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.

Autopsy:

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from Wikipedia:

The Commodore CBM-II series was a short-lived range of 8-bit personal computers from Commodore Business Machines (CBM), released in 1982 and intended as a follow-on to the Commodore PET series.

The CBM-II had two incarnations, the P series (P = personal, or, home use) and the B series (B = business use). The B series was available with a built-in monochrome monitor (hi-profile) with detached keyboard, and also as a single unit with built-in keyboard but no monitor (lo-profile). These machines were known as the “Porsche PETs” for their unique styling.

The P series used the VIC-II 40-column color video chip like the C64. It also included two standard Atari-style joystick ports. The 6509 CPU ran at 1 MHz in the P series due to the use of the VIC-II chip.

The B series used a 6545 CRTC video chip to give an 80-column “green screen” monochrome output more suitable for word processing and other business use than the VIC-II’s 40-column display. Most models have the Motorola 68B45 installed which is a pin compatible variant rather than the MOS 6545A1 2 MHz part. On the B series the 6509 CPU ran at 2 MHz.

Features common to both the P and B series included an MOS Technology 6509 CPU, an enhanced version of the venerable 6502, that was capable of addressing up to 1 megabyte of RAM via bank switching (however, no CBM-II model came with more than 256 kilobytes of RAM, 1/4 megabyte). The sound chip was the 6581 SID, the same one that was used in the popular Commodore 64 (C64) but with some limitations as it was over-clocked to 2 MHz. Additionally, the CBM-II had an industry-standard RS-232 serial interface and an IEEE-488 parallel bus (for use by disk drives and printers) just like the PET/CBM series. The CBM-II’s built-in operating system used an enhanced version of CBM BASIC version 4.0.

An optional Intel 8088-based coprocessor board allowed the CBM-II series to run CP/M-86 1.1 and MS-DOS 1.25; however, the computers were not IBM PC compatible and very little, if any, software taking advantage of this capability ever appeared. The coprocessor board only ran on hi-profile machines due to power supply and mechanical spacing requirements.

The production naming within the United States and Canada was the B128/B256 and CBM128-80/CBM 256-80 while in Europe they were known as the 600 and 700 series respectively (no “B” in front of the model number). The P machine was known worldwide as the 500 series. There are prototype models though such as the B500 (earlier B128 design) and B700 (earlier CBM 128-80/CBM 256-80 design) known to exist.

Due to the popularity of the C64, the P series was cancelled in the United States before it could be officially released; however, a few dealers who received preproduction units sold them. As these computers had not received approval from the Federal Communications Commission, this caused legal problems for Commodore. The units were recalled and destroyed, but a very small number exist today, in private collections. At least one model, the P500, was commercially released in Europe but only sold in small numbers.

source: wikipedia

Autopsy:

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I have received this computer to be repaired for a friend with a classic startup fault; the Black screen of Death.

After careful analysis of the problem and thanks to Alessandro Polito for the test, the failed component was the CPU 6509.

from Wikipedia:

The Commodore CBM-II series was a short-lived range of 8-bit personal computers from Commodore Business Machines (CBM), released in 1982 and intended as a follow-on to the Commodore PET series.

The CBM-II had two incarnations, the P series (P = personal, or, home use) and the B series (B = business use). The B series was available with a built-in monochrome monitor (hi-profile) with detached keyboard, and also as a single unit with built-in keyboard but no monitor (lo-profile). These machines were known as the “Porsche PETs” for their unique styling.

The P series used the VIC-II 40-column color video chip like the C64. It also included two standard Atari-style joystick ports. The 6509 CPU ran at 1 MHz in the P series due to the use of the VIC-II chip.

The B series used a 6545 CRTC video chip to give an 80-column “green screen” monochrome output more suitable for word processing and other business use than the VIC-II’s 40-column display. Most models have the Motorola 68B45 installed which is a pin compatible variant rather than the MOS 6545A1 2 MHz part. On the B series the 6509 CPU ran at 2 MHz.

Features common to both the P and B series included an MOS Technology 6509 CPU, an enhanced version of the venerable 6502, that was capable of addressing up to 1 megabyte of RAM via bank switching (however, no CBM-II model came with more than 256 kilobytes of RAM, 1/4 megabyte). The sound chip was the 6581 SID, the same one that was used in the popular Commodore 64 (C64) but with some limitations as it was over-clocked to 2 MHz. Additionally, the CBM-II had an industry-standard RS-232 serial interface and an IEEE-488 parallel bus (for use by disk drives and printers) just like the PET/CBM series. The CBM-II’s built-in operating system used an enhanced version of CBM BASIC version 4.0.

