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

Have been replaced 4 tantalum capacitors short-circuited with 4 electrolytic capacitors. The computer has been tested and works perfectly.

Autopsy:

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The motherboard is the same of Commodore VIC-1540 (Rev A/B PCB 1540007 (C) 1981 made in Japan) with a old HIGH Rom MOS “901229-03″ instead of “325303-01″.

The Commodore 1541 (aka CBM 1541, and originally called VIC-1541), made by Commodore International, was the best-known floppy disk drive for the Commodore 64 home computer. The 1541 was a single-sided 170 kilobyte drive for 5¼” disks. The 1541 followed the previous Commodore 1540 (meant for the VIC-20).

Here you can find the US version of the Commodore Single Drive Floppy Disk VIC-1541.

Testing the Floppy Drive:

Autopsy:

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The Commodore Printer 4023 is a printer with a IEEE-488 Bus and may be daisy-chained with other IEEE-488 devices. This printer is fully compatibile with all computers Commodore PET/CBM.

Model 4023 Printer Specifications:

• Printing Method: Serisal Impact Dot Matrix.
• Print Rate: 45 LMP with 80 columns printed. 78 LPM with 40 columns printed. 124 LMP with 20 columns printed.
• Print direction: Bi-directional.
• Column Capacity: 80
• Character Font: 8 x 8
• Line Spacing: Programmable.
• Character Size: 0.094″ high, 0.08″ wide
• Copies: 3, including original.
• Ribbon Type: Cartridge.
• Ribbon Life: 1.2 x 10(6) characters.
• Ribbon Cartridge: Commodore P/N 613160550
• Paper Width: 10″ computer folded paper.
• Forms: 7.5 + (0.5 x 2 sprocket margins) Pin-to-pin distance .5″ longitudinally, 9.5″ laterally, 5/32″ diameter.

Commodore Printer 4023 self test:

Autopsy:

from Wikipedia homepage:

The Timex Sinclair 1000 (TS1000) was the first computer produced by Timex Sinclair, a joint-venture between Timex Corporation and Sinclair Research. It was launched in July 1982.

The TS1000 was a slightly-modified Sinclair ZX81 with an NTSC RF modulator instead of a UK PAL (Units sold in Portugal have a PAL RF modulator) device and the onboard RAM doubled to 2K. The TS1000′s casing had slightly more internal shielding but remained the same as Sinclair’s, including the membrane keyboard. It had black-and-white graphics and no sound. It was followed by an improved version, the Timex Sinclair 1500.

Like the Sinclair ZX81, the TS1000 used a form of BASIC as its primary interface and programming language. To make the membrane keyboard less cumbersome for program entry, the TS1000 used a shortcut system of one-letter “keywords” for most commands (e.g. pressing “P” while the cursor was in “keyword mode” would generate the keyword “PRINT”). Some keywords required a short sequence of keystrokes (e.g. SHIFT-ENTER S would generate the keyword “LPRINT”). The TS1000 clued the user in on what to expect by changing the cursor to reflect the current input mode.

The TS1000 sold for $99.95 in the US when it debuted, making it the cheapest home computer to date at the time of its launch (its advertising angle was “the first computer under $100″.) This pricing initiated a price war with Commodore International, who quickly reduced the price of its VIC-20 to match and later announced a trade-in program offering $100 for any competing computer toward the purchase of a Commodore 64. Since the TS1000 was selling for $49 by this time, many customers bought them for the sole purpose of trading it in to Commodore.

source: wikipedia

I have gathered all photos of some phases of the work that i have done on the Atari 1200XL.

Below the descriptions:

• SIO 5v Enabled (you have to short-circuit the resistor R63 to get the 5v on the SIO of the Atari 1200XL)
• Repairing Keyboard (i have stretched the springs of a few keys for make the right pressure. The work must be completed using the liquid graphite where the contacts are more ruined)

Autopsy:

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from AtariMuseum homepage:

In 1982 Atari’s Home Computer Division (HCD) introduced the new replacement computer to its aging Atari 400/800 line. The new computer brought to Atari’s home computers line a high-tech and sleek low profile modern look. The case design and the “XL Look” were created by Regan Cheng of Atari’s Industrial Design group. The all new design took the 7 separate boards that made up the Atari 800 (Main, Power, CPU, OS and 3 16K Memory boards) and integrated them into a single motherboard with 64K of memory. The system also brought with it probably “THE” best keyboard for any Atari system.    

The system featured many new internal and external enhancements. Some of the obvious ones were the new Function keys and built-in HELP key that programmers could incorporate their usage into future programs. The tangle of wires from the system were now out of the back making for a clean and uncluttered arrangement. The cartridge port and controller jacks were now on the left side of the system. The new OS was designed for a new era of SIO “Plug n Play” devices to automatically load their device drivers and even on-board applications right into the 1200XL memory, also an International Character Set and built-in Diagnostic features were now part of the system. Other OS enhancements were included as well.    

