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i miss the old days

September 9th, 2023 1 comment

I have nothing else to say except that i miss the old days. :’(

Monitor TVM-10 APF Electronics, Inc.

August 12th, 2023 No comments
Monitor TVM-10 APF Electronics, Inc.

First of all, i thank my friend Gerben for giving me the monitor.

This is a Black and White monitor but for some reason a thin transparent film has been applied to the front of the cinescope to simulate the tonality of an amber cathode ray tube, furthermore the APF logo placed on the front of the monitor to the right of the power light is masked.

The TVM-10 APF Monitor is approximately 43 years old and was used with the Computer APF Imagination Machine I/II.

The Monitor had several functioning problems, below is the description of the work that has been done.

  • Removing the colored film.
  • Replacement of all electrolytic capacitors.
  • Replacement of a ceramic capacitor.
  • Horizontal synchronism calibration (H-HOLD) by delicately removing the wax that was melted inside the variable inductor.
  • Installation of a 1uf polyester capacitor in parallel with the 1.5uf one present for width adjustment horizontal (H-WIDTH) of the image, unfortunately the ferrite core inserted into the variable inductor for manual adjustment is blocked, probably with glue, forcing is not a good idea.
  • Check of the Diodes.
  • Calibration using the trimmer placed on the front of the PCB of the monitor for the power supply voltage which must be 12v.
  • Geometry adjustment.
  • General cleaning.

Only one geometry problem remains; the image on the top left side of the CRT tends to bend slightly for about 1cm and the left side of the image is slighty rounded, problem surely attributable to some polyester capacitor or resistance that has lost the capacity/value of the time.

Needless to say i checked almost all the polyester capacitors and resistors in the horizontal section and didn’t find nothing scandalous.

The photo gallery contains all the photos i made during the repair, i take this opportunity to thank a user of the plcforum who gave me tips on how to proceed with the repair.

Gallery of the repair:

Brazilian Odyssey 2 (Philips Videopac+ G7400) Cartridges

November 3rd, 2022 No comments
Brazilian Odyssey 2 (G7400) Cartridges

Brazilian Odyssey 2 (Philips Videopac+ G7400) Games:

  • 06 AV 9448 Serpente do Poder! Translation: “Power Snake!”
  • 06 AV 9475 Comando Noturno! Translation: “Night Commando!”

source: the-nextlevel.com/odyssey2/faq/brazil/

Sega Megadrive Mini 2

October 30th, 2022 No comments
Sega Megadrive Mini 2

Some time has passed since the last and useless purchase and like the previous ones there is little to say all the “mini” are practically identical, change the external box, the menu and some chips inside that for the occasion are the latest version (more or less).

I used a very lame HDMI to Composite Video converter to try it with a CRT monitor.

Gallery:

G&W Nintendo S.Mario Bros & The legend of Zelda

December 4th, 2021 No comments

Against all trends, a simple photo without unboxing.

Commodore (Siemens) Bildschirmtext II Decoder Cartridge

July 31st, 2021 1 comment
Commodore (Siemens) Bildschirmtext II Decoder Cartridge

Bildschirmtext (Btx) was a German online service that existed from 1983 to 2001.

To use the service with a C64, this decoder cartridge was required, which connected to the expansion port.

The cartridge is actually a Siemens product, it’s just Commodore-branded.

The sticker says:

  • SIEMENS
  • Universal Btx Decoder
  • S30817-S721-B101-7/02 EX/W8
  • A30817-X732-B100-4-11
  • Commodore Artikel Nr. 606491

The box with the Deutsche Bundespost logo is the registration (A506 131V). At the time, only explicitly Post-approved devices and software were allowed to be used for participating in Bildschirmtext.

(This is the “Btx Decoder Modul II”, even though the cartridge doesn’t say so. There was a completely different first model.)

There are three DIN ports at the back, from left to right:

  • Modem: This connects to the proprietary Deutsche Bundespost “DBT-03” modem (1200 baud down, 75 baud up).
  • RGB: This is for connecting an analog RGB monitor.
  • FBAS: This port is identical to the C64 video port and allows using a C64 monitor.

The Post-approval for participating in Bildschirmtext required the decoder to be able to show a pixel-exact image of the service (480×240 pixels with 32 out of 4096 colors)1. Since the VIC-II in the C64 could not meet this, the decoder cartridge had its own video controller and therefore its own video ports.