An optional Intel 8088-based coprocessor board allowed the CBM-II series to run CP/M-86 1.1 and MS-DOS 1.25; however, the computers were not IBM PC compatible and very little, if any, software taking advantage of this capability ever appeared. The coprocessor board only ran on hi-profile machines due to power supply and mechanical spacing requirements.

The production naming within the United States and Canada was the B128/B256 and CBM128-80/CBM 256-80 while in Europe they were known as the 600 and 700 series respectively (no “B” in front of the model number). The P machine was known worldwide as the 500 series. There are prototype models though such as the B500 (earlier B128 design) and B700 (earlier CBM 128-80/CBM 256-80 design) known to exist.

Due to the popularity of the C64, the P series was cancelled in the United States before it could be officially released; however, a few dealers who received preproduction units sold them. As these computers had not received approval from the Federal Communications Commission, this caused legal problems for Commodore. The units were recalled and destroyed, but a very small number exist today, in private collections. At least one model, the P500, was commercially released in Europe but only sold in small numbers.

source: wikipedia

These two computers had the classic fault: Black screen of Death.

The first one was repaired by replacing a ram chip (4264) partially interrupted, the other one had One of the two chip PLA dead.

I have to thank my friend Andrea for providing me a motherboard of a 8296 for spare parts, where i have recovered the PLA which i needed.

This gallery shows some stages of cleaning the Commodore CBM 8050 Dual Drive Floppy Disk. Below the defects and replacement parts.

Defect:

• Died – Status LED: RED (5 Flash) Zero page error.

Replacement parts:

• 1 x 6502
• 1 x 6532
• 1 x 6522
• The connectors of write enable sensors are inserted incorrectly.
• Missing +5v on the PCB of the sensor circuit.
• Dirtiness in the write enable sensor drive 0
• Cleaning floppy drive heads.
• Cleaning belt of the floppy drive.
• Removing the filter capacitor.
• The Analog PCB of the Floppy Drive is not fixed properly.
• The Locking screws of the external box are not original.
• Lost the felt which push the Floppy Disk vs the head.
• Disk is present (Switch Motor) dirty.
• General Cleaning.

Test formatting floppy disk:

Autopsy:

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from Wikipedia:

The Commodore 8050 and Commodore 8250 were dual unit 5¼” floppy disk drives for Commodore International computers. They used a wide rectangular steel case form similar to that of the Commodore 4040, and used the IEEE-488 interface common to Commodore PET/CBM computers.

The 8050 was a single sided drive, whereas the 8250 could use both sides of a disk simultaneously. Both used a “quad” density format storing approximately 0.5 megabyte per side. The density of media was similar to later PC high density floppy disks, but the 8050 and 8250 could not use PC high density disks reliably. Since “quad” density disks were rare even at the time, users quickly found that typical double density floppy disks had enough magnetic media density to work in these drives.

These drives were not dual mode, so they could not read or write disks formatted by the more common lower capacity Commodore 1541 or Commodore 4040 models. Some variants of these drives existed. The Commodore 8250LP was the 8250 in a lower profile, tan-colored case. The Commodore SFD-1001 was a single drive version of the 8250 in a Commodore 1541 style case (similarly to the Commodore 2031LP), often used by bulletin board systems for their physical similarity to 1541s and high capacity and speed.

source: wikipedia

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Commodore CBM 8032 fully functional but without Monitor donated by Andrea Pierdomenico.

I have received this motherboard of a CBM 8032 to repair from Rossano T.

The motherboard was devastated by rust, many components are short-circuited due to rust that was abundant on the pins side of the chip. Unfortunately the computer was turned on to test it, causing the total breakdown of more components.

I have installed 40 socket because some components are rusty other are dead, however some traces under the chips are eaten by rust and and i had to rebuild.

The repair and cleaning took me a very long time and a lot of patience, it took me about 10+ hours.

Components Replaced:

• 1 x 4650 (6845P) CRT Controller
• 3 x 4116 RAM
• 2 x 2114 Video RAM
• 5 x 74LS244
• 3 x 74LS74
• 1 x 74LS02
• 1 x 1uf 100v Capacitor

Phases of the repair:

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I thank my dear friend for the donation of the motherboards.

• Commodore Dual Drive Floppy Disk CBM 8250
• Commodore CBM 8296

Detailed photo:

I have used the CIF Power Clean and Sponge dishes, with the porous Bakelite (this keyboard) you can also use the rough side of the sponge without any problems. Don’t use the rough side with the plastic.

