Corcomp 9900 disk controller problems

[+Ksarul]

Based on your smptoms, I would look at the signals between the disk controller chip and the disk connector. It looks like some of the control signals are making it through--but not all. I put the CorComp schematics up in the schematics thread last year (just find the one that matches your card), which will show you which signals show up on each pin.

[HOME AUTOMATION]

Fujitsu M2551A. 

[wolhess]

54 minutes ago, Ksarul said:

Based on your smptoms, I would look at the signals between the disk controller chip and the disk connector. It looks like some of the control signals are making it through--but not all. I put the CorComp schematics up in the schematics thread last year (just find the one that matches your card), which will show you which signals show up on each pin.

Thank you for your suggestions, I found the right schematic I think.

 

I will check the WD1773 on PIN 16, 17, 21, 22, 19, 23, 24 and 25 and the signals on the bus after the 7406.

 

 

[wolhess]

Yuppie!!,

 

my CorComp FDC controller is up and running!

 

The WD1773 chip was defective. Today I replaced the chip and also changed the two eproms to the version of Millers Graphics DOS.

 

Now the card is working with two drives, the standard TI drive SSSD and the Mitsubishi 5.25 "MF501B-312M" in DSDD mode.

 

 

On page 48 of the manual it says that there is a Disk Manager floppy disk with some tools for the controller.

Do we have this disk somewhere for download or can someone provide me with such a disk?

 

Thanks in advance,

 

Wolfgang

 

 

[sparkdrummer]

I think this was Corcomp's final version.

 

The manager can be accessed from basic command line with CALL MGR.

MGR_VER2_3.DSK

[wolhess]

2 hours ago, sparkdrummer said:

I think this was Corcomp's final version.

 

The manager can be accessed from basic command line with CALL MGR.

MGR_VER2_3.DSK 90 kB · 4 downloads

Thank you for providing this disk, I didn't found it on AA or whtech.

[+acadiel]

My Corcomp Mini PES sidecar had two issues with it crop up about five years ago:  the PSU went out (which I found a good one - it had the same type of voltage requirements as the console replacement PSU I was using), and the 9901 for the disk controller board went out.  What’s strange is that nothing was plugged in incorrectly, it just stopped working.  
 

That reminds me that we need to make some new disk controller boards for the Mini PES systems - a lot of them are missing the disk controller boards because they weren’t ordered with them.  

[snume]

On 8/30/2020 at 9:47 AM, acadiel said:

That reminds me that we need to make some new disk controller boards for the Mini PES systems - a lot of them are missing the disk controller boards because they weren’t ordered with them.  

Yeah, I'm definitely in for a new one for a CC9900 sidecar. Mine never had the disk controller and I was just happy to get one fairly cheaply at all.

[Fritz442]

I also have a Corcomp fdc story, I have 3 corcomp fdc's(2 are mine and 1 is a friends) with the 2793 chips. I purchaced both about 5-6 yrs ago
and both controllers didn't work correctly, they had inconsistant/flaky operation, error 16, 'not initialized' messages. Both would not
read/write/format DD disks. They would sometimes read/write SD disks but were inconsistant. I tried to repair one of them about 3 yrs ago by cleaning terminals,

testing voltages, replacing the ele. capacitors, swapping the socketed chips...with no improvement. Then just put them aside and moved on to other projects.
Reading this topic got me thinking about these cards again, so I broke one out. Started testing again and adjusting the 50k and 10k var. resistors
again with no improvement, so I reset them back. I then went to the var. capacitor and adjusted it with no improvement again. I looked very closely
and saw slight green funk in\under the capacitor, on the schematic it shows a fixed 10pf & var. 4-60pf capacitors on that circuit for a total of 14~74pf.
Not having any variable capacitors, I just clipped on a 22pf cap(across either capacitor) for a total of 32pf and the card came to life. It formatted/reads/writes DD and SD
disks with '0' failures. I let it run for about a week cycling on and off, tested with diff. drives and disks again with '0' failures. So I broke out
my 2nd controller, removed the cover and simply clipped on the same 22pf cap. and turned it on...0(zero) failures! I tested it like the other one for about 3 days

reading, writing, formatting with no failures.
So I got a hold of the 3rd card and we did the same thing, clipped on the 22pf cap. On first test it was a little lazy and said 'not initialized' once,
then after about 30 seconds it began to read/write correctly. I swapped it with a 27pf cap. and it began to work flawlessly, I kept the card for about
a week testing cold startup and long runs, '0' failures ever since. I ordered some variable caps(5-50pf) and replaced them now all 3 cards work.
Maybe this will help someone else.

