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Atari 1050 UDN5713M chips question


kbj

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My bad, never mind about the pin advice as they completely repurposed the pin's use at the chip level which means they also included a pull down resistor on the chip to ensure a non-floating pin even when it is cut off which is the new "purpose" for single sided drives only. But the above advice is still sound for most other pins, never leave one floating or you can expect random results.

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@1050 Not a problem - thanks for confirming what I was reading about pin 25.  On mine it's definitely been cut off straight from the body of the chip - such a waste... But t hen I supposed if the FDC is dead, not so much so ?

Edited by kbj
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On 2/21/2021 at 1:55 AM, 1050 said:

. I would attempt to use a bit of thin wire stuck into the the socket and soldered onto what ever is left of the cut off pin right away. You don't leave pins to float since their logic state can change from internal chip leakage and that gets you random results any way you can slice that cake.

Not necessary, as it's an output that's unused, it's not a 3 state pin so can't actually 'float', it is set to logic 0 at power-on/reset and

is never changed, so it's fine as it is.

 

Edit: Sorry @1050 just saw your updated post

Edited by TGB1718
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Hi All,

 

So an update on this evil 1050 drive ?

 

I got 2 new FDC chips and replaced the one in the drive - still no joy - drive still not working.

 

I replaced the (tested!) working 6810 SRAM and still nothing.

 

I cleaned the pins on the 6532 again and what do you know!?  The drive now has gone from the spindle motor running continuously to now doing the 2 second start stop motor spin.  The stepper motor is still not moving so I checked the resistance at the stepper motor and I have what looks like 1 of the windings sitting at >9MR and another open circuit.  The other windings appear ok (about 34R) ?

 

Looks like I'm looking for a stepper motor.. any ideas where I can get one of those these days?

 

1050Stepper.jpg

 

I appreciate all the help you guys have given me!

 

Mark.

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1 hour ago, kbj said:

I got 2 new FDC chips and replaced the one in the drive - still no joy - drive still not working.

 

I replaced the (tested!) working 6810 SRAM and still nothing.

 

I cleaned the pins on the 6532 again and what do you know!?  The drive now has gone from the spindle motor running continuously to now doing the 2 second start stop motor spin.  The stepper motor is still not moving so I checked the resistance at the stepper motor and I have what looks like 1 of the windings sitting at >9MR and another open circuit.  The other windings appear ok (about 34R) ?

 

Looks like I'm looking for a stepper motor.. any ideas where I can get one of those these days?

I just tested in a 1050 with a stock Rev. L ROM with the stepper disconnected at J15.

 

If the head is positioned at track 0, the drive will power up, spin for 1 second, then spin down. (Great!)

If the head is positioned anywhere OTHER than track 0, the drive will fall into the POST failure 2s on/2s off loop.

 

Please also test your drive with J15 disconnected, and powering up with the head manually positioned at track 0 and again with the head positioned elsewhere other than track 0 and report back with your findings.

 

You may actually have a faulty track 0 sensor if you always get 2s on/2s off loop.

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22 minutes ago, Nezgar said:

You may actually have a faulty track 0 sensor if you always get 2s on/2s off loop.

When I had a faulty track 0 sensor, head did not move on powerup unless I physically moved the head

away from the sensor, then when powered on the head tracks back to the sensor position and stops, then again

it will not move.

 

I started a thread some time ago showing a track 0 sensor replacement, I'll see if I can find it, just in case you need one.

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it's 33 ohms per phase...   you stated that the stepper moved forwards and back then vibrated at one point. so unless you somehow cooked or broke it.. it should have been fine... this sounds like a track zero problem of either emitter/detector ...  so long as the fdc and rom are tested as good then that's where troubleshooting would have continued (track zero sensor). Give the stepper a full stroke with power off by hand leaving it halfway out... then power on and see if it moves at all anymore. It should either step forward and not back, or step forward and then all the way back, or step forward and back right where it is. This will give a clue about the track zero sensor.

 

If it returns to the sensor location and doesn't jam up tightly against the stopper then the track sensor should be good. If not check the sensor or replace, then move on to the possibly now damaged stepper.

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3 hours ago, kbj said:

The stepper motor is still not moving so I checked the resistance at the stepper motor and I have what looks like 1 of the windings sitting at >9MR and another open circuit.  The other windings appear ok (about 34R)

Please describe your measurements compared against mine below, which has a discrepancy?

