Like we know well the keyboard of the Commodore 116 may NOT be fixed because you can’t open it without break it.

The only way is break the plastic pins that hold the keyboard PCB and find the right way to close the whole thing, i leave you the right way for do this.

Once you have open it, we realize that this keyboard is a colossal shit, the conductive material of the keys is ridiculous a thin layer that is consumed very briefly.

The only way before you throw it is use the “Kontakt Chemie Graphit 33” but without spraying directly on the tiny conductive part of the key but first try on a plastic surface and then with a very fine brush take the graphite to paint the conductive part of the key.

The “Kontakt Chemie Graphit 33” with the days/months or years tends to dry, this solution make a new life to the keyboard, but not for always.

Another classic failure and is the FPC Connector (18 pins) for the keyboard flat that can be easily replaced if you find an FPC connector with 18 pins ;-D

The conditions of this Commodore 8296 (TAN Case) are really bad. The CBM 8296 is left for over 25 years in a dovecote.

The cleaning, repairing and restoration have taken a very long time, but the result is more than acceptable.

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Defects:

• The Commodore 8296 was completely dead (Black screen of death).
• Little problems of CRT geometry.

Replaced parts:

• Replaced PLA U6 with a OTP EPROM 27C512R 70ns + Adapter
• Replaced the ROM 2 x 2764 Eprom with 1 x 27C128 Eprom (spare parts from a original cbm pcb)

Note:

I have replaced the original ROM (2 x EPROM) pcb because the PLA adapter is fat. I could insert a small castle (photo) between the ROM pcb and the Main Motherboard but in this time i have prefered to replace with a single Eprom.

Gallery of repair and cleaning:

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This is a Commodore CBM 8296-D Motherboard repaired for a Friend.

Gallery of the repair:

Defect:

• Black screen of death without startup beep and after replacing U5 and U6 black screen of death with startup beep.

Replaced parts:

• Replaced PLA U5 with a original PLA MOS 324745-01.
• Replaced PLA U6 with a OTP EPROM 27C512R 70ns + Adapter
• Replaced a dual FlipFlop 74LS74 UD4.

* The replacement of the two PLA has already been made earlier by my friend.

The conditions of this Commodore 8032-SK (Gold Label) are really bad. The CBM 8032-SK is left for over 25 years in a dovecote.

The cleaning, repairing and restoration have taken a very long time, but the result is more than acceptable.

Defects:

• The Commodore 8032-SK was completely dead (Black screen of death).
• Little problems of CRT geometry.

Repair:

• Replaced the CPU 6502.
• Yoke calibration of the CRT

Gallery of repair and cleaning:

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The conditions of this Commodore Dual Disk 8250 LP are really bad. The CBM 8250 LP is left for over 25 years in a dovecote.

The cleaning, repairing and restoration have taken a long time, but the result is more than acceptable.

Defects:

• Floppy Disk Drive completely dead.
• Main motherboard failure: Status LED green but with the Floppy Disk Drive LEDs (red) that blink 3 times and then repeat in loop.
• Directory displayed with extra chars.

Repair:

• Replaced all the electrolytic capacitors of the two Floppy Disk Drive.
• Replaced the IC RIOT MOS 901869-01 (Memory, I / O, Timer array)
• Replaced the IC RIOT MOS 6532 (RAM-I/O-Timer)

Gallery of repair and cleaning:

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Gallery of repair and cleaning:

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This computer is arrived for a repair from a friend. The defect is the classic Black Screen of Death and also the PCB has certainly seen better days.

Defects found:

• Short circuits.
• Tracks interrupted or broken.
• Tracks partially raised.
• Jumpers with flying leads.
• Some components are partially unsoldered and soldered to other components.

Repair:

• Rebuild all the tracks interrupted or partially raised.
• Arrangement of all components removed or partially unsoldered.
• Removing flying jumpers
• Replaced CPU Zilog Z80
• Replaced a RAM 2114
• Replaced a Multiplexer 74LS157
• Replaced the ZX-81 Rom with a Eprom 2532 with programmed the ZX-80 Rom.

Mod:

• Composite video output (simple version without Transistor). It was made only to make easiest the repair.

This gallery shows some stages of the repair of the Sinclair Spectrum 48k.

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Defects found on the Sinclair Spectrum #1:

• Black Screen of Death/Garbage Screen.

Components replaced:

• 8 x 4116 RAM
• 1 x Z80 CPU

• Extra:
  • Composite Video

Defects found on the Sinclair Spectrum #2:

• There are no colors.