I have to thank Andrea for giving me this keyboard. The keyboard has replaced the wrong one of my 8296-D.

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.

Autopsy:

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from Wikipedia:

The Commodore PET (Personal Electronic Transactor) was a home/personal computer produced from 1977 by Commodore International. A top-seller in the Canadian and United States educational markets, it was Commodore’s first full-featured computer, and formed the basis for their entire 8-bit product line.

The PET 2001 was announced at the Winter CES in January 1977 and the first 100 units were shipped later that year in October. However, the PET was back-ordered for months and to ease deliveries, early in 1978 Commodore decided to cancel the 4 kB version.

Although the machine was fairly successful, there were frequent complaints about the tiny calculator-like keyboard, often referred to as a “chiclet keyboard” because the keys resembled the gum candy. This was addressed in upgraded “dash N” and “dash B” versions of the 2001, which put the cassette tape recorder outside the case, and included a much larger keyboard with a full stroke motion. Internally a newer motherboard was used, along with an upgrade from static RAM to dynamic RAM and 8, 16, or 32 KB, known as the 2001-N-8, 2001-N-16 or 2001-N-32, respectively.

Sales of the newer machines were strong, and Commodore then introduced the models to Europe. The result was the CBM 3000 series (‘CBM’ standing for Commodore Business Machines), which included the 3008, 3016 and 3032 models. Like the 2001-N-8, the 3008 was quickly dropped.

The final version of what could be thought of as the “classic” PET was the PET 4000 series. This was essentially the later model 2000 series, but with a larger black-and-green monitor and a newer version of Commodore’s BASIC programming language.

Commodore tried to update the PET line with a new redesign called the CBM-II series (also known as the B series). These were not as successful and were ultimately abandoned. However, due to demand, the original PET machines were revived and the CBM-II case style was retained. These were known as the SK’s (due to the separated keyboard). They also had a swivel monitor. Originally, standard 8032 boards were retrofitted into these cases. Later the SK models got a new mainboard that already included the 64 kB extension directly on the board and were sold as 8296 or, with a built-in 8250 dual disk drive, as 8296-D.

source: wikipedia

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) (870)
• EDIT Rom 324243-02b (860)

Sorry, this entry is only available in Italian.

Autopsy:

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The Commodore PET 2001-N (the N was short for “New”) is a successor to the Commodore PET 2001, it has a bigger keyboard and 32KB dynamic RAM memory. The larger keyboard means that the first cassette drive now has to be an external unit.

from Wikipedia:

The Commodore PET (Personal Electronic Transactor) was a home/personal computer produced from 1977 by Commodore International. A top-seller in the Canadian and United States educational markets, it was Commodore’s first full-featured computer, and formed the basis for their entire 8-bit product line.

The PET 2001 was announced at the Winter CES in January 1977 and the first 100 units were shipped later that year in October. However, the PET was back-ordered for months and to ease deliveries, early in 1978 Commodore decided to cancel the 4 kB version (also because the user would be left with barely 3 kB of RAM).

Although the machine was fairly successful, there were frequent complaints about the tiny calculator-like keyboard, often referred to as a “chiclet keyboard” because the keys resembled the gum candy. The key tops also tended to rub off easily. Reliability was fairly poor, although that was not atypical of many early microcomputers. Because of the poor keyboard on the PET, external replacement ones quickly appeared.

In 1979, Commodore replaced the original PET 2001 with an improved model known as the 2001-N (the N was short for “New”). The new machine used a standard green-phosphor monitor in place of the light blue in the original 2001. It now had a conventional, full-sized keyboard and no longer sported the built-in cassette recorder. The kernel ROM was upgraded to add support for Commodore’s newly-introduced disk drive line. It was offered in 8kB, 16kB, or 32kB models as the 2001-N8, 2001-N16, and 2001-N32 (the 8kB models were dropped soon after introduction). Finally, Commodore added a machine-language monitor to the kernel ROM that could be accessed by jumping to any memory location with a BRK instruction. It did not include a built-in assembler and required the user to enter hexadecimal numbers for coding.

Sales of the newer machines were strong, and Commodore then introduced the models to Europe. The result was the CBM 3000 series (‘CBM’ standing for Commodore Business Machines), which included the 3008, 3016 and 3032 models. Like the 2001-N-8, the 3008 was quickly dropped. The change to CBM occurred because of a trademark dispute with Philips over the PET name.

source: wikipedia