Testing Apple Disk ][ Interface card?

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gmc
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Testing Apple Disk ][ Interface card?

I've got a Apple IIe which came with a Disk ][ interface card. (With the 2 x 20 pins connectors)

 

I've also bought a Disk ][ Floppy off eBay which was sold as faulty. It would not spin up  and after testing all the chips I found a dead chip on the speed controller board.  Replaced and the drive appears to work in that it does all the right actions, but I cannot read/write any disks.

 

My issue now is I'm not sure if its the floppy drive, or the interface card that is faulty. I'm beginning to think the interface card as I've also built a sdisk2 and can't get that working either.  (But it could be a case or either/or both being faulty)

 

Is there any standalone testing (maybe with some kind of looback connector) I can do on the interface card to first make sure that is working as expected (The obvious test would be to test it against a known good floppy, but there lies the problem)

 

I've tested all the logic chips on the interface card and they all work fine. Nothing is getting warn on the card either.

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First thing to do with faulty Disk II drives ...

... change the 74LS125. This IC usually gets destroyed when the 20-pin header is plugged into the "other" style of Apple II disk sockets that can be found i.e. in the Apple IIc.

 

If this does not help, replace all the electrolytic capacitors.

 

This is about as much as you can do without an oscilloscope and some other items found in a well equipped electronics lab.

 

- Uncle Bernie

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On the Disk II card the PROMs

On the Disk II card the PROMs have been known to die. Also the  capacitor sometimes go bad. If you post your location, maybe there’s someone locally with a good card and drive willing to help.

gmc
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On the interface crd I've

On the interface crd I've tested all the logic chips as well as the transistors - all good.

 

I've also built a arduino jig to read and compre the proms - all test good there.

The only thing I haven't been able to test yet is the NE556 chip. I guess I could take it out of circuit and build a time circuit on breadboard to see if it's working.

 

On the disk drive, I have also tested the 74125 - all good, but replaced it anyway. Tested all other logic chips, diodes, transistors. Guess I could replace the caps and hope for success.

 

Supply rails on both boards are present and good.

 

I've got access to a digitcal scope, logic analyser and a bunch of other tools if that helps and someone can point me in the right direction. 

 

I'm in the UK - North West.

 

 

 

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gmc wrote:I've got access to
gmc wrote:

I've got access to a digitcal scope, logic analyser and a bunch of other tools if that helps and someone can point me in the right direction.

 

Well, that should help... :)

Start by probing the RD DATA signal. This is the raw "magnetic flux" signal returned from the disk II drive to the interface card. When the drive is spinning and a disk is present, you should see the signal toggling at TTL level all the time. When no disk is loaded, the signal is constant (even when the drive is spinning). If the signal is dead with a good disk spinning, then you need to invesitgate the drive itself (broken r/w head or dead drive electronics).

If you do see a toggling TTL signal, you can make a simple test of the interface card.

Enter the monitor. Then enter:

  C0E9:00

to switch on the drive 1 motor. Now the disk is spinning.

Then repeatedly read the disk II interface's read latch (just enter "C0EE<RETURN>" and the monitor will show the current value of the disk read latch):

  C0EE

  C0EE

  C0EE

  C0EE

When a disk is spinning, you should see changing values. Then stop the motor by entering

  C0E8:00

and, again, read the C0EE latch repeatedly. When the motor is stopped, the read latch needs to return constant data (whatever data was in the latch last, will no longer change).

If these register tests do not behave as expected, but you did see a toggling TTL signal from the disk II drive, then you clearly have an issue with the interface card (bad address decoding logic, dead P6 PROM or shift register IC).

If the register tests do work, then this still leaves a number of options (bad disk, misaligned drive head to a bad (but not completely dead) P6 PROM)...

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Take it back to the basics.

Take it back to the basics.

 

Can you verify the speed of the disk drive?  That would be the first thing to check if your drive isn't reading or writing.  Especially since you changed components on the spindle motor circuit board.

Next I'd check the physical connection to the read/write head connector and the analog board on the drive itself.

 

Have you tried an analog board from a known-good drive to see if the issue is there?

 

Next I'd tackle the drive's alignment, but only if you can get the speed correct.  You can adjust the drive speed under a lamp using the stobe disc on the drive spindle for a rough adjustment and then dial it in using some diagnostic software (most Apple II diagnostic software tools like Apple Cillin and Aptest have some sort of drive speed check)

gmc
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Finally got some more time to

Finally got some more time to look at this. 