However the downside was that many programs by both 3rd party companies and even Atari itself were incompatible with this new OS in the machine. The loss of 2 of the 4 original controller jacks from the earlier Atari 400/800 systems didn’t seem like much of a big deal to the 1200XL engineers, however the end users did seem to mind. The system was supposed to have a better video display output signal, however to most end users, the system appeared to have a fuzzier display then the Atari 800. The true sticking point for consumers:  No expansion whatsoever.   While the idea of a “Closed Box” design seemed like a good idea to Atari’s Marketing Department, the consumer felt exactly the opposite.

Atari’s whole design philosophy for their home computer line was that these would be Consumer Oriented, not Hobbyist Oriented Systems. Therefore that meant buffering the user from the actual electronics and chips within the machines. This design was very well executed on the Atari 800 with its easy to remove top cover and its various OS and Memory modules fitted into easy to install packages. The SIO connector also gave users a universal, easy to handle and understand expansion system. Atari felt it could take this philosophy to the extreme with the 1200XL and completely cut the users off from ANY internal access. Even the simplest of users still wanted to tinker and expand their systems and the 1200XL just didn’t give them the flexibility found in Apple ][e’s, C64s or Atari’s original 800 line of computers. The collective shortcomings of the 1200XL unfortunately overshadowed its many new enhancements. Atari’s new prodigy became its “Edsil” The introduction of the new 1200XL actually increased sales of the Atari 800. Users began to buy 800′s in fear that they would be stuck with a closed and incompatible system.

Atari 1200XL Video:

source: atarimuseum.com

Autopsy:

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from Wikipedia homepage:

The Laser 128 was a clone of the Apple II series of personal computers, first released by VTech in 1984. Unlike the Apple II clones from Franklin, VTech reverse-engineered the Apple ROMs using a clean room design rather than copying them. Apple Computer challenged VTech in court, but unlike its efforts directed at Franklin, Apple was unable to force the Laser 128 off the market.

As its name suggests, the Laser 128 had 128 KB of RAM. Like the Apple IIc, it was a one-piece semi-portable design with a carrying handle and a single built-in 5¼-inch floppy disk drive. Unlike the Apple IIc, it had a numeric keypad and a single Apple IIe-compatible expansion slot, which gave it better expansion capabilities than a IIc. VTech offered a metal 2-slot card cage that sat alongside the Laser 128 and attached to the computer’s single slot, allowing for even greater expansion flexibility. The Laser 128 retailed for about $700, substantially less than the price of an Apple IIc.

Apple countered the Laser 128 with its upgraded Apple IIc Plus. VTech responded with the Laser 128EX and the Laser EX2. The Laser 128 was aggressively marketed, both by mail order firms and in retail and catalog stores such as Sears. Even though its ROM was not derived from Apple’s ROM, the Laser 128 series had a high degree of compatibility with its competition from Apple.

VTech owed much of this compatibility to the fact that they were able to license Applesoft BASIC (which constitutes the largest and most complex part of an Apple II’s ROM contents) from Microsoft just as Apple did, heavily reducing the amount of code that had to be reimplemented. Microsoft had made most of its money by keeping the rights to the software that it sold to others. Likewise, Apple had failed to secure an exclusive distribution license for the Applesoft dialect of BASIC, and VTech was free to buy it. Much Apple software depended on various assembly routines that are a part of BASIC in ROM, and it’s quite likely that the Laser would not have been as successful had it not had compatible ROM entry points.

Download:

• LASER 128 ROM Version v2.9 (1285)
• Laser 128 and 128EX - User\'s Guide and Basic Manual (493)
• Laser 128 Technical Reference Manual (547)
• Laser 128 Manuals (410)

Game loading:

source: wikipedia

I have gathered all photos of some phases of the work that i have done on the Tatung Einstein TC01.

Below the descriptions:

• Replaced 2 x 74LS157 (IOO6/IOO7) Multiplexer.
• Replaced UK Power Connector.
• Repaired some not working keys.
• External Floppy Drive 3.5″. Yes, it’s better than 3″ ;-D

Todo:

• Repair the defect of the vertical sync of the Monitor Tatung TM01

Autopsy:

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from Wikipedia homepage:

The Einstein was released in the United Kingdom in the summer of 1984, and 5,000 were exported back to Taipei later that year. A Tatung monitor (monochrome or colour) and dot matrix printer were also available as options, plus external disc drives and an 80 column display card. It was also capable of emulating the Spectrum 48k with the “Speculator” addon.

More expensive than most of its rivals, and lacking an obvious niche market other than technically-advanced home programmers, the Einstein was commercially unsuccessful. A later, revised version, called the Tatung Einstein 256 suffered a similar fate.

The machine was physically large, with an option for one or two built-in three-inch floppy disk drives manufactured by Hitachi. At the time, most home computers used ordinary tape recorders for storage. Another unusual feature of the Einstein was that on start-up the computer entered a simple machine code monitor, called MOS (Machine Operating System). A variety of software could then be loaded from disk, including a CP/M-compatible operating system called Xtal DOS (pronounced ‘Crystal DOS’, created by Crystal Computers in Torquay), and a BASIC interpreter (Xtal BASIC). Thanks to the reliability of the machine, and ample memory, the machine proved useful by many software houses to use for programming, and then porting the code to the machines they were made for, Spectrum 48k, Amstrad CPC, Commodore C64, this later stopped when the PC and Atari ST would emerge as the development systems of choice.

source: wikipedia

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I have gathered all photos of some phases of the work that i have done on the TRS-80 Model 1.

Below the descriptions:

• Cleaning of Nicotine.
• Replaced a bad capacitor.
• Testing.
• Floppy Drive before restoration.
• Replaced Australian Power Connector of the Floppy Drive.
• Restoration phases of the Floppy Drive.
• *Making the floppy disk for TRS-80 Model 1.
• Audio patch cable to hear the sound of the games.

*Is not been easy to make the Floppy for the TRS-80 Model 1 SSSD 35 TRK in FM format. Fortunately i have a old motherboard Pentium 133 with the right IO chip that supports writing format: MFM / FM SSSD.

Download: Some TRS-80 Model 1 games in ImageDisk format. (1121)

Video:

• Radio Shack TRS-80 Model 1 (Testing Floppy Drive)
• Radio Shack TRS-80 Model 1 (Frogger with Sound)
• Radio Shack TRS-80 Model 1 (Attack Force with Sound)

Autopsy:

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from Wikipedia:

TRS-80 was Tandy Corporation’s desktop microcomputer model line, sold through Tandy’s Radio Shack stores in the late 1970s and early 1980s, and one of the earliest mass-produced personal computers. The first units, ordered unseen, were delivered in November 1977, and rolled out to the stores the third week of December.

The line won popularity with hobbyists, home users, and small-businesses. Tandy Corporation’s leading position in what Byte Magazine called the “1977 Trinity” (Apple, Commodore and Tandy) had much to do with Tandy’s retailing the computer through more than 3,000 of its Radio Shack storefronts. Notable features of the original TRS-80 included its full-stroke QWERTY keyboard, small size, its floating point BASIC programming language, an included monitor, and a starting price of $600.

The pre-release price was $500 and a $50 deposit was required, with a money back guarantee at time of delivery. One major drawback of the original system was the massive RF interference it caused in surrounding electronics. Stricter FCC regulations on interference led to the Model I’s replacement by the Model III.

Radio Shack announced the TRS-80 (Tandy Radio Shack) at a New York City press conference on August 3, 1977. It cost $399, or $599 with a 12″ monitor and a Radio Shack tape recorder as datacassette storage. Before this, the most expensive product Radio Shack sold was a $500 stereo.

The company hoped that the new computer would help Radio Shack move into higher-priced products, and improve its “schlocky” image among customers. Small businesses were the primary target market, followed by education, then consumers and hobbyists. Despite its hobbyist customer base, Radio Shack saw hobbyists as “not the mainstream of the business”. Although the press conference did not receive much media attention due to a terrorist bombing elsewhere in the city that day, “six sacks of mail” arrived at company headquarters asking about the computer, and over 15,000 people called Tandy to purchase a TRS-80, paralyzing its switchboard.

Unlike competitor Commodore—which had announced its PET several months earlier but had not yet shipped any—Radio Shack began shipping computers by September. Still forecasting 3,000 sales a year, the company sold over 10,000 TRS-80s Model Is in its first one and a half months of sales, and over 200,000 during the product’s lifetime.

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)

Autopsy:

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The collection includes:

• Mattel (Radofin) Aquarius Home Computer System (boxed).
• Mattel (Radofin) Aquarius Mini Expander Module (boxed).
• Mattel (Radofin) Aquarius Game Cartridge Night Stalker (boxed).
• Mattel (Radofin) Aquarius 4k Memory Expansion (boxed).
• Mattel (Radofin) Aquarius Data Recorder (boxed).
• Mattel (Radofin) Aquarius Thermal Printer.

from Wikipedia homepage:

Aquarius is a home computer designed by Radofin and released by Mattel in 1983. It features a Zilog Z80 microprocessor, a rubber chiclet keyboard, 4K of RAM, and a subset of Microsoft BASIC in ROM. It connects to a television set and uses a cassette tape recorder for secondary data storage. A limited number of peripherals, such as a 40-column thermal printer, a 4-color printer/plotter, and a 300 baud modem, were released for the unit.

Looking to compete in the standalone computer market, Mattel Electronics turned to Radofin, the Hong Kong based manufacturer of their Intellivision consoles. Radofin had designed two computer systems. Internally they were known as “Checkers”, and the more sophisticated “Chess”. Mattel contracted for these to become the Aquarius and Aquarius II, respectively. Aquarius was announced in 1982 and finally released in June 1983, at a price of $160.

Production ceased four months later because of poor sales. Mattel paid Radofin to take back the marketing rights, and four other companies—CEZAR Industries, CRIMAC Inc., New Era Incentives, Inc., and Bentley Industries—also marketed the unit and accessories for it. Bentley Industries (of Los Angeles) and New Era Incentives, Inc. (of St. Paul) are still in business, though they no longer have any affiliation with the Aquarius product line.

source: wikipedia