Author Topic: TANDY 1000SX Restoration  (Read 2813 times)

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Offline rkabzTopic starter

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  • Country: au
TANDY 1000SX Restoration
« on: November 15, 2021, 06:48:49 am »
Hi group. I have recently come across an ancient Tandy 1000SX computer. I only have the base unit and it came with a 20MB Kyocera HDD and one 5.25" 360K TEAC floppy drive. I have disassembled the unit and was going to recap the power supply, so removed all caps and tested each one with an ESR tester. All were good, capacitance within limits and no leakage out of the ordinary. To make sure all caps would not stress out on power up, I 'formed' each one at rated voltage (this was a secondary leakage test) on a DC power supply, (200V mains caps at 50 volts). I then put them back in, hooked up mains power and loaded the PSU up with requisite minimum load as per tech manual. Low and behold, PSU ran perfectly, voltages near spot on and ripple OK and nothing exploded! So that saved a recap. Next on to the main board. Due to age I removed all socketed IC's and checked for corrosion and then put them back. I hooked up a composite monitor (NTSC compatible) and powered up the board. Garbage video. But there was one line that vaguely resembled text, so not all was bad and the board not completely dead. Anyway, removed all socketed IC's again. This time I cleaned all pins and because sockets were not machine pinned but old leaf contact types, I cleaned and lubed each IC pin with a switch cleaner/lubricant...made them a bit easier to get in and out. After quite a while of doing this I replaced all IC's and powered on again. And this time - a flashing cursor at top left and text on screen announcing "err I/O  3F8", some progress at least. No doubt the error has something to do with the printer interface which is a custom IC, thanks Tandy :()...anyway the board is now stuck in a loop trying to, I guess, read from the port to see if it's there...So a question to the group - does anyone out there have any experience with what the Tandy BIOS is looking for here, or 1000SX's or EX's for that matter? And does anyone have any Tandy 1000SX or EX parts? Any help much appreciated. By the way, the HDD was MFM type which would have been great, but it did not spin up...and after trying to rotate the motor gently with no luck, I decided to take the cover off and found that one head is essentially welded to the platter due to a head crash. Damn.
 


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