned which is not the case. Try another TV or monitor. Try the same TV with another Apple2 computer and then listen to illogical advice from doubtful parties.

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