Re: Floppy drive on K2500R mounting problems

Hello Roger,

I did some more digging and I sent a couple of pictures for you to see. The good FDD drive that works in my other K2500R. If you look it clearly is jumpered to DSO or A . If you look at the blown drive it is jumpered to SO or A also and it used to work before the 12v accident. Both units have HDs also. Is there any communication between SCSI and floppy bus?

I’m not opposed to putting a dab of solder on S1 and cutting the connection at SO and giving it a go. It just seems weird that it would read that drive if it was jumpered incorrectly. What do you think?

Richard

From: <[email protected]> on behalf of "Roger J [email protected] [KurzList]" <[email protected]>
Reply-To: "[email protected]" <[email protected]>
Date: Saturday, May 4, 2019 at 4:46 PM
To: "[email protected]" <[email protected]>
Subject: Re: [KL] Floppy drive on K2500R mounting problems



First, L2 is removed keyboards, as this is the clock for the Digi effect chip and the keyboard model had a separate clock source closer to reduce RFI.  You will have to add a jumper or another inductor, probably using a jumper will be fine.

Early floppy drive needed 12v and 5 volts.  Different vendors used different connectors.  Some connector could go on backwards, reversing the 12 and 5 volts.  I always looked at the floppy drive circuit board for silkscreening of 5vdc to confirm.

FDD have two channel, the A or 0 and the B or 1.   Later FDD in the 90s came jumpers for A only, as then plug n play configured.  The drive must be set for B or 1, as the FDD control want to see B channel.
This is a DOS era drive.

Yes, could be the controller chip, it is not fun to replace, as it is a PLCC style chip, typically placed in a PLCC socket.  As I recall, you may have to remove components to solder back in.  I would remove with a small heatgun, beating the center of the chip until all 44 pins get hot and it slides off with gentle pleasure.  Place a strip of metal as a heat shield to prevent other components from also being heat too much.

I have once or twice replaced the FDD controller chip, no joy, only to find other failures to be the cause of no mount.

Do you actually need a floppy?   You can install setups from a hard drive.  The hard drive is DOS 512.  The installer asks for source, FDD or one of 8 scsi channels.

You could also place your CPU Daughter board in a good unit and update the setup or o/s.  Make sure it is seated properly, as it is easy to do wrong!

Not sure I cover all your questions, reply if not so.

Best,
Roger

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On Fri, May 3, 2019 at 3:29 PM, Richard Ufheil [email protected] [KurzList]
<[email protected]> wrote:


Hello Roger,



I’m sorry to bother you but I’m turning to you for your advice. I will try to make this as succinct as possible. I have a second K2500R with a floppy drive that will not mount. Here are the facts.



  1.  The drives power supply was connected to the HDD power connection thus it was getting 12v DC instead of 5v DC.
  2.  I reconnected the power supply to the FDD connector. On power up an IC on the floppy drives integrated PCB blew.
  3.  I replaced the drive with a new floppy which I confirmed was good by mounting in my main K2500R.
  4.  The drive will not mount and fails both drive tests in diagnostics.
  5.  I swapped all cabling from my other unit and still it would not mount..
  6.  This leaves me to believe the FDD controller chip is toast.

My question is have you ever encountered this before? If I replace the FDD controller chip should that cure the problem?  Are there any other components that might need to be replaced in order to get this floppy to mount?



I have done hard resets and I even reinstalled the operating system. There are no jumpers on the floppy drive so I guess the drive allocation is predetermined in the OS.



One more question for the expert. Can I use an engine board from a keyboard unit in a rack unit. It appears that the engine and daughter board are the same as those used in the keyboard vs the rack. I see that the rack unit has a location of L2 which is not used on the keyboard unit.

Thanks,



Richard



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Posted by: Richard Ufheil <[email protected]>
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