Gallery:

Replacement NiCd Battery of a Commodore SR4190R Calculator.

Defect:

• Battery Leaks.

Replaced parts:

• Replaced 3 x NiCd Rechargeable Batteries 1.2v.

Gallery:

Commodore SX64 (USA/NTSC) Repair.

Defect:

• Black screen and then noise of a misaligned drive (don’t read anything).

Replaced parts:

• Replaced 1 x 906114 PLA (UE4)

Other things:

• Aligned the Floppy Drive using the original copy of the Free Spirit Software Drive Alignment.
• Removed the broken switch to disable the write protection and disconnected a LED on the front side of the SX64.
• Connected the sensor wires cut.
• Cleaning the Floppy Drive.

Apple IIc Rom v4 Upgrade & Repair.

Defect:

• The second RAM in the auxiliary memory is faulty.

Replaced parts:

• Replaced 1 x RAM 4264 (ARD1)

Upgrade:

• Apple IIc ROM upgraded to the latest version V4 (MON)

Download:

• Apple IIc v4 ROM + Installation Manual (1399)

Commodore CBM/PET 3032 Motherboard Repair.

Defect:

• Garbled screen and then “Illegal Quantity Error” message or 31 Bytes free

Replaced parts:

• Replaced 1 x NE555 (A2)
• Replaced 2 x Unstable RAM 4116 (I2/I3)
• Replaced 1 x 74LS153 (E4)

Atari Disk Drive 1050 #1

Defect:

• SIO bus unresponsive.

Replaced parts:

• Replaced 1 x LM3086N (U1)

Atari Disk Drive 1050 #2

Defect:

• SIO bus unresponsive + no reset cycle of the Disk drive on poweron.

Replaced parts:

• Replaced 1 x RAM-I/O-Timer (RIOT) 6532 (U7)

Gallery:

Commodore 64 ASSY 250407 Empty PCB + some Working components.

The horizontal measuring was made calculating the ledge at the base of the monitor.

Unfortunately, this monitor suffers from a serious problem of image quality.

The monitor become very hot and the adjustment resistance (trimmer) of the Focus controls that is inside the flyback loses its original value.

After nearly an hour of operation, the image becomes blurred and we must adjust the trimmer of the focus located inside the monitor, that’s why i have made this modification to the external case of the monitor.

The flyback is NOT longer exists as a spare parts.

Datanetics Apple Keyboard Fix.

After a few cold solder joints redone the keyboard works almost perfectly.

Todo:

• The “V” key is totally dead.
• The keys are a bit tired, don’t return always in the original position.

Overall is fine.

Datanetics Apple Keyboard *update*

I found a temporary solution for the tired keys they don’t return always in the original position. I have put a small spring (see the picture). Now the keys works correctly.

About the “V” key completely dead, i have desoldered it and i have tried to spray a air into the slots without having any results, so i have tried a extreme thing, i have used the key switch like a whistle. ;-D I have blown inside several times, the result is the key switch now are working again. I have made the same thing for the “right arrow”.

Macintosh Plus repair.

Defect:

• Mac sad face with error code not readable.

Replaced parts:

• 2 x ROM (342-0341-B / 342-0342-A) replaced with two EPROM 27C512 (pinout compatible)

Note:

All roms that i have found on the net or sent by friends are not working.
I had to do a dump of the Rom of my Macintosh Plus and at this point everything has worked immediately.

Download: Macintosh Plus ROM (27C512 Splitted) (1353)

Apple IIe STK Asic Clone (Maybe Orange) repair.

Defect:

• Short-circuit on all voltages.
• Black/Garbage screen.

Replaced parts:

• 10 x Tantalum Capacitor 4.7uf (replaced with Electrolytic Capacitors)
• 3 x RAM OKI M3764A-15 in Short-circuit.
• 1 x ROM 1 (EPROM 27128)

Note:

I have to thank immensely my friend Alessandro Polito for providing me the dump of the ROM 1 of the Orange (Apple IIe Asic Clone)

Download: Orange Apple IIe Clone Roms (1303)

Gallery:

Commodore 64 ASSY 250425 Empty PCB + some Working components.

Gallery:

Example of replacing exhausted Electrolytic Capacitors.

My advice is always to replace all capacitors although at first view does not seem exhausted with acid leakage.

Someone has to repair these computers! ;-D

In the photo you can see: Commodore 64(C) motherboard, Commodore Amiga 500 motherboard, Commodore Amiga 600, Sinclair QL, Commodore 128 motherboard and some Amiga keyboard.

Repaired for a friend a Commodore CBM 8296 Motherboard.

Defect:

• Black screen of death without startup beep.

Replaced parts:

• Replaced PLA [UE6] with a OTP EPROM 27C512R 70ns + Adapter.
• Replaced PLA [UE5] with a original one MOS 324744-01
• Replaced [UC8] 3-State Driver Bus MOS 65245 (74LS245)

I have received a Lemon II computer (Apple ][+ / Europlus Clone) in a good cosmetic condition but with a serious problem at the keyboard, here below defects and repairs that has been made.

Cleaning comparison (before / after):

Gallery of the repair:

Defects:

• First problem: When a keyboard key is pressed is always displayed the same character, in this case the character “O”
• Second problem (which i have only noticed after solving the first one): The keyboard works correctly, all characters are displayed in the correct way, but sometimes the character displayed does not match with the key pressed. Example: when pressing many times the letter “I”, after a while is displayed the character “Y” and after a while it show the right character “I”.

Components Replaced:

• 2 x 74LS191 (UP/DOWN Counters)
• 1 x SMC KR2376-ST (Keyboard Encoder)

I have to thank my friend Luca that called me to inform me that there was still a piece of the SMC KR2376-ST available in the store.