 

I checked the drive speed using a lamp and then  also using my super slow motion camera on mobile phone (They are really handy)

It's bang on 300 fps. 

 

Next I probed the RD Data signal (TP1) - when I power on the Apple for about 1 second I see this (Happens with or without a disk (blank))

 

 

After that the signal is 0V and drive keeps spinning (I don't have a know good disk, only blank disks. Also don't have a known good interface card  which is not helping matters)

At least something is happening. Not sure what it's supposed to look like.

 

I've read through the SAMs manual and checked the head resistances but the colour wires and resistances don't match so it must be a different model. Can't find what they should be.

 

Have traced the connectors on the header:

 

 [RW (Black)]    [CT (White)]  [Erase (Green) ]    X      [RW (Red)]

Red - Green 32 ohms

Red - White 20 ohms

Red - Black 6k8

Green - White 12 ohms

Green - Black 6k92

Black - White 6k9

 

Next I tried the commands (still with a blank disk so not sure if it's a viable test?)

]CALL -151

*C0E9

C0E9 - A0

*C0EE

C0EE - E0

*C0EC

C0EC - E0

*C0EC

C0EC - E0

 

I have also retested the 74LS125 and it's good. Replaced anyway and no change.  Unfortunatly don't have a known good analog board or interface board. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Can you get DOS into your

Can you get DOS into your computer somehow?

Via a hard disk emulator or a modern device like a Floppy Emu?  Or can you bootstrap the machine using ADTPro?  Have you got a serial card?

If you can get DOS 3.3 into your machine somehow then try an "INIT HELLO" command with a blank floppy in the drive and see what happens.  It shold grind up agaist track zer and go through it's track-by-track initializatio after which a readable diskette shold result.

 

With only blank disks there is nothing much that can be done, practically...

The drive on power-up should send the head to track zer (and bounce off of track zer a few times) then try to read something at track zer.  If there is nothing to read then your troubleshooting stops right there...

 

 

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Download disks through the tape port
baldrick wrote:

Can you get DOS into your computer somehow?

Via a hard disk emulator or a modern device like a Floppy Emu?  Or can you bootstrap the machine using ADTPro?  Have you got a serial card?

If you can get DOS 3.3 into your machine somehow then try an "INIT HELLO" command with a blank floppy in the drive and see what happens.  It shold grind up agaist track zer and go throug

Don't overlook the simple method of downloading whole disks and programs to an Apple //e from ASCIIEXPRESS.NET

 

If your disk drive is sufficiently functional, it'll take about two minutes to create a DOS 3.3 disk through the tape port.  If you're new to this, I recommend the instructional video on their README page.

There are also programs that you can download and run directly from the ASCIIEXPRESS.NET web site without using a disk drive at all.

gmc
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Some progress but in the

Some progress but in the wrong direction. 

 

I managed to get adtpro running by loading it via audio. When trying to format a disk it's not detecting the disk drive, so it's back to square one

 

 

Either disk interface card or logic board on disk drive is faulty. 

When I do a rescan on adtpro format menu, the drive light comes on and the disk spins for a few seconds, but it fails to detect anything. 

 

I've retested all the chips on the interface card so I'm pretty sure it's working. 

Have also tested all the chips on the disk drive, well all except the MC3470 so have ordered another one and will retest.

 

With adtpro failing to detect the disk does this indicate a issue with the logic board, or will it only detect something if it succesfully reads the disk? (So for instance won't pick up anythng if the heads are faulty)

 

 

 

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While it won't pick up

While it won't pick up anything if the heads are faulty, there could be other issues at play.

For instance, have you cleaned the heads?

Have you inspected the floppy disk itself?

 

If there is any buildup on the head,not only will the head fail to read (or write) it will also damage the diskette itself.

 

If after cleaning the heads and checking the physical media (look on the underside of  your diskette - if there is a narrow concentric scratch at track zero near the outer perimiter, that diskette is scrap)

Next I'd suspect something going on with the drive's analog board.  Probably something going on with the MC2470 chip which is a read-write amplifier.  If that chip is faulty the drive won't read or write, although it will move the head around and try to do both until the computer realizes that nothing is being read back.

