Sam Drive

Built-in


MGT


1990

The Coupé could support two 3.5” Ultraslim Citizen Double Density drives each with their own WD-1772-02 disc controller allowing both drives to operate independantly.

Unformatted capacity 1Mb, formatted as double sided, 80 track per side, 10 sectors per track, to the IBM 3740 standard gives 800kB with 780kB usable after directory space subtracted.

Having the drive controller within the drive housing meant that the floppy drive connectors could be used for other devices, most notablty the ATOM IDE interface.

Drive Connectors:

Connections to the two drives are made via two 32-pin Euroconnectors, with rows A and B connected. Drive 1 is on the left of the machine and drive 2 on the right. A list of signals available at these sockets are shown below.

PINSIGNALPINSIGNAL
1A0 VOLTS1BWR
2A0 VOLTS2BAO
3A0 VOLTS3BAI
4A0 VOLTS4BDO
5A0 VOLTS5BD1
6A0 VOLTS6BD2
7A0 VOLTS7BD3
8A0 VOLTS8BD4
9A0 VOLTS9BD5
10A0 VOLTS10BD6
11A5 VOLTS11BD7
12A5 VOLTS12B8 MHz
13A5 VOLTS13BRST
14A5 VOLTS14BNo connection
15A5 VOLTS15BA2
16A5 VOLTS16BDISK 1 OR DISK 2

Drive Maintenance:

With age the drive belt can stretch, break or even turn into a gelatinous mess depending on it’s composition.

A suitable replacement belt is a 71mm diameter flat belt 2.8mm high and 0.6mm thick although there have been reports of mixed reliability.

To replace the belt you must remove the drive from its plastic shell, unscrew the metal shield and the motor to get access to the drive flywheel.

Clean the drive thoroughly to remove dust and fluff from the unit, clean the edges of the flywheel, jockey wheel and the motor spindle with a suitable cleaner on a cotton bud - also check the drive head worm gear for fluff build up abd re-grease if required.

Take the opportunity to clean the drive heads using isopropyl alcohol and a foam/chamois bud (not cotton), and clean the skid plate under the head assembly.

Fitting the belt can be done without having to remove the drive cage if you have two pairs of tweezers to hold the belt:

With the drive slot facing you:

  1. Place the belt around the flywheel.
  2. Using one pair of tweezers grip the belt about 10mm from the loose end so that it forms a small loop and bring the left side of the belt around the outside and under the silver jockey wheel and the right hand side to the right of the post so that they come almost together.
  3. Bring the loop to the hole below where the drive spindle sits.
  4. Bring the other pair of tweezers up the hole and grip the belt loop.
  5. Whilst holding the loop, drop the motor back into position through the loop you are holding, push the loop up as you bring the motor down and it should hook on.
  6. screw the motor back down.


Presumably, three editions of the user’s guide were published. The 3rd edition can be found as a PDF Manual Scan at www.samcoupe-pro-dos.co.uk


There is a bug that can cause disc corruption if a disc is left in the drive and the reset button pressed.

vl1772

no chance of reading hi density or extended density drives?
would the disc controller chip need a dma to be capable of doing this like the spectrum mb-02+ disc interface - now down to £150.00 from €cu 499.00

re: vl1772

No, you’d need entirely different circuitry to read HD floppy disks.



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