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Corcomp 9900 disk controller problems

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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.

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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.

image.thumb.png.86f3d0eb5857a248cd68b027799597df.png

 

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.

 

 

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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.

 

image.thumb.png.fc84cceb2f94af40b87fb3097e41390b.png

 

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

 

 

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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.  

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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.

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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 by Fritz442
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