MFM/RLL HDD spins and initializes but is not found by DOS

[Coder]

Hello everyone. I recently acquired a Sharp PC-7200. I knew it wouldn't boot from the hard drive before purchasing. I thought it was going to be a PLUS+ HardCard like the PC-7100 and figured it just needed the rubber bumper replaced. Unfortunately, I found the 7200 is not a hard card, but instead has a small NCL MFM controller board and a JVC 20MB 3.5" MFM hard drive. When powered on, you can hear the drive spin and it sounds like it does that quick burst of initializing the disk. But DOS 3.2 doesn't see the drive. The setup program doesn't have a hard drive setting, so I believe the values are hard-coded for this one drive type. I'm not as familiar with MFM drives. Are there any diagnostics I can do to maybe coax the drive back into the land of the living? None of my DOS 3.2 5.25 floppy disks have FDISK, so I haven't tried that yet. I may hook up my Win98 box and write a new boot disk to give it a try, but I wanted to make sure there wasn't maybe something I needed to put in Config.SYS in order to have the drive recognized.

 

[modem7]

Hello everyone. I recently acquired a Sharp PC-7200.

I see some photos at [here].

.. but instead has a small NCL MFM controller board and a JVC 20MB 3.5" MFM hard drive.

What are the model numbers of both?

When powered on, you can hear the drive spin and it sounds like it does that quick burst of initializing the disk.

That may be the result of the hard drive doing a self test when it receives power.
How to tell: Disconnect the data and control cables from the drive, then apply power, then listen out for the same sounds.

The setup program doesn't have a hard drive setting, so I believe the values are hard-coded for this one drive type.

Allowable hard drives will be under the control of the hard disk controller. Per [here], there may be jumpers or switches on the controller. The user manual for the controller should reveal a lot.

Are there any diagnostics I can do to maybe coax the drive back into the land of the living?

Are there any error messages on-screen? A lot of XT-class hard disk controllers only display an error code, '1701'.

See what the RAYXTMFM tool at [here] reports. If you use the /file option, a text file will be created that you can attach here. I am not expecting 'part 2' to identify the PC-7200's BIOS ROM.

 

[Coder]

I see some photos at [here].

I'll have to post some pictures of mine once it's put back together. Mine is the dark gray variant. They're interesting systems. They even support a single full-length 8 or 16 bit ISA option card; a detail I'm surprised isn't discussed more when talking about these.

That's a neat site. I hope they get the floppy drive working. I was lucky that mine works well. I wonder if they know you have to push the button in after inserting a disk before it will read. It's not very intuitive. You press it again to eject the disk. Something else interesting in their article is those bodge wires. My motherboard doesn't them. I wonder if it's a different revision of the board or if someone did repairs that required bypassing some damage.

What are the model numbers of both?

The controller board has "DUNTK 1693 ACZZ" at the top. There's another number on the lower left corner, but the motherboard has the same number, so I don't think it identifies the controller specifically. The main controller chip is a NCL NDC864. I only know this is the main controller IC because of the technical service manual. Unfortunately the manual doesn't go into detail about how the drive is detected or configured. At least not in any terminology that I understood.



The drive is a JVC JD-3824R0S0. I found this site and this site that have some information on the drive, including the pinout and other info. The second site mentions that the drive won't spin up without being initialized by the controller, so does that indicate that the controller is at least aware that the hard drive is there or is it blindly issuing commands?

That may be the result of the hard drive doing a self test when it receives power.
How to tell: Disconnect the data and control cables from the drive, then apply power, then listen out for the same sounds.

Unfortunately, the drive uses the same cable for power and data. I could apply 12v/5v to the correct pins using the pinout from those sites, but it sounds like the drive doesn't spin until commanded to by the controller.

Allowable hard drives will be under the control of the hard disk controller. Per [here], there may be jumpers or switches on the controller. The user manual for the controller should reveal a lot.

There is a jumper labeled "JP21". It has 3 positions that are labeled "4 5 6". The jumper is at position "6". I haven't touched this jumper. Thanks for that article. It was very informative.

Are there any error messages on-screen? A lot of XT-class hard disk controllers only display an error code, '1701'.

No errors except for an invalid configuration message. Oddly, changing the BIOS configuration doesn't seem to clear this error, even though the values save successfully. I wonder if that's related. I have a new 3.6v Ni-Mh battery on it's way. Hopefully there's not some other corruption of the BIOS information going on.

See what the RAYXTMFM tool at [here] reports. If you use the /file option, a text file will be created that you can attach here. I am not expecting 'part 2' to identify the PC-7200's BIOS ROM.

I'll do that as soon as I can and report back. Hopefully tomorrow. I've been working a lot of late nights the past couple of weeks, but, with luck, that ended tonight.

 

[modem7]

The second site mentions that the drive won't spin up without being initialized by the controller, so does that indicate that the controller is at least aware that the hard drive is there or is it blindly issuing commands?

Reading the second site, the drive only spins the spindle when the controller takes the /MOTOR ON' pin to LOW. And the drive probably needs to see '/SELECT' at LOW as well.
Presumably, once the spindle is up-to-speed, the drive will then take the 'READY' line to LOW in order to inform the controller that it is ready to accept commands.

See what the RAYXTMFM tool at [here] reports. ...

I'll do that as soon as I can and report back. Hopefully tomorrow.

Your computer is quite non-standard. Therefore, any problems reported by RAYXTMFM may be false negatives.

 

[lyonadmiral]

Is there no advanced diagnostics disc equivalent for this unit?

 

[Coder]

Reading the second site, the drive only spins the spindle when the controller takes the /MOTOR ON' pin to LOW. And the drive probably needs to see '/SELECT' at LOW as well.
Presumably, once the spindle is up-to-speed, the drive will then take the 'READY' line to LOW in order to inform the controller that it is ready to accept commands.

Looks like I may need to learn how to use that fancy oscilloscope I bought months ago. I should probably start by taking it out of the box...

Your computer is quite non-standard. Therefore, any problems reported by RAYXTMFM may be false negatives.

Yeah, these Sharps are definitely non-standard. Hopefully it's "standard enough" to glean some useful info from.

Is there no advanced diagnostics disc equivalent for this unit?

I haven't been able to locate any of the original software for it. Or a user manual, for that matter. Ironically, the only original documentation I can find is the service manual, which is helpfully detailed. But doesn't go into how to configure or use any diagnostic software. It does have a section on diagnosing the hard drive but a lot of it's waaaaaay over my head.

 

[tradde]

You ordered a fancy o-scope and when delivered you left it in the box? I couldn't wait to try mine. Yeah, you need to let it breathe fresh air and learn to use it.

 

[jafir]

Some early Toshiba laptops, like the T1600, used a JVC interface hard drive, so perhaps there will be some useful information in the service information for those products.