 

 

gmc
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I've cleaned the head - it's

I've cleaned the head - it's spotless. Also the tracks move easiely and nothing getting stuck. 

I have a few new floppy disks - prestine condition, no mark or defects.  Tried a few - no luck.

 

I'm beginning to suspect the MC3470 as well - It's the only chip I can't really test. All the other test ok. (I even build a circuit on breadboard to test all the other chips out of circuit)  I'm hopeing the MC3470 is faulty and have ordered a replacement. Will  report back when I get it. 

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gmc wrote:With adtpro failing
gmc wrote:

With adtpro failing to detect the disk does this indicate a issue with the logic board, or will it only detect something if it succesfully reads the disk? (So for instance won't pick up anythng if the heads are faulty)

 

With no disk in the drive ADTPro will still be able to detect the drive.

I do not know how ADTPro is programmed, I have not seen the source code, so I could be wrong here, but my guess is that ADTPro tries to read the boot code from the Interface Card's P5 rom, in order to determine if there is an Interface Card / Drive it can use.

I say that because that's how I would try to program such a detection. I don't think there really is any other way to detect an interface card / drive.

So my guess is that either the P5 rom is faulty or something else on the interface card is faulty which prevents the P5 rom code from being read.

One way to to test the P5 rom code, is to boot the machine with the interface card in slot 6.

Enter monitor with CALL-151 (return) and type C600L (return), that should produce a fine listing of the boot code.

What does your machine show?

 

gmc
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I've tried C600L and it lists

I've tried C600L and it lists the ROM code which I compared to the .bin file and it matches. So no issues reading the ROM. I have also tested both P5 and P6 with some arduino code which verifies the ROM content. No issues there. 

 

Found another post where someone suggested running C600LLLLLLL to list the entire ROM and seeing if it locks up - no issues running that. No corruption. 

Have also removed all the logic chips and tested them out of circuit - all working. Transistor tested ok too. The only thing I can think of is if the interface card is faulty then there must be a broken track.

 

I might try to beep out all the tracks on the card to double check - looking at the schematic it's not too complicated. 

 

 

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Based on your analysis of the

Based on your analysis of the card, and its PROMs I don't think there's anything wrong with it.

 

And ringing out each trace to the connector is a trivial (if tedious) affair.

My money's on the MC3470 on the drive's analog board...

 

 

gmc
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Finally made some good

Finally made some good progress. I got hold of another Apple Disk II drive and it works perfectly with that. At least this means my disk interface card is 100%

 

I swapped the MC3470 between boards and it didn't solve the issue on the faulty drive, so back to square one.  (I was convinced this was the issue)

 

At least now I have a working and non working drive I can compare. 

 

Before I destroy anything, I first want  to check. Is it safe to swap the logic boards. Both look the same component wise, but one of them has a square hole in the PCB and the other doesn't. The PCB model numbes are both 065-0103

 

After that if both logic boards work, is it then also safe to swap the speed controllers?

 They are diffent though. One has a LM2917 on, and the other  (confirmed working one) one a Sanyo CX.065.  

I'm hopeing there is some faulty on one of these boards and not the heads  :(

 

 

gmc
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Update: Instead of swapping

Update: Instead of swapping tthings around I compared the resistances on the heads -  my worst fears....the RW coil is dead :(

 

Seems an impossible task to find replacement heads for this.  Don't suppose heads can be used from different 5.25 drive? Otherwise has anyone been crazy/bored enough to remove and rewind the coil. 

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gmc wrote:Update: Instead of
gmc wrote:

Update: Instead of swapping tthings around I compared the resistances on the heads -  my worst fears....the RW coil is dead :(

 

Seems an impossible task to find replacement heads for this.  Don't suppose heads can be used from different 5.25 drive? Otherwise has anyone been crazy/bored enough to remove and rewind the coil. 

 

 

That is the first read/write head coil failure I have ever seen.

That said, I think that you could cannibalize a dead Commodore 1541.  That is, if your Apple disk drive is a newer Alps based one, but even if it isn't I'll bet the R/W head would fit.

Or a dead Shugart SA400 drive - those were extremely common and would have a direct replacement part (if your Disk II drive is a Shugart based drive)

 

I'm saying all this but it might simply be easier to just buy another disk drive.

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