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PC floppy disk drive in a 810


ebiguy

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Several years ago, I got a 810 with all the boards working but no disk drive mech.

Buying one from France is a no go because the price+shipping+taxes are close to $100.

I was wondering if someone had the idea of using a PC 5.25 360K floppy disk drive with all the boards of the 810.

Maybe removing the board with the IDE connector from the PC floppy disk drive to get the most bare disk drive.

Is it possible?

How to make the connections with the Atari board?

Is the rotation speed compatible?

Would there be some changes in the ROM (adapt step logic and maybe more...)?

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If you can locate a Tandom TM100 drive (these were used in the original IBM PC), you can remove the top board, and re-pin some of the wires, you can connect that up to the boards in an 810.

 

It is harder, but you can find MPI mechs intended for a PC.

 

If you want genuine Atari replacement mechs, I believe both Best Electronics (http://www.best-electronics-ca.com/) and B&C Computervisions (http://www.myatari.com/

) would have them available.  Shipping of course would be from the states.

 

You also hadn't mentioned if your 810 was an MPI or Tandon mech drive (MPI mechs have the push button and large door, Tandons have the usual 'flap').  a Tandon mech will work in either drive, but you might have to leave the front off if it is an MPI one as it might interfere with use of the flap.

 

The PC Tandon mech will be a two head drive, but the top head you would not connect.

 

I had a Tandon based 810 where the head failed for some reason.  I was able to use an IBM PC compatible Tandon TM100 that the upper head was broken off of, and put the upper pressure pad assembly from my 810 on, adapt a few wires (drive rotated backwards for one w/o changes ? ), and it works great now.

 

Good luck !

 

What I'd like to do is using the PCBs available that re-implement the XF551, put a 360K MPI PC class drive (MP-52?) and make a stock looking 810 that has the electronics of an XF551 and get 360K (or using the 80 track quad density MPI drive) get 720K in what looks like a perfectly stock 810 :-).

 

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Thanks for your answer

 

My 810 is a garage door version (with no more mech inside but I have all the boards including the one that goes on top of mech).

You are talking about TM100 or other drives that will fit nicely into the 810 but it is almost the same price with shipping (quite heavy) and taxes as buying a full 810.

It would be a miracle if I find a TM100 at a very low price. But if it happens, I will ask you more information on how to make the changes to adapt to the 810.

 

EDIT: Just looked at eBay, myAtari sells a "TANDON DISK DRIVE MECHANISM NEW Atari PARTS for 810 Disk Drive 800/XL/XE" at $89,95 + $70,90 for shipping = $160.85 and there is a chance (not the right word indeed) to have 30% taxes on top of that = $210. Who would pay $160 to $210 for a new mech in his 810?????

All TANDON TM100 sales are located in the US these days.

 

I asked for a 360K floppy drive because I have some of them (like PANASONIC JU-455 and TEAC FD-55BR).

So back to my question, is there a way to connect for example a PANASONIC JU-455 to the 810 boards even if the 360K drive does not fit nicely into the 810 shell.

 

Edited by ebiguy
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You would need to spec out head current, stepper motor degree, stepper motor phases, feedback, and power/current requirements.. if those match up then disconnecting circuit board on the mech and directly wiring all of that up... you may be able to transplant or use the other ir led and detector pairs for needs... again you'd have to make them fit and wire them up. So yeah anything is possible... but it sure is an undertaking. You were given sound advice from cwilbar.

Edited by _The Doctor__
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On 7/11/2020 at 2:57 AM, ebiguy said:

I asked for a 360K floppy drive because I have some of them (like PANASONIC JU-455 and TEAC FD-55BR).

So back to my question, is there a way to connect for example a PANASONIC JU-455 to the 810 boards even if the 360K drive does not fit nicely into the 810 shell.

 

It won't work. Not without too much pain. As the doctor is saying, everything is feasible. But here it might require major surgery.

 

It is much easier trying to adapt a full height drive as cwilbar suggested. Mainly because full height drives have the bare mechanism separated from the digital logic, and most of the logic is discrete anyway which makes it much easier to adapt. Even then I'm not sure you can (easily) change the rotation speed from 300 RPM back to 288 RPM on every full height drive. But of course, a full height drive would be very expensive to ship internationally and they are not that easy to find anyway.

Edited by ijor
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On 7/11/2020 at 1:23 AM, cwilbar said:

If you can locate a Tandom TM100 drive (these were used in the original IBM PC), you can remove the top board, and re-pin some of the wires, you can connect that up to the boards in an 810.

