+kheller2 Posted October 25, 2018 Share Posted October 25, 2018 Just to keep things lively, this is the set of all (known to me) XF schematics. Maybe this way I can find them easier the next time I look for them. Mariusz Geisler From: http://blog.3b2.sk/igi/post/Chyby-v-scheme-ATARI-XF-551-Bugs-in-circuit-ATARI-XF551.aspx Igor Gramblicka V1 Igor Gramblicka V2 From: https://atariwiki.org/wiki/Wiki.jsp?page=Atari%20XF551 Atari Japan Preliminary XF551_schematic.pdf And from the FAQ: The reverse side of a 2-sided "flippy" disk may be used by inserting the disk into the drive upside-down. But note: Chinon-built XF551--CANNOT read/write/format disk backside if the disk has no 2nd timing hole Mitsumi-built XF551--CAN read/write disk backside if the disk has no 2nd timing hole, but CANNOT format the backside without the 2nd timing hole. Discussion here: http://atariage.com/forums/topic/138304-cant-flip-disk-on-xf551/ 5 Quote Link to comment Share on other sites More sharing options...
Level42 Posted October 26, 2018 Share Posted October 26, 2018 Nice. I never realized the simplicity of the XF551 PCB design compared to the 1050.....really makes building a drive "from scratch" possible. Since the drive uses a "standard industry (shugar?) FDD connection, would it be possible to hook up a Gotek ? not that it would be the most logical option for our A8 (f.i. Sdrive Max is a more logical and economical solution) but it would be fun if it would be possible. Quote Link to comment Share on other sites More sharing options...
SoundGammon Posted October 26, 2018 Share Posted October 26, 2018 Take a look at C102, 4700uf/35v, in SERIES to the diodes to supply the the 12 volt rectifier? How does the DC voltage get to it??? Quote Link to comment Share on other sites More sharing options...
+Fred_M Posted October 26, 2018 Share Posted October 26, 2018 (edited) I recognise the PDF I made of the Japanese preliminary schematic The original place where this PDF was posted is atariwiki.org: https://atariwiki.org/wiki/Wiki.jsp?page=Atari%20XF551 Edited October 26, 2018 by Fred_M 1 Quote Link to comment Share on other sites More sharing options...
1050 Posted October 26, 2018 Share Posted October 26, 2018 The full wave rectifier is a 7 volt rectifier not a 12 volt rectifier. C102 is not in series to the DC side of the full wave rectifier, it is in series to one AC side of the full wave rectifier which is how a voltage doubler circuit works. 1050 drive also has this circuit. D2 conducts during one half of AC cycle and D3 conducts during the other half of AC cycle. Together with help from C103 to establish 7 volt positive to push from, they pump the voltage up to 21 volts during D3 conduction half cycle at C104 which holds the very choppy 21 volt charge for the 12 volt regulator to work with. Suffice to say it works? You can boggle your mind as to exactly how on your time as I may not have explained it in a manner you need to hear in order to make any real sense for you. Teaching is a talent and I may posses little if any. I'm also firmly entrenched in electron flow theory rather than conventional current theory - I maybe just confusing you then. Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted October 26, 2018 Author Share Posted October 26, 2018 Nice. I never realized the simplicity of the XF551 PCB design compared to the 1050.....really makes building a drive "from scratch" possible. Since the drive uses a "standard industry (shugar?) FDD connection, would it be possible to hook up a Gotek ? not that it would be the most logical option for our A8 (f.i. Sdrive Max is a more logical and economical solution) but it would be fun if it would be possible. Yes, its eerily similar to the unreleased 1053 that used a 8039/8049 and 2797: http://www.atarimuseum.com/computers/8BITS/XL/xlperipherals/1053/1053-diskcontroller-schem.gif Quote Link to comment Share on other sites More sharing options...
Level42 Posted October 26, 2018 Share Posted October 26, 2018 (edited) This all makes so much sense now. When the XF551 was released I was totally amazed. I hadnt expected Atari Corp to still make such a big effort for the 8 bit series....it was SO late...the XEGS was already there.... Basically, from what I googled, it seems safe enough to sum it up like this: - Corp. never had interest to release a new FDD for the A8, they happily advertised the 130XE with a 1050 next to it.... - Corp. was sued by Nintendo because commercials claimed the XEGS to be possible to turn in a real computer yet there was no FDD for it. - Corp. panicked, jumped into the technical archives, dug out an old design, adapted it to use the WD1772 they used for the ST series and bam...there was the XF551, with a possible idea for going 3.5 FDD considered briefly... - Corp. launched the XF551 with DOS 2.5, hiding the true power of the drive, but they needed to hurry because of Nintendo... - Corp. found an old DOS 2.5 document, replaced 1050 with XF551 and published as the XF551 DOS 2.5 manual.....the specs page even lists a 6507 and all the other 1050 specs for the XF551, bunch of liars Edited October 26, 2018 by Level42 1 Quote Link to comment Share on other sites More sharing options...
