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400k Drive Repair Guide - A Call to Arms!!!!!!

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13 hours ago, pbertolo said:

Hello JDW,

seen you video and checked your images.

Seems to me the image is somehow corrupted, some stuff is somehow missing.

 

Start from images you can download from Macintosh Garden, transfer them to a 68k Mac, I used a Mac SE/30 in the process.

Mount them with Disk Copy 6.3: eventually you will get an error, but images will be mounted nonetheless as a “floppy” on the desktop.
Then you save the virtual floppy in Disk Copy 4.2 format, using which you can finally create a physical copy (only way for writing 400k floppies). 

I’ve had no success with the image on Macintosh Garden. I see in your video though that you have two working disks. Could you please make a disk image of each of your disks, ZIP them, upload to the cloud and then provide a download link here?

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7 hours ago, JDW said:

I have not cleaned the felt pad, because I honestly don’t know how to clean it properly.

There’s no point in cleaning the felt pad, just desist. The only adjustment is about the tension, but that one is also normally unnecessary.

 

Just clean the head, very gently and very carefully with isopropyl alcohol.

 

Of course you need to take out the drive and swap it with the good one.

 

Then use the good drive for booting the Mac, use a known good floppy and start recording the error message when you try to read, format etc.


If you have to go for a track zero alignment, I warmly recommend NOT to follow Larry Pina’s procedure on the rotor alignment, it’s just too difficult to remain in control of it.

 

Instead, adjust the position of the sensor board (see some previous post).

 

Again, at your own risk, it can turn out into a frustrating failure.

 

Finally, here the link to my public Dropbox with the disk images, let me know if they work.

 

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6 hours ago, pbertolo said:

Finally, here the link to my public Dropbox with the disk images, let me know if they work.

Thank you.  I am able to get both of those images to boot my Mac 512K using my FloppyEMU.  But let it be known that they will NOT boot Mini vMac.  You get weird lines on the display in Mini vMac.

 

I also get the same "apparent freeze" in Sony Test on both of your images; HOWEVER, the key is to INSERT A DISK!  That's it.  If you don't insert a disk, you get the redraw "freeze" I spoke of.  I got that before because I was working exclusively off my FloppyEMU.  But I used Copy II Mac 7.0 to create a copy of your images to real 400K floppies, and that seems to solve the problem.  By the way, when I did a Sector Copy of your Sony Test 7 image, I got a Read error on Track 0, so after the Sector copy finished, I used Bit Copy on track 0, with synchronize tracks and keep track length enabled.

 

Within Sony Test 7, in the "Notes" window in the upper right of the display, I see the following errors when I test my internal drive (my bad drive) using the "start test" button:

 

Adr Mark Errs

or

Error in Speed

 

I incrementally changed SpdAdj and clicked "start test" multiple times, and I hear the speed increase as I increment, but I still get "Error in Speed".

 

When I click "speed chk" though, the RPM value is between the Hi & Low every time -- no problem.

 

I cannot format a disk in the internal drive either.  External drive tests work fine, including format.  For example, I set "Test Seq" to "seq +" and the clicked "start test" with a disk in my external drive, and it went through all 80 tracks without a single error.  But again, my internal drive won't do this.

 

It's also interesting that Sony Test keeps the disk spinning for as long as you have the disk in the drive.  

 

I really wish there was documentation for Sony Test.  It seems like a very powerful tool to diagnose problems, assuming you know how to use it.

 

 

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2 hours ago, JDW said:

It's also interesting that Sony Test keeps the disk spinning for as long as you have the disk in the drive. 

I really wish there was documentation for Sony Test.  It seems like a very powerful tool to diagnose problems, assuming you know how to use it.

You can start/stop the drive with the Sony Test software.

 

 

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2 hours ago, JDW said:

When I click "speed chk" though, the RPM value is between the Hi & Low every time -- no problem.

Mind that low and high readings are the actual low and high rpms recorded during the test. Cross check how far these values are from the nominal ones (I posted here some values some posts ago).

There’s a button in the test window which reads “recalibrate”. It’s a software adjustment (speed is controlled by the Mac), but it gives an indication.

