Blogs

All members are invited to blog on Applefritter. Weblogs should generally be of a technical nature and should be written in such a way as to still be readable and useful 50 years from now. Please do not embed outside media. Images and videos can be uploaded via the Media Browser. Files should either be attached to the blog post or uploaded to the file libraries.

When you post to your blog it will appear on this index and on your personal blog page. Once you've made a few posts, contact me about having a graphic added on the top of this page.

A few tests for a non-booting Disk II controller

Submitted by S.Elliott on April 1, 2023 - 12:23am
A collection of simple (simplistic) tests for diagnosing a non-booting Disk II or A2 disk controller:
  • Monitor commands to test 6 of the 8 data latches in the 9334 chip
  • Monitor commands to load just one sector, then beep and break
  • Attach an LED to troubleshoot individual latches Q0 through Q3
  • Use a flashlight to "candle" circuit traces
  • Use wood or bamboo to scrape debris off the circuit board
Tags: 
troubleshooting

Clumsy (but pretty!) attempts to map video scanner's memory access

Submitted by S.Elliott on March 28, 2023 - 10:30pm
Some experiments and variously messy results from trying to map how often the video scanner reads each byte of screen memory while creating each video frame.

Green indicates bytes that were detected only once per frame.

Purple indicates bytes that were detected twice per frame.

Orange indicates bytes that were detected thrice per frame.

Blue indicates bytes that were detected four times or more per frame.

Tags: 
vaporlock

Upgrade the Disk II controller with shrouded headers

Submitted by S.Elliott on March 21, 2023 - 12:45am
Apple chose bare headers for the disk connectors on the Disk II controller, which make it notoriously easy to connect the drive cable incorrectly.

Jameco's "Shrouded Box Header 20 Pin 2316R-20G" makes an ideal replacement.

Tags: 
hardware

Pages

Subscribe to RSS - blogs