Zarcon Dee Grissom's Idea Page
EV9
Updated 08APR2008
Home > Meet the computers > SuperCalc1 
Why did this little 25MHz 286, get called SuperCalc AKA Super-Calculator?
Well in short, it became a desktop calculator with far more capabilities then Any hand held calculator. just fire up Qbasic, and type in print followed by just about any formula, run the program, and it would display the results. When the handhold calculator just didn't have the functionality, capacity, or shear amount of digits, SuperCalc could do the job.
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That piece of cardboard, is nothing more then a baffle, to force ALL the incoming air past the guts, to cool them, before being exhausted out the back by that PCI-slot fan. That heat sink, is indeed after market, and helps cool the brain of the computer, the 286. This computer has the entire Meg of RAM, along with whatever amount of video RAM for the on board video chip. it seams to be a rarity to come across an on-board video solution that dose not leach off the main memory. The black stuff on the top cover, is rubberized undercoat, to further reduce noise. the cloth looking stuff on the hard drive bracket, is friction tape, to help act as a vibration bushing of sorts.

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Last week I got some coffee in the keyboard, that prevented the keys from coming back up after being pressed. terrible waste of coffee, for witch I hope the great coffee gods, may some day forgive me for. I turned off the computer and cleaned out the keyboard. when I turned on the comp again, it had forgotten everything. A sure sign that the BIOS battery (now over 17 years old) was dead. I took the opportunity to open up the computer to clean out the cobwebs, and years of dust. Then decided to double check all them aging electrolytic caps in the power supply. yep, there quite dried up. A 2200uf cap, should not measure in at less then 500uf.

Well the first thing I did was to take pictures of ALL the jumpers I could find, to ensure that if they fell off, I would know where they belonged. They seem to be labeled, however my guess is probably as good as yours as to what they actually do. I didn't bother trying to find documentation as to what they did. this computer runs in it's current configuration, as it did back in 1991, so I will leave the jumpers alone.

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the camera refused to focus for this one... w.t.a.l.
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the camera refused to focus for this one... w.t.a.l.
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Then I replaced the dead BIOS battery, and cleaned out the socket with alcohol. this particular clip, can be very deceiving, that metal piece on top of the battery only springs up so far before the entire battery socket busts into a million bits and pieces. the battery needs to be gently lifted, then slid out away from that metal retaining clip thing.

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Last I pooled out the power supply modal thing, to do a quick visual inspection. the tainted/burnt spots on the PCB are a sign that the components in that location are getting hotter then they should be getting. given the age of this computer I did not hesitate to locate identical ratted caps to replace the seven-teen year old ones. the decreased physical size of the newer components, allowed barely enough room for some additional metal film caps, a slight improvement. then I drilled/cut some vents for air to help cool the hotter components. I thought about replacing the old diodes (0.7v) for newer high-efficiency Schottky (0.135v) ones, and decided that would probably throw the output voltages beyond adjustable limits.

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well in closing, this unit uses a -12 white, +12 purple, COM black, COM black,  +5 red, +5 red,  power supply. The amp ratings on the board are labeled as -12v 0.11A, +12v 0.6A, and +5v 3.3A. The board dose not appear to have any kind of booster inductor ("forward" or "buck") circuit, indicating a much lower switching frequency. and the input full bridge 120VDC input circuit indicates that this unit is strictly for 120VAC mains.


Gallory TBD


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