Edited September 13, 2020 by Fritz442

[ChrisSpiel]

On 8/30/2020 at 10:47 AM, acadiel said:

My Corcomp Mini PES sidecar had two issues with it crop up about five years ago:  the PSU went out (which I found a good one - it had the same type of voltage requirements as the console replacement PSU I was using), and the 9901 for the disk controller board went out.  What’s strange is that nothing was plugged in incorrectly, it just stopped working.  
 

That reminds me that we need to make some new disk controller boards for the Mini PES systems - a lot of them are missing the disk controller boards because they weren’t ordered with them.  

Hey, did this ever come fruition?  I have a CC 9900 Micro put it does not have the 32k/Disk daughter board.  I'm either looking for detailed photos or schematics for it.  Wondering if I can design one with 32K/TIPI as well.  Just need a starting point.

[apersson850]

I've had the TMS 9901 in my console die just like that. Had to remove and replace it. Then the machine worked again. It's now socketed in my main console, and I have a few TMS 9901 as spares in a box. From the time when you could easily buy them over the counter.

[+Torrax]

On 8/30/2020 at 9:47 AM, acadiel said:

My Corcomp Mini PES sidecar had two issues with it crop up about five years ago:  the PSU went out (which I found a good one - it had the same type of voltage requirements as the console replacement PSU I was using), and the 9901 for the disk controller board went out.  What’s strange is that nothing was plugged in incorrectly, it just stopped working.  
 

That reminds me that we need to make some new disk controller boards for the Mini PES systems - a lot of them are missing the disk controller boards because they weren’t ordered with them.  

 

Could this be similar to the problems I'm currently having with my CC9900MES??  Also what are the signs of a failing WD1773 chip.  Are they similar to a failing 9901?

 

[+acadiel]

 
Could this be similar to the problems I'm currently having with my CC9900MES??  Also what are the signs of a failing WD1773 chip.  Are they similar to a failing 9901?
 

If I recall, I had no disk access at all. I don’t remember if the light went on or not, but the drive didn’t do anything. I swapped out the PSU and WD chip,
And I think It was Gazoo who suggested checking the 9901 next.

[justacruzr2]

Hey everyone.  It's been about 7 years since my last visit.  So many things happened that I was unable to to keep up with things here, including being T-boned by a person running a red light.  It broke my collar bone in 2 places (2 surgeries) and only now is the lawsuit being settled.  Anyway, there was a gentleman here who was assembling a TI archive and I promised to give him a copy of everything I had.  I haven't forgotten that and the problem at the time was that my floppy disk system wasn't working.  I did repair the controller card but still cannot read a disk.  The problem seems to be that the head is not seeking.  Just to check if the seeking motor was bad I moved the head all the way to the hub position.  When the drive is accessed it moves back to the outer edge of the disk position.  Seems like the motor is OK but I guess I can't dismiss that the motor is bad in one direction.  I have tried this with 2 other drives and the result is the same.  Hard to believe that all 3 are bad.  So my question is does anyone know whether it's the controller card that controls the seeking process or the floppy drive?  Trying to nail down who's the bad guy here.  Here is a reply to a similar problem on another website:

 

"There may be a failure of the motor driver circuit/s on the controller board. Unless severely over voltaged, the stepper motors themselves rarely, if ever, fail.

The Track 0 sensors tended to fail (the embedded LED failed). With the LED not lit, the drive thinks the head is already at track 0 and only "bumps" the motor to verify. If that fails to detect the head moving then the drive issues an error and shuts down. Common failure, so it wouldn't be unusual for both drives to have the same problem."

[+arcadeshopper]

16 hours ago, justacruzr2 said:

Hey everyone.  It's been about 7 years since my last visit.  So many things happened that I was unable to to keep up with things here, including being T-boned by a person running a red light.  It broke my collar bone in 2 places (2 surgeries) and only now is the lawsuit being settled.  Anyway, there was a gentleman here who was assembling a TI archive and I promised to give him a copy of everything I had.  I haven't forgotten that and the problem at the time was that my floppy disk system wasn't working.  I did repair the controller card but still cannot read a disk.  The problem seems to be that the head is not seeking.  Just to check if the seeking motor was bad I moved the head all the way to the hub position.  When the drive is accessed it moves back to the outer edge of the disk position.  Seems like the motor is OK but I guess I can't dismiss that the motor is bad in one direction.  I have tried this with 2 other drives and the result is the same.  Hard to believe that all 3 are bad.  So my question is does anyone know whether it's the controller card that controls the seeking process or the floppy drive?  Trying to nail down who's the bad guy here.  Here is a reply to a similar problem on another website:

 

"There may be a failure of the motor driver circuit/s on the controller board. Unless severely over voltaged, the stepper motors themselves rarely, if ever, fail.

