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How to repair an 810?


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#1 nevets01 OFFLINE  

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Posted Mon Mar 5, 2018 12:45 PM

So I was given three boxes of old Atari stuff from a friend who had a too-cluttered attic. I've got an 800 and an 810, and the 800 works beautifully (except for that horrid RF out. I'll eventually get an S-video or RGB mod/cable), however the 810 appears to not.  

 

What I've got - condition  

Atari 800 - completely functional

Atari 810 - nonfunctional, will not write or read diskettes

homebrew SIO2PI cable - verified to work with several disk images  

box (one of those plastic disk rolodexes) of Atari 5.25" disks - functionality not known, they appear perfectly fine (i.e. media isn't scratched/scratching off under the drive head).

 

What I've tried - result:

booting from diskette officially labeled as Atari Dos 2.5 - drive goes "BRRRRTrrrrrrrrrrrrrrrrrrBRRRRRTrrrrrrrrrrr", 800 shows a string of "BOOT ERROR"s which accumulate with frequency approximately equal to that of the BRRRRTs from the drive, which occurs every 10-15 seconds

cleaning head with isopropyl alchohol and piece of facial tissue - no result

booting from diskette hand-labeled "Master diskette" - drive goes "BRRRRTrrrrrrrrrrrrrrrrrrrr", 800 shows a somewhat faster string of "BOOT ERROR"s.

booting atari dos from SIO2PI - works as expected

booting with a game from SIO2PI - M.U.L.E. theme is now stuck in my head.

formatting diskette- drive goes "BRRRRTrrrrrrrrrr-rr-rr-rr-rr-rr-rr-rr-rr-rr-rrrrrrrrrrrrrrrrr" and remains spinning for between 30 and 60 minutes (I had left the room at around 30, and came back around 60). Eventually it stops, and DOS gives error 173 ("BAD FORMAT")

 

I disassembled it to make sure everything was doing what it should, and everything looked in order. Belts were tight, no debris or other obvious problems, head went back and forth like it should. 

 

Is there anything I'm missing? (other than speed; I have no way of measuring drive speed and from what I've gathered, it shouldn't effect formatting or disks formatted by that drive)



#2 Nezgar ONLINE  

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Posted Mon Mar 5, 2018 1:02 PM

The 810 only supports single density. Dos 2.5 added support for 'enhanced' density for the 1050 drive. it's possible that your dos 2.5 disk is formatted with enhanced density, and is thus unreadable in your 810.

Rpm could be a possibility, but it should usually still read sectors with a wide tolerance, possibly slowly as skew will be out of time. You need to be able to read sectors to run an rpm utility. (Ie that included with SpartaDOS or RealDOS)

Good that you indicated you cleaned the head. It still sounds like the drive is just having trouble reading your disks. I personally have found my 810 is way less tolerant of marginal quality disks compared to my 1050. Do you have access some sealed new-in-box disks? Also try same disks in a 1050.

Formatting 'could' be affected if the RPM is too slow, causing the last sector to overwrite the first...

Also verify your 810 has the data seperator, analog power board, and rev C ROM upgrades. it's pretty rare to find one without. Easy way to tell is if you have a circuit board above the drive mechanism, and the side board usually has a 'C' sticker. If not, inside the sideboard shield there will be a daughterboard attached to one of the sockets.

#3 _The Doctor__ OFFLINE  

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Posted Mon Mar 5, 2018 2:58 PM

810's are notorious for needing a cleaning/re seating of card edge connector after sitting forever in an Attic/Basement/Root Cellar/Garden Shed....

 

Make sure you try only single density disks, once that happens run happy software to see if it's been modded, then you can try other things after that.

So try DOS 2.0S, not 2.0D or any other higher density dos until you know what you have.



#4 rdea6 OFFLINE  

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Posted Mon Mar 5, 2018 6:48 PM

The floppy's should also be check to ensure the media will spin inside the folder..  Shake the floppy and with finger in the hole move media back and forth..



#5 nevets01 OFFLINE  

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Posted Mon Mar 5, 2018 7:42 PM

The floppy's should also be check to ensure the media will spin inside the folder..  Shake the floppy and with finger in the hole move media back and forth..

They do. I check each disk for scratches along the entire circumference, which necessitates at least one complete rotation.

 

The 810 only supports single density. Dos 2.5 added support for 'enhanced' density for the 1050 drive. it's possible that your dos 2.5 disk is formatted with enhanced density, and is thus unreadable in your 810.

