Low-Noise 7805/7812 Drop-In Replacements

Linear voltage regulators such as the 7805 and 7812 are ubiquitous in vintage electronic equipment, and especially in home computers of the late 1970s and early 1980s. They have many advantages are very reliable. Their biggest drawback is their heat dissipation. The variants in metal TO3 packages are only available used or as new old stock. So if you want to replace them with a cooler running variant these brand new drop in replacements based on modern switching regulators might be worth a try. These particular variants have extremely low switching noise, so should be very usable in devices such as the Commodore 1541 floppy drive. So we will repair one of my broken 1541s and also fit it with the modern DR340 voltage regulator!

Original GameBoy: IPS Mod Horizontal Lines

The IPS display mod for the original GameBoy from a couple of weeks ago already developed a fault. bright horizontal lines run through the display, and it seems a full replacement of the LCD panel is needed. It seems these mods are a bit fragile. Also the display lens is a bit crooked and needs fixing. So off to another round of DMG modding!

Original GameBoy IPS Mod

A friend gave me two GameBoys, one of which he wanted back after the repair. The other one was dead and I could keep it. So after a quick testing I determined that only the display board was broken due to quite severe battery damage. While maybe salvageable I decided to use a drop in IPS LCD replacement board, as the original DMG screen is pretty abysmal anyway. This mod is relatively easy to install, and requires no soldering!

Upgrading the PET 3016 to 32KB RAM

A couple of years ago I got a PET 3016 from 1979. The machine comes stock with 16KB of RAM and back then we upgraded it using a RAM/ROM expansion, giving it 32KB of SRAM and BASIC V4 ROMs. However it never ran stable in this configuration. It turns out the SRAM was not playing nice with the system. So in this video we will use new old stock 8116 DRAM chips to upgrade the mainboard to its maximum and hopefully get a stable system.

ZoomFloppy+OpenCBM+8050

The main issue with the Commodore 8050 and 8250 drives is: How do you get data onto them? The units use 100tpi floppy drives that are incompatible to the regular 48tpi and 96tpi disk drives used in the 1541 and in PC DD and HD drives. So there is no chance using those. However there is the ZoomFloppy, which is an implementation of the XUM1541 interface and it comes with an optional IEE488 plug! We can attach the 8050 to that, and use the OpenCBM tools to read and write data to and from the floppies.

Let’s Code MS DOS 0x24: Low Level Keyboard Programming

Getting input from the keyboard can be as easy as calling the getch() function. But for games we need a better solution. For games on MS DOS machines you need quick, unbuffered input. To simply get the state of keypresses we need to talk to the keyboard controller directly. Let’s have a look at how that’s done!