This computer is of a dear friend; Paolo Cognetti.

Short story of the repair:

I have checked the voltages and are correct, although a couple of capacitors on the power stage need to be replaced.

I have tried to turn on the computer and i have see immediately a problem, the screen is full of random characters, with the oscilloscope i have tried to see if i have data stream on the CPU (Z80), interrupts and so on.., nothing, it seemed completely dead, replaced.

The computer has started better then before but with some video glitches, raster lines scrolls from bottom to the top and some characters scattered on the screen. I double checked the voltages and i have realized that the 12v are gone and the 7812 warmed a lot, about 80 degrees after 2 minutes.

Almost all tantalum capacitors of 1uf and 33uF on the 12v line are shorted, i have decided to replace them all (22 pieces)

After the replacement of all tantalum capacitors and two electrolytic capacitors on the power supply stage the computer has started to work correctly but with some video problems, characters scattered on the screen, after replacing two Static RAM 2114 everything works perfectly, including the Basic Cartridge that until now had never worked.

Works that have been made:

• Fixing broken Fuse Holder.
• Fixing a cold welding of a capacitor on the power supply stage.
• Testing Voltages.
• Replaced CPU Z80.
• Replaced 12 x Tantalum Capacitors (1uf)
• Replaced 10 x Tantalum Capacitors (33uf)
• Replaced 1 x Axial Electrolytic Capacitor (470uf)
• Replaced 1 x Axial Electrolytic Capacitor (1500uf)
• Replaced 2 x NMOS 2114 Static Ram.
• Fixed the botton cover with two missing screws.
• Cleaning the top cover using only water and a sponge.

Exidy Sorcerer II Repair Gallery:

Exidy Sorcerer II Gallery:

source: wikipedia

Sinclair ZX Spectrum 128k (Toastrack) Repair

Defect:

• Garbage screen on bootup.

Repair:

• Replaced 7404 (74LS04)

Note:

• Missing one HEX Inverter between Pin 11 and 10.

Gallery of the repair:

I have exhumed my old Macbook Core 2 Duo 13″ (late 2007) to install a Linux OS (Linux Mint) but before doing this work i wanted to give a nice internal cleaning and replacing the thermal paste of the cpu.

Gallery:

Commodore Floppy Disk Drive 1541 Repair (#1)

Defect:

• Motor runs continuously.
• Loading a Program or a Directory freeze the computer.
• Misaligned.

Repair:

• Replace 901229-05 (UB4)
• Replace 7414 (UA1)
• Head Alignment.

Gallery of the repair:

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Commodore Floppy Disk Drive 1541 Repair (#2)

Defect:

• Write Protect Problem.

Repair:

• A wire of the infrared LED was broken. The problem is remove the glue and the heat shrink tube around the LED.

Gallery of the repair:

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Commodore Floppy Disk Drive 1541 Not Repaired (#3/#4/#5)

Defect:

• Don’t read anything.

These Floppy Disk Drive have the Read Head interrupted. This seems to be the most common problem in the Mitsumi (Newtronics) drives.

Gallery:

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Commodore Floppy Disk Drive 1541 Repair (#6)

Defect:

• Loading a Program or a Directory freeze the computer.

Repair:

• Replace VIA 6522 (UC3)

Gallery of the repair:

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Commodore Floppy Disk Drive 1541 Repair (#7)

Defect:

• Loading a Program or a Directory freeze the computer.

Repair:

• Replace 7414 (UA1)

Gallery of the repair:

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Commodore Floppy Disk Drive 1541 Repair (#8)

Defect:

• Motor runs continuously.
• Loading a Program or a Directory freeze the computer.

Repair:

• Replace CPU 6502 (UC4)
• Replace 7414 (UA1)

Gallery of the repair:

Commodore 64 [ASSY 250407] Repair (#1)

Defect:

• Startup screen Scrambled/Garbage.

Repair:

• Replaced the IC socket of MOS 6569 (VIC-II) oxidized.

Gallery of the repair:

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Commodore 64 [ASSY 250407] Repair (#2)

Defect:

• Garbage Graphics.

Repair:

• Replaced MOS 6569 (VIC-II).

Gallery of the repair:

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Commodore VIC-20 [ASSY 250403] Repair

Defect:

• Black Screen.

Repair:

• Replaced MOS 6502 (UE10).

Gallery of the repair:

Amiga 600 (REV1.5) badly Distorted Clipped Saturated audio Repair

This Amiga 600 has suffered several months ago serious problems of the leakages capacitors.

The amiga has worked for a period and then the sound has stopped to working with the classic distorted/clipped audio defect.

