810 - Diagnostic help needed

[Rybags]

I just picked up a gifted 400 with 810 drive today.

 

I've got a PDF of the Field Service Manual but it seems not to be entirely useful. As far as I can see, it doesn't even describe test points on the power board to verify correct voltages.

 

As for the drive itself - it was looked after during it's life, and probably spent 15+ years stored in a box. It's the "big mouth" door type which opens leaving the great 6x1 inch gap exposing the innards. I've only pulled the cover off so far, the power board looks fine in that there's no swolen caps.

 

Power up: the drive powers up OK and the LED comes on with the drive spinning. But, if the drive is connected to a computer via SIO and the computer is powered on, the drive will not stop spinning (no I/O operations are occurring, though). When the computer isn't powered, the drive stops spinning after the normal 5 seconds or so.

Also, it manages what seems like maybe 1 track of seek movement - regardless of what position I put the head in. The band around the stepper motor seems to be fine though.

 

Operational: I've left the switches as drive 1, connected to my 130XE with DOS already loaded. Tried issuing directory command for Drives 1 through 4, no response at all - just Timeouts. So, it seems the drive doesn't want to talk to the outside world.

 

 

Also, the FSM makes mention of a head alignment disk - is this the type of thing which can be created on a known good drive? Is this disk anything special, or does it just contain a bit of software and some nice repeating data patterns?

Edited March 13, 2009 by Rybags

[Bryan]

I believe that when the drive is first turned on the first thing it should do is find track 0 by stepping backwards 40 times or so (there is no T0 sensor). If it doesn't do that, then it either can't move the stepper properly or the firmware has crashed.

 

(big mouth means MPI mechanism instead of Tandon)

Edited March 13, 2009 by Bryan

[Rybags]

Just pulled it down - removed side board, top board. Quick check of tracks/joins, pushed socketed chips down. Aside from a bit of dust and the normal sporadic bubbling of the laminate, everything looked normal.

 

No difference. Seems like it steps once, then no further action regardless of head position.

[Bryan]

Well, the things I can think of are:

 

1. Check pin 3 of the voltage regulators (78xx) and make sure they are within spec.

 

2. Sometimes the connector between the back board and the side board becomes flaky. You probably would have discovered this problem while playing with the open drive, though.

 

3. Start replacing things on the side-board if you can pull spares from something else. The fact that it stops spinning on its own indicates that it half-works.

 

It's been a while since I worked on 810's, but I always had another one to swap parts with to figure it out.

[+Larry]

I just picked up a gifted 400 with 810 drive today.

...

Also, the FSM makes mention of a head alignment disk - is this the type of thing which can be created on a known good drive? Is this disk anything special, or does it just contain a bit of software and some nice repeating data patterns?

 

This is the "cat's eye" alignment disk. Requires a 'scope to be used properly. However, a known good disk (especially a commercial disk) can be substituted with some caveats. (Presume this is what you are referring to in the FSM.)

 

-Larry

[Rybags]

OK. Voltage Regulators checked. Reading around 12.25 and 5.25.

 

Can't really "swap out parts" since this is my only 810 - only got 2 x 1050s.

 

I guess I can replace stuff on the side-board if they happen to be generic LS off-the-shelf ICs.

[sup8pdct]

Do you have a logic probe? One trick that sometimes works for me is to check each data and address line from the processor while going to see if each is pulsing.

The ram, processor and 6532 are common with the 1050. Maybe an option there if you are willing to swap them.

 

James

 

OK. Voltage Regulators checked. Reading around 12.25 and 5.25.

 

Can't really "swap out parts" since this is my only 810 - only got 2 x 1050s.

 

I guess I can replace stuff on the side-board if they happen to be generic LS off-the-shelf ICs.

[Rybags]

Nope. Just got an oscilloscope and multimeter.

 

Guess I could just hook the scope up and see if there's life.

[sup8pdct]

Guess your multimeter doesn't have a logic function like mine does.

 

The scope.... DROOL!!!!!!!

 

James

 

Nope. Just got an oscilloscope and multimeter.

