Task: Replace the Track 0 Sensor on an Indus GT Floppy Disk Drive for the Atari 8-Bit Computers
Needed: Web browser, Indus GT, Track 0 Sensor, Soldering Iron
Time: 30-60 minutes
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Introduction I have four Indus GT floppy disk drives that I have accumulated over many years. I recently pulled them out to test them and found that one would power on but would not boot. The LED showed a G5 error on the LED which indicates a read-write error according to the field service manual. I cracked open the case and discovered the head was not seeking to track 0 upon power up. Interestingly, it would boot just fine if I moved the head to track 0. This was a good sign and pointed to the track 0 sensor. Inspection of the sensor showed that the wire connections to the sensor were falling apart. This did not see reparable given how small and fragile the plastic case of the sensor is, so I ordered and installed a new one. This fixed the problem and now I have four working Indus GTs.
Below are instructions for this replacement assuming this is the correct diagnosis.
Instructions
First, order a new track 0 sensor from Digi-Key or similar electronics provider. I got mine for $5.31 plus shipping from Digi-Key. The manufacturer part number is OPB840W51Z and the Digi-Key part number is 365-1929-ND.
Second, open up the Indus GT case to expose the insides. This can be done by removing the four screws on the bottom plate and the two screw holding the plastic molding piece to the back of the drive. The metal case should slide off toward the back of the unit.
Third, remove the old track 0 sensor by removing the two screws holding it down. You will need to cut the existing wires leaving some length to attach the new ones from the new sensor. I used a sharpie to add tick marks on each wire indicating whether they were attached to pin 1 (bottom left), pin 2 (bottom right), pin 3 (top left), and pin 4 (top right) with directions from looking at the back of the sensor where the pins are. This is important to make sure they get connected correctly to the new sensor.
Fourth, cut the wires on the new sensor to match the length needed to connect to the wires from the Indus GT.
Fifth, strip the rubber coating off the end of the wires so they can be connected to each other. Before connecting then place some rubber shrink wrap tubing over each wire that will later be heated to protect the exposed wires from shorting. You can also use some electrical tape after the fact.
Sixth, connect the wires using the tick marks as a guide. Then apply a small amount of solder to hold them together. Note that the red wire on the sensor is the 5v power line. You can confirm you have the right wire coming from the Indus GT by powering it on and testing that line with a multimeter.
Seventh, heat the shrink wrap tubing to cover the connections. Alternatively, wrap them with some electrical tape.
Eighth, screw the new sensor to the board.
Ninth, plug in the Indus GT and try to boot a disk. You should see the head seek to track 0 when you power it on. You may need to adjust the sensor by loosening the screw and moving it forward or backward.
Tenth, reassemble the casing and finish.
Comments This is a pretty easy and inexpensive fix if you don’t mind a little soldering. The soldering is optional if you can find a way to keep the wires connected to each other with some tightly wrapped electrical tape, for example.
This repair should work well for the Atari 1050 drive that also uses the same Tandon drive mechanism.