The board reveals that the cartridge doesn’t only have its own video chip, it also has its own CPU, RAM and ROM – it’s a complete computer that only connects to the C64 in order to reuse the keyboard and the disk drive.

These are the major chips:

  • Motorola MC6803: a 6800-family microcontroller
  • Motorola MC68HC34: Dual-Port Memory Unit
  • 64 KB RAM (two 41464 64Kx4 DRAM)
  • 32 KB EPROM
  • D65040GF206: NEC µPD65000 series CMOS gate array

The communication with the modem, the decoding of the CEPT data stream and the interaction with the Btx service are handled by 6800 CPU and the software in the EPROM.

I am assuming the software writes the RGB values of every single scanline into the dual-port memory in real-time, which the gate array then reads to generate the video signal – like on the Atari VCS and the Sinclair ZX81. This keeps the complexity of the video hardware minimal.

The chipset and the firmware are probably very similar to the technology used in dedicated Bildschirmtext terminals.

Gallery:

source: pagetable.com

Selcom Lemon II Floppy Drive Repair and Clean

April 7th, 2021 No comments
Selcom Lemon II Floppy Drive Repair and Clean

Selcom Lemon II Floppy Drive Repair and Clean.

Defect: The Floppy Drive motor spins and the LED stays on but the R/W head does not move and don’t read anythings. This is a classic failure due to incorrect insertion of the Floppy Drive connector into the male connector on the side of the Floppy Drive Controller card.

By inserting the connector moved one row externally the supply consequently go to in the wrong places and the first IC to explode in the true sense of the word is the 74LS125 (see photo).

Replaced the component, everything has started to working again.

Taking advantage of the repair, i have cleaned the inside of the LEMON II Computer and done a DUMP of the EPROM, i also cleaned and lubrificate the mechanical parts of the Floppy Drive.

Gallery of the repair:

Download: Selcom Lemon II ROM EPROM Dump (710)

2 x Atari Lynx II Repair and Recap

March 21st, 2021 No comments
2 x Atari Lynx II Repair and Recap

2 x Atari Lynx II Repair and Recap.

The first Atari Lynx II did not turn on but when powering the console at 5v bypassing the power stage it worked properly.

I had to replace all the electrolytic capacitors and the critical components of the power stage.

  • 1 x MOSFET MTDJ055E with a equivalent one.
  • 2 x Transistor 2N3906.
  • 1 x Zener Diode 1N5991B.
  • 1 x 120 Ohm resistor.

The second Atari Lynx II working correctly so consequently i have only replaced the electrolytic capacitors.

Gallery of the repair:

Commodore 64 Communications Modem (Compunet)

February 27th, 2021 No comments
Commodore 64 Communications Modem (Compunet)

This is a Modem for Commodore 64 to allow the connection to the Compunet services.

Compunet was a United Kingdom based interactive service provider, catering primarily for the Commodore 64 but later for the Commodore Amiga and Atari ST. It was also known by its users as CNet.

Compunet hosted a wide range of content, and users were permitted to create their own sections within which they could upload their own graphics, articles and software. A custom editor existed in which the “frames” that made up the pages could be created either offline or when connected to the service.

The editor’s cache allowed users to quickly download a set of pages, then disconnect from the service in order to read them, thus saving on telephone costs.

Gallery:

Commodore Modem 1670 (Boxed & Wrapped)

February 27th, 2021 No comments
Commodore Modem 1670 (Boxed & Wrapped)

I don’t feel like unwrapping the Modem box so i will only take a pictures of the outside.

The 1670 was Commodores first “Hayes Compatible” modem. Hayes compatibility meant that the modem understood a series of control commands that had become the standard modem “language” (a language still used today).

Commodore marketed the 1670 at Commodore 128 users, even going so far as to claim that the Commodore 64 was too slow to use the 1670 at 1200 baud.

This was false, however; the Commodore 64 could use the 1670 without problems. The original 1670 also had an annoying feature of answering your phone on the first ring automatically whenever it was plugged in.

Later, a newer version of the modem was released with a dip switch allowing you to turn this “feature” off. This later version was called the “New 1670″ or the “1670CR”, and except for the extra dip switch in back, was identical to the old 1670 modem.