Components replaced:

• 5 x Electrolytic Capacitors 22uf / 16v
• 1 x SN94459 (LM 1889) Tv video Modulator IC with Chroma Reference Signal (Color)

Defects found on the Sinclair Spectrum #3:

• Jaundice problems.

Calibration:

• Calibration of Trimmer (VR2)

Defects found on the Sinclair Spectrum #4:

• Black Screen of Death.

Components replaced:

• 1 x RAM TMS4532
• 1 x Transistor ZTX650

• Extra:
  • Composite Video
  • Conversion from Spectrum (Issue 2) To Spectrum +

Defects found on the Sinclair Spectrum #5:

• Garbage Screen and high absorption on the 12v line and 0v (ground) with explosion of the transistors ZTX-650 (651) and ZTX-213

Components replaced:

• 1 x Zener 5v1
• 12 x Electrolytic capacitors
• 3 x 4116 RAM (two of these in total short circuit between pin 8 and 16)
• 8 x OKI 3732 RAM
• 1 x Sinclair ROM
• 1 x 74HCT(LS)32
• 1 x Transistor ZTX-213
• 1 x Transistor ZTX-650

• Extra:
  • Composite Video

• Info:
  • About the explosion of the transistors i have isolated the problem, are the ram (LOW).

    The bad way used some years ago was cut the pin 8 of the all 4116 ram to isolate the bad one, in this case, i didn’t cut the pins of the ram, but i have cut the track of 12v which is part of all the 4116 ram, doing so, the transistor ZTX650(651) doesn’t explode.

    At this point there is a short in one or more RAM between +12 and 0v. I have measured the absorption where i have cut the track and it absorbs too much.

    I just have to unsolder the pin 8 of the 4116 ram and trying to isolate it for find which ram is short-circuited.

• …it was not over:
  • When the repair is finished and i have replaced all OKI 3732 RAM with a new one, another IC has decided to die, a 74HC(LS)32. I have no words.

Defects found on the Sinclair Spectrum #6:

• Faulty / AutoLoad.

Components replaced:

• 1 x TMS 4532 RAM

• Extra:
  • Composite Video

Sinclair Spectrum Faulty / AutoLoad Video:

Small and Convenient retro-keychain.

This gallery shows some stages of repairing the Commodore PET 2001-8C

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Two months have passed since i have received my Commodore PET 2001-8 Chicklet exchanged for a Sharp MZ-80K, was the day 28/08/2013.

The motherboard was in disastrous conditions, it took two months and a lot of patience to repair it.

Defect:

• Garbled characters at boot.
• Tape Recorder (Datassette) Motor Tired.

Replaced parts and various repairs:

A large number of short circuits visible and not visible (under the ic sockets)

• 2 x 6540 ROM Basic 1.0
• 2 x 74LS00
• 3 x 74LS157
• 1 x 7805
• 2 x Electrolytic Capacitor / Tantalum.
• 1 x Tape Motor
• 16 x 2114 RAM

I want to dwell on the ram, i noticed that the PET 2001-8 Chicklet does not digest very well all ram.

These ram don’t work properly for my PET 2001-8 Chicklet:

• TESLA 2114 (2/8)
• MM2214N
• SY2114-2
• HKE2114L-2

I had to buy several stocks of ram in 2114 to find the right ram that work correctly. The ram that work very well are the ELCAP 2114L-3.

I have to thank Andrea Pierdomenico for the ROM test on his PET 2001-8C and Alessandro Polito. for the exchange.

This gallery shows some stages of repairing the Commodore CBM 610.

Defects found on the Commodore CBM 610:

• Random raster lines on the screen.

Components replaced:

• 2 x 74LS245
• 1 x 74S32
• 1 x 74S05
• 1 X 74LS14
• 2 x Capacitor 22uf 10v
• 2 x Capacitor 1uf 50v

I have passed three weeks of suffering for repairing this CBM 610. The finding of the fault is not has been easy, the key component of the failure was the IC 74S05 (U96) followed by the other components.

Autopsy:

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This computer/console in good cosmetic condition is arrived for a repair from a friend a few weeks ago. The defect is The Black Screen of Death, the computer turns on but doesn’t turn off, the standby LED remains faint green.

Unfortunately after several hours spent to trying the fault and i have tried just everything, the computer is still dead, my suspicion falls on the Custom Chip “SCOTCH” IX 1267CE from Sharp.

