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

[pbertolo]

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.

 

[JDW]

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?

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.

 

[pbertolo]

[SIZE=10pt]Hello,[/SIZE]

[SIZE=10pt] [/SIZE]

[SIZE=10pt]Rotational speed is controlled by the Mac, so “recalibrate” is just a software tweak, for sure no firmware update![/SIZE]

[SIZE=10pt] [/SIZE]

[SIZE=10pt]If the rpm are indeed out of range, hall effect sensors may be the culprit (please refer to my previous posts).[/SIZE]

[SIZE=10pt] [/SIZE]

[SIZE=10pt]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.[/SIZE]

[SIZE=10pt] [/SIZE]

[SIZE=10pt]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.[/SIZE]

 

[JDW]

[SIZE=10pt]...unless they are used out of application range (mainly temperature / humidity etc), they may well be still good today, needing no replacement.[/SIZE]

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:

[SIZE=10pt]If the rpm are indeed out of range, hall effect sensors may be the culprit (please refer to my previous posts).[/SIZE]

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!

 

[JDW]

@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!

 

[MOS8_030]

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.

 

[pbertolo]

 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?

 

[JDW]

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.

 

[JDW]

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.

View attachment 31956

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!

 

[pbertolo]

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...

 

[petteri]

Continuing here as this thread seems to be more appropriate. This 400kB drive is driving me crazy...

Beginning of the story:





The mechanical parts are moving fine, nothing visibly broken or bent and the drive head moves smoothly (guide and worm gear cleaned). There is some play sideways when a diskette is inserted but I think that is normal?

The read/write head has been cleaned couple times and looks good, no scratches or dirt visible. I'll try to get a close up photo to see it better. The pressure pad spring is firm and it lands down on the magnetic media when a disk is in the drive. I don't see scratches on the disk after running tests.

Speed control is stable and seems to be good. But the read/write operations of the drive is pretty flaky. Sonytest format fails with errors 69-72, I guess those are track numbers?

Individual track tests work sometimes, depending of the data written on the disk. 

When disk is rotating in the drive it seems to wobble visibly. The edge of the magnetic media moves, it almost looks like the magnetic media is not cut to a circle or the rotation axis is not exactly center.

Any advices? I wouldn't like to start adjusting every sealed screw randomly.

 

[petteri]

Cleaned up everything really carefully, still not working fine.

Speedtest results after pressing recal:

Track 0: 393-395

Track 40: 473-476

Track: 79: 595-600

Based on the track tests it looks like it isn't able to write properly on the disk. I assume the first track alignment has nothing to do with that?

 

[petteri]

Does anyone have idea what the gain and phase potentiometers do on the PCB?

 

[Crutch]

Just throwing this on here as seems like a good place - anyone have advice for a 400k drive that won’t spin at all?  Head moves fine and eject works but there’s no spinnage.  Just a bad motor that needs to be swapped out, I assume, but would love to hear some genius fix.  (It’s not the capacitors, swapping out the PCB doesn’t help.)

 

[bibilit]

IIRC the motor is driven through the right sensor, while the left one is for write protection. 

Can be that or a bad motor, spinning by hand first doesn’t help ?

 

[KGLlewellyn]

Thank you everyone for the info in this thread, it's been very helpful in helping me troubleshoot my 400k drives. Currently, I've got two 400K drives of the exact same model, that being the Sony OA-D34V-02. I've got one of these internally installed in my Mac 512k and one in an external closure, and both seem to have the same fault. Here's what I've noticed:

-Both drives now have repaired and working eject mechanisms.

-Both drives report Error 067 when trying to format with SonyTest 7

-Both drives don't move the head when trying to initially read the a disk, but you can here the RPM changing. (Makes the durr-durr-duurrr noise before ejecting at waiting on floppy screen)

-Both drives heads move happily when manually told to do so via SonyTest 7.

-Both drives are detected by the OS but will immediately fail to format a floppy, again making the durr-durr-durr noise before ejecting. Sounds like it's having trouble reading the disk.

-RPMs for both drives appear to be correct, so Hall Sensors are probably okay.

-I have attempted adjusting the height of the reader on one of the drives, to no avail. Although I noticed the adjustment screw was completely loose, indicating that the varnish has disappeared.

-Both the felt pads on the black arm on the top of the drive appear to have disappeared. They were never there when I opened up either drive, so I assume they've basically decomposed? Are these felt pads essential for the drive to read disks at all. Anyone know where to get a replacement?

I'm taking a guess that the missing felt-pad and/or the head height might be at fault. Maybe alignment, but no idea on that front. Thoughts?