 

J15 pins are in this order:

  1. Yellow
  2. Brown
  3. Orange
  4. Black
  5. Red (+12V)
  6. Red (+12V)

I measured the following:

 

Individual coils:

  • Red pin 6 to Yellow pin 1 - 32Ω
  • Red pin 5 to Brown pin 2 - 32Ω
  • Red pin 6 to Orange pin 3 - 32Ω
  • Red pin 5 to Black pin 4 - 32Ω

And combining coils:

  • Yellow to Orange - 64Ω
  • Brown to Black - 64Ω
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Hi @Nezgar

 

J15 pins are in this order: (Same as mine - yellow pin on J15 toward the 5v regulator)

  1. Yellow
  2. Brown
  3. Orange
  4. Black
  5. Red (+12V)
  6. Red (+12V)

I measured the following:

 

Individual coils:

  • Red pin 6 to Yellow pin 1 - 32Ω (My Measurement: Open)
  • Red pin 5 to Brown pin 2 - 32Ω (My Measurement: Open)
  • Red pin 6 to Orange pin 3 - 32Ω (My Measurement: Open)
  • Red pin 5 to Black pin 4 - 32Ω (My Measurement: Open)

And combining coils:

  • Yellow to Orange - 64Ω (My Measurement: 62.92R)
  • Brown to Black - 64Ω (My Measurement: 60.34R)

 

I made other measurements according to another post I read:

 

  • Red pin 5 to Yellow pin 1 - 31.36R
  • Red pin 6 to Brown pin 2 - 30.12R
  • Red pin 5 to Orange pin 3 - 31.76R
  • Red pin 6 to Black pin 4 - 30.4R

 

Looks like I have open circuit coils in the stepper then?  But then I've just thought, combining the coils shouldn't show nearly correct values?

 

I should also say that I measured J15 with the plug removed from the board. 

 

If I plug J15 back into the board, I get the following:

 

Individual coils:

  • Red pin 6 to Yellow pin 1 - 32Ω (My Measurement: 31.38R)
  • Red pin 5 to Brown pin 2 - 32Ω (My Measurement: 30.18R)
  • Red pin 6 to Orange pin 3 - 32Ω (My Measurement: 31.75R)
  • Red pin 5 to Black pin 4 - 32Ω (My Measurement: 30.48R)

And combining coils:

  • Yellow to Orange - 64Ω (My Measurement: 62.92R)
  • Brown to Black - 64Ω (My Measurement: 60.34R)

 

 

Mark.

 

Edited by kbj
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14 minutes ago, kbj said:

I should also say that I measured J15 with the plug removed from the board.

Sorry I just want to clarify here - I measured the connectors on the plug of the wires that lead to the motor itself, while it was disconnected from the motherboard. Not measuring the pins on the motherboard PCB.

 

If your measurements of of the motor directly are 30.4-31.76 as you wrote, then I think your stepper is OK, and we should continue to focus on the tests to confirm if the track 0 sensor is working... (powerup + spindown after 1 second when manually positioned at track 0, and powerup + 2s on/2s off motor cycling when manually positioned away from track 0)

 

Also - does your stepper move freely if moved manually when the drive is powered off? How about while the drive motor is on?

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3 minutes ago, Nezgar said:

Sorry I just want to clarify here - I measured the connectors on the plug of the wires that lead to the motor itself, while it was disconnected from the motherboard. No measurement on the PCB itself necessary.

 

If your measurements of of the motor directly are 30.4-31.76 as you wrote, then I think your stepper is OK, and we should continue to focus on the tests to confirm if the track 0 sensor is working... (powerup + spindown after 1 second when manually positioned at track 0, and powerup + 2s on/2s off motor cycling when manually positioned away from track 0)

 

Also - does your stepper move freely if moved manually when the drive is powered off? How about while the drive motor is on?

 

When I measured the pins with J15 removed from the board, directly on the plug, I get the first set of measurements:

 

Individual coils:

  • Red pin 6 to Yellow pin 1 - 32Ω (My Measurement: Open)
  • Red pin 5 to Brown pin 2 - 32Ω (My Measurement: Open)
  • Red pin 6 to Orange pin 3 - 32Ω (My Measurement: Open)
  • Red pin 5 to Black pin 4 - 32Ω (My Measurement: Open)

And combining coils:

  • Yellow to Orange - 64Ω (My Measurement: 62.92R)
  • Brown to Black - 64Ω (My Measurement: 60.34R)

 

If I measure the pins with J15 plugged back into the board, directly on the plug, I get these measurements:

 

Individual coils:

  • Red pin 6 to Yellow pin 1 - 32Ω (My Measurement: 31.38R)
  • Red pin 5 to Brown pin 2 - 32Ω (My Measurement: 30.18R)
  • Red pin 6 to Orange pin 3 - 32Ω (My Measurement: 31.75R)
  • Red pin 5 to Black pin 4 - 32Ω (My Measurement: 30.48R)

And combining coils:

  • Yellow to Orange - 64Ω (My Measurement: 62.92R)
  • Brown to Black - 64Ω (My Measurement: 60.34R)

 

The stepper moves freely when the power is off or if it's on.. no difference..

