I have disabled the mod to make the screen in reverse (white chars on black background), i have also made the composite mod with the right resistor value for the best quality video output.

Replacement:

12►

Simple steps to replace the keyboard Membrane of the Sinclair ZX Spectrum 128k (heatsink).

• Buy a new Sinclair Spectrum 128k Keyboard membrane.
• Unscrew the eight screws on the bottom.
• Kindly disconnect the keyboard from the connectors on the main pcb.
• Remove the back of the keyboard.
• Unscrew the block that holds the cable.
• Remove the old membrane.
• Clean the keyboard with air-spray and a soft brush.
• Install the new membrane.
• Close the back of the keyboard.
• Very kindly put the block of the flat cable and screw in.
• The keyboard is ready to be connected.
• Very kindly insert the flat cable into the connector.
• Your Sinclair ZX Spectrum 128k is like new.

source: rwapsoftware.co.uk

I thank my dear friend for the donation of the motherboards.

• Commodore Dual Drive Floppy Disk CBM 8250
• Commodore CBM 8296

A dear friend sent to me a few things to repair or test, i will see to do my best.

Things to repair/testing:

• Commodore 64/128 – 1764 Ram Expansion (dead)
• Commodore 64 Power Supply for the Commodore 1764 Ram Expansion (pcb broken)
• ZX Spectrum Plus (7805 over burned)
• Texas Instruments TI-99/A (black screen)
• Amstrad 464 + (replace case and keyboard)
• Kung-fu Master Jamma pcb Board (no audio)
• Arabian Sinclair Spectrum 2+ (dead + tape problem + keyboard problem)
• Sinclair ZX81 (video problem / testing)
• Sinclair ZX80 (video problem / testing)
• Sega SC-3000 (cpu bad socket)

Things for spare parts or to keep:

• Sinclair ZX80 Original Power Supply.
• Commodore VIC-20 Boxed cartridges.
• Sega SC-3000 Basic cartridge.
• Commodore Dual Floppy Drive 8250 motherboard (spare parts)
• Commodore CBM 8296 motherboard (spare parts)
• Sharp CE-510F Dual Floppy Drive for Sharp PC-5000 (Boxed)
• Chalkboard Powerpad + Expansions (Boxed)
• Tape Recorder for Commodore (spare parts)

Replaced a old yellowed Amiga 1200 keyboard with a new one.

I have made some works for a friend and i didn’t want money, the friend then wanted to contribute to my Electronic Lab with this Hot Air Desoldering Station. Thanks, i appreciate it.

Video demostration:

source: aoyue.com

I have repaired an Commodore VC-1541 Floppy Drive donated by Alessio. The Floppy Drive doesn’t take any commands via IEC.

The components that have been replaced are:

• 1 x 7406
• 1 x 74LS14

Material donated:

• Commodore VC-1541 (need to fix it)
• Microcomputer Data Recorder Klain for Commodore 64/VIC20/PET.
• Some IC.

Thanks Alessio for the donation.

12►

I had several problems with the repair of the Hewlett-Packard HP-85.

The first problem was the way to reconstruct the pinch roller using a latex tube, this is a very bad choice, then i have used a 10mm heat shrink, this choice instead is very good.

The second problem was the rubber parts of the pinch roller are literally dissolved and the rubber is went to cover the optical diode and part of the pcb and of course nothing has worked and the tape drive was always in stalled state.

After cleaning, the drive started to work perfectly. The last problem are the magnetic tapes 3M DC-1000 instead of HP DC-100, for the correct operation you must perform a modification by adding a resistor of 2kohm in parallel to the already present on the pcb. After this mod you need to format the tape with the “erasetape” command.

I must also thank John of the site vintagecomputers.freeserve.co.uk for the support.

Download:

• 3M Data Cartridge Compatibility List (1786)
• Athana DC100A / 3M DC-1000 Fix (1475)

source: voidware.com/calcs/hp85rep hp9845.net vintagecomputers.freeserve.co.uk

Replacement:

12►

Simple steps to replace the keyboard Membrane of the Sinclair ZX81. The removal of the old keyboard is not illustrated but it is a very easy job.

• Open the Sinclair ZX81.
• Place the membrane.
• Remove the adhesive protection.
• Place the membrane and press firmly.
• Check the Membrane Connector.
• Gently insert the connectors on the pcb side.
• Close the Sinclair ZX81.
• Enjoy.

source: rwapsoftware.co.uk

I have repaired an motherboard of a Commodore CBM 4008 for a friend. The computer at the start-up shows only a black screen

The components that have been replaced are:

• 1 x Video Ram 2114
• 2 x SN74LS244
• 1 x 6520

The computer after the repair works perfectly. You can see from the Photo.

Homemade video connector for the computer Enterprise 64/128.

source: enterprise.iko.hu

I have repaired an Enterprise 64 (SixtyFour) for a friend. The defect via Composite or RF was a Black Screen but with the RGB output you could see a video signals without vertical sync.

The components that have been replaced are:

• 1 x BC337
• 1 x 74LS86 (HSync/VSync to Csync)
• 1 x 74LS32 (HSync/VSync to Csync)

The computer after the repair works perfectly. You can see from the Photo.

Download: Enterprise 64/128 Schematics (1143)

source: enterprise.iko.hu

Console Amstrad GX4000 Repaired.

The fault is was caused by a wrong power connection. It was ‘resting’ the power plug of 11v on the power plug of 5v (monitor input).

Replaced parts:

• 1 x Z80A
• 2 x RAM 41464P

The components have been recovered from the Amstrad 464+

TI-99/4A MBX Expansion System Repaired.

The interface MBX Expansion System was dead and the power voltage was in short-circuited. The failure was caused by the filter between the power supply and the 7805.

Video: