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:

Autopsy:

How you can see from the gallery i had to remove the scotch tape that has been glued on the keys, the scotch tape with the long time has dried and detached, now the keyboard is perfect.

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The Peters WS128 Home Computer is a Russian Clone of a Sinclair Spectrum 128 but with the addition of some features.

• Built-in printer port (centronics).
• The power switch.
• A internal power supply.
• Built-in ROM: Tetris Game, Assembler Monitor, Video Tester, Text Editor.

The Company Peters, then Peters Plus Ltd. is a company of microelectronic and computer founded in the year 1990 in St. Petersburg, known especially for the clone Sprinter.

Download: Spectrumpedia (1377)

Gallery:

On the occasion of my birthday i have bought the Weller WS81 solder station that replaces my old station Weller WHS40 who has almost 13 years behind him.

The Weller WHS40 solder station was designed for a hobby use and was no longer suitable for my current use.

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.

Autopsy:

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This Commodore PET 2001 also includes the Expansion Memory ExpandaMem made by CompuThink

from Wikipedia homepage:

The Commodore PET (Personal Electronic Transactor) was a home/personal computer produced in 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.

In the 1970s Commodore was one of many electronics companies selling calculators designed around Dallas-based Texas Instruments (TI) CPU chips. However, in 1975 TI increased the price of these components to the point where the chip set cost more than an entire TI calculator, and the industry that had built up around it was frozen out of the market.

Commodore responded to this by searching for a chip set they could purchase outright. They quickly found MOS Technology, who were in the process of bringing their 6502 microprocessor design to market, and with whom came Chuck Peddle’s KIM-1 design, a small computer kit based on the 6502. At Commodore, Peddle convinced Jack Tramiel that calculators were a dead-end. In September 1976 Peddle got a demonstration of Jobs and Wozniak’s Apple II prototype, when Jobs was offering to sell it to Commodore, but Commodore considered Jobs’ offer too expensive.

Tramiel demanded that Peddle, Bill Seiler, and John Feagans create a computer in time for the June 1977 Consumer Electronics Show, and gave them six months to do it. Tramiel’s son, Leonard, helped design the PETSCII graphic characters and acted as quality control. The result was the first all-in-one home computer, the PET, the first model of which was the PET 2001. Its 6502 processor controlled the screen, keyboard, cassette tape recorders and any peripherals connected to one of the computer’s several expansion ports. The PET 2001 included either 4 kB (2001-4) or 8 kB (2001-8) of 8-bit RAM, and was essentially a single-board computer with discrete logic driving a small built-in monochrome monitor with 40×25 character graphics, enclosed in a sheet metal case that reflected Commodore’s background as a manufacturer of office equipment. Designed on an appliance computer philosophy similar to the original Macintosh the machine also included a built-in Datassette for data storage located on the front of the case, which left little room for the keyboard.

The data transfer rate to cassette tape was 1500 baud, but the data was recorded to tape twice for safety, giving an effective rate of 750 baud. The computer’s main board carried four expansion ports: extra memory, a second cassette tape recorder interface, a parallel port (mainly used for disk drives and printers) and an IEEE-488 port (mainly used for modems).

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).

source: wikipedia

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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You can use any power supply with 6v / 1.5 amp with the polarity described below:

Polarity is positive + on the outside or barrel and negative - on the inside or tip

from Wikipedia and The National Valve Museum homepage:

The Sinclair TV80, also known as the Flat Screen Pocket TV or FTV1, was a pocket television launched by Sinclair Research in 1984. Unlike Sinclair’s earlier attempts at a portable television, the TV80 used a flat CRT with a side-mounted electron gun instead of a conventional CRT; the picture was made to appear larger than it was by the use of a Fresnel lens.

The set has a 2 in. screen, measures 5= x 3= x 1< in. and weighs 9= oz. A special Polaroid flat battery that provides 15 hours’ operation has been produced to power it — there’s also a mains adaptor. The set itself goes on sale at #79.95, with the 6V Polaroid lithium batteries in packs of three at #9.95 per pack and the adaptor at #7.95, all prices inclusive of VAT, postage and packing. Normal retail and export sales are expected to start during the first half of 1984. Sir Clive Sinclair predicts sales rising to a million or more a year worldwide, and speaks of the set ‘achieving for television what the transistor radio did for wireless, creating a new one-per-person product’.

The set has some interesting technical features. It is for example a multi-standard receiver with automatic switching between most UHF standards worldwide except for France. Most of the circuitry is contained within a single ic that uses innovative digital techniques to monitor the vision and sound signals and adjust the circuitry automatically to suit the transmission standard. The ic was jointly developed by Ferranti and Sinclair Research and is being produced by Ferranti. Manufacture of the flat-screen tube (the gun is mounted to one side and the phosphor is deposited on the rear section of the viewing part) has been subcontracted to Timex in Dundee, using Sinclair designed and owned automatic plant. Assembly of the sets has been subcontracted to Thorn.

Apart from the tube and the ic, the main electronic items consist of the video output transistor, line and field output stages, the tube power supply generator and the tuner. The latter measures just 31 x 23 x 11 mm and uses hybrid microminiature components with advanced surface mounting. It’s output is at 230 MHz, which has been chosen to avoid image frequency problems in the UHF band.

It was a commercial failure, and did not recoup the £4m it cost to develop; only 15,000 units were sold. New Scientist warned that the technology used by the device would be short-lived, in view of the liquid crystal display technology being developed by Casio.

Download: Service Manual Sinclair FTV1 & FTV2 (2274)

Video:

source: wikipedia r-type.org

Finally i have found a small CRT Color TV with Composite input and an External RF Antenna input. This is a very useful in my lab where the free space is always a problem.

Autopsy:

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I thank a friend for the donation.

Donated item:

• Fenner MX-66 (Monochromatic Monitor)
  • The Mx-66 was a green phosphor CRT-based monochrome monitor manufactured in Italy by Fenner.

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

Thanks go to: Damiano (manosoft) and my Brother Alessandro.

Things that have been donated:

• 4 x Box of Verbatim Datalife 3.5  2HD Floppy Disk.
• 1 x Apple Keyboard for my iMac G3 “Bondi Blue” M5521
• 1 x Iomega Zip Drive SCSI + Cable.
• 1 x Iomega Zip Drive USB + Cable.
• 11 x Zip Disk.
• Some 3.5 Floppy Disk.

Autopsy:

The Mupi CineVisor was a must in the 70/80′s year and was used to project movies on the small screen.

The CineVisor was very cheap compared to a classic projector and perfectly manageable by children, don’t require special aptitude like the super8 projectors.

Autopsy:

Finally i have replaced my old and inaccurate Capacitor tester with a better one. My lab is beginning to have a semblance semi professional ;-D

Download: Peak Atlas ESR+ 70 User Guide (1368)

Video Review:

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.