As for the Address Mark Errors, can be whatever, but for the drives I’ve dealt with so far was indicating zero track alignment issue.

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7 hours ago, MOS8_030 said:

You can start/stop the drive with the Sony Test software.

I only used the "Error Rate Test" window, so I assume you are referring to a control on one of the other two windows?

 

7 hours ago, pbertolo said:

There’s a button in the test window which reads “recalibrate”. It’s a software adjustment (speed is controlled by the Mac), but it gives an indication.

As for the Address Mark Errors, can be whatever, but for the drives I’ve dealt with so far was indicating zero track alignment issue.

I was afraid to click "recalibrate" for fear it would write something to the drive's firmware that I later could not correct.  Do you know exactly what it does?

 

By the way, my "bad" drive was actually a "good" drive until after I made my 400K drive recapping video.  If you watched my 400K recapping video, you will see that I test the drive and even boot from Winter Games (with disk in my internal drive) at the close of my video.  Everything was working perfectly.  I even used Copy II Mac to make copies without problem!  But later as I was continuing to test several other 400K disks in my collection, I heard the drive motor speed vary in an unusual way, and after that, despite numerous restarts of the Mac 512K, the internal 400K drive won't read any known-good disk now.  It's really odd.  Not sure what to think, which is why I am trying to use Sony Test to diagnose this mind-boggling problem.

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Hello,

 

Rotational speed is controlled by the Mac, so “recalibrate” is just a software tweak, for sure no firmware update!

 

If the rpm are indeed out of range, hall effect sensors may be the culprit (please refer to my previous posts).

 

As for re-capping, even though I replaced hundreds of capacitors, I’m always skeptical. I recently did check caps on a 400k drive of mine, they were all still perfectly in range, I just soldered them back.

 

The whole frenzy about recapping stemmed from some infamous, defective SDM caps which were indeed bad to the point today they are surely gone and may surely be damaging the boards (e.g. Mac Classic, Portable, SE/30 etc). But radial / axial electrolytic caps are more robust and unless they are used out of application range (mainly temperature / humidity etc), they may well be still good today, needing no replacement.

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15 minutes ago, pbertolo said:

...unless they are used out of application range (mainly temperature / humidity etc), they may well be still good today, needing no replacement.

It's important to keep in mind that the Macintosh 128K, 512K and even the Plus did not have an internal fan, so all the caps are running hot.   Even when running those machines on a cool day, about an hour after you've switched on power, if you put your hand above the air vents that are above the analog board, the heat coming off is quite intense.  If you open the case and then touch some of those capacitors, they are hotter than you may expect.  And most all of those are rated at 85°C as opposed to the 105°C caps we more commonly see today (which are the ones I use to recap).  And that's why it came as no surprise when I saw the following axial cap on a Macintosh 128K analog board I recently recapped:

 

LeakyCap.thumb.jpg.1161c45d6709683f91855d5c77b224f1.jpg

 

15 minutes ago, pbertolo said:

If the rpm are indeed out of range, hall effect sensors may be the culprit (please refer to my previous posts).

Here is your earlier post.

But as I mentioned in my earlier post, RPM values tested to be within the Hi and Low range, which means the RPM speeds are perfectly fine and therefore it must be some problem other than those hall effect sensors.  And again, the drive worked perfectly fine, as you can see in my video.  It just suddenly stopped working a day later as I was testing it with various 400K disks.  That's really what has me dumbfounded.  It worked fine, then suddenly stopped working!

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@MOS8_030 & @pbertolo

 

I just removed my "bad" internal drive and connected it as an external, putting my external drive mechanism internal.  Now both drives work fine.  Please watch this short video.  I would appreciate hearing your thoughts!

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Ha ha ha! That floppy drive is messing with your mind!

Ok, now swap them back and see if the problem returns...

 

Just kidding, don't do that.

No telling why the internal drive works externally, perhaps some anomalous electrical interaction between the drive and the internal vs external bus.

Personally I would just accept it, put the former internal drive into the external case and move on.

 

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17 hours ago, JDW said:

 I would appreciate hearing your thoughts!