Rpm could be a possibility, but it should usually still read sectors with a wide tolerance, possibly slowly as skew will be out of time. You need to be able to read sectors to run an rpm utility. (Ie that included with SpartaDOS or RealDOS)

Good that you indicated you cleaned the head. It still sounds like the drive is just having trouble reading your disks. I personally have found my 810 is way less tolerant of marginal quality disks compared to my 1050. Do you have access some sealed new-in-box disks? Also try same disks in a 1050.

Formatting 'could' be affected if the RPM is too slow, causing the last sector to overwrite the first...

Also verify your 810 has the data seperator, analog power board, and rev C ROM upgrades. it's pretty rare to find one without. Easy way to tell is if you have a circuit board above the drive mechanism, and the side board usually has a 'C' sticker. If not, inside the sideboard shield there will be a daughterboard attached to one of the sockets.

Unfortunately, I do not have access to either a 1050 or any new disks (though some of the ones in that box appear blank, including the one I attempted to format). I've tried it with various disks in that box, and none of them seem to work. The bizarre thing is that there was an 800XL in the box as well as the 800 (idk if it works, haven't tried it yet since it seems like a rehash of the 800 with a bit more ram), and upon closer inspection, several of those disks were doubledensity -- but several were not, and there was no sign of a 1050 in the box (oddly enough, there was a commodore printer in there too... I still have yet to figure that out).

Later tonight I'll do some more extensive checking if I have time.

I checked, and yes, the sideboard does have a "C" sticker



#6 nevets01 OFFLINE  

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Posted Mon Mar 5, 2018 9:00 PM

810's are notorious for needing a cleaning/re seating of card edge connector after sitting forever in an Attic/Basement/Root Cellar/Garden Shed....

 

Make sure you try only single density disks, once that happens run happy software to see if it's been modded, then you can try other things after that.

So try DOS 2.0S, not 2.0D or any other higher density dos until you know what you have.

I tried all the disks in the box that said "For 810" or "single density", none of them worked. I took the drive apart, but couldn't find any edge connectors, only pins (all of which I reseated, but to no avail). Could you clarify?



#7 Stephen OFFLINE  

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Posted Mon Mar 5, 2018 9:18 PM



The floppy's should also be check to ensure the media will spin inside the folder..  Shake the floppy and with finger in the hole move media back and forth..

Beavis so wants to say "That's what your mom said"

110204-beavis-butthead.png



#8 Nezgar ONLINE  

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Posted Mon Mar 5, 2018 11:37 PM

(oddly enough, there was a commodore printer in there too... I still have yet to figure that out).

I checked, and yes, the sideboard does have a "C" sticker

 
OK.. If the printer had a standard 36-pin centronics connector on it, it could probably be used just fine on the Atari with the likes of an 850, a P:R: Connection, or various dedicated SIO to printer adapters. Most dot matrix printers had some sort of epson printer emulation for compatibility.

 

C sticker means your drive should be the have the more common updated boards. You probably also have an "810 Analog Board" above the drive mechanism then.  So thats all good...
 

I tried all the disks in the box that said "For 810" or "single density", none of them worked. I took the drive apart, but couldn't find any edge connectors, only pins (all of which I reseated, but to no avail). Could you clarify?

 
Hmm. He probably meant the pin header where the side board is connected to the rear power board near the back of the drive. Couldn't hurt to remove the screws so you can lift that out, and reseat it. Reseat any other pin-header wires that connect between boards as well.

 

I just took this pic of a stock Rev C MPI 810 i have open here, and I've highlighted a bunch of spots for you. :) Let us know if you have any EXTRA wires in your 810 that might indicate modifications.

 

RED: pin connectors to disconnect/reconnect

GREEN: the pin header where the side board connects to the rear power board - reseat this, some screws secure the side board in place.

YELLOW: RPM Adjustment. probably best to leave this until you have a way of measuring

 

IMG_20180305_2317542a.jpg


Edited by Nezgar, Mon Mar 5, 2018 11:39 PM.


#9 _The Doctor__ OFFLINE  

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Posted Tue Mar 6, 2018 10:07 AM

and down at the bottom where the side board meets the power board.



#10 nevets01 OFFLINE  

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Posted Tue Mar 6, 2018 9:08 PM

Okay, so I reseated all the pins and things that you highlighted. No go. Even made sure they were all hooked in the right way round, in case some doofus got them backwards. No mods, as far as I can tell. No extra wires or boards. Sure enough the board above the drive mechanism says "Analog BD". The sideboard says it's revision A.  

I devised a method to measure speed, primitive as it is: I marked a mark on the flywheel and filmed some video of it spinning, then compared timestamps before and after 10 rotations. Some maths gave me the number 4.76 rotations per second, or 285 rpm, within margin of error of the intended 288 rpm, so it's not the speed, I don't think.