 

More than 10 years ago I had a little project to try connecting a PC drive to a 1050 PCB. From the TM-50 and TM-100 PC drive schematics I had learned that the 1050's electronics are very similar. Roughly said everything between the front of the 1050's PCB and the 5 large IC's (CPU, FDC, RIOT etc.) is identical to the TM-50/TM-100. Due to the TM-100 being a double head drive, said circuitry is present twice on it. I abandoned the project due to lack of time and prospects of incompatibilities. There should be some posts by me on this subject hidden deeply in AA's archive.

 

Sadly I lost both the TM-50 and the TM-100 PC drive schematics when one of the harddrives in my 2-bay NAS died all of a sudden without any warning (thanks Seagate for installing cheapskate desktop harddrives in your BlackArmor NAS...). I'm sure the schematics are still available for download somewhere, but just can't remember where I had found them back then. IIRC it was on a website about early TRS-80 models.

 

re-atari

 

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I haven't looked, but bitsavers.org probably has the Tandon drive schematics.

 

MPI made full height PC compatible mechs (with the large door with pushbutton release).  But they are uncommon.  I suspect that if one did fine a 180K/360K one that with a bit of re-pinning it could be used as a replacement in an MPI mech 810 like the Tandon TM100 PC mech can be made to work in a Tandon 810 (it will work in an MPI mech 810 too, but you need to to change the 810s face to a Tandon one).

 

The TM-100 drives regularly come up on eBay, mostly in the states, and not usually for the money I'd pay.  But sometimes the pop up (I did get one for $35 shipped within the last  6 months as I have a PC 5150, and PC 5160 to put back together (from piles of parts).

 

I think a cool 810 would be one upgraded with an XF551 (clone) circuit board.  I have a QD MPI big door 'PC' drive that I could do 720K with.  That would be cool in an 810, as it would be a 'sleeper' but be able to do 720K instead of 92K :-).  I don't think you can maintain single density 40 track compatibility with this however.  Alternately if you could put two half height mechs in and do something cool around that too.

 

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On 7/13/2020 at 9:47 AM, re-atari said:

The attached document (in German language) by Bernhard Engl might give you some inspiration. Take note he did not build the described interface, it was more of a survey if and how building a 1050 clone using a PC drive could be done.

 

Interesting. Thanks for the post. Note however that there were several similar projects and some of them were actually produced and sold commercially. The main reason was that at some point it was much cheaper to build a clone using a PC drive than buying a 1050, especially in some overseas countries.

 

But these project normally had a custom board specifically designed for this purpose and with a custom firmware. It is quite a different task to attempt to use a PC drive on a 810 (or 1050) using the original Atari logic and firmware. Of course, using a full height floppy drive makes things much easier. But were they cheap and widely available? I think I never seen one personally. I owned a couple of full height hard disks, but never full height floppies. They must have been obsolete quite early?

Edited by ijor
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It is not difficult at all, I have installed IBM/ Tandon TM-100-2 (dual heads double sided) drives in four (4)  810 drives and they all work GREAT!

Also, using the double sided mech permanently eliminates the problem of worrying about the rabbit-hair top pressure pad wearing out.

 

Funny you guys are talking about this, I almost made a Youtube video on how to do this....

 

Edited by ColleenLover
grammar
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5 hours ago, ColleenLover said:

It is not difficult at all, I have installed IBM/ Tandon TM-100-2

 

On 7/11/2020 at 1:23 AM, cwilbar said:

If you can locate a Tandom TM100 drive (these were used in the original IBM PC), you can remove the top board, and re-pin some of the wires, you can connect that up to the boards in an 810

 

Could one of you describe how you "re pin" the the wires to the 810 board?

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Well, the connectors are the same, just some of the wires are in different positions.  I did not make note of it.  I'd have to look at an unmodified Tandon and an Atari Tandon (or my modified PC Tandon) to determine the changes.

 

There was a change needed for the drive motor (or IIRC it spins in reverse).... I think 2 wires need reversing.  And I think that the stepper motor wiring was different.  IRIC the head wiring might have been the same, but I'm not 100% sure at this point.

 

And in my case, the drive was a parts drive, so the top board on the PC donor drive was already removed.  I did remove a small PCB from the back of the drive (which I think was for drive motor control).

 

If nobody else has these, I can see if I can recreate the info by comparing drives again :-).

 

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  • 2 weeks later...

