Choosing between three Sony MPF-920 drives

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Re: Choosing between three Sony MPF-920 drives

Post by exxos » Thu Oct 12, 2017 1:58 pm

Pacman wrote:
Thu Oct 12, 2017 11:14 am
So you're saying that the drives that progressively got worse started out working fine, but within a couple of hours permanently became useless, or it worked fine again the next time you powered up the computer, then once again stopped working an hour or two later? Perhaps due to heat or something... Or maybe just one of those unsolvable computer mysteries :?
The drives initially was working fine, I did buy a lot of use drives a while ago, something like 20 of them, I gave them all a quick test they all seem to working fine. They were supposed to be serviced and tested, but I think a lot of them wasn't. Even so I gave them all a quick test, half of them work, I cleaned them all up and retried them still some of them did not work at all. The ones that did work I was using one in my Falcon, and it tested fine. Thereafter maybe two hours use progressively got worse in reading discs and eventually just stopped. I tried the same drive I think, on a STE, and that would not read the drive either.

I have not really investigated this, or really taken much time to investigate it. Once the drive failed I have just been basically binning them. I have spent a lot of time in the past trying to service drives and get them working, but the majority the time I just basically gave up.

I can only really assume that once the drive starts warming up starts to malfunction. But I think the lack of pullups on the DNA databus could be a reason why the Sony drives are not working. Maybe the BH chips work better without the pullups. It could down to be tolerances, I really cannot say.

I can only really suggest formatting a floppy, at the control panel and some auto folder program is, just something to autoload from it, then maybe every five minutes reset the machine and see if it loads fine from the floppy drive. Basically leave the machine on all day and keep rebooting it and see if the drive faster malfunction at some point later. It is basically what I was doing.

I think I had this problem on the STFM as well with the Sony drives. I would have used this machine when I initially wrote the article my website a long time ago, but I never investigated it or kept any real notes about it.

Though I do remember I did have a teac drive and some others, I think the teac drive was about £60 back in the day, it was supposed to be a really good drive, but I remember I had nothing but trouble with it and in the end I just chucked it. I know I did test a lot of other drives makes and brands are the time and I gave up with basically all of them other than the Sony ones. Obviously later I discovered there was some drives which were malfunctioning also, which I concluded that the Sony IC drives were all the ones which were malfunctioning.

I think it would be unlikely that so many drives would fail like this, so I think it is just basically a databus falls, as there is no pull-up resistors on the DMA databus. It could just be noise as well, as I found noise understood that every signal anyway. Then if I do come across a Sony IC drive again does show signs of malfunctioning I may try and investigated a little further.

In any case I would recommend pullups on the DMA databus anyway. I did find, I think on the STE, but even the BH drives were showing read errors after a while and it was solved with the pullups. Though of course I cannot really draw any conclusions as are never documented or tested all of this much.

Last time I tested a lot of drives out, I was actually doing some booster work, I thought the changes I was making to the booster code with the reasons for the malfunction, but it did not work even as a stock machine. I remember it annoyed me as I wasted probably two days trying to fix faults which were nothing to do with the booster. As I was busy at the time working on the boosters, I did not really want to start diagnosing floppy drives as well, like I say, I just bend all the if the drives as I don't really have time to mess about with a lot of stuff.
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Re: Choosing between three Sony MPF-920 drives

Post by Pacman » Thu Oct 12, 2017 11:17 pm

Good suggestion to boot (and reboot over time) from a floppy with some AUTO folder software in it!

I should probably do that DMA pullup modification you refer to. As I understand, it either improves stability or makes no difference (but won't cause any ill effects), right?

I have some new findings regarding the "disk detection" switch:
As you already know I1ve only modified the newly acquired Sony MPF-920 E/131 drive in two ways: moving the DS1 "jumper" (zero-Ohm SMD resistor) over to DS0, and soldering a wire from the HDIN (HD detect) switch so it can be used with your version 6 HD module in the STe later on.
I also have a modified Sony MPF-520, which is the floppy drive I've used for years with the Mega STe. It's been modified in the same way as described above but also in two more ways: a wire soldered across the CTIN (disk detect) switch, and a second wire from the HDIN switch which connects to pin 2 of the 34-pin flat-cable data connector).
I believe I need to connect a wire across the CTIN switch of the MPF-920 E/131 drive as well, and here's why:

1) On the TOS 2.06 desktop I open up a window showing the floppy disk content (pressing ALT-A to open up drive A and show its content)
2) I close that same window (pressing C)
3) now I eject the floppy disk, then insert another disk
4) I then open up the drive again (pressing ALT-A to open up drive A and show its content)

At this stage, here's what differentiates the two drives:
- with the (fully modified) MPF-520 drive, a new window is opened while floppy drive starts spinning, reading the disk's content
- with the (much less modified) MPF-920 drive, a new window is opened without spinning up the floppy drive, showing the content of the previous floppy disk!

So my conclusion is that I definitely need to solder a wire across the CTIN (disk detect) switch in order to rectify this problem.
Since you chose not to do this, have you had different experiences, or have I gotten it all wrong?
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Re: Choosing between three Sony MPF-920 drives

Post by exxos » Thu Oct 12, 2017 11:50 pm

This is my observations... Though likely with TOS104, can't remember if I tried TOS206 with media change.

http://www.exxoshost.co.uk/atari/last/f ... dex.htm#V6

I only ever used 920 drives though. So can't comment on anything on other drives. Never used them personally.