Mathy Posted October 26, 2018 Share Posted October 26, 2018 Hello guys Years ago, Atari Benelux released a lot of their schematics to the SAG. We probably have Guus Assmann to thank for this, as he was the president of the SAG and at one point in time was an employee of Atari Benelux. Among the schematics release where the schematics of the XF551. As soon as I found out how to properly scan the schematics, I'll upload them here. Tips are welcome. Sincerely Mathy PS members of the ABBUC will probably find the schematics (of not only the XF551) on the ABBUC website. Quote Link to comment Share on other sites More sharing options...
+mytek Posted October 26, 2018 Share Posted October 26, 2018 This all makes so much sense now. When the XF551 was released I was totally amazed. I hadnt expected Atari Corp to still make such a big effort for the 8 bit series....it was SO late...the XEGS was already there.... Basically, from what I googled, it seems safe enough to sum it up like this: - Corp. never had interest to release a new FDD for the A8, they happily advertised the 130XE with a 1050 next to it.... - Corp. was sued by Nintendo because commercials claimed the XEGS to be possible to turn in a real computer yet there was no FDD for it. - Corp. panicked, jumped into the technical archives, dug out an old design, adapted it to use the WD1772 they used for the ST series and bam...there was the XF551, with a possible idea for going 3.5 FDD considered briefly... - Corp. launched the XF551 with DOS 2.5, hiding the true power of the drive, but they needed to hurry because of Nintendo... - Corp. found an old DOS 2.5 document, replaced 1050 with XF551 and published as the XF551 DOS 2.5 manual.....the specs page even lists a 6507 and all the other 1050 specs for the XF551, bunch of liars That's got to be one of the strangest lawsuits ever, and I suspect there is more to it than what has been stated. Whether or not a FDD was available doesn't negate the fact that it was indeed a real computer. If you can enter a program via a keyboard and run that program, it's a computer. Saving to and/or loading from floppies is a plus, not a necessity in order to be called a computer. On top of that, it did come with the standard SIO port same as all the other 8-bit Atari computers. So you could still use any of the peripheral storage, modem, and printing devices that Atari (and others) had previously made for the computer line. Quote Link to comment Share on other sites More sharing options...
+CharlieChaplin Posted October 26, 2018 Share Posted October 26, 2018 ... this of course means, that all PC's without FDC (and thus without FDD) are not real computers. Nintendo should start sueing them... 1 Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted October 27, 2018 Author Share Posted October 27, 2018 Hello guys Years ago, Atari Benelux released a lot of their schematics to the SAG. We probably have Guus Assmann to thank for this, as he was the president of the SAG and at one point in time was an employee of Atari Benelux. Among the schematics release where the schematics of the XF551. As soon as I found out how to properly scan the schematics, I'll upload them here. Tips are welcome. Sincerely Mathy PS members of the ABBUC will probably find the schematics (of not only the XF551) on the ABBUC website. Is there a list of all the materials that were released? Quote Link to comment Share on other sites More sharing options...
Level42 Posted October 27, 2018 Share Posted October 27, 2018 Hello guys Years ago, Atari Benelux released a lot of their schematics to the SAG. We probably have Guus Assmann to thank for this, as he was the president of the SAG and at one point in time was an employee of Atari Benelux. Among the schematics release where the schematics of the XF551. As soon as I found out how to properly scan the schematics, I'll upload them here. Tips are welcome. Sincerely Mathy PS members of the ABBUC will probably find the schematics (of not only the XF551) on the ABBUC website. When was Guus president of SAG ? “In my time” it was Casper Jansen..... I received this set of schematics from Atari Benelux because I was secretary of SAG Regio Rijnmond for a while....and did the technical support stuff... still have them, mostly ST though....if not only ST.....they are printed on red paper to prevent copying them on photocopier machines....LOL. Don’t think the XF551 is in that set as I received the set before the XF was released.... Quote Link to comment Share on other sites More sharing options...
Mathy Posted October 27, 2018 Share Posted October 27, 2018 Hello Andre Not sure when. But Guus probably knows. I have a set including the 600XL, 800XL, 130XE, 1010, 1020, 1027, 1029, 1050, 850 and 1064. And a similar envelope of the SAG with the schematics of the XF551. Sincerely Mathy 1 Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted October 28, 2018 Author Share Posted October 28, 2018 Hello Andre Not sure when. But Guus probably knows. I have a set including the 600XL, 800XL, 130XE, 1010, 1020, 1027, 1029, 1050, 850 and 1064. And a similar envelope of the SAG with the schematics of the XF551. Sincerely Mathy Is there a club reason these haven’t been published? Quote Link to comment Share on other sites More sharing options...
