The Atari ST - Operation, Connectivity and Restoration keyboard

All computers of the ST range (except the Mega ST series) use a keyboard with conductor domes. This type of design is based on three main elements:

• Key removable plastic
• Hardened PVC diver
• Rubber Dome driver – rubber pad ensuring electrical contact

Mechanical Overview

[TOUCHE PLASTIQUE] ← removable individually
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[PLONGEUR PVC DURCI] ← vertical support guide
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[RUBBER DOME CONDUCTEUR] ← closes the electrical circuit
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[PCB RIGIDE AVEC PISTES MATRICIÈRES] ← detects support
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[PUCE DE CONTRÔLE HO6301V1P ou variante] ← encodes supports before transmission
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[NAPPE VERS LA CARTE MÈRE] ← connects to the rest of the system

Operation

When you press a key :

1. The key down with his diver
2. Diver compresses the rubber dome against two PCB tracks
3. This closes an electrical circuit between two lines of the matrix keyboard
4. The chip HO6301V1P (or variant) encodes support
5. The signal is sent to the motherboard via the flexible tablecloth
6. The tactile return is made thanks to the elasticity of the rubber dome

Connectivity and handler ports

The keyboard map has several elements:

• Tablet towards the motherboard – flat cable connecting to the main processor
• Two DIN 9 pin ports – for mouse and analog controller (DB9 ports)
• Hole HO6301V1P – keyboard controller based on Motorola 6805

Although the controller/mouse ports are mounted on the keyboard card, their electronic management is done via the MFP controller on the keyboard motherboard. Common problems often arise from welds cracked around connectors.

Restore Keyboard – Practical Guide

Over time, the keyboards of theAtari ST may have several defects:

• Oxidation of contact on rubber domes
• Deterioration of PVC divers
• Welds cracked on DIN 9 pin ports
• Damage to the flexible tablecloth
• Corrosion or general wear of printed circuits

Here are the recommended steps to restore this type of keyboard:

1. Remove keys – they come out one by one
2. Demonstrate keyboard enclosure – necessary to access internal elements
3. Check the rubber domes – replace those who are fluctuating or not
4. Clean the PCB carefully
5. Welding of DB9 ports
6. Replace tablecloth if necessary
7. Check the HO6301V1P chip – make sure it is well welded

FAQ – Frequently Asked Questions on the ST Keyboard

Can I remove the keys without dismantling everything ?
Yes, each key can be extracted individually without opening the entire keyboard. For deep cleaning or serious repair, however, it is necessary to open the whole.

Is there a chip on the keyboard card ?
Yes, the HO6301V1P chip (or variant of the MC68HC05C9) is present on the keyboard map. It manages matrix scanning and encoding of supports before transmission to the rest of the system.

Are the controller ports on the keyboard card ?
Yes, both handle/mouse ports are located on the keyboard map. They use the DB9 connector ( DIN 9 pin port). Their management is done via the MFP controller on the motherboard.