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:

12►

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:

12►

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

12►

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)

I have gathered all photos of some phases of the work that i have done on the Tatung Einstein TC01.

Below the descriptions:

• Replaced 2 x 74LS157 (IOO6/IOO7) Multiplexer.
• Replaced UK Power Connector.
• Repaired some not working keys.
• External Floppy Drive 3.5″. Yes, it’s better than 3″ ;-D

Todo:

• Repair the defect of the vertical sync of the Monitor Tatung TM01

123►

I have gathered all photos of some phases of the work that i have done on the TRS-80 Model 1.

Below the descriptions:

• Cleaning of Nicotine.
• Replaced a bad capacitor.
• Testing.
• Floppy Drive before restoration.
• Replaced Australian Power Connector of the Floppy Drive.
• Restoration phases of the Floppy Drive.
• *Making the floppy disk for TRS-80 Model 1.
• Audio patch cable to hear the sound of the games.

*Is not been easy to make the Floppy for the TRS-80 Model 1 SSSD 35 TRK in FM format. Fortunately i have a old motherboard Pentium 133 with the right IO chip that supports writing format: MFM / FM SSSD.

Download: Some TRS-80 Model 1 games in ImageDisk format. (1202)

Video:

• Radio Shack TRS-80 Model 1 (Testing Floppy Drive)
• Radio Shack TRS-80 Model 1 (Frogger with Sound)
• Radio Shack TRS-80 Model 1 (Attack Force with Sound)

I have received this computer Commodore CBM 8296-D 1 year ago. The computer has never worked, it only displays a black screen without any sound beep at the startup boot.

The repair it was very simple, 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.

Download:

• PLA Rom 8296(D) (931)
• EDIT Rom 324243-02b (922)

Sorry, this entry is only available in Italian.

I was very lucky in this repair, the fault is a broken belt that is used for the operation of the Floppy “Quick Disk”.

?hd=1

I post some screenshots and a video of the repairing of a NEC PC-Engine LT console.

Defect in the console:

Some capacitors have leaked acid on the pcb, i had to clean with the right product made especially for cleaning the pcb before proceeding with the replacement operation. The LCD screen is was disassembled to remove the dirt inside.

This is a little description of the repair of a Radio Shack TRS-80 Model 1 for a Friend.

The computer comes with several problems.

• Some IC are dead or in shorted state.
• Keyboard flat cable.
• One key “L” is dead.

Finding the cause of the fault has not been easy, i had to ask for a help to Ian, this dude is an expert of TRS-80 repairs.

How you can see from the photos, i had to replace a number of IC.

• 4 x Video RAM 2102 (Z62 / Z63 / Z46 / Z48)
• 1 x Z80 (Z40)
• 1 X 74LS157 (Z31)
• 1 X 74LS93 (Z32)

Stage of the defect (before and after):

Keyboard repair (replacement of internal contacts):

Micro Computer Technical Reference Handbook:

Download: TRS-80 Micro Computer Technical Reference Handbook (2498)