Search Posts:

Comparing Altair 680 motherboards

View Entire Thread

Return to Threads
SHARE
  by Bill Degnan - 06/20/2009 23:58
First of all the power requirement the SWTPc MP-M boards is 3amps 5V. So far I was not able to find an adequate power supply. I am going to try to find a better solution for RAM.

Strangeness comparing Altair 680 motherboards.

Worked with Herb Johnson on this project, he provided detailed analysis vs. my shot gun repair approach.

The ePROMS on the Altair 680 with the flat paddles and 1-6 motherboard - not working. DC voltage problem. Should have +5 on pins 15, 12, 13, 23 of each 1702 PROM. Also should have -9 to pins 16 and 24.

Took a look at the transistor near Q1 and zener diode to see if it's correctly helping set voltage ..

I need to replace transistor Q1's associated SZ 10.9V Zener Diode and the nearby voltage regulator. Tried a 5.1 Zener from Radio Shack, a little low to power the PROMS.

This motherboard is a 1-6 (not a 1-6x like my other Altair 680).

Side note -

Wonder why my other, working Altair 680 with the 1-6X motherboard has a 7805 regulator in Q1, and not a TIP30 pass transistor to regulate the -9 voltage for ROMS.

Reply

Resources:

  • Home
  • Manufacturer photos, software, docs
  • Disk Images
  • Computer History Articles Scans and Files
  • YouTube.com Videos
  • Sale/Trade/Wanted/Miscellaneous
  • Photo Gallery
  • The Ultimate Vinage Computing Links List
  • Switch to DOS Prompt view

    • Buy a Commodore Computer Poster

    Popular Topics and FAQs


  • Commodore B Series Tips and Tricks
  • Aerocomp TRS 80 M 1 Expansion Unit DDC
  • Items Wanted
  • Lobo Max 80
  • Zenith Z-19-CN
  • Prototype PET 2001 photo
  • Using Toggle Switches to Analyze Memory
  • Commodore Disk Archive Project
  • PET 2001 Prototype at Gametronics 1977
  • Jim Butterfield Photo
  • IMSAI 8080 With Processor Tech. Cutter
  • Secrecy is the keystone of all tyranny
  • Cromemco System Three
  • Northstar Horizon - Boot Problem
  • Computer History and Restoration Links
  • Commodore BX-256-80 - 8088 Co-processor
  • S-100 board testing with Z-80 ICE
  • Donner 3500 - an early portable computer
  • Digital (DEC) PDP 11/05 NC Assembly
  • Univac 1219 rescue
  • IMSAI 1.4 BASIC vs. MITS 8K BASIC
  • Fido BBS listing node list 6-13-1986
  • PDP 8e
  • MITS 88-2 SIO (2SIO) for BASIC
  • Visual Technology Inc Model 1050
  • Amiga 2500 Restoration
  • The Evolution Of IBM Computers
  • Replacement teletype print hammer head
  • Archiving and Copying Software 101
  • Computers Built 1940 - 1950
  • CBM B-520 (a.k.a B256-80 or B500 256)
  • RCA COSMAC Microkit
  • Commodore 64K C-116 Mods
  • MITS 8800b Turnmon 9600 baud
  • Catweasel, 8in and 5 1/4
  • Raspberry Pi as Gateway to Internet
  • Digital PDP11 late 1969 early 1970
  • PDP 11/40 72 inch cabinet model
  • PDP 11/40 Industrial 11 model
  • Digitial MicroVAX 3100 30 System
  • Digital VAX 4000-200
  • Commodore 64 / 1541 DRIVEKNOCK
  • Booting the System Using RL02 drive
  • PACS: Reflections by Kathleen Mauchly
  • Tele-Graphic Computer Systems Inc.
  • Commodore B Series SID Jukebox?
  • Installing Core into PDP 11/40
  • Setting Up OpenVMS 7.1 DNS CLERK
  • Felt-Tarrant Comptometer Model J
  • NextStation Color
  • Digital Rainbow (PC100-B2)
  • 1970 Compusad Compulogical Tutor
  • Archiving Papertapes Using DSI NC 2400
  • 1976 P.C.C. Features the MAI JOLT 6502
  • 1961 Beckman DEXTIR Computer
  • UNIVAC 1 and UNIVAC File Computer 1

    • Past Issues:

  • Vintage Computer Festival East 3.0 June 2006
  • Commodore B Series Prototypes July 2006
  • VOLSCAN - The first desktop computer with a GUI? Oct 2006
  • ROBOTS! - Will Robots Take Over? Nov 2006
  • Magnavox Mystery - a Computer, or? Jan 2007
  • The 1973 Williams Paddle Ball Arcade Computer Game Feb 2007
  • The Sperry UNIVAC 1219 Military Computer May 2007
  • VCF East 2007 - PET 30th Anniversary June/July 2007
  • The Electronic Brain August 2007
  • Community Memory and The People's Computer Company October 2007
  • Charles Babbage's Calculating Machine December 2007
  • Vintage Computing - A 1983 Perspective February 2008
  • Laptops and Portables May 2008
  • From Giant Brains to Hobby Computers - 1957 to 1977 August 2008
  • Historic Computer Magazines November 2008
  • World's Smallest Electronic Brain - Simon (1950) December 2008 - Feb 2009
  • Free Program Listings Spring 2009
  • Computer Music Summer 2009
  • Popular Electronics Jan/Feb 1975 - Altair 8800 Fall 2009
  • Early Microcomputer Mass Storage Summer 2010

    • 3000 4

    This image was selected at random from the archive. Click image for more photos and files from this set.