 

Guess I could just hook the scope up and see if there's life.

[Rybags]

Nah. Just cheapie $8 jobs from Dick Smith/Jaycar.

 

'Scope is the base $155 one from Jaycar... 10 MHz, more than enough for Atari stuff.

 

Would have liked one of the multi-channel USB-based samplers but you're looking at $400+ for anything decent.

[sup8pdct]

You said the head only steps once. I would start by swaping the common major chips with a working 1050 then looking at the driver chip for the stepper motor. Scope the power rails for ripple. If you have an atari cart with chip sockets, remove the rom and put it in one socket and see if the rom compares ok with a known good one.

 

James.

 

 

Nah. Just cheapie $8 jobs from Dick Smith/Jaycar.

 

'Scope is the base $155 one from Jaycar... 10 MHz, more than enough for Atari stuff.

 

Would have liked one of the multi-channel USB-based samplers but you're looking at $400+ for anything decent.

[Rybags]

Cool.

 

Looks like I have to pull the extra board off then...

 

[Rybags]

Well, epic fail on the copy operation. All I managed to get were returns of the address lines.

Used a Computer Chess shell though, which only has one of the two sockets occupied - don't know if that makes a difference, I suspect it might be a 4K cart to start with so maybe some lines aren't connected.

 

Whatever - since I had the thing pulled down I took the time to slightly lift and reseat most of the other ICs. I'll finish putting it back together and test it again later.

[Rybags]

Tested again - no change.

 

Could it be something on the power board, given that it acts strangely (keeps spinning) if connected to a powered up computer when I turn it on, but seems normal otherwise (although of course, isn't responding to any commands).

[sup8pdct]

Bugger about the rom It is only 2K so will only apear in a small window as long as the chip select lines are the right way round.

I just fired up my 810 to remember what it is supposed to do at turn on.

The head is supposed to step back to track zero then to track 40 (mine has the archiver chip in it so could be different).

Noted yours has a data seperater board.

Maybe something is wrong the 6532 in your drive.

Just make sure the 2 5 pin sockets are on the right header pins on the side board. The rear one goes to the head stepper motor.

Could try swaping the 3086 chip.

 

James

 

 

Tested again - no change.

 

Could it be something on the power board, given that it acts strangely (keeps spinning) if connected to a powered up computer when I turn it on, but seems normal otherwise (although of course, isn't responding to any commands).

[Rybags]

I just put the cover back on... might leave it for now, it's distracted me from other stuff that otherwise might have been finished (ie Interlace).

 

Thanks for the tips, next time I have some hours to throw into it I might risk doing some component swapovers.

 

I should really have checked the PS board properly, I didn't pull it out because I just CBF'd with the whole doing the heat transfer compound business... I'm like that with my CPUs too - the stuff starts to dry up and I finally put new stuff on when the CPU hits alarming temperatures.

[Novell2NT]

Well, the things I can think of are:

 

1. Check pin 3 of the voltage regulators (78xx) and make sure they are within spec.

 

2. Sometimes the connector between the back board and the side board becomes flaky. You probably would have discovered this problem while playing with the open drive, though.

 

3. Start replacing things on the side-board if you can pull spares from something else. The fact that it stops spinning on its own indicates that it half-works.

 

It's been a while since I worked on 810's, but I always had another one to swap parts with to figure it out.

 

I know this is an old thread, but I am trying to rebuild an Atari 810 myself right now, and could use some help with the various Test Points.

 

I can tell you right now, that my 7805 Votage Regulator looks good with +11.7V and +5V but my 7812 only has +2.7V and .16mv This one does not seem right to me.

 

On the Power Board at the various test points I get:

 

TP1 = +6.23V

TP2 = +6.23V

TP3 = +12V

TP4 = -12V

TP5 = +5V

 

I also probed the Crystal on the Side Board and it seemed to be oscillating and producing a clock frequency.

The A203 chip on the side board seemed to have a lot of activity / signaling going on.

[DavidMil]

Is your 7812 getting very hot? Something may have shorted out.

 

DavidMil