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3.5 inch floppy drive controller


Keith
 

Hi All,
I recently bought a Mk4 compact 5 cnc lathe which is fitted with a 3.5 inch floppy drive instead of the usual tape drive.
Unfortunately the floppy does not work.
All the manuals that came with the machine only have instruction for the tape unit.

Does anyone have a schematic or any details of the floppy drive interface or how it is controlled.

Keith


Dieter
 

Hi Keith,

I noticed only a few months ago on a french site that a floppy drive existed for the C5.

Have you tried with different floppy types ( 720 kB and 1.44 MB or commodore compatible)?
Perhaps they need to be formatted/erased with the ERASE procedure described in the tape instructions.

I haven't found any information about floppy drives on C5.
I'm really interested about the floppy controller, so could you show some pictures about the circuits and
look for the brand, type and serial number on the floppy drive, perhaps we can find the floppy type to be used.

Dieter


Keith
 

Hi Dieter,
My machine was built in 1987 and is mainly grey in colour.
If you look on YouTube you can find one very similar to mine with a FDD instead of a Tape.
The FDD drive interface is connected to the main CPU board in the same way as the tape drive is except that the 5 volt line is not used.
I understand that the 5 volts are provided by the interface from the 16 volt rail.
The FDD is the type you find in older PC's and is made by TEAC (FD-235HF) Part No 19307344-29.
The interface board is marked 2665 WA85094.
Ther is an Emco EPROM on the interface which is marked P2831155 2.32
The interface board has two connections to the FDD one is a short standard FDD cable and the other is the 5 Volt supply.
Following advice found on various forums I have tried both 720 and 1.44 floppy disks.
I did find some information on one site that said that the disks are only readable by the lathe and cannot be read by another FDD in a PC.
I have tried all the Instructions for the tape and I only get alarms. A10, A5 and A9.
A10 is the common one (write protect) It comes up if you have the disk write protected or not.
My current thinking is that the interface board is faulty.
There is no 5 Volt supply at any of the chips or the FDD.
I have tried everywhere I can think of to find a schematic but no luck up to now.
The rest of the lathe is working OK now so I will keep trying to find further information.

Keith


Dave Leer
 

Keith, here is another thought about the 3 1/2 floppy. In the early years of the PC, HP computers used a 710 floppy. I don't remember
the details, (late 80s, early 90s) but if you get that figured out, it can be read on a pc

On 7/28/2020 11:48 AM, Keith via groups.io wrote:
Hi Dieter,
My machine was built in 1987 and is mainly grey in colour.
If you look on YouTube you can find one very similar to mine with a FDD instead of a Tape.
The FDD drive interface is connected to the main CPU board in the same way as the tape drive is except that the 5 volt line is not used.
I understand that the 5 volts are provided by the interface from the 16 volt rail.
The FDD is the type you find in older PC's and is made by TEAC (FD-235HF) Part No 19307344-29.
The interface board is marked 2665 WA85094.
Ther is an Emco EPROM on the interface which is marked P2831155 2.32
The interface board has two connections to the FDD one is a short standard FDD cable and the other is the 5 Volt supply.
Following advice found on various forums I have tried both 720 and 1.44 floppy disks.
I did find some information on one site that said that the disks are only readable by the lathe and cannot be read by another FDD in a PC.
I have tried all the Instructions for the tape and I only get alarms. A10, A5 and A9.
A10 is the common one (write protect) It comes up if you have the disk write protected or not.
My current thinking is that the interface board is faulty.
There is no 5 Volt supply at any of the chips or the FDD.
I have tried everywhere I can think of to find a schematic but no luck up to now.
The rest of the lathe is working OK now so I will keep trying to find further information.

Keith


Keith
 

Hi Dave,
Thanks for your suggestion.
I suspect the floppy is used in a standard way driven by the interface attached to it.
As I have never seen it running I cannot record anything on the discs.
Alarm 10 comes up most of the time "Disk Write Protected".
There is no 5 volt supply to the FDD or to any of the chips on the interface so I suspect that this is the reason it does not work.
I have been trying to find a schematic so that I can investigate properly but no luck up to now.
It could well be that the CPU board sends signals to turn the 5V rail on.
When I can have another go at it I will get my oscilloscope on various pins to see what happens.
I have tried once but it didn't tell me a lot.
Next time I will use a dual trace scope and see if that helps.

