Tips 'N' TRicks
80-Column Switcher, Rev. 2
In the April '91 issue of Current Notes there appeared an article by The 8-Bit Alchemist titled "80-Column Switcher" describing how to build a switchbox so you can use the same video monitor with both your XEP80 and your computer's standard 40-column output. Immediately following the publicaton of that article, The Alchemist was deluged with requests from people asking him to "please build me one". None of those requests was ever satisfied.
But, you can build your own with readily available stuff from Radio Shack. For under $10, and you don't need any tools (bare hands will suffice). This is a guaranteed success for even the most ham-fisted technophobe. Purchase one each of #15-1247B (Mini A/B Video Switch) and three each of #278255A (Male F-Connector to Female Phono Jack Adapter). Just screw the adapters onto the three threaded connectors on the switch, and you've got yourself a genuine 80-Column Switcher!
There are some screws and double-stick tape and stuff you can use to fasten the Switcher to the top or side of your monitor if you wish. Connect your monitor to the center jack, and your computer and XEP80 to the ones on either side. You might need short lengths of RCA phono cables for this. Radio Shack sells them. Most people end up with a few spare RCA cables from their stereo system. You might want to rummage in your spare audio cable box before running to the Rip-Off Shack for cables.
Setting up the Switcher is a little tricky. Horizontal sync on the XEP80 is a slightly higher frequency than on your 40column output. So, if you adjust your monitor for a stable 80column screen, you'll find the picture shearing badly when you switch to 40 columns. When you adjust for a stable 40-column display, it wll be out of adjustment when you switch back to 80 again. This will drive you nuts.
Use the M-test to fix it. Boot up your computer with the XEP80 and use either BASIC or an 80-column wordprocessor to fill the screen with capital M's. (The middle of the M is exactly one pixel so a screenful of these is nice for monitor adjustments, especially focus.) Leave the XEP80 on, turn off the computer, re-boot in 40 columns, and again fill the screen with capital M's. Adjust your monitor for a stable 40-column display and make any sort of convenient index mark to note the control setting. Then switch to 80 columns (the XEP80 will still display the test screen which stays stored in its onboard SRAM as long as power is applied). Adjust the monitor for a stble 80-column display and note how far from the 40-column setting you had to turn the control. Now reset the control to a point midway between the 40- and 80-column settings, and you should find a stable display in either position. The exact settings will vary from monitor to monitor, but in general you should be able to locate a central point on the horizontal control that will provide a stable display in either 40- or 80column mode without having to re-twiddle the control each time you switch.
Parts Sources
With the heavy emphasis on hardware hacks in this issue of AC it might be handy to pass on word of some parts sources that carry items of more general interest than the usual fare found in Atari-specific vendors such as CSS, Best, ATV or B&C. Or maybe you're just tired of running to the Rip-Off Shack, whatever. The following suppliers are mailorder sources for electronics parts, tools, and supplies. Contact these folks and be sure to get their catalogs before you try to order stuff.
B.G. Micro P.O. Box 280298, Dallas TX 75228 USA. 214271-5546. VISA/MC. Excellent source for cheap DRAMS if you're doing a RAM upgrade. Would you believe a set of nine 150nS 256K DRAMS for $9.95? 1-megger DRAMS for $4.40 (not bad). How about a replacement 2793 for that aging 1050? They gottum, seven bucks. Replacement 6264 SRAMs for the XEP80, $1.40 (cheap!), and 32K SRAMs for the Black Box print buffer, five smackers (decent). And if you decide to build the SIO2PC (AC, Feb. '93), BG sells the MAX232 for a buck sixty-five. Nice mailing list to be on.
JAMECO Electronics 1355 Shoreway Road, Belmont CA 94002-4100 USA. Orders toll-free 800-831-4242. VISA/MC. A general source for a wide variety of general electronics parts, they sell everything required for any of the upgrades described in this issue of AC. Jameco publishes two separate catalogs: one for electronics parts and one for computers. You'll want both. In their computer catalog you'll have to wade through a ton of stuff for IBMs, but there are useful items in there such as rebuilt monochrome TTL monitors for under $100 or new ones for a little more. Also chips, DRAMS, soldering supplies, etc. Even a few items for the Apple 8-bits, Jameco is one of the last to support the old Apples.
JDR Microdevices 2233 Samaritan Drive, San Jose CA 95124 USA. Orders toll-free 800-538-5000. VISA/MC/Discover. Analogous to Jameco, slightly different stuff, a tad pricey. Also two separate catalogs for computers and parts, get both. Good selection and good service.
Digi-Key Corp. 701 Brooks Ave. South, P.O. Box 677,. Thief River Falls MN 56701-0677. Orders toll-free 800-3444539. VISA/MC. A hard-core supplier of parts, instruments, and supplies for your engineering-types, lots of interesting tekkie data on the parts they sell. Single-unit sales or bulk-lot OEM purchasing for big savings if you spend big bucks.
Mouser Electronics 2401 Highway 287 North, Mansfield TX 76063-4827 USA. Orders toll-free 800-346-6873. VISA/MC/AMEX/Diners/Discover/Carte Blanche. Another hard-core electronics part supplier, on the same order as DigiKey. Faster delivery in the US/Mexico/Canada since they have several regional mailorder distribution centers. Active/passive electronic parts and supplies. These guys will even sell you a bench-mounted hand press for cutting/stamping your own custom sheet metal chassis if you're into that sort of thing.
