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XF551 Updates



Well,  sorry about the silence.  It’s not that I haven’t been working.  I am finalizing what I hope to be the production models. I will be selecting two people one here in the US and one overseas to do final testing and review. For something this big and expensive I want to make sure I didn’t foul this up. They’ll be able to look at and use the finished product and make recommendations etc. They will also be helping with front panel display designs so they will need to have the ability to draft a cutting template and make quality cosmetic mods to the XF551 top case. Something I am not very good at. I tend to take a blow torch approach. Not very cosmetic I’m afraid.  Laughing

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XF551 Small update



Just a small update:  I recieved what I hope is the last prototype boards in yesterday.  On these I’ll be testing the full blown board operation including the alternate osc circuit, front panel mods and the fit and trim of the boards.  I’ve started installing the parts tonight.  Hopefully I’ll have a ready to test board in about three days.   At this point I still am employed, so that has to come first.  🙂

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XF551 Updates



I have to tell you I have been riding on the leftover euphoria of finally getting the XF551 board working for the last couple of weeks.  I know it’s sad.  A thirty something year old piece of equipment kicked my butt for almost two years.  But heck you try to get it working when you have only a draft set of schematics from Atari missing parts info,  a error filled set of schematics from sobra, no Sam’s booklet, a sometime working physical drive unit, and the need to school myself on two different pcb softwares, less than part time time to work on it and all the normal drama of simply living.  Alright…. alright I’ll shut up.  Smile

I have been working on cleaning up the schematics, making it pretty and creating the fully implemented board to test all the mods with.   I send that off to the board house along with the front panel display/switch board hopefully by Monday.  I should have the boards in in about 2 weeks.  A few days to solder the board together and test and cross my fingers I’ll be able to offer the boards for sale.  Just about two full years after I started this crazy idea of a summer project.  Who’da thunk?

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XF551 Updates – Basic Board is Working !!!


I have not completely ceased working on the XF551 board.  Contrary to my earlier  announcement.  Damn thing has a hold on me.  Yell  My last board has yielded some positive results.

I went back to square one so to speak.  I decided to design a board with just the bare essentials necessary.  Hopefully to eliminate possible complications due to the mods I wanted to incorporate.  It reduced the board space needed and therefor also the cost to manufacture.

On the last test my previous board had failed the drive power on test.  I had the data cable on wrong and the cable itself was not made right.  I replaced the cable.  Then after retracing the board traces I found some mistakes.  That’s when I decided to go bare essentials.  A few weeks later new board in hand I proceeded to solder in parts.  Soldering complete, I inserted my chips. Did a fast power on test and no billowing smoke or loud pop.  Good….    Then I attached the new data cable and drive and powered on.  I was able to get the drive to spin up briefly when powered on, just like the original.

I began to get encouraged.  I plugged in the SIO cable from an functioning 800XL.  Powered the drive and then the 800XL and the drive light comes on and stays on.  The 800XL beeps and displays ‘Boot Error’. Well… not exactly success, but it tells me that the computer is seeing the drive and communicating with it.  At least to some degree.  The drive is not spinning, or attempting to seek.

So now I start looking for possible problems with chips and drive.  I replaced all the chips except for the ROM and now the drive attempts to load.  It gets about a third into the load sequence and then the drive starts chunking every few seconds.  Okay,  a little further down the road.   What if the drive is bad?  So I replaced the drive and now it’s singing.

I just about fell down and kissed the ground.  So for the record I have a very basic mainboard using a modern power supply and it is loading a DOS 2.5 disk.  Here’s the YouTube videos I made.

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XF551 Update


I’ve resisted updating for the last couple of weeks.  Partly out of depression and partly out lack of time.  Lets get the bad news out of the way right now.  It’s a mixed bag, but there is some hope.

As I last reported the power supply seemed to be working and no fizzes, blue/black smoke or loud bangs to signal fatal failure.  I then proceeded to make the power and data cables to go from board to drive housing.  I verified pin to pin as best I was able to that my cables matched and mated with the originals.   As I placed them on the board it became apparent that some design assumptions would have to be changed.  Nothing fatal, just some more research and parts sourcing.

Then I placed the board into the case.   The fit of the board in the case is near perfect.  A tiny adjustment here and there and that part of the project is done.

DSC_1715M    DSC_1716M

Then I fitted the drive housing on it’s piers.  It fit and layed flat, but I could see barely a few mils between the OS chip in its socket and the bottom of the drive housing.    The bottom of the drive housing is not filled flat.  There are large open spaces around the spindle and drive motor so depending on the height of the other parts not installed yet I could have a fit issue between the board and the drive housing.  Or not.  Certainly something to think about.

After connecting the power and data cables I was ready for the acid test so to speak.  Would the drive/new board behave as the original?  Remember there is no connection to a Atari computer at this point yet.  I tested first the reaction of an original drive with only power applied as a gauge.    The power light comes on briefly and the motor seems to spin up and then come to rest, the power light goes off.  If I could get my board to do the same, then I could proceed to the next step of checking SIO signals from the connector to see if there was any danger of foreign voltage on the connector.

