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) (1440)

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 (1411)
• Orange Apple IIe Clone (Roms1 now is Correct) (135)

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.

Autopsy:

1234►

Olivetti S.p.A. is an Italian manufacturer of computers, tablets, smartphones, printers and other business products such as calculators and fax machines. Headquartered in Ivrea, province of Turin, the company has been part of the Telecom Italia Group since 2003.

The primacy of the first PC can be assigned to Olivetti thanks to Programma 101, which was produced in 1964 and had a big success in the U.S. market.

Olivetti’s first modern personal computer, the Olivetti M20, featuring a Zilog Z8000 CPU, was released in 1982. In 1983 Olivetti introduced the M24 and in 1984 the M21 (the first and last of transportable of Olivetti), a clone of the IBM PC using DOS and the Intel 8086 processor (at 8 MHz) instead of the Intel 8088 used by IBM (at 4.77 MHz).

The M24 was sold in North America as the AT&T 6300. Olivetti also manufactured the AT&T 6300 Plus, which could run both DOS and Unix.

The comparison (before / after):

Repairing & things before of the Cleaning:

12►

Defects:

• Mirror image.
• Sometimes garbled image with using the ISA Bus.

Replaced parts:

• Replaced a 74LS245N on the motherboard side.
• Replaced a 75LS244N on ISA expansion Module.
• Removed the battery for the Realtime Clock.

Upgrade:

• Bios v1.36 to v1.43 (latest).

source: wikipedia

Autopsy:

1234►

Kaypro Corporation, commonly called Kaypro, was an American home/personal computer manufacturer of the 1980s. The company was founded by Non-Linear Systems to develop computers to compete with the then-popular Osborne 1 portable microcomputer. Kaypro produced a line of rugged, portable CP/M-based computers sold with an extensive software bundle which supplanted its competitors and quickly became one of the top selling personal computer lines of the early 1980s.

While exceptionally loyal to its original consumer base, Kaypro was slow to adapt to the changing computer market and the advent of IBM PC compatible technology. It faded from the mainstream before the end of the decade and was eventually forced into filing for bankruptcy in 1992.

Kaypro began as Non-Linear Systems, a maker of electronic test equipment, founded in 1952 by Andrew Kay, the inventor of the digital voltmeter.

In 1981, Non-Linear Systems began designing a personal computer, called KayComp, that would compete with the popular Osborne 1 transportable microcomputer. In 1982, Non-Linear Systems organized a daughter company named the Kaypro Corporation and rechristened the computer with the same name.

The first product, the Kaypro II, carried the Roman-numeral designation because one of the most popular microcomputers at the time was the Apple II. The Kaypro II was designed to be portable like the Osborne. (When battery-powered laptop computers became available, the larger machines came to be called transportable or luggable, rather than portable.) Set in an aluminum case, it weighed 29 pounds (13 kilograms) and was equipped with a Zilog Z80 microprocessor, 64 kilobytes of RAM, and two 5¼-inch double-density floppy-disk drives. It ran on Digital Research, Inc.’s CP/M operating system, and sold for about US$1,795.00.

Kaypro’s first computer, the Kaypro II, had a 2.5 MHz Zilog Z80 microprocessor; 64 Kb of RAM; dual, single-sided, 191 kB 5¼ inch floppy disk drives; and an 80-column, green monochrome, 9″ CRT.

Early in the Kaypro’s life, there was a legal dispute with the owner of the Bigboard computer who charged that the Kaypro II main circuit board was an unlicensed copy or clone.

he outer case was constructed of painted aluminum. The computer featured a large detachable keyboard that covered the screen and disk drives when stowed. This and other Kaypro computers (except for the Kaypro 2000) ran off regular AC mains power and were not equipped with a battery.

The comparison (before / after):

Defects:

• Black screen of death.

Replaced parts:

• Removed the filter capacitors.
• Replaced some Electrolytic Capacitors exhausted (PSU).

source: wikipedia

Gallery of the repair:

Defect:

• Black screen of death.
• Improper adjustment of Contrast and Brightness.
• Power Supply “tired”.

Replaced parts:

• Removed the filter capacitors.
• Replaced all Electrolytic Capacitors exhausted .
• Contrast and Brightness adjustments.