In this rainy day i have decided to commit myself to create a boot floppy disk for my Tandy Radio Shack TRS-80 Model 4P.

The right steps to create the boot disk:

Download LS-DOS or TRSDos (DMK version) floppy image from here , now you need to use the DMK2IMD program, a tool inside the package ImageDisk to convert the DMK floppy image to IMD (ImageDisk), then … burn it with ImageDisk.

Download:

• LS-Dos v6.3.1 (IMD) (1637)
• TRSDos v6.2 (IMD) (1706)

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I have found a Kaypro 4/84 in a non working state and some days ago i have decided to open it and i have realized that some components of the power supply are exploded and the video pcb was cracked.

I have not repaired the power supply because some components like the two burned transistors (Motorola W30 and V30) are not on the market, if you have more information about these components please leave me a message.

I had to fix the video pcb and i have installed a 200w Slim ATX power supply inside the Kaypro. I have made also other improvements to the computer, replaced the battery, totally exhausted and installing the KayPlus rom that offers some enhancements to this computer.

Below you can find the image of the Floppy Disk CP/M 2.2F 62k patched + Tools KayPlus in IMD format (ImageDisk) for the Kaypro 4/84.

Download: Kaypro 4/84 CP/M 2.2F 62k + Tools KayPlus (1408)

In these days i have had the necessity of a computer with the DOS operating system to create Boot Disk with the ImageDisk program, so i decided to retrieve my old Olidata P133 and install FreeDOS.

I have installed:

• 3COM 3C905 PCI Ethernet Card.
• TCP/IP Stack via 3COM 3C905 Packet Driver.
• Amstrad 1640 5 1/4 Floppy Drive (I had to change a jumper, see photos)
• Upgraded SIMM Ram (100 Mb)
• DOS Driver for Crystal 4232 Sound Card (SoundBlaster Compatible)
• A small fan for the cpu.
• Some Games and Utility.

Gallery:

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My Work Bench for small electronic Repair.

I am very happy to have repaired for my friend four PCB Commodore in one and half hour.

The defects are:

• Motherboard Commodore 64 ASSY 250466 with IEC bus broken. (replaced ic 7406 – U8)
• Motherboard Commodore 64 ASSY 250407 with a Video Output problem with some programs, like FIBR File Manager. (replaced ic 6526 – U2)
• Motherboard Commodore 64 ASSY 250425 with strange character at startup. (replaced ic 4264 – U12)
• Motherboard Commodore Floppy 1541 ASSY 1540050 REV C with IEC bus broken. (replaced ic 7406 – UB1 and ic 7414 – UA1)

My Modern PC with a 5.25 Floppy Drive (Epson SD-600).

This Floppy Drive model works perfectly with the programs: Omniflop / winImage / raWrite.

Download: Diskette Configuration Guide (1380)

I have recovered a Osborn 1 in pretty nice cosmetic conditions but broken ;-(

List of broken stuff:

• Startup Garbage screen.
• Long startup beep.
• Reset works 1 times out of 20.
• Modem port desoldered.
• Powersupply ripple.
• Some screws missing.

Solutions & Fixes:

• Powersupply Ripples: Replaced some capacitors.
• Modem Port de-soldered: Fixed the cold solder.
• Startup garbage screen/long beep/reset: I have replaced a broken 4116 RAM.
• Screws missing: Replaced with a new one.

I have to thank Terry ‘Tezza’ of Classic Computers Blog for the piggyback ram guide.

I used an oscilloscope to find the faulty ram cause all ram in my motherboard seemed to work well. In the photo #9 you can see the signal of the pin 2 (data in) of a faulty ram, while in the photo #8 the same signal of a working a ram.

Retro Innovations ROM-el:

To program the ROM-el chip by Retro Innovations you need a Adapter. The ROM-el chip uses a Atmel flashrom AT49F001AN (128K x 8) and we must build an adapter that converts the pins of the 2364 PROM Commodore 64 Kernel, which is used in ROM-el chip, to the original state of the chip AT49F001.

After this work, you can use the Willem programmer to program the FlashROM with one or more C64 kernel.

Nano SwinSID Prototype by x1541:

This project is based on the microcontroller ATMEGA88PU from Atmel and the emulation code is written by Swinkels.

The prototype of Nano SwindSID is a scaled down version of the Micro SwinSID, so far so good, and here’s my initial impression.

x1541, a user of the forum64.de has made a very nice work, the pcb has the same size of the original SID chip (6581/8580), the components are arranged very well and the entire space of the pcb was used. I can just say to buy it when the Nano SwinSID kit will be available, your money will be spent well.

Nano SwinSID Features:

• ISP Connector.
• Same size as the original SID.
• 6581/8580 Jumper.
• Smd ATmega.

source: forum64.de

This is a very old project published in a Dutch magazine to capture the state of the IRQ for Commodore 64 (vic-20) with a LED. After many years i have decided to make it.

On the photo you can see the project and the right connections on the cartridge port.

Components:

• 1 x IC 74LS04.
• 1 x Bicolor LED.
• 2 x 330 ohm resistors.
• Tiny wires.

How it work?

When the CPU generates an IRQ the green LED lights up, otherwise is red, if the irq is turned on and off quickly the led is orange.

I continue to upgrade my Amiga 2000 PAL REV 4.5. After the upgrade of the chip Fat Agnus and the Kickstart/4MB, today i have replaced the Denise chip with a new one. The Super Denise chip is capable of still higher resolutions and bit depths.

I have created a funny Poster with some things from my Museum.

Download: NightfallCrew Poster (29Mb / 4677 x 3307)

Finally i had time to finish the enhancements of my Commodore 64, below a brief description of what you see in the photos.

Enhancements description:

• 1541-III bulk version.
• Reset Switch.
• Multi Kernel with Atmel flash rom.
• Multi Kernel Switch.
• Eprom homebrew PLA.
• Cartridge ON/OFF Switch.
• DualSID with separate output (6581 / 8580)
• 2 x Fan Cooling.
• Fan Cooling Switch.
• Bright Blu Power LED.
• 1541 Ultimate REV1 with v2.0 Firmware.

DualSID KIT by Tomi Malinen:

DualSID is a device which allows you to plug in two different SID models to your Commodore 64.

You can set the second SID‘s address to five different memory locations. For more information and price visit the Tomi Malinen homepage

Download: DualSID V3 PCB Scan (476)

I had to make this change to get the Expansion Ram 320XL running on my Atari 800XL:

• 5v Power wire on PBI connector.
• Stabilize the clock signal for PBI Devices. (link #1 – link #2)

source: atariage.com