This is interesting, I have experienced similar situation on some other Macs with 800k drives and corresponding flat cable. 
Don’t remember the details, but one key part of the story was the flat cable, featuring a yellow line or a red line. Some versions of the drive would work as internal drive only in combination with one of the two flat cables. I remember going through the Apple Hardware reference and found some kind of explanation (lines which were connected or not). But for 400k drives it’s unheard of, to me at least.

Are the two drives exactly the same or do they belong to different series?

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23 minutes ago, pbertolo said:


This is interesting, I have experienced similar situation on some other Macs with 800k drives and corresponding flat cable. 
Don’t remember the details, but one key part of the story was the flat cable, featuring a yellow line or a red line. Some versions of the drive would work as internal drive only in combination with one of the two flat cables. I remember going through the Apple Hardware reference and found some kind of explanation (lines which were connected or not). But for 400k drives it’s unheard of, to me at least.

Are the two drives exactly the same or do they belong to different series?

Regarding the ribbon cable, it's important to consider that I am using the same cable for the internal drive.  Yet, when I swapped drives, then the both started working.  If the cable was an issue, I would expect to see the same problem on the internal drive even after I swapped drives.

 

Regarding drive type, please see my video @10:38. The "bad" drive that originally was my internal, is the Jan. 1984 (OA-D34V) and the "good" drive that was previously my external is the no-label (OA-D34V-??) drive shown in my video.

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On 3/22/2020 at 2:23 AM, pbertolo said:

Good old Larry Pina's "The Dead Mac Scrolls" suggests a very painful zero track alignment procedure by rotating the stepper motor stator housing.

At first, I would always suggest to play with zero track alignment sensor, which is adjustable on 400k drives too (the board mounting hole is elliptic).

Adjustments are extremely difficult as each track is 0.1875 mm and allowed off track is just +/- 0.035 mm, but it's worth giving a serious try at it.

IMG_3935.jpg

 

 

I have yet another bad 400K floppy drive about which I made a short video below.  I am curious about the above post from @pbertolo, whether I should touch that particular screw or not.  I'm also curious about the direction it allows the that small PCB to slide.  Sliding it only 0.1875mm in either direction would be quite near impossible though!

 

 

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Hello, 

the sad Mac is indeed curious, which code is it?

As for the second floppy, the fact that the drive is struggling may indeed indicate lack of alignment.

Did you already go through the problem catching procedures suggested by Pina?

Out of alignment normally results into format failure and error messages when you exchange disks with known working drives.

Anyhow, the screw is not for adjustment, it’s just for keeping the board with the optical sensor into place. The sensor is allowing the drive to set the position for/of the track 00.

The hole in the small board is oblong, allowing for adjustment.

This means that you have to loosen the screw, *manually* reposition the board, tighten the screw, check if everything works (it won’t), do it all over again until - more by luck than anything else - the drive will not just work, but also keep compatibility with other drives.

Unfortunately, there seems to be no other way, as factory procedures for alignment are not available and would in any case require dedicated hardware.

By the way, if you pay attention there’s a slit and a corresponding “V” shape in the metal cast right beneath the “N” of the Sony stamp on the board, I guess that was allowing some external tool to be used for super fine position adjustment.

I did this adjustment on most of my drives, but every time I swore to myself it would be the last, as it’s indeed boring and may get frustrating beyond imagination.

Keep in mind that we’re talking about a fraction of a tenth of a mm, so impossibly tight.

Mark the current position as reference and imagine that the adjustment will correct this position by a hair or less in either direction.

Using the Sony Tool you will be able to see at which stage the format will fail. If right off the start at track 00, means you are really out of alignment, if half way into it or near the end means that you are very close.

Mind however that successful formatting is just one part of the issue, you must also be able to exchange floppies with other drives. In this regard, the ideal condition is achieved when you can exchange floppies with known good drives and you pass w/o any error the read / write tests in the Sony Tool.

Anyhow, why drives are loosing the adjustment is a mystery to me, as all sensitive parts are sealed into place. I’m not able to tell, I may guess it comes from mechanical wear and/or de-rating of the electronics...

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