 

If I move it away from track 0 (sensor) and switch on, it doesn't move or make any noise..

 

Hope that clarifies?

 

Mark.

Edited by kbj
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6 minutes ago, kbj said:

Individual coils:

  • Red pin 6 to Yellow pin 1 - 32Ω (My Measurement: Open)
  • Red pin 5 to Brown pin 2 - 32Ω (My Measurement: Open)
  • Red pin 6 to Orange pin 3 - 32Ω (My Measurement: Open)
  • Red pin 5 to Black pin 4 - 32Ω (My Measurement: Open)

Are you sure your probes were making contact to the terminals? That's the only explanation I can see while also being "in spec" when plugged back into the motherboard... (well... other than the stepper being FUBARed of course heh)  I had to stick my multimeter probes in from the top of the connector, where the wires lead out to the motor to make contact...

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7 minutes ago, kbj said:

If I move it away from track 0 (sensor) and switch on, it doesn't move or make any noise..

And what about if switched on while manually moved to track 0?

 

And also how about both conditions with J15 disconnected?

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28 minutes ago, Nezgar said:

And what about if switched on while manually moved to track 0?

 

And also how about both conditions with J15 disconnected?

Ok..

 

Sorry, just replaced the header for J15 as a pin broke off when I removed it...

 

I stuck a header temporarily into J15 and measured from the header - same results, all O/C.  I even measured continuity from the bottom of the temporary header to the tops of each crimped wire connector and all were good - no bad crimps that I can see.

 

Measured again from the top of each wire where it goes into the individual crimps on each wire in the socket, same - O/C

 

If J15 is connected and I switch on and manually move the head to track 0, it moves freely by hand and nothing happens.

 

If I disconnect J15, the same.  Moving the head manually does nothing.

 

I've also ordered this TT ELECTRONICS / OPTEK TECHNOLOGY SLOTTED OPTICAL SWITCH, 3.18MM, PANEL OPB842W51Z: Amazon.co.uk: Business, Industry & Science from Amazon as someone else in a forum suggested it was a drop in replacement for the track zero sensor...

 

Head hurting now! Thanks for the help!

Edited by kbj
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4 minutes ago, kbj said:

If J15 is connected and I switch on and manually move the head to track 0, it moves freely by hand and nothing happens.

 

If I disconnect J15, the same.  Moving the head manually does nothing.

I meant move the head to track 0 *before* switching on the drive.... In a good drive that should produce 1 second of disk rotating motor time, then off. Is your disk spinning motor even turning anymore?

 

With the head not at track 0 when switched on, with J15 disconnected, expected behaviour is the disk spinning motor to loop 2s on / 2s off.

 

Before you had it doing 2s on/2s off somehow?

6 hours ago, kbj said:

The drive now has gone from the spindle motor running continuously to now doing the 2 second start stop motor spin. 

 

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4 minutes ago, Nezgar said:

I meant move the head to track 0 *before* switching on the drive.... In a good drive that should produce 1 second of disk rotating motor time, then off. Is your disk spinning motor even turning anymore?

 

With the head not at track 0 when switched on, with J15 disconnected, expected behaviour is the disk spinning motor to loop 2s on / 2s off.

 

Before you had it doing 2s on/2s off somehow?

 

Ahh - that's what I meant - I moved the head back into the sensor and switched it on - nothing - no movement.  With J15 disconnected and doing the same, same issue.

 

The drive is still doing the 2sec on / off thing.

 

Mark.

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12 minutes ago, kbj said:

Ahh - that's what I meant - I moved the head back into the sensor and switched it on - nothing - no movement.  With J15 disconnected and doing the same, same issue.

I would hope there is no movement with J15 disconnected. That should be impossible.  :)

 

12 minutes ago, kbj said:

The drive is still doing the 2sec on / off thing.

So does it ALWAYS do the 2sec on / off thing no matter where the head is positioned? (track 0 / elsewhere)

 

If so, that points to a faulty track 0 sensor. (always registering NOT at track 0)

 

To confirm: Disconnect J10. (The second-furthest back jumper block at the back left of the drive) This will trick it to think it's "always" at track 0. With that disconnected, see if the drive now powers up with motor on and spindown after 1 second instead of the 2sec on / off thing.

