ATARI 1050 Drive - Head only moves forward and no led activity

[asapreta]

Hi all.

 

I am trying to fix my Atari 1050 floppy drive.

 

When I got it, the stepper motor was kinda stuck. I ordered a new one and a PIA IC too because people told me as the motor was "stuck" the PIA could have been damaged too

.

Today I replaced both but its behavior didn't change: when I power it up, power led lits, the main motor spins (I replaced the belt too), the head moves forward a bit and the activity led won´t lit.

 

If I continue to power off and on again the head will reach the "upper" limit and keeps there.

 

It happens connected or not to a Atari XL (tested on a 600XL and a 800XL)

 

I was worried someone tried to mess with it before and double checked all cable connections inside.

 

But now, I don't know what is happening.

 

Any clues?

 

Thanks

[asapreta]

A friend just found this video and looks like it is my problem, probably as the head moves back when J10 pins 1-2 are shorted, I may have a dead sensor.

[_The Doctor__]

correct that is a bad track zero sensor indication.

[guus.assmann]

Hello,

 

This behaviour would happen if the track zero sensor is not working.

It can be checked quite easy.

One side is an infra-red Led. Just see if there's a voltage drop across it, or accross the resistor that feeds it.

And the foto transistor on the other side can be checked as well.

Just measure the voltage across it. This should be low when the led is active and shining on the transistor.

The voltage should change if you put a piece of paper in the gap.

You can also check the voltage on the input of the PIA that processes the signal of the Zero-sensor.

Just check the schematic diagrams for this part.

 

BR/

Guus Assmann