Re: 26 pin MFM drive

On 11/5/21 6:09 PM, Paul wrote:
> On 11/5/2021 4:08 PM, philo wrote:
>> In my box of obsolete computer parts, I found a JVC   LD3824R00-1   20 
>> Meg MFM drive. It has a 26 pin connector and no separate power pins.
>>
>>
>> No idea where it came from. Does anyone know anything about this drive?
>>
>>
>> It's the same size as a standard IDE drive.
> 
> The disk drive industry, must have been a train wreck
> at some point. There used to be a lot of disk drive companies.
> JVC was one of them (so not just a rebranding exercise).
> At first I thought, if it was made by someone else, we'd
> need to figure out who that was.
> 
> https://en.wikipedia.org/wiki/List_of_defunct_hard_disk_manufacturers
> 
> *******
> 
> Badcaps.net has a thread for this. This is the text from the PDF
> file in one of the attachments---
> 
> The JVC JD-3824R00-1 harddisk
> 
> This is the internal hard disk of a Toshiba T-3100. It uses a
> custom interface, probably similar to the ST-506 harddisk interface,
> but fewer pins. Both signals and power are combined in one 26 header.
> 
> Other machines using this type of hard disk interface:
> 
> Epson PX-16
> Epson Equity LT
> Epson Portable PC (Q150A)
> Sharp PC-7200
> Data General One Model 2T ?
> GRiDCase 3 Plus
> Toshiba T1200 ?
> Wang WLTC Laptop
> 
> 3. Parameters (2 heads, 34 sectors, 615 cylinders)
> 4. 2-7 RLL coding
> 5. Spindle Rotation: 2597 rpm
> 6. Data Transfer: 7.5M bps
> 7. Average Access: 78ms
> 8. Power Voltage: 5V and 12V
> 
> This is the controller from the Toshiba T-3100. The chip numbers are: 
> T7518 (large one), DC2090P166A
> (smaller one), TC57256AD-20 (EPROM). All are of the Toshiba brand.
> 
> Pin 1 GND (20- 2)                   Pin 2 -Read Data (20-18)
> Pin 3 GND (20- 4)                   Pin 4 -Write Data (20-14)
> Pin 5 GND (20- 6)                   Pin 6  Reserved
> Pin 7 -Drive Select/+Power Save (-) Pin 8 -Ship Ready (-)
> Pin 9 GND (20- 8)                   Pin 10 +Read/-Write control (34- 6)
> Pin 11 -Motor On (-)                Pin 12 Head Select(+Head 0/ - Head1) 
> (34-14)
> Pin 13 -Direction In (34-34)        Pin 14 -Step (32-24)
> Pin 15 -Write Fault (34-12)         Pin 16 -Seek Complete (34- 8)
> Pin 17 -Servo Gate (-)              Pin 18 -Index (34-20)
> Pin 19 -Track 000 (34-10)           Pin 20 -Drive Ready (34-22)
> Pin 21 GND (20-11)                  Pin 22 +5V (-)
> Pin 23 GND (20-12)                  Pin 24 +5V (-)
> Pin 25 GND (20-15)                  Pin 26 +12V (-)
> 
> The signals have the same name as the ST-412/ST-506 interface 
> (between'()'),
> but the read/write signal is not differential.
> 
> *******
> 
> This is the badcaps.net page where I got the PDF dump in
> the previous section.
> 
> https://badcaps.net/forum/showthread.php?t=64108
> 
> The two JPGs. Reposted via Postimage.
> Use the "Download original" to get full res (3000x1688 using bad quality 
> lens).
> 
> One is a picture of the Toshiba adapter board, which
> appears to convert from one useless standard (26 pin) to
> another useless standard (34 pin). It was popular in those
> days, to throw a thousand dollars worth of electronics
> at a simple serial stream. Mainly, because the boards
> might be available in some catalog, and you "just buy them"
> rather than wasting time on more engineering effort.
> 
>     https://i.postimg.cc/VvynLk0b/20170824-190914.jpg
> 
>     https://i.postimg.cc/VLWnm1fd/20170824-190846.jpg
> 
> One of my guys at work did that. That's why my best
> guess at the design, is it was a "catalog engineering job",
> joining one defacto standard to another.
> 
>       Paul



Thanks Paul.

I shall keep the drive in my collection of oddities but will never know 
if it's working or if there is any data on it.