The Track 0 sensors tended to fail (the embedded LED failed). With the LED not lit, the drive thinks the head is already at track 0 and only "bumps" the motor to verify. If that fails to detect the head moving then the drive issues an error and shuts down. Common failure, so it wouldn't be unusual for both drives to have the same problem."

clean and lubricate the rails on the heads and also the stepper motors may need lubrication  this is common to cause the heads to stick on the rails and not seek properly as well as the led issue or track 0 sensor as it is called some drive use leds some switches pretty sure the controller card tells the drive to seek track 0 and waits for the sensor to show it is there

[justacruzr2]

4 hours ago, arcadeshopper said:

clean and lubricate the rails on the heads and also the stepper motors may need lubrication  this is common to cause the heads to stick on the rails and not seek properly as well as the led issue or track 0 sensor as it is called some drive use leds some switches pretty sure the controller card tells the drive to seek track 0 and waits for the sensor to show it is there

Motor and rails OK.  Moves freely.  Didn't get a reading on the sensor though.  Spun up the drive and put test leads on the contacts of the sensor but no reading.  Thought I would get something as the hole and sensors line-up but I suppose it could happen so fast that the meter doesn't register.

[+OLD CS1]

While not likely to be the culprit, it is also worth checking the rotation sensor as many drives will not send data if it does not detect the disk is rotating.

[+arcadeshopper]

6 minutes ago, OLD CS1 said:

While not likely to be the culprit, it is also worth checking the rotation sensor as many drives will not send data if it does not detect the disk is rotating.

is that the sensor that looks for the index hole?

[+OLD CS1]

6 minutes ago, arcadeshopper said:

is that the sensor that looks for the index hole?

It is.  3.5" drives got smart and put a hall effect sensor next to the spindle motor, which is actuated by a small magnet attached to the motor.

[Stuart]

3 hours ago, justacruzr2 said:

Motor and rails OK.  Moves freely.  Didn't get a reading on the sensor though.  Spun up the drive and put test leads on the contacts of the sensor but no reading.  Thought I would get something as the hole and sensors line-up but I suppose it could happen so fast that the meter doesn't register.

As you get the same problem with three floppy drives, it sounds more like a controller card problem than a floppy problem.

 

Connect the meter to pin 26 of the floppy connector. This should be logic high, but go low when the head is at track 0. You can check it by moving the head towards the hub, then checking the voltage as the controller seeks back to track 0. Also check write protect on pin 28 - you should see high with a disk that is not write protected, and low with a disk that is write protected (will probably only show the correct logic level as the controller tries to access the disk). The four inputs from the floppy to the controller - track 0, write protect, index, and read data - are pulled high by a resistor pack on the card and fed to the WD1773 chip. The index signal is possibly too quick to see on a multimeter - would need a scope or logic tester. If the signals look good, I'd be inclined to replace the WD1773 floppy controller as a next step.

[justacruzr2]

On 4/11/2023 at 5:28 PM, Stuart said:

As you get the same problem with three floppy drives, it sounds more like a controller card problem than a floppy problem.

 

Connect the meter to pin 26 of the floppy connector. This should be logic high, but go low when the head is at track 0. You can check it by moving the head towards the hub, then checking the voltage as the controller seeks back to track 0. Also check write protect on pin 28 - you should see high with a disk that is not write protected, and low with a disk that is write protected (will probably only show the correct logic level as the controller tries to access the disk). The four inputs from the floppy to the controller - track 0, write protect, index, and read data - are pulled high by a resistor pack on the card and fed to the WD1773 chip. The index signal is possibly too quick to see on a multimeter - would need a scope or logic tester. If the signals look good, I'd be inclined to replace the WD1773 floppy controller as a next step.

 

While not completely discounting the controller card,  I did rebuild it by replacing everything on it with new components including the IC's.  2 of those 3 drives were connected to the controller card when the static discharge went thru the controller card, so I'm leaning a bit towards the drives right now.  On the one drive, I have replaced many of the components already but not all.  I'm actually using the 1st release controller card.  I think the pins to check on that one are probably different than the REV A card.  I did find something that previously never came up in a Google search...the Fujitsu factory documentation for their floppy drives which includes mine.  Probably decided to release that info now that it's been 33 years ago.  It's dated 1990.  I want to look thru this first to see if there's anything useful for this repair.  And thanks for your input.  I'll keep it for when I'm checking the REV A card.  The link if anyone's interested is:

http://www.bitsavers.org/pdf/fujitsu/Fujitsu_America_Computer_Products_Reference_Guide_1990.pdf

[Fritz442]

2 hours ago, justacruzr2 said:

 

