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Atari 1050 - Disconnected Drive Mechanism

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I received an untested 1050 drive from eBay and found the floppy connections were all disconnected (J1,J6,J10,J11,J12,J14,J15)

 

There are no labels on the connectors themselves to indicate which "J" they should go to and the colors don't match what was shown in the 1050 service manual on page 27. See below the colors associated with my connections.

 

Can anyone post their connector setup if it is similar to the one below?

 

 

IMG_20180930_150017032(1).jpg

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You have a made in hong kong WST mech, later production, so that's why it doesn't match the earlier tandon FSM.

 

I can post a picture from mine a bit later you can use to match up.

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After a significant amount of image searching, I was able to find an image which matched my drive, however, the drive still doesn't work.

 

My symptom:

  • No drive activity at all when putting a disk in the drive and closing the level.

 

Things I've tested so far:

  • Voltages at T13 (+5), T14 (+12)
  • 74LS00
  • Voltages and grounds on all chips

 

I attach an image here for the next person in the same position:

img_20180930_163347481996359384.jpg?w=63

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Good Internet scavenging :) What happens when you turn on the computer with the drive on? Do you get boot error instead of BASIC "READY" prompt?

 

If so, that would indicate 1050 CPU, ROM are OK and passed self test, just not communicating with the mech. If not, something else is wrong, and you'd start by swapping out the main IC's one by one: 6810 RAM, ROM, RIOT, CPU.

 

Edit: does the mech turn the centre spindle at all when initially turned on?

 

Note, every WST drive I've seen uses an EPROM, so you won't be able to directly swap a mask ROM from a Tandon equipped drive without changing the jumpers above the socket. If you have an EPROM programmer, you can dump the existing ROM as a 27C32, and see if contents are readable, and then compare to previouslty dumped WST rom.

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Page 17 of the Sams Computerfacts Manual for the 1050 has an illustration which helped me determine the following.

 

http://www.atarimania.com/documents/Atari_1050_Disk_Drive_Sams_Computerfacts_Technical_Service.pdf

 

J1: 4-pin, spindle motor

J10: 4-pin, Track 0 sensor

J11: 4-pin, write protect sensor(not shown in illustration)

J12: 2-pin, drive motor on LED(not shown in illustration)

J14: 3-pin, diskette enable switch

 

J5: 5-pin, read/write head

J15: 5-pin, stepper motor

 

The WST mechanism appears to have 2 2-pin connectors which would connect to a single 4-pin header, likely J10.

You should be able to determine this using the above mentioned illustrations and tracing the wires.

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Nezgar:

>does the mech turn the centre spindle at all when initially turned on?

No spin, Power LED is on

 

> Do you get boot error instead of BASIC "READY" prompt?
No boot error, just the "READY" prompt -- listening to the power up audio, it's the same regardless if the drive is on or off

>If so, that would indicate 1050 CPU, ROM are OK and passed self test, just not communicating with the mech.

No such luck

 

>If not, something else is wrong, and you'd start by swapping out the main IC's one by one: 6810 RAM, ROM, RIOT, CPU.
I don't have another drive to swap stuff with yet

 

BillC:

Thanks for the info

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BillC:

Do you happen to know what voltage (+12?) is needed for J1/4 - would like to see if I can get the motor to spin at least.

 

The drive motor circuit is fairly compex, involving U5, Q4, Q6, CR14 and numerous capacitors and resistors to regulate the speed. The portion of the schematic concerning it is near the middle right of page 3 of the manual I linked.

 

The bottom of page 6 has some troubleshooting instructions.

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