Mathy Posted October 28, 2018 Share Posted October 28, 2018 Hello kheller2 SAG seized to exist when internet wasn't available to the public yet. And I guess nobody's had the idea to publish them on the net. Except IIRC ABBUC, but you have to be a member to be able to download them. ABBUC is some cases also the complete SAMs manuals. Sincerely Mathy Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted October 28, 2018 Share Posted October 28, 2018 so if abbuc gets it from anywhere you have to join abbuc to get it from them if you can't find it anymore... yeah that's not sketchy at all. Quote Link to comment Share on other sites More sharing options...
Mathy Posted October 29, 2018 Share Posted October 29, 2018 Hello Doctor Just like with every other club, members have privileges. Sincerely Mathy Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted October 29, 2018 Share Posted October 29, 2018 (edited) And that's how not to get new members. Or former members to re-join Edited October 29, 2018 by _The Doctor__ Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted March 14, 2020 Author Share Posted March 14, 2020 I'm not sure where I got this from, and wish I did so I could offer credit. This has the missing 2nd sheet for the first post's Japan schematics. XF551 Final.pdf Quote Link to comment Share on other sites More sharing options...
Mathy Posted March 14, 2020 Share Posted March 14, 2020 (edited) Hello Karl 3 hours ago, kheller2 said: I'm not sure where I got this from, and wish I did so I could offer credit. Maybe here? Sincerely Mathy Edited March 14, 2020 by Mathy 1 Quote Link to comment Share on other sites More sharing options...
+mytek Posted August 3, 2023 Share Posted August 3, 2023 I think I'll give this thread a bump and ask a couple of questions while I'm at it. So I was looking at the schematics for the XF551 both the ones posted here and also one that had been drawn by Mariusz Geisler back in 1993 and was very curious about a couple of things that Atari had done (particularly the areas I circled in red). So first up would be the pull-up resistor R8 (3.3K). I'm assuming since U3A was feeding into a Schmitt Trigger Inverter (74LS14), they wanted to modify the normal hysteresis to have a faster transition making it akin to using a 74LS04 instead. Because to my knowledge using a pull-up resistor on the output of an LS device was usually only called for when driving into a CMOS gate which requires a higher voltage than LS normally outputs for a high. Moving on... But what totally baffles me is the reason for the 3.3V zener regulated power supply feeding only one input of U3D which is a NAND gate inverting the Write Gate output of the WD1772 prior to connection to the floppy drive. Why the lower voltage on that pin? ------------- EDIT: Just found the answer to my first question about the pull-up resistor. The 74LS38 has an open collector output, so the pull-up resistor gives it an actual high state which it normally wouldn't have. EDIT2: Since I wasn't having much luck looking for the answer to my 2nd inquiry via Google, I decided to try their ChatGPT experiment BARD instead and here's what came back as a response... Quote There are a few reasons why one input of a 74LS 2-input NAND gate might be tied to a voltage between GND and VCC. To create a logical constant. If one input is tied to a high voltage, the NAND gate will always output a low voltage. This can be used to create a logical constant, such as a 1 or a 0. To create a wired-AND function. If two NAND gates are connected with their outputs tied together, and one input of each gate is tied to a high voltage, the output of the combined circuit will be a logical 1 only when both inputs of the first gate are 0. This is the same as the wired-AND function. To create a level shifter. If one input of a NAND gate is tied to a voltage that is different from the supply voltage, the output of the gate will be at a different voltage level. This can be used to shift the voltage level of a signal from one level to another. I think the 3rd possibility of it being a level shifter seems the most plausible. And that surprised me, since I never knew something like that would even be possible with a standard 74LS part. Mariusz Geisler Full Schematic Spoiler Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted August 3, 2023 Author Share Posted August 3, 2023 Why would you need 3.3 shifted on the WG signal to the floppy mech write enable? I don't think they did that on the 1053... Quote Link to comment Share on other sites More sharing options...
+mytek Posted August 3, 2023 Share Posted August 3, 2023 2 minutes ago, kheller2 said: Why would you need 3.3 shifted on the WG signal to the floppy mech write enable? I've been thinking the same thing. And the level shifting aspect wouldn't work for the 74LS38 which is open collector and hence has no HIGH level of it's own anyway, thus relying on the 'normal' high state of the Write-Gate signal line on the floppy drive. So I'm once more baffled by what this circuit is truly suppose to do ??? Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted August 3, 2023 Author Share Posted August 3, 2023 Perhaps a holdover from the failed XF351 3.5" that used ST drives? Quote Link to comment Share on other sites More sharing options...
+mytek Posted August 3, 2023 Share Posted August 3, 2023 8 minutes ago, kheller2 said: Perhaps a holdover from the failed XF351 3.5" that used ST drives? Did the ST drives use a lower 3.3V interface? But for that circuit to level shift it would need to be a standard TTL output NAND gate if Bard's response were correct. And with the 74LS38 being open collector, no level shifting would seem to be necessary anyway since Write-Gate is a active low signal. I think I have a partially disassembled XF around my shop somewhere. Perhaps that'll be my project for today to get it up and working, and then see what that circuit is truly doing or even if it's necessary. Quote Link to comment Share on other sites More sharing options...
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