I pressed the power switch on.

The power light came on and the drive spun up.  And kept on spinning and spinning and spinning.  The light stayed on.

I turned the power switch off.

At least the power switch worked.  The power light went out and the drive stopped spinning.  Conclusions were that yes I had the power cable right.  But I couldn’t say for sure much else was right.  Two areas I began to investigate– 1) reexaming the board schematics to see if I had pins connecting to the wrong part (I swear I am beginning to see these schematics in my sleep) and 2) data cable mismatch.  I found errors in both.  The data cable I could fix immediately but I had run multiple pins to the wrong parts.  Perhaps a hold over from the Eagle design days.  That was not so easily fixed.

Coupled with other design changes I intended to make I decided to make one more proto board.  That new board should arrive next week.  Look for an update around the first week or two in March.

PS Feb 25 — The protoboard arrived today.  Along with the first proto of the front panel board for the led display and drive select etc.  I probably won’t come up for air for at least the next two days or so.




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XF551 Update


Recieved what I hope is the final proto boards in Monday.  Over the last few days I have soldered in all the essential parts.  Not the front panel mods.  That area is still in development and could change.  But all parts necessary for the operation of the board have been soldered in except for the power and data cable for the drive.  I have power tested the board and nothing blows up, some chips get warm but no sauna chips and no exploding caps or resistors.  Since there are no Sam’s manual for the XF551 and therefor no documented measurements I can check against, that may mean nothing at all, but I am cautiously optimistic.  Smile

Next up is the attachment of the power and data cables for the floppy and the installation of the board and drive into the case.  Then the next major test is the power up w/o connection to the Atari.  Does the drive power up like a normal XF551?  Is there backfeed through the SIO connectors etc? I don’t want to fry an Atari computer.

I am using the modern format XF551 to test with.   It should prove the hardest to get up and running.  What I learn here on this one will allow me to get the original setup quicker.  I suppose I could have gone the other way around but I only had enough money to send 1 board format to manufacture.  $80 for 5 boards 15cm X 15cm plus shipping.   It ain’t cheap.  Frown

Next update should come by the end of this next week.




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XF551 Update


Decided against doing the OSC and LED test boards.  The OSC mod just allows a 33.333MHZ OSC to be used instead of the Atari specific 8.333MHz.  Igor has already tested his LED mods.  So I sent what I hope to be the final proto board to the board house.  I should get it in sometime next week.

I have to say that using the Diptrace PCB software is such a joy after struggling with Eagle for the last two years or so.  Even the free/trial version is light years ahead of Eagle.  I will never go back.  Maybe it’s because Diptrace acts like a Windows app and Eagle like the DOS based program it is with a Windows 3.1 GUI tacked on.  Sorry about the dig, but I stopped using Windows 3.1 about 20 years ago.   Atari is the only retro I want to do now.  🙂

In the mean time I am sourcing parts and trying to shave as much cost off the board production as I can without losing quality.  Right now it’s looking like the board costs are running around $80.00 for the basic board with $20 more getting you the front panel parts and boards.   Stay tuned.



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XF551 Update



[dropcap]O[/dropcap]kay time for an update.  I recieved the modern power supply test board about a week or two ago.  Soldered everything in and it is working with a 24V 1.5 A DC wall plugin.  So that is a big step for the modern version of the XF551.  I am currently about ready to send the alternate osc circuit and the LED test boards to Itead for manufacture.  In about two weeks or so when they come in I can test them and if they pass, that’ll be the final phase before sending the complete modern XF551 board in.


Not so good for the original power supply test board.  I got the test board in yesterday and finished soldering the parts in tonight.  It didn’t blow or let out black smoke but there is no voltage at the drive connector.    I know the Atari transformer is working because I can power a 1050 with it.  So either I wired the DPDT switch wrong or something else in the wiring is wrong.  So it’s back to the schematics to see if I can rewire the test board to see if I can get it to work.


Yipee!  It was in the schematic.  Had the switch wired wrong.  Cut the wrong trace and wired it right.  Success!!!  Now both the modern and original power supplies are working.


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XF551 update:



Well here it is nearly Christmas.  I have a modern power supply test board coming in hopefully by the end of the week.  Put together and tested ok should be a big step towards the final board.  The board itself appears to be approaching the size of the original, as I have added things.  I wonder how that happened…..:)

A big question remains.  I am considering going to a four layer board, but my current board house prices for four layer boards  is literally five times more expensive for a small batch. (50 count)  So I may have to stay with 2 layer.  It might not do much to reduce the size anyway.  I am working with non SMD parts for the most part.  It would be nice to go SMD, but I see no realistic way I can do that much SMD soldering.  My eyesight just will not allow it.  I’ve toyed with the idea of having my board house do the SMD assembly, but the additional costs could push the total cost of the board beyond that sweet spot that most Atarians will pay.  Kinda defeats the purpose.

Anyway,  I have a couple more projects in development too.  Those boards should come in this week too.  Stay tuned for more info.

Happy Holidays everyone!


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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.
[hr] [quote style=”boxed” float=”left”]

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