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.

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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 (1603)
• Athana DC100A / 3M DC-1000 Fix (1361)

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

Replacement:

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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 (1053)

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:

A few things to repair for a friend.

• Enterprise 64
• Archimedes 310

Defect: unknown.

I have repaired an Atari 800XL for a friend. The failure was caused by a faulty cpu, the computer freezes after 10 minutes of operation, using an oscilloscope i have noticed that the clock pin of the cpu did not give me more signal but when i have used the synthetic ice spray on the cpu has resumed to work.

This type of cpu (Atari customized 6502 – C014806-12 Sally) is not easy to find but fortunately a friend of mine (Carlo) has found a spare part for me.

Details:

Jump here for the commercial RGB mod for the Mattel Intellivision

I have found this RGB mod for the Mattel Intellivision console fom a site, i have searched on the net if anyone has tried this mod, but nothing, so, i have tried to do it myself.

This mod is not easy to do, especially if one has no experience in electronics, however the result at the end is spectacular.

Schematics (click to zoom):

Autopsy:

You can found Parts list and Schematics here

from wiki.intellivision.us Homepage:

The Intellivision directly generates composite video using the AY-3-8915 Color Processor and a set of resistors. This video gets fed to the ASTEC UM1285-8 video modulator for conversion to RF for display on a television set. It is possible to tap this composite video directly to avoid the distortion and static associated with RF modulation and demodulation. On older units, the RF modulator can decay rather noticeably, leading to very low quality video.

Typical composite video inputs have an input impedance of 75Ω. In contrast, the composite signal generated by the Intellivision has a very high output impedance. (We estimate the output impedance is around 2KΩ.) Tapping this output and feeding it directly into a typical composite monitor does not work. (It will work if your monitor has a “high impedance” input, but such monitors are atypical.) Thus, an amplifier/impedance matching circuit is necessary.

It is also possible to tap the audio the Intellivision generates. The audio output by the Intellivision is nearly directly suitable for feeding line-level inputs on most AV equipment. All that’s required is a coupling capacitor.

The modification should work equally well on all Intellivision variants, including the Intellivision 1, Intellivision 2, the various rebranded units (Sears, Tandy), and the later INTV releases.

source: wiki.intellivision.us