While not completely discounting the controller card,  I did rebuild it by replacing everything on it with new components including the IC's.  2 of those 3 drives were connected to the controller card when the static discharge went thru the controller card, so I'm leaning a bit towards the drives right now.  On the one drive, I have replaced many of the components already but not all.  I'm actually using the 1st release controller card.  I think the pins to check on that one are probably different than the REV A card.  I did find something that previously never came up in a Google search...the Fujitsu factory documentation for their floppy drives which includes mine.  Probably decided to release that info now that it's been 33 years ago.  It's dated 1990.  I want to look thru this first to see if there's anything useful for this repair.  And thanks for your input.  I'll keep it for when I'm checking the REV A card.  The link if anyone's interested is:

http://www.bitsavers.org/pdf/fujitsu/Fujitsu_America_Computer_Products_Reference_Guide_1990.pdf

Personally, I would connect a 3-1/2 floppy drive with a straight cable (this will be DSK2) to your controller card, cover the 720k hole on the 3-1/2 floppy disk

and then try formatting it to test the controller card.

Edited April 13, 2023 by Fritz442

[justacruzr2]

21 hours ago, Fritz442 said:

Personally, I would connect a 3-1/2 floppy drive with a straight cable (this will be DSK2) to your controller card, cover the 720k hole on the 3-1/2 floppy disk

and then try formatting it to test the controller card.

That's a great idea.  Several years ago I actually attached 1 of the the 5.25" drives to the connector in my older IBM clone to see if it worked.  That comuters BIOS supports 5.25 360K floppies along with all the more modern formats (eg. 3.5 720K 1.2K 1.44K etc).  It's one of the reasons I keep that computer.  It has great backward compatibility and it does support 2 floppy drives.  It did turn on but, of course, couldn't read the floppy.  That, however, was before I rebuilt the controller cards.  Thanks.

[justacruzr2]

Here's a question I'm hoping someone can answer.  I am going to be testing those Fujitsu M2251A floppy drives this weekend on my PC.  The connector I need just arrived today that will convert the PC clone twisted floppy cable to the TI standard flat ribbon cable.  Should they fail, I might be able to get 2 TEAC FD55FV drives.  These are 720K drives with 96TPI.  If I understand floppy drives correctly, the capacity and TPI are governed by the controller card.  So if the CC9900 controller card can only do DSDD 360K then the TEAC drive should still work and would only format them for 360K.  I just wouldn't be using it to it's full capacity.  Also the TEAC drive writes its tracks at half the width of the Fujitsu's.  So, if what I read somewhere on the web is correct, that shouldn't be a problem either.  The heads on the TEAC should still be able to read the wider tracks of the floppies that were originally created with the Fujitsu drives.  It just doesn't work in reverse.  The Fujitsu would not be able to read the smaller width tracks.  Is this correct?  I just don't want to buy 2 drives that aren't going to work with the CC9900 Controller card.

Edited April 27, 2023 by justacruzr2
more info

[+Ksarul]

27 minutes ago, justacruzr2 said:

Here's a question I'm hoping someone can answer.  I am going to be testing those Fujitsu M2251A floppy drives this weekend on my PC.  The connector I need just arrived today that will convert the PC clone twisted floppy cable to the TI standard flat ribbon cable.  Should they fail, I might be able to get 2 TEAC FD55FV drives.  These are 720K drives with 96TPI.  If I understand floppy drives correctly, the capacity and TPI are governed by the controller card.  So if the CC9900 controller card can only do DSDD 360K then the TEAC drive should still work and would only format them for 360K.  I just wouldn't be using it to it's full capacity.  Also the TEAC drive writes its tracks at half the width of the Fujitsu's.  So, if what I read somewhere on the web is correct, that shouldn't be a problem either.  The heads on the TEAC should still be able to read the wider tracks of the floppies that were originally created with the Fujitsu drives.  It just doesn't work in reverse.  The Fujitsu would not be able to read the smaller width tracks.  Is this correct?  I just don't want to buy 2 drives that aren't going to work with the CC9900 Controller card.

Will the FD55F drives work? Yes, with a really big caveat: the drive controller does not know to double-step the heads, so it only sees the first 40 tracks on each side of the disk. Why is this datum important? the disk will work fine in any 80-track drive with your CorComp, but it will not even be readable in a 40-track drive, as that drive will only see 20 formatted tracks per side. It "may" be possible to set the drive to automatically double-step, but you would have to read the technical manual for the FD55F drive to see if that is a possibility. On a side note, when used in a Geneve9640, your CorComp controller will actually be able to format and use 80-track drives, so you could get the full 720K formatted capacity the drives are capable of.

 

It would also have issues reading the normal 40-track disks, for the same stepping issue identified above. The controller does not know it needs to double-step, as the firmware in the CorComp expects a 40-track drive.