I'm assuming you soldered the pad on the V6 module to enable media change detect ?
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Re: Choosing between three Sony MPF-920 drives

Post by Pacman » Fri Oct 13, 2017 6:29 am

exxos wrote:
Thu Oct 12, 2017 11:50 pm
I'm assuming you soldered the pad on the V6 module to enable media change detect ?
Aha! I think I understand: you designed the V6 module's logic specifically for the MPF-920, so together they work as expected and there's no need to short the disk detect switch. But when the drive is used with other HD modules (or in my case, a different computer using different HD/DD logic: the Mega STe) those additional modifications are needed. Does that sounds about right?

No, I haven't gotten that far and have only used the disk drive in the Mega STe. The V6 HD module is finished, but I haven't yet connected the wires and need to look further into your instructions for that.
What happens if I short the disk detect wires on the drive (so it'll work properly in the Mega STe), then use it with the v6 HD module? Will it cause problems or just be ignored?
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Re: Choosing between three Sony MPF-920 drives

Post by exxos » Fri Oct 13, 2017 8:18 am

I never played around with CTIN. Though what is it supposed to do ? I mean TOS needs to know the disk has changed, pin 34 is not used on the MSTE or STE from what I can see. So bridging over it would do nothing. The ST hardware does not support the signal. Would need the data sheet for the floppy controller or more information to what CTIN does.

I had a quick google and as you say, people say bridge over it, but why ? what EXACTLY does it do ?, and what does this change exactly in relation to the drive and what TOS does ?

The V6 kit should work with all drives, though I generally dont bother testing any anymore. TOS looks for MD change by looking for WP going low when the drive is inactive. So unless CTIN sends WP low when the drive spins down, then I don't really see it changing anything.

I will try my MD program if I get chance later and bridge over the switch, see if it results in TOS detecting a media change.
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Re: Choosing between three Sony MPF-920 drives

Post by Pacman » Fri Oct 13, 2017 10:56 am

I've just tried it (soldering a wire across the two CTIN switch pins) and just as I expected it works a whole lot better now:

So now, when I exchange floppies, then open up a new window showing its content, the drive is forced to spin up and re-read the floppy (instead of displaying the content from last time I had the window open).
I also tried showing a floppy disk's content, closing the window and reopening it again without exchanging floppies. This time the drive didn't spin up and re-read, so obviously things are working as they should now.

I really don't know the details of how all this stuff works, but asked around, experimented and compiled information on this subject back in the 90s. All I know is that by shorting the disk detect (CTIN) switch, floppies are forced to be re-read. I also remember when experiementing without CTIN shorted that I could totally mess up floppies when swapping them, so that confirmed what I had been told in the various forums and newsgroups back then.

Mind you, I haven't tried any of this with your v6 HD module in the STe yet, but the above is how things are working in a Mega STe.
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Re: Choosing between three Sony MPF-920 drives

Post by exxos » Fri Oct 13, 2017 12:05 pm

From what I remember proper "atari" drives set WP low when the motor stops, forcing media change. Though as a lot of drives don't do that, I emulated it on the V6 kit.

If you could check WP on the 920 with and without soldering over that switch then we should know if that is the case with that drive or not. Though back in the day, I didn't want to limit hacks to the drive itself as it would need every drive documenting and hacking difference, even so, some still probably wouldn't work. So I opted not to mess about with the drive, and do a universal solution in the V6 kit instead.

Just like PP did with this...

http://atari.8bitchip.info/flomodam.html

Its fine if the drive can set WP low as Atari drives do, and fine if they can be enabled, like ( I assume) the CTIN is doing on the 920. Though a lot of drives can't or haven't been tested or documented.

It would be needed if you wasn't using my V6 kit, then hacks to the drive would be needed. Though people with my V6 kit, just don't have to bother hacking stuff about.
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Re: Choosing between three Sony MPF-920 drives

Post by Pacman » Tue Oct 17, 2017 3:04 pm

A silly question..... how/where do I check write protect?
Is that a high (2V-5V) and low (0-0.8V) signal to check at some particular pin with a voltmeter/multimeter?
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Re: Choosing between three Sony MPF-920 drives

Post by exxos » Tue Oct 17, 2017 3:30 pm

Pacman wrote:
Tue Oct 17, 2017 3:04 pm
A silly question..... how/where do I check write protect?
Is that a high (2V-5V) and low (0-0.8V) signal to check at some particular pin with a voltmeter/multimeter?
Would assume on the back of the switch. Assume 5V when switch up , and 0V when switch down.
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Re: Choosing between three Sony MPF-920 drives

Post by Pacman » Sat Oct 21, 2017 12:37 pm

I've taken a closer look at the CTIN switch of my Sony MPF-920E E/131

First, removing the wire across the two pins (i.e. like it was from the factory):
Now, the topmost pin (closest to the insertion end of the floppy) is permanently connected to GND (as you can see from the PCB ground-plane).
The bottom pin reads +5V whenever there is no disk (i.e. the switch is "open" or "off"), but read GND whenever a floppy disk is inserted.
That's it. it doesn't change when the motor spins or ESC pressed but simply detects if a floppy is present or not.
I traced the lower pin to somewhere on the big square Sony chip (next to the big blue capacitor, and marked IC1 in the bottom photo), but couldn't find it on the big 34-pin Shugart connector.
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Next I soldered a wire across the two pins of the CTIN switch and measured it. It shows 0V all the time.
What I don't understand is how the disk drive "knows" when a disk has been ejected and a new one (or the same one for that matter) has been inserted, causing the drive's motor to spin up and re-read the floppy, now that the CTIN switch is permanently switched on (i.e. "a floppy disk is always in the drive) so it must use some other method to detect that.
But like I said previously, if I don't short the CTIN switch and close a floppy disk window on the desktop, swap floppies, then open up a new floppy disk window it won't re-read the new floppy but display the contents of the previous one. Shorting CTIN solves this problem.

I don't know if any of these observations helped, but that's what I've figured out. All this is on a Mega STe.
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