Keith


Dieter
 

Hello Keith,

If I have correctly understood your C5 has the same commands as for a tape drive, so the floppy controller emulates the old tape drive.
This controller looks more complex than the CPU.

Is your floppy controller wired to the X43 connector on the CPU?

Look at the X43 connector on the CPU, in the maintenance manual page 5.18 it says: wired from and to interface for cassette recorder, 5 V supply and signalling.

Unfortunately there is no description for the CPU connectors, one has to find out by measuring and back tracing with the opposite connectors which are described
in the manual only for the power supply points.

Here is the datasheet for the floppy drive:

https://www.pro.logitec.co.jp/products/others/FDD/FD-235HF-C891.pdf

It seems to be used in Amiga's and then the density is either 1 or 2 MB.

Repairing a drive:

https://www.nightfallcrew.com/31/08/2017/teac-fd-235f-recap-amiga-floppy-drive/

Good luck
Dieter


Keith
 

Hi Dieter,
Thanks for your reply.
The interface board is both complex and has mainly Surface Mounted Devices (SMD) so they are small.
The floppy seems to be OK when connected to a normal PC.
There is no 5V supply on the interface but neither is there a connection to the 5v rail as there is in the drawings for the tape.
All the other wires are exactly the same as the tape drive.
Pins 9 and 12 are not connected to anything on the interface board.
I have not worked out how the 5V supply is derived but it must be on the interface from the 16 volt rail.
Later today I will have another look and see if I can do some measurements.

Keith


Keith
 

Hi All,
I remove the CPU PCB this morning to check the wiring from plug X43.
The plug is connected to the same Peripheral Interface Adaptor chip (PIA) that feeds the stepper motors.
I could not see any broken or burnt tracks.
I re assembled everything and checked all the leads with an oscilloscope and there is no activity on any of them.
At the moment I am wondering if a section of the PIA maybe failed.
They are not expensive but it would be a bit of a toil to change as they are 40 pin chips directly soldered into the PCB.
Before I do that I think I will wait and see if anyone has a later manual with the floppy drive instructions.
MFI works well with my C5 so I can up/download to my PC OK.
I found the service and manual for the floppy drive but unfortunately nothing for the interface PCB.
I'm sure there must be many C5 MK4 with floppy drives out there along with the manuals so I hope someone has one, fingers crossed.

Keith


Dieter
 

Hi Keith,

Really funny not to use the 5 V directly from the X43 or from wiring to the power supply.

Does your serial interface work? I don't use the tape anymore and replaced the drive by an self made extended keyboard
to emulate the G66, INP-FWD and INP-REV by a single key stroke.

By pushing the serial link to 9600 Bd instead of 300 Bd transferring programs is a bit faster now.
Has your C5 still the unreasonable 110/300 Baud rate?
By changing one EPROM you can go without problems to 1200 Bd, above (up to 9600) it is a bit more tricky, one must insert 10 ms line delay
by using a terminal program and the real transfer rate PC to C5 is then about 5000-6000 Bd, from C5 to PC there is no restriction.

Dieter


Keith
 

Hi Dieter,
Thanks for your message.
Yes it is strange that the 5 volts is not taken from the PSU.
I am not too bothered about the disc for the moment as my PC interface works very well even at 300 Baud using MFI.
I don't find the slow speed much of a problem.
My other CNC Lathe (Conect Cadet Plus) is 9600 Baud but it is software driven (DOS) running in DosBox on windows10.
I will keep looking for information about the FDD it will eventually turn up somewhere.
I have only had the C5 for a month and nothing worked properly when I got it.
Now everything except the FDD works so I am happy with that.

Keith


Keith
 

Hi All,
Today I plugged in a monitor to the C5 to see what happened when I loaded a programme from MFI.
I also tried to save the programme to Floppy Disc.

The commands used for the FDD are the same as those used fir Tape.
 
The Monitor has the information Save to Disk, Erase and load from Disk.

The word Disk must programmed into the video EPROM so I now know that the instructions are the same.

However the Disk (disc) drive does nothing and alarms appear both on the machine and repeated on the monitor.

I am beginning to wonder if someone has in the past changed something on the interface to FDD board.

As I have mentioned before there is no 5 Volt supply to the FDD or any of the chips on the interface card.

There is a power transistor on the interface board but I would have expected to see a fixed 5 volt regulator.

One mystery solved but another one to solve.

Keith


johnb
 

Hi Keith,

I have been following your progress with interest on the various forums.

