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Reimaged Atari XF551 Floppy Drive Board (Part 1)


[dropcap]X[/dropcap]F551 was Atari’s attempt to use the more standard 5 1/4 disk drive with it’s 8bit computer line.  It was released as the company faced certain failure and suffered from Tramel’s cost cutting mentality.  The single sided near perfboard quality main board is much maligned for it’s frequent power and SIO connector failures.  I never owned a XF551 Floppy Drive back in the day.  I lusted after it, but never quite could afford it.  And then life intervened and I moved on.  Fast forward some twenty years. I finally have the means and the knowledge to own and fix some of the short commings of that floppy drive board.

I started this project a little over a year ago as a summer project.  After some success with the GTIA-PAL adapter board and the MMU adapter board for Candle’s Ultimate 1MB, I was feeling my oats so to speak.  I thought I would stretch myself.  And I thought I would have some fun even if I didn’t succeed.  As you can tell, it’s turned into something more than a summer project.  Along the way I stretched myself way out of shape.  🙂  But it has been very fun.
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Legacy Atari 3rd party hardware boards…  These products, while technically may not be abandoned by their respective makers, are not being supported or manufactured and have not in twenty years or more.  I wanted to keep alive as much of the original experience of owning them as possible by reproducing the physical boards.  This website is a direct result of that.

[/quote]Okay, let’s start at the beginning.  In the beginning I wanted to fix the obvious flaws mentioned above.  I also at first did not want to include internal power supply circuitry.  There was much disscusion in the thread I started on AtariAge on the advantages/disadvantages of that.  It seemed split evenly and I was without enough information to recreate the original power supply circuit.  I later ordered a copy of the preliminary XF551 schematic from Best Electronics and found most of the information there.  But not all.  Key parts were not labeled with values and a close inspection of the board parts yielded no more info.  So finally I decided to forego internal power supply.  Then it became a question on how to get both 5V and 12V to the drive and chips inside.

That’s where I got stuck for months.  I tried different schemes.  Had multiple proto boards made and had them fail miseribly.  Each cycle took almost a month for the redesign, board manufacture and receipt, assembly and testing.  I could only work on it parttime as I have a full time job.  Guss Assmman provided immeasurable help, even going so far as sending his own working board and testing one of my proto boards.   I kept finding mistakes I had made, some assumptions I should have known better than to make.  Okay I was learning…….   but it was begining not to be fun anymore.

Family emergencies didn’t help, at one point stopping work cold for several months.  That work stoppage and a decision to put the project on hold for awhile allowed me to gain some distance and allowed my subconcious to work in the background.  In the meantime I directed my attention to other ideas that had been bubbling on the side.

Okay here we are nearly a year and a half later after starting this project.  From the knowledge and additional experience gained by smaller projects I think I can resume and complete this now.  I continued to research anything and everything about the XF551 in the meantime.  During my research I came across Igor Gramblicka’s website .  He has created/designed some fantastic mods for the XF551.  He has graceously given permission to allow me to incorporate some of them into my project.

So here is what I want to try to do:


Choice of:   Original XF551 PS or Modern XF551 PS


  • Jumper Selection of Intel 8040 or 8050 CPU
  • Jumper Selection of 2in1 OS
  • Jumper Selection of Density Sensor
  • Board will be populated except for Eprom (it is socketed on the original board) for as long as supplies last

Planned Expansion Kit:Front Panel Controls/LED

  • Drive LED Display
  • Drive Select Switch
  • Reset Switch
  • OS Selector Switch


1 thought on “Reimaged Atari XF551 Floppy Drive Board (Part 1)

  1. Glad to hear this still has forward momentum. I am still interested in 4 boards. I have most of the necessary chips already.

    Best regards

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