Components that have been tested and replaced:

• Tested all capacitors.
• Tested all transistors.
• Tested all SMD fuses.
• Test all the Coils.
• Tested all voltages.
• Replaced 74LS08 ic that controls the logic of power on/standby.
• Replaced 74LS244 ic that controls the logic of power on/standby.
• Replaced the power supply.

Download: Sharp X68000 Schematics (1598)

from Wikipedia:

The Sharp X68000, often referred to as the X68k, is a home computer released only in Japan by the Sharp Corporation. The first model was released in 1987, with a 10 MHz Motorola 68000 CPU (hence the name), 1 MB of RAM and no hard drive; the last model was released in 1993 with a 25 MHz Motorola 68030 CPU, 4 MB of RAM and optional 80 MB SCSI hard drive. RAM in these systems is expandable to 12 MB, though most games and applications did not require more than two.

The X68k ran an operating system developed for Sharp by Hudson Soft, called Human68k, which features commands very similar to those in MS-DOS (typed in English). Pre-2.0 versions of the OS had command line output only for common utilities like “format” and “switch”, while later versions included forms-based versions of these utilities, greatly improving their usability. At least three major versions of the OS were released, with several updates in between. Other operating systems available include NetBSD for X68030 and OS-9.

Early models had a GUI called “VS” (Visual Shell); later ones were packaged with SX-WINDOW. A third GUI called Ko-Windows existed; its interface is similar to Motif. These GUI shells could be booted from floppy disk or the system’s hard drive. Most games also booted and ran from floppy disk; some were hard disk installable and others require hard disk installation.

Since the system’s release, Human68k, console, and SX-Window C compiler suites and BIOS ROMs have been released as public domain and are freely available for download.

Early machines use the rare Shugart Associates System Interface (SASI) for the hard disk interface; later versions adopted the industry-standard small computer system interface (SCSI). Per the hardware’s capability, formatted SASI drives can be 10, 20 or 30 MB in size and can be logically partitioned as well. Floppy disks came in a couple of different formats, none of which are natively readable on other platforms, although software exists that can read and write these disks on a DOS or Windows 98 PC.

source: wikipedia

I have received these computers to be repaired for a friend.

Defects found on the Commodore VIC-20:

• Error message (device not present) when trying to access the IEC devices, like a Floppy Drive.

Defects found on the Commodore 64:

• Black screen of death after installing the missing roms.

The repair of the Commodore VIC-20 was made by replacing a HEX Inverter Buffer 7406.

The repair of the Commodore C64 was made by replacing the MOS 906114-01 (PLA – Programmable Logic Array).

Gallery of repairs:

Mentor Colour 6 (Pong clone) has been Repaired

Defects:

• Black screen of death.
• No sound.

The problem of the power supply has been fixed by replacing the transitor CS 9013 that is used in a very bizarre way to lower the voltage from 9v to 6.85v. The problem of the audio was always caused by a transistor CS 9013 brutally in short circuit. In this case, the transistor is used like a amplifier.

The transistor CS 9013 can be replaced with a BC 337 that it’s equivalent.

This gallery shows some stages of the cleaning and repairing the Commodore CBM 610.

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Defects found on the Commodore CBM 610:

• Black Screen of Death.
• Garbage characters on the screen.
• Keyboard Yellowed.
• Filter capacitor exploded.

The black screen of death was fixed by replacing the CPU MOS 6509A and the problem of garbage characters on the screen was fixed by replacing the ROM characters with a EPROM 2532 suitably programmed.

The yellowed keyboard was replaced with a new one in good condition of the Commodore CBM 710. I like Commodore. What will be the difference of a CBM 710 and a CBM 610 keyboard? nothing, are the same! no! on the keyboard of the CBM 710 has two wires reversed! (brown/red) ;-D

The filter capacitor exploded has been removed.

This gallery shows some stages of the repairing of the two Floppy Drives Commodore SFD-1001.

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Defects found on the two Floppy Drives:

• Both floppy drives had the capacitors that leaked acid on the motor control pcb.
• Both floppy drives had the closing arm cracked.

The difficulty was rebuild the tracks of the pcb and remove the most of the leaked acid of the capacitors. Unfortunately on the aesthetic level this type of repair are not perfect, but i’m glad that now work.

To test the correct operation of the Floppy Drives i have used a Commodore CBM (PET) 2001, and a Commodore CBM 610.