My System 4

My System 4 Photo

Top from left to right:

6HP Panel  
Vero Bivolt PK60 PSU module (8HP) providing 5V@6A and +12V@2A
LCD Monitor Module my design
Dual 5.25" Floppy Disk Module (Horizontal) (42HP) my design fitted with a 5.25" TEAC FD-55BR (40T DS) drive and a GOTEK in a 3.5" bay adapter

Bottom from left to right:

14HP Panel  
6502 CPU Board trev_ham replica
Keyboard, Display & Cassette Interface Board trev_ham replica
40x25 VDU (Teletext) Interface Board my replica
Versatile Interface Board my replica
8K RAM + 8K ROM Board my replica
Floppy Disk Controller Board my replica
32K Dynamic RAM Board original Acorn board
Econet Node Board my replica
PROM Programmer Board my replica
4 spare slots  

 

The CPU Board is fitted with DOS in a 2532 EPROM, the memory board is fitted with BASIC and FP Extension in 2532 EPROMs.

Rather than use a pair of 3U Card Frames attached one above the other, as I think the original Acorn System 4 was built, I have built a 6U high Card Frame.  This is fitted with an original Acorn 14-slot Backplane, this has had the Side-B connections made as well using a a length of Veroboard.

My System 4 Rack Photo

  Acorn must have had a bespoke PSU module that plugged into the 32-way sockets on the left of the backplane.  I have used a Vero Bivolt PSU which plugs into an H15 type socket, this is attached directly to the card frame and the power supply wired to the backplane.  The 14HP panel conceals the two 32-way sockets and provides a mounting for a reset switch, the mains on/off switch is attached to the upper 6HP panel.

My System 4 Photo Rear

Card Frame Details

The Card Frame is 6U high, 84HP wide and 240mm deep (1U = 1¾" or 44.45mm, 1HP = 5.08mm).

Part

Dimensions

Quantity Required

Original Vero KM6 Part No.

VeroTec KM6-II Equivalent  Part No.

End Plate

6U x 240mm

2

173-12535J

950-202788E 

End Plate Front Angle

6U

2

173-12540J

 950-202784B

Upper Front Tie Bar

84HP

1

173-12552K

 950-202644G

Lower Front Tie Bar

84HP

1

173-12551B

 950-202643J

Upper Rear Connector Mounting Rail

84HP

1

173-13018E

 950-229781E

Lower Rear Connector Mounting Rail

84HP

1

173-12701A

  950-229781E

Front Location Moulding

 

2

173-12557F

not required

Rear Location Moulding

 

2

173-12558C

 not required

Tapped Strip

84HP

 4

173-12704C

950-202001E

Card Guide

160mm 

44

173-12553G 

 950-232662J

Module Guide

160mm

4

173-12554D

 950-232664E

Front Panel

3U x 5HP 

as req'd

174-12903K 

 957-235349H

Front Panel

3U x 6HP

1

174-12904G

957-235351K

Front Panel

3U x 14HP

1

174-12910D

957-235357J

Module

3U x 42HP x 160mm

1

174-12929F

957-235950K

Screws

M4 x 12mm

10

173-12529A

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