1200XL NiCon Capacitors

[Leone]

Hi all!

I've had a 1200XL in the closet for the last 10 years, and decided it was finally time to get to work exploring the Atari world. Aside from borrowing a neighbor's 800XL for a few days as a kid, my experiences from the era involved mostly the C64, then Amiga.

Perusing photos, it seems the 1200XL came with (mostly, at least) 2 brands of capacitor--Elna (made in Japan), and NiCon. Mine had the latter, and from what little I could gather online, these are Chinese.

I tested the NiCon caps with an ESR meter, and found all well within in spec save the 22UF/16V parts. Of these, most tested near the threshold (1 to 2 ohms), but one was clearly defective at 45 ohms! I also noticed the "rotten fish" smell while desoldering some of them, the typical hallmark of leaked electrolyte. I replaced every axial cap on the board with Nichicon VX series (same values and sizes as the originals, made in USA), the large one Nichicon VR.

FWIW, the original Japanese parts on my C64's (Nichicon, Elna, Shoei, KYOEI) have all tested OK (ESR similar to new ones of the same values). My suspicion is that if your 1200XL has the Elna capacitors, they are probably still just fine.

After replacing the caps, I fitted an Ultimate 1MB, Side2 cartridge, and one of Simius' RGB boards (this thing is RIDICULOUS with my old Sony PVM, stunning picture quality!). Absolutely loving this setup so far. My 4 year old son and I have been playing "Rescue on Fractalus" together the last few days... what an amazing game!

[Gunstar]

Glad you are liking your Atari. It's good you seem to know what you are doing too, since the 1200XL has a few issues from stock condition with compatibility, but since you already installed an U1MB, and video upgrade, you've already taken care of the major fixes needed, whether you knew it or not, when you did the U1MB and video upgrades...

 

Many 1200XL's have an issue with the keyboard where the ribbon cable connects to the keyboard as well, have you had any issues with the keyboard?

Edited November 4, 2018 by Gunstar

[Frankie]

Lets see a pic of the inside with all the goodies installed!

[gilsaluki]

Good news is, if the keyboard has gone south, Brad @ Best Electronics has replacement mylars. God Bless The Bradley.

[Leone]

Thanks for the comments guys!

 

I noticed the poor video quality immediately. It appeared someone had already monkied around with it (a few wires soldered on the board). I first tried the "Clearpic 2002" modification--night and day! However, it's night and day again with RGB. Aside from the razor sharp scanlines, darker tones are easily visible now without the need to crank brightness. For example, dark squares in the "Rainbow Walker" game aren't easily confused with the black ones anymore. I attached a picture (left RGB, right Y/C), but it stinks--it looks much, much better in person.

 

I ran the ribbon cable from the Sophia over the top of the SIO port... didn't want to cut any plastic.

 

The U1MB install went fairly smooth. I had to solder a few pins in for the ROM socket (lazy man's method ), then soldered the 4 wires to a separate socket under the CPU, which worked OK (attempting to keep everything somewhat easily returned to an unmolested state). I couldn't easily upgrade the U1MB firmware, since the Side2 didn't want to recognize .rom files for some reason. I had to pull the chip from the Side2 and flash it, after which the U1MB updated fine. I also read here about a capacitor modification for the U1MB/1200XL combo... without it, there was definitely some weirdness on occasion.

 

I forgot to mention the keyboard--yes, this was the worst part of the whole project! I bought the new mylar, after repeated tries managed a good connection, and all seems to be well. Some miniature spring contact setup there would be awesome.

 

This forum is an incredible resource, really made this job so much easier than it could have been!