 

[JDW]

I'm taking a guess that the missing felt-pad and/or the head height might be at fault. Maybe alignment, but no idea on that front. Thoughts?

No felt pad is a no-go for those drives. You need to cut a thick circle of felt to fit the plastic holder, then test again.

 

[KGLlewellyn]

No felt pad is a no-go for those drives. You need to cut a thick circle of felt to fit the plastic holder, then test again.

Okay thanks! I'll see if I can source some. Is there any replacement felt that you'd recommend in particular?

 

[JDW]

Honestly, I've never had to replace the pads.  I simply have read about other people doing that for many years with success.  I would say "soft on the surface yet firm" should guide your felt selection, as well as thickness.  The felt needs to be thicker than the depth of the circular plastic pressure pad holder, and it should then stick out beyond the holder 2-3mm.  Your circular cut obviously won't be a perfect circle, so there is some concern your replacement handmade felt part might nit fit tightly.  In that, case, you should probably put a tiny dab of white Elmer's glue on the bottom of the felt that makes contact with its holder.  That way you know it won't pop out over time.

 

[KGLlewellyn]

Okay...new felt pads have been applied. Only tested the external drive and it seems to have the same issue as before, so I'm gonna play around with the size of the pad and see if it makes any difference.

I've tried adjusting the head height to no avail. So I'm wondering if it's more of an alignment issue.

When running the formatting process in SonyTest, it usually fails at Track 4, but sometimes gets to track 6. Individually formatting tracks always fails with a 0067 error. When I run the actual test it sprouts out near consistent addr mark errors. I'm not sure how these differ from data mark errors. Does it look like we're dealing with an alignment issue in this case?

 

[zastin17]

Adjusting the head is in most cases not necessary.

Make sure your drive is complete: check that the pressure pad is still there. Without that, the drive will never work.

Here's how to clean and lubricate the drive.

- Remove the complete top assembly that holds the floppy disc ( release the lever from the eject motor )

- The mechanism will be completely stuck due to old grease that has hardened. Soack the assembly in WD40 for a few hours or if you have the WD40 Spray: spray all the moving parts multiple times, leaving 1/2 hour between treatments, until you can move the mechanism again.

Patience is the issue: do not try to move the mechanism with force, wait until the WD40 has solved all the old grease and dust.

- Once the mechanism is moving smoothly again, then clean all the WD40 from the assembly.

- Lubricate all the moving parts with a small amount of white lithium grease

- Now is a good time to clean the Head: clean it with at least 99% pure Isoprophyl Alcohol.

- Mount the assembly back on the drive and re-connect the lever to the eject motor.

Now try test the drive. First verify that all parts work. Insert a Double Density disc and see if the main motor spins the disc and the head moves.

Also try the eject mechanism.

If everything works, then mount the drive back in it's enclosure ( external is best to test ) and connect the earth wire.

Now try to initialize the floppy disc: If it formats without bad sectors, then the drive is repaired.

If not then inspect the head under a magnifying glass: it it's scratched or damaged then it's beyond repair.

Otherwise you have to adjust the head.

Look at your floppy disk for damage: if the head pushes too much on the floppy disc, then you will see circle scratches on the disc.

Best practice is to set the head as low as possible and keep trying until you can initialize your floppy disc without problems.

For adjusting the head, you needs to remove the PCB at the bottom to get to the screw.

You can find a detailed explanation here:

http://lowendmac.com/tech/after.html

I would not recommend to turn the screw fully clockwise, but do it with little steps of 1/4 turn clockwise until it works.

I know it's a time consuming job, these 400K drives always are....

Good Luck,

Nico

Thanks for this Info. That website link is gone. Can anybody sum up what it said exactly? I am trying to Archvie more stuff for 400K drives. Very little is out their. I transplanted a head from one 400K drive to another. As I damaged it years ago. I managed to format a couple disks just fine after 50+ attempts of "failing to initialize", lol ") track 0 is misaligned at this point of course. But boots from its own floppies fine if I do manage to format a disk.

95% of attempted formats fails in "initialization failed" Sometimes it goes all the way down the disk, then reverses direction to verify, Failing in the middle, or sometimes at the very end of the disk. And sometimes it simply succeeds to format and the disk reads and boots fine. Very intermittent reliability.

The next day, these same floppies no longer read for some strange reason as if something drifted overnight, and I am running out of ideas what to do next. Why would the drive not work with the same disks the next day? Strange to me.

And my next idea is Head height alignment. Maybe my transplanted Head Carriage is slightly misaligned to this new other 400k donor drive mechanism.

But before I touch the Head height screw thats locked by green nail polish, I want to make sure I will not mess anything up unintentionally.