Aw yes, that is correct, the wiring plugs themselves are the same, all I had to do, was to compare the IBM plugs to the plugs on the Atari mech I just removed, and their were an obvious handful of wires that had to be moved to a slightly different pin location. (also, cutting out and removing all of the unused extras, like the optical speed sensing strobe 2nd head wiring, etc, etc), then after you hook it up; the 1st thing you need to due is LUBRICATE the new MECH, (they are always dried out) and adjust the SPEED to 288 RPM... .

 

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Since the speed was controlled on a board removed from the PC TM100, and controlled by the board in the 810, if the speed is set correctly in the 810, when the PC TM100 is installed, it will spin at the 288RPM, not the 300RPM (as the PCB that controlled motor speed in a PC has been removed from the PC TM100).

 

I dropped one right in to replace one that the head crapped out on.  The PC donor drive was a parts drive that I received with the top head ripped off.  Hung onto it for years.... and it finally came in handy ?

 

 

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I don't know if I am the only one interested in the wiring but could one of you list the way you connect the TM100 to the Atari board ?

Maybe some pictures of the actual wiring of your TM100 would be enough.

It would be great to get the information here.

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I'll see if I still have that drive by the bench.  If I do, I'll open it up and see if I can document it.

 

If not, I've got another Tandon TM100 that is destined for an IBM 5150, and I can look at that and a 810 Tandon and re-determine the wiring

 

If you have a 810 Tandon mech to compare to, it is easy to determine the changes.  If you don't have one to compare to...... thats where things get a bit harder.

 

 

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OK.... here we go ?

 

(Note:  I'm not sure if I've got pin #s correct (LtoR/RtoL) on these connectors, but the resulting instructions will work regardless.

 

Connector 12 is the stepper (5 pin connector):

PC: White, Green, Brown, Red, Black

Atari: White, Red, Green, Brown, Black

 

Connector 21 is the motor (5 pin on Atari, 4 pin on PC)

PC: Yellow, Green, Red, Blue

Atari: Yellow, Green, Blue, Red, N/C

 

Head connector 9 is the head (head 1 on the PC drive)

PC: Shield, Black, Blue and Yellow, White, Red

Atari: White, Black ,Yellow, Shield, Red

 

Connector 8 is write protect:

on the PC this is a 4 pin connector, on the Atari, a 5 pin connector

 

To use a TM100 in a Tandon Atari 810:

 

Connector 12 (stepper):

Remove the Green, Brown, and Red wires, place Red where the Green wire was located, place the Green wire where the Brown was located, and place the Brown wire where the Red was located

(follow the Atari color map from the tables above)

 

Connector 21 (motor):

Swap the Red and Blue wires

when plugging the connector into the Atari, leave pin 5 unconnected (leftmost pin when looking at the pins from above with the front of the drive towards you)

 

Head connector 9 (head 0):

remove the shield (bare wire), and white wires and swap them

 

Connector 8 (write protect switch):

no change, plug the 4 pin connector onto the 5 pin header on the 810 sideboard with the two wires connecting to the 2 bottom pins (leaving the top pin unconnected to anything)

 

Connectors 9, 10, 11 (index LED, index sensor, track 0 sensor):

leave unconnected, these are not used on the Atari 810 

I left these dangling but they can be cut off, the sensors removed, etc if so desired.

 

Head connector 10:

leave unconnected, the 810 doesn't support 2 yeads.

If you so desire and can get the parts (i.e. B&C, Best Electronics, etc) you can remove the upper head and replace it with rabbit hair pad, arm, spring, and 'spring bracket'.

 

If you do not swap the red and blue wires on the motor connector (#21), the disk will spin backwards !

I have no idea what will happen if you get the stepper wires wrong.... either no stepping, or erratic stepping, buzzing stepper motor, possibly damaged 810 electronics ?)

I would be afraid of damaging the head or electronics if the head wiring was wrong, though the most likely outcome is it wouldn't read or write anything.  If incorrect, you could probably erase a disk you attempt to boot (or scramble its data).

 

I have attached pictures of the connections on the swapped drive for further aid to the explanations above.

 

 

0724201845_HDR.jpg

0724201846a_HDR.jpg

0724201846_HDR.jpg

0724201847_HDR.jpg

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8 hours ago, cwilbar said:

here we go

Thank you very much for all the details and the pictures.

I appreciate that you took the time to open your 810.

 

By the time I started this thread, I found a TM-100 (not an Atari one) in Europe that I have not received yet.

So this will be very helpful when I have the drive.

 

EDIT: I think you gave enough details to perform the surgery but I may ask some more questions when I apply the changes.

Edited by ebiguy
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