Gallery:

Commodore VICModem 1600 (Boxed)

February 27th, 2021 No comments
Commodore VICModem 1600 (Boxed)

The VICMODEM it’s been the first modem to cost under 100$ and the first to sold over a million units, contributing to the diffusion of online services and BBSes outside laboratories, universities, big Companies and military agencies.

Much of the credit for the project goes to Michael Tomczyk, who also created the Commodore Information Network to decrease the workload of the customer service department of the company. In 1982 the section with the most traffic on Compuserve was the Commodore network.

The modem connects to the user port of the Commodore VIC 20/64/128; on one side there’s a switch to choose if the computer answers the call (A) or originates it (O).

On the back there’s the plug for the cable that usually is connected to the phone handset – the modem couldn’t directly dial the number, so you had to dial it on the phone and then connect the modem in place of the handset.

You can read the full article by Giacomo Vernoni here

Gallery:

Modem and Software for C64 by Total Telecommunications

February 6th, 2021 No comments
Modem and Software for C64 by Total Telecommunications

Modem and Software for Commodore 64 by Total Telecommunications.

Full-duplex 300 Baud CCITT V21 Modem with Auto Dial, Auto Answer complete with software and manual for Commodore 64.

Gallery:

Siel Midi Interface for Commodore 64 & Sinclair ZX Spectrum

February 6th, 2021 7 comments
Siel Midi Interface for Commodore 64 & Sinclair ZX Spectrum

The Siel Midi interface allows the connection of one or more electronic synthesizers to a C64 or a Spectrum.

The interface communicates with the instruments through a standard communication protocol developed expressly for the interconnection of electronic instruments and called MIDI (Musical Instruments Digital Interface).

Produced by the Italian SIEL, manufacturer of popular electronic keyboards in the 80s, this MIDI interface is equipped with appropriate software application that also allows you to compose music, archive the compositions and listen to them again, save and program instrument timbres and other things.

The device is supplied with a special connector enabling immediate connection to the Commodore 64 and Sinclair ZX Spectrum.

Gallery:

Download: Siel Midi-CMK49 C64 Software (881)

source: MCmicrocomputer #39 (March 1985)

Commodore Color Printer Plotter 1520 (Mint Boxed)

February 6th, 2021 2 comments
Commodore Color Printer Plotter 1520 (Mint Boxed)

The Commodore 1520 is a printer/plotter made by Commodore and the printer mechanism made by Alps. The printer has a IEC interface and is a device that draws computer graphics on paper using fiber pens.

The advantage of this device compared to a printer is the good resolution and especially the precision. The second advantage was that these were the first color printers.The main disadvantage is the very low printing speed and that you could not print areas so well with plotters.

Plotters were primarily intended for technical drawings, as the typeface usually looked very scrawly.

Gallery:

Commodore 1581 Disk Drive (Boxed)

February 6th, 2021 No comments
Commodore 1581 Disk Drive (Boxed)

The Commodore 1581 is a 3½-inch double-sided double-density floppy disk drive that was released by Commodore Business Machines (CBM) in 1987, primarily for its C64 and C128 home/personal computers.

The drive stores 800 kilobytes using an MFM encoding but formats different from the MS-DOS (720 kB), Amiga (880 kB), and Mac Plus (800 kB) formats.

With special software it’s possible to read C1581 disks on an x86 PC system, and likewise, read MS-DOS and other formats of disks in the C1581 (using Big Blue Reader), provided that the PC or other floppy handles the “720 kB” size format.

This capability was most frequently used to read MS-DOS disks. The drive was released in the summer of 1987 and quickly became popular with bulletin board system (BBS) operators and other users.

Specifications:

  • Onboard CPU: MOS Technology 6502 @ 2 MHz
  • RAM: 8 kB
  • ROM: 32 kB
  • Disk controller: WD1770 or WD1772
  • Communications controller: MOS Technology 8520A
  • Transfer protocols: Standard and fast serial; burst mode; and commands for parallel interface (the latter not used)
  • Disk type: 3.5″ inch
  • Storage format: MFM, double density, double-sided
  • Interface: CBM’s proprietary serial IEEE-488
  • Power: 5 V @ 1 A (5 VA) – 12 V @ 0.5 A (6 VA)

Gallery: