34-pin to 50-pin Converter Card

[david]

Colleagues,

I am moving this from the H-47 8" drive thread to its own thread so as not to clutter-up the other conversation.

I got a quote for Mark Blair's 34-pin to 50-pin converter board, and they are quite inexpensive -- $0.39 each before tooling and shipping.  Most of the cost was in tooling and shipping.  To spread out the overhead, I ordered 50 and will keep them in inventory.  I expect the final price will be less than $2.00 + postage.  The quote for 10 boards is attached so you can see details.  I am awaiting a new quote for 50 boards.

FYI, I used OurPCB.  They do good work and can usually get me the boards in about 10 days.

If you want one just send me a private message and we can work out the details once I they arrive.

David

[Lee Hart]

david wrote:
> I got a quote for Mark Blair's 34-pin to 50-pin converter board, and
> they are quite inexpensive -- $0.39 each before tooling and shipping.
> Most of the cost was in tooling and shipping. To spread out the
> overhead, I ordered 50 and will keep them in inventory. I expect the
> final price will be less than $2.00 + postage. The quote for 10 boards
> is attached so you can see details. I am awaiting a new quote for 50
> boards.

I'm confused. I thought that this board connected a 50-pin disk
controller (i.e. an 8" drive controller) to a 34-pin cable (so you could
connect it to a 5.25" floppy drive that supports the 1.2meg format, or a
3.5" floppy drive that supports the 1.44meg format (i.e. one that
behaves electrically like an 8" drive). Is that correct?

Or, does it go the other way around: Does it connect a 34-pin controller
(i.e. one that only supports 5.25" and maybe 3.5" drives) to an old 8"
drive (with the 50-pin connector)?

--
You never change things by fighting the existing reality. To change
something, build a new model that makes the existing model obsolete.
-- R. Buckminster Fuller
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com

[david]

I think it is an inline cable-to-cable converter.  Some 3-D renderings from KiCad are given at the end.

It looks to me like both board connectors are male and would mate with a cable.

[Kenneth L. Owen]

Hi David,

 

I believe Lee makes a good point.  The board is labeled for the 50 pin connector to go to the controller and the 34 pin connector to go to 3.5” or 5.25” drives.

 

-- ken

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[dwight]

The board is a passive device. Other than the high track signal, it should work either way.

Dwight

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[david]

Yes, you are correct.  Sorry about that Lee.  I will cancel the order because the board is not what we want.

In early April I will do a converter board based on Norby's H89-Z37 controller.  That should work with properly configured H8-Z37 cards and regular soft sectored controller modified to support 8" drivers.  I'll post again when it is done.

[david]

I did a quick compare of the schematics, and you are right.  It is essentially the board I would have made.

I think it is a passive inline cable converter, which is part of what is needed for 8" support.  The H8-Z37 needs to be jumpered properly.  For the standard soft-sector controller you need to follow the instructions in REMark Issue 40 1983, which Ken posted earlier and I repost.  BTW, the cable adapter pinout is given on the second page of the article.  Posts in the related thread indicate a driver is also needed to access all the tracks.

Are there any remaining concerns?  I think this board is a part of the solution for using 8" drives on a 5.25" controller.

Thanks for the comments.  They help bring understanding and reduce mistakes.

Here is the converter board schematic:

And here is a extract of the relevant part of the H89-Z37 card:

[david]

I did a quick compare of the schematics, and you are right.  It is essentially the board I would have made.

I think it is a passive inline cable converter, which is part of what is needed for 8" support.  The H8-Z37 needs to be jumpered properly.  For the standard soft-sector controller you need to follow the instructions in REMark Issue 40 1983, which Ken posted earlier and I repost.  BTW, the cable adapter pinout is given on the second page of the article.  Posts in the related thread indicate a driver is also needed to access all the tracks.

Are there any remaining concerns?  I think this board is a part of the solution for using 8" drives on a 5.25" controller.

Thanks for the comments.  They help bring understanding and reduce mistakes.

Here is the converter board schematic:

And here is a extract of the relevant part of the H89-Z37 card:

On Friday, March 9, 2018 at 8:30:57 PM UTC-6, dke...@hotmail.com wrote:

[G. Beat]

Lee -

You are correct. Mark’s board design was based on Frank Durda’s earlier notes.

The original design by Frank Durda IV was for the Radio Shack/Tandy model II, 12, 16 and 6000 computers.
He desired to connect 5.25" floppy disk drives to that system (which had 8” disk drive in desktop case)

Here is Frank’s URL describing his original need and process.
http://nemesis.lonestar.org/computers/tandy/hardware/model16_6000/floppyfix.html

The board is a cable adapter to allow 3.5" or 5.25" floppy disk drives to be connected to legacy computer systems
with floppy disk controllers that are designed for use with 8" floppy disk drives.

greg
chicago

[G. Beat]

Changes to this adapter board, should be for additional configuration options desired.
The classic issues with Floppy Drives interfacing with controllers are handling of:

Disk Change
Disk Density
Disk Ready
IBM specific changes with some of their drives.

greg

[G. Beat]

Mark’s README.md at GitHub
This also has list of parts.
https://github.com/NF6X/fd50to34

Features

Jumper-selectable double-sided disk support.
Jumper selection allows drive motors to be strapped on all the time, or controlled by either the head load or in-use/door-lock signal.
Bank of shorted resistor footprints allows easy drive select number remapping.
Drive signals are labeled on bottom of board for debugging purposes.
—
JP1: Double-Sided Media Detect
Install a jumper at JP1 to enable double-sided disk support. If any single-sided disks will be used, remove this jumper while accessing them, since installing this jumper makes the controller think that all drives are reporting double-sided media.

If desired, connect a remote SPST switch to this jumper, and close it to enable double-sided media.
—
JP2 and JP3: Motor Control
Frank recommends strapping the motor control line to ground to force the drive motors on, since 8" drive motor control works differently than 3.5" and 5.25" drive interfaces expect. To get this behavior, install a jumper between pins 2 and 3 of JP3 (labeled MTRON and GND on the PCB). JP2 is ignored in this configuration.

Some drives can be configured to qualify their motor controls with the drive select signals. With these drives, you may wish to experiment with different motor control schemes. To enable these schemes, first move the jumper on JP3 to pins 1 and 2. Then, install a jumper on JP2 to connect the motor control signal to either the head load signal or the door lock signal.

When connecting a Lotharek floppy drive emulator to a TRS-80 Model II/12/16/6000, the door lock signal seems to work well for drive motor control. For this configuration, install a jumper between pins 1 and 2 of JP2, and another jumper between pins 1 and 2 of JP3.
—
JP4: Density Select
Some floppy drives use J2 pin 2 to select different density modes. On compatible 3.5" drives, pulling this pin down will select a 360 RPM mode which may work well on systems expecting 8" floppy drives. To do this, install a jumper between pins 2 and 3 of JP4. Install no jumper on JP4 for default behavior.

Installing a jumper between pins 1 and 2 connects the reduced write current signal on the 8" interface to J2 pin 2, which is also used to select reduced write current on some 5.25" drives. This option is experimental.
—
R1-R4: Drive Select Remapping
If you need to remap the drive select signals, first cut the exposed traces on the top side of the board which short out resistors R1 through R4 (which are not normally installed). Then, solder wires between the pads of R1-R4 to map the drive select signals as needed.

[Norby]

What kind of breakout board do we need?

1. From H8-Z37 to 50 pin 8” floppy drive?
2. Or ?

Norby

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