Replacement:
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 (1112)
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:
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
Kernel JiffyDos Installation and Keyboard Repair for my friend Damiano (manosoft.it). To repair the keyboard you must clean the contacts very well on the pcb.
Powerup and Testing my Sinclair Spectrum 128k (RGB with Bright MOD) after a long time.
Video:
I received this computer to be repaired for a friend some days ago. The computer displays only a black screen and some times a random character without any sound beep at the startup boot.
I have replaced the PLA IC 324745-01 (UE5) and 324744-01 (UE6) with two EPROM 27C512 70ns (suitably programmed), the Universal PLA adapter was kindly donated by Manosoft.
The computer also had another defect, apparently the fault was not only in the two PLA. The computer starts with the classic beep but the screen remain black, the faulty is the IC 6545 (CRTC) and that was replaced.
This model uses a ROM daughterboard instead of a single 23128 ROM (EPROM 27C128 pinout compatible). I have made an adapter to preserve the original state of 8296 and allow the insertion of the daughterboard after the replacement of the two PLA that are different (in size) to the original one.
Have been replaced 4 tantalum capacitors short-circuited with 4 electrolytic capacitors. The computer has been tested and works perfectly.
I have gathered all photos of some phases of the work that i have done on the Atari 1200XL.
Below the descriptions:
- SIO 5v Enabled (you have to short-circuit the resistor R63 to get the 5v on the SIO of the Atari 1200XL)
- Repairing Keyboard (i have stretched the springs of a few keys for make the right pressure. The work must be completed using the liquid graphite where the contacts are more ruined)
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