I also noticed that when attempting to load a program, there wasn't any noise. When I loaded anything from my floppy emulator, the computer would make constant beepy noises, however, when using the actual drive, all I got was a singular boop when the drive head re-zeroes. Perhaps this is significant? What it seems like to me is that the drive is not seeing/depositing anything on the disks, either that or it's not telling the computer anything about what it's reading. IDK though, I'm a bit of a noob at all this...



#11 Nezgar ONLINE  

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Posted Wed Mar 7, 2018 1:21 AM

I'm very impressed by the ingenuity of your method to test RPM!!

 

Running out of ideas. At this point, I personally would be starting to swap parts with one from another 810, starting with the drive mechanism to see if that makes any difference. Any chance you can post a video of the behaviour you describe?

 

It does seem from your description the drive read head is not 'seeing' anything on the disk... Its obviously receiving the command to read the disk, seeking the head, etc which would imply processor/controller is working so everything checking out but the mech itself...

 

Another thought... Inside the big metal shield around the side board is a series of socketed chips, and a daughter board with even more socketed chips. Carefully lift/reseat all of those chips. Also can't hurt to reseat all other small socketed chips you see anywhere else on that board, and the rear/top boards.


Edited by Nezgar, Wed Mar 7, 2018 1:22 AM.


#12 nevets01 OFFLINE  

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Posted Wed Mar 7, 2018 8:58 AM

So I lifted up the metal shield and everything looked fine. I don't have any other disk drives or anything (other than some half-height 5.25" drives like what would be in a newer DOS machine; I doubt any parts are compatible) with which I may swap parts.

 

However, I did come across a major breakthrough. Right before I went to bed, I tried loading a floppy with the cover off, and pressing down gently on the top head thingy. There was a series of bips, but after that I must have instinctively let up on it since there was nothing else. Mildly discouraged, I opened the drive and removed the disk, only to look up to see "MISSION: Asteroid, Game load in progress, please wait..." had been displayed on the screen. So... something's working! It was pretty late though, so I stopped after that. More experimentation to come, possibly to-night.

 

As for the printer (VIC-1521), it's not got a centronics port, it's one of those ports that's the Commodore version of SIO



#13 Nezgar ONLINE  

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Posted Wed Mar 7, 2018 9:21 AM

Oh excellent, that's the pressure pad, a little felt pad. Maybe the pad needs replacing, some more head cleaning is still in order, or the tension spring isn't applying enough pressure, or the magnetics on the disk are really weak from age...

#14 nevets01 OFFLINE  

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Posted Thu Mar 8, 2018 11:14 AM

Fixed! woohoo!

I put a pad of e-tape under the other side of the spring, and bent the head-side down a bit, to get greater springy force, and it read! Tried a bunch of disks, most worked, a couple didn't (one of which turned out to be doubledensity). Curiously, about half the disks are doubledensity with no sign of a 1050. There's one on shopoodwill I've got my eye on though, unless it gets bid way up. However, I still like this 810 better, if only because it matches the 800 better.



#15 Nezgar ONLINE  

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Posted Thu Mar 8, 2018 12:16 PM

Excellent, great to hear! I'm thinking this fix will help one of my 810's too!

Keep in mind a stock 1050 can do single density and 'enhanced' or 'dual' density, not 'true' double density. you'll need a mod like us doubler, happy, speedy, etc to add full double density (256 byte sectors) support.

Your disks could be either of those densities.

#16 nevets01 OFFLINE  

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Posted Thu Mar 8, 2018 3:27 PM

Another question: can I reformat disks of other formats to work in my 810? Say I had some IBM-formatted diskettes that I wanted to use, or some of those "double" density disks, and I didn't care about what was on them?



#17 Nezgar ONLINE  

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Posted Thu Mar 8, 2018 3:31 PM

Yes of course! The format process starts by erasing a track before writing an entirely new sector layout. Any single/double density, even single sided except "high density" disks are basically the same magnetic formulation. "High density" disks will not work at all.

Formatting is the best way to determine the health of a disk, as after the layout and empty sectors are written,they are verified and the drive will error if it fails. Watching with the cover off you can get a general idea of where the problem track is, and soemtimes you can look for dirt on the surface to clean which may help it pass a subsequent format.

#18 DrVenkman OFFLINE  

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Posted Thu Mar 8, 2018 4:13 PM

Another question: can I reformat disks of other formats to work in my 810? Say I had some IBM-formatted diskettes that I wanted to use, or some of those "double" density disks, and I didn't care about what was on them?

 

Beware though - some IBM-formatted disks, many in fact, used HD (high density) disks, not the common DD (double density) disks most people used in the 8-bit era. HD disks are generally incompatible with Atari stuff and cannot be reliably formatted for re-use. 






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