💾 Archived View for uscoffings.net › retro-computing › systems › Tandy › t › hd1400.txt captured on 2023-01-29 at 05:38:31.
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Sb: 1400LT Hard Disk Fm: Stephen Lankton 70305,1142 To: jim tilly 76010,3227 (X) Jim, here is the fix I am using on the LT1400 for the problem I used to have where the use of the HD with the power adapter would discharge the battery. I unscrewed all the things necessary to get the mid chassis out. disconnected the red and black wire to the power suppy. unbent the little tabs on the PS cover and removed it. removed the PS board with 4 screws. On the 3500 there is a resistor in the lower right (as you look from the on/off switch side to the PS) and on the 3500A it is on the upper-left of the PS board. This is a part named R554 on the board with white paint. It is a 27 ohm resistor (mine was red, purple, black, red bands on baby-blue). Cut this out or unsolder it and replace it with an insultated wire. Now put this resister in the wire from the hard drive controller to the battery. Cut the red wire between the battery clip and the little black rubber thing on the wire from the HD controller board (the black rubber thing is a fuse). Solder the resister in there a 27 ohm, 2%, 2 watt should do it. But remember to put shrink wrap on the wires first AND you must do one more thing. Put a diode in parallel with this resistor. It can NOT, repeat NOT, be purchased at Radio Shack. It must be a Schottky barrier diode and no Archer/Radio Shack part is equivalent. Mine is a ECG586 and I am sure that an ECG585 will work. I tried the TNE585 and it is NOT equivalent and I also tried the Archer/RS 1N4001 and it is NOT equivalent. I should be a 1N5817 Schottky and the ECG works fine. Solder the anode end (the non-banded end) toward the battery. Then put the heat shrink on it, tuck it in, connect the red and black wire clips and cover to the power supply. screw it all back together and it ought to work just fine. $2 worth of parts, a soldering gun, screw driver and tape or heat shrink are all the tools you'll need. Oh, yes, and about an hour of time.