I have a working c5 except the cassette, I first thought I cannot be bothered moving

the lathe to sort out after I tried previously alternative interface board and cassette unit.

Then I was making a batch of 50 identical parts cycle time 8.1/2 minutes involving a few stops for coffee food etc. making these I though it actually would be nice to save the running program instead of bringing the computer out to the workshop each time.

So being as I only wanted to save the running program I looked round for a storage

unit to save it as serial data from the rs232 port via g66.

I came up with a universal serial buffer W&T 88642 4mb storage off ebay (quite expensive new) this works ok to upload and download from the c5 or MFI

Im sure other units may be similar, although it can only save 1 program this is ok as it can be left next to the lathe during stops.

John


Keith
 

Hi John,
Thanks for your message.
I have a permanent PC in my workshop so its easy to use mfi.
My problem is the fact I don't like things that don't work.
As everything else now works I can now try the lathe.
I have been giving some thought to using an arduino or a raspberry pi to store to a usb stick but it's only a thought.
If I sort it I will write up what I find.

Keith


Dieter
 

Hi Keith,

-The word "Disk" must programmed into the video EPROM so I now know that the instructions are the same.

Just for info: All text on the screen is stored on the CPU EPROM's in a data field, the video EPROM stores the character set.
I made some extensions for my C5 with the EPROM file from Kapsi Ketturi, I can now display lowercase letters and a lot of special characters
because I can load a comment which is displayed on the MAN screen. (workpiece name, tools etc, this nearly empty screen must be used :-) )
and it is better readable with mixed characters; all this just for fun, I like experimenting. (the special characters from EMCO are untouched of course)

https://ketturi.kapsi.fi/2017/10/reverse-engineering-emco-cnc-video-controller/

So EMCO made however some modifications to the source code. Do you have the possibility to readout the CPU EPROM's,
I am curious about the differences between tape equipped and disk C5.

By the way you would have a backup of the EPROMS in case they fail.

Dieter


Keith
 

Hi JG,
Thanks for your message.
I suspect that the fault lies with the FDD/Interface because of the lack of the 5 Volt rail.
As everything else on the CPU board seems to work well it is as you say unlikely to be on that board.
I did a basic machine code / robotics course in the early eighties but I have forgotten most of the useful stuff.
As my old boss used to say "there are no problems only solutions".
Another check of the interface board for failed components.

Keith


Keith
 

Hi All,
The 5 Volt rail would appear to be the problem.
There is a link on the PCB to all the components that run on 5V.
I decided to open the link and provide a 5 volt supply from a separate PSU.
The drive then senses a disc and opens the cover on the floppy.
I no longer get the error codes but the drive does not load or save programmes or erase discs.
Trying to draw out part of the circuit but its very tiny and difficult to see.
I currently suspect that the 5 volt rail should only be turned on when some action is required.
Further investigations later today.
There is a strip of links on the PCB but nothing is linked, this may be correct or links could be missing.
A schematic must be out there somewhere.


Keith


Dieter
 

Hi Keith,

-There is a strip of links on the PCB but nothing is linked, this may be correct or links could be missing.

If there were links missing one must see burned or scratch traces.

Ask for pictures from the board to compare with your board from an owner of a disk equipped C5.

Dieter


Keith
 

Hi Dieter,
Thanks for your message.
Unfortunately I have not had any replies from anyone with a C5 with floppy drive.
There are three DIP header links on the board.(green)
2 have no links connected the third has a link, at the side of the large blue capacitor.
There is a strip of links (coloured green in the photo I posted above.
No links are fitted in this block.
It may all be correct but as the back was off the lathe when I bought it I don't know its history.
If anyone does have a C5 with a floppy I would be grateful if they could see how it is connected.

Keith


Dieter
 

Hi Keith,

Very difficult to see details on the picture, the resolution is to bad.
You can send me a better and brighter picture with the highest resolution, look in the address book.

Look also at the cap's like "J G" did or replace them immediately, perhaps one fails,
of course if you have a good "desolder iron".

Dieter


Keith
 

Hi Dieter,
The electrolytic capacitors have been checked with several instruments and both are OK and hold a charge.
The blue one can be taken out of circuit with the link next to it.
I do have a desoldering iron but decided not to remove the caps as they test OK.
I don't have another photo at the moment but here is a brighter version of the original.
I am still convinced that someone has been playing about with this interface before I bought the lathe.
The row of links can be seen at the top left of the picture there is a brass link fitted but it is turned round so it does not currently do anything.

Keith