I have replaced the usual LF374 SMD with a TL084C 100% compatible and everything has started to work perfectly.

Gallery of the repair:

Commodore Amiga 500 (ASSY 312510 REV.5) Repair

Defect:

• Black Screen.

Repair:

• Replaced a 74LS244 (U35)
• I have removed a rusty part of the pcb to see if the tracks are interrupted or in a bad state.

Note:

• This Amiga has already been repaired in years past, not from me.

Gallery of the repair:

This is another nice test cartridge can help a little bit the repairs, many thanks to the author of the DIAG264 software.

Gallery:

source: diag264 blog.tynemouthsoftware.co.uk

Damn! the case Housing of the Power Supply is glued and is not a nice thing.

Defect:

• +5v is missing.

Replaced components:

• 1 x IC CA723CE (Precision Voltage Regulators)

Analysis of the defect:

• Tested the cable.
• Tested the transistor TIP41C soldered on the PCB.
• Unsoldered the transistor TIP41C and i have again tested to make sure 100% that is not died, the transistor was not in short circuit or interrupted.
• With the transistor TIP41C unsoldered i have tested the output of the IC CA723CE PIN 10 VOUT which appeared to 0V instead of +5v  while the input voltage (unregulated) PIN 12 measured +17v and VREF 6 PIN was correct.

Gallery of the repair:

Commodore CD32 Revision 3 (Boxed) Full Recap

Capacitors replaced:

• 2 x 1000uF 10v (VERTICAL)
• 1 x 470uF 10v (VERTICAL)
• 9 x 100uF 6,3v (SMD)
• 6 x 22uF 35v (SMD)
• 5 x 47uF 16v (SMD)
• 4 x 10uF 35v (SMD)
• 4 x 4,7uF 35v (SMD)

Reversed the polarity of the two capacitors by 1000uF because in the revision 3 of the CD32 and earlier are wrong. (the label of the polarity on the PCB is not correct)

Gallery:

Commodore 16 Repair

Defect:

• Don’t works any program that requires too much memory.

Replaced Components:

• 1 x MB81416-12 (U5)

Note:

I have used for the first time the DIAG264 (Kernel version, but there is also a cartridge version) and i must say that it works well.

Gallery of the repair:

Sega SC-3000 Repair

Defect:

• The graphics of the games is not displayed correctly.
• The BASIC cartridge does not work.

Replaced Components:

• 2 x MCM4517-15 RAM (IC12/IC13).

Note:

I have replaced the two RAM MCM4517-15 with a classic RAM 4164 (also used in the Commodore 64) paying attention to short-circuit the pin 9 and 10 of the 4164 RAM.

The MCM4517-15 RAM are 16,384 Words x 1 bit while the 4164 is 65,536 x 1 bit, both are PINOUT compatible except for the pin 9 which in the MCM4517-15 is not used while in 4164 is A7.

This “tricks” to short-circuit the pin 9 and 10 instead of using a resistor of pull-down is also used in some coin-op arcade boards that use the same RAM.

Gallery of the repair:

Mattel Intellivision with ZOE RGB (Limited Edition)

Why is Limited Edition?

Because i have made these works:

• Shielded cord Male MiniDIN Scart (cable length: 2,5 meters) also the cable that connecting the female connector MiniDIN to the PCB of the ZOE RGB is shielded.
• Female connector MiniDIN installed in the RF signal output hole and strongly fixed.
• Removed the RF Modulator.
• Installed a electrolytic capacitor in series of the output audio.
• Minimized the flat that connects the ZOE RGB with the Intellivision Motherboard.
• Installed the metal cover on the solder side of the motherboard.

Gallery:

12►

The TI 99/4A Flash ROM Cartridge, or FlashROM 99 for short, is a cartridge for the TI 99/4A home computer that allows for running ROM cartridge images stored on an SD card.

The FlashROM 99 supports ROM-only images of up to 32K that use the write-to->60xx bank switching scheme. It will not work with programs using GROMs or CRU-based bank switching. The cartridge does not require the Peripheral Expansion Box and runs on both PAL and NTSC consoles.

FlashROM 99 is released as Open Source Hardware under the CERN OHL license and the GNU GPL license. Both hardware design files and firmware sources are available on GitHub.

The project homepage is hosted at GitHub.

Gallery:

Download: FlashROM 99 SD Card (1208)

source: endlos99.github.io/flashrom99 ti99iuc.it

Texas Instruments TI-99/4A – Navarone’s Widget Multi Cartridges Fixed.

Works that have been made:

• Annoying short circuit under the cartridge connector on the slot 3 between the pins: 4,6,8,10