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1 minute ago, Nezgar said:

So does it ALWAYS do the 2sec on / off thing no matter where the head is positioned? (track 0 / elsewhere)

 

If so, that points to a faulty track 0 sensor.

 

To confirm: Disconnect J10. This will trick it to think it's "always" at track 0. (The second-furthest back jumper block at the back left of the drive) With that connected, see if the drive now powers up with motor on and spindown after 1 second instead of the 2sec on / off thing.

Yes, it always does the 2sec on/off no matter where the head is on power up.

 

I disconnected J10 and no matter where the head is before power up, it still does the 2sec on / off..

 

Mark.

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Just now, kbj said:

I disconnected J10 and no matter where the head is before power up, it still does the 2sec on / off..

Wow, so confirmed not stepper, confirmed not T0 sensor. Something else thats triggering the power on self-test failure conditions!

 

? ?

 

Since you indicated cleaning the 6532 improved the situation, maybe we still have a situation with bad IC contacts in sockets. The original sockets are only single wipe and prone to corrosion - maybe something to start planning replacing the sockets. You could temporarily place the IC's machine sockets, then stack those into the existing sockets to see if that improves things (maybe better conductivity etc)...

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1 minute ago, Nezgar said:

Wow, so confirmed not stepper, confirmed not T0 sensor. Something else thats triggering the power on self-test failure conditions!

 

? ?

 

Since you indicated cleaning the 6532 improved the situation, maybe we still have a situation with bad IC contacts in sockets. The original sockets are only single wipe and prone to corrosion - maybe something to start planning replacing the sockets. You could temporarily place the IC's machine sockets, then stack those into the existing sockets to see if that improves things (maybe better conductivity etc)...

Even with the O/C reading on J15, you think that the stepper is okay then?

 

When looking at the output pins on the 6532 that go to the 8 pin driver IC's, it just appears that there's noise on them?  Also looking at the pins on the 8 pin drivers, I don't see the expected waveforms as indicated in the service manual - could I have another bad 6532 IC maybe?  I would have thought that removing J15 and checking the pins on the 6532 (19,20,21,22?) that I would expect to see some pulses..

 

The main IC's (CPU, ROM, RAM) have all been checked and even replaced with known good chips - and I see data on the databus and addressbus - and all looks normal.. and with the post 2sec on/off I think we can be sure that the CPU etc. are running code from the EPROM and the stack for the 6507 must be available etc you think?

 

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32 minutes ago, kbj said:

Even with the O/C reading on J15, you think that the stepper is okay then?

We have eliminated the stepper from the equation, so I guess there still could be an issue there - but I have a drive apart here with J15 + J10 disconnected and it powers up with a happy 1 second motor spin that I'm referencing against. If your stepper is bad, we can't test it for now because we know now there's something else up with your motherboard logic that needs to be sorted out first.

 

There's RAM in both the 6810 and 6532 that could be at fault. (or maybe some of the data/address line pins are not making good contact, causing them to appear bad) I'd have to review the 1050 source listing to get some more ideas of conditions that can cause it to go to that failure mode.

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Just now, Nezgar said:

We have eliminated the stepper from the equation, so I guess there still could be an issue there - but I have a drive apart here with J15 + J10 disconnected and it powers up with a happy 1 second motor spin that I'm referencing against. If your stepper bad, we can't test it because we know now there's something else up with your motherboard logic that needs to be sorted out first.

 

There's RAM in both the 6810 and 6532 that could be at fault. I'd have to review the 1050 source listing to get some more ideas of conditions that can cause it to go to that failure mode.

The 6532 I have is from a working 2600 - which works fine - controllers and all.

 

I have also changed the 6507 from the same working 2600 with no difference to the original 6507 (which is back in).

 

The 6810 has been changed for another working spare I have - and I have a chip tester pro from the 8-bit museum which tells me over and over that the 6810 is fine.

 

I read the Tandon EPROM in my burner and compared it to one I got from another user - all compared fine.

 

I even bought another FDC IC - no change - original back in.

 

I replaced U11 (I think) in case that was an issue (from a previous post here).

 

I've replaced both the UDN chips with 75478 equivalents (apparently) - no change so originals back in..

 

I could have built a new drive! ?

 

I think that all that's left here at this stage is to replace all of the sockets as you say - which I'll do tomorrow and post a reply here..

 

Thanks Nezgar, for all of your help tonight - I really appreciate it.  I fix old retro hardware as part of my IT business, but this is my first time working on a 1050 - and it's kicking my a$$ ?

 

I'll post again once I change all of the sockets.

 

Mark.

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