• Please review our updated Terms and Rules here

MAI Basic Four anyone?

Caluser2000

Banned
Joined
Jan 3, 2010
Messages
5,533
Location
New Zealand
Again, your replying to a post from 2 and a half years ago. That member only posted here twice and hasn't been seen in almost 2 and a half years. I dont think your going to get a reply.
There are still current active members who have contributed to this thread in the past...
 

btb

Member
Joined
Nov 2, 2021
Messages
46
I just had a 7250 terminal fall into my lap. Unlike the other ones I've seen in photos, this one is blue:
View attachment 1249432
It seems to work, mostly. A bit of garbage on the screen, so maybe some failing ram. I'd love to find some documentation. At first I thought the 7270 must be pretty close, but nope! The 7270 is Z80-based and this one is all discrete. Pretty surprising to me seeing as it appears to have been built in 1980 and has service stickers as late as 1990.

I'm also interested in upgrading mine with lowercase. It uses a General Instrument RO-3-2513-001 character generator for uppercase, and there appear to be two empty sockets for other character sets. Could it be as easy as dropping in an eprom adapted to the right pinout?
Following up, was working to get this terminal restored, but it's taken some steps backward. On the power supply, a TO-3 7912 regulator failed, sending around -29V into the logic board, which took out some number of components. I replaced that regulator and now I'm slowly figuring out the bad chips and replacing them. I also reverse engineered the whole logic board, finding the schematic to be very very close to that of the 7230 which is available at bitsavers. The service manual for that machine is also starting to come in handy.

The front panel is made of acrylic or something similar, and is pretty hazy. I imagine I will have to try to carefully polish it.
 

JeffC

New Member
Joined
Jan 11, 2024
Messages
1
There are still current active members who have contributed to this thread in the past...
I worked at MAI/Basic-Four 1988-1990 at the Corporate campus in Tustin, CA. Really enjoyed working there. I've enjoyed reading these threads, looking at the pics
 

VERAULT

Veteran Member
Joined
Jan 30, 2012
Messages
7,945
Location
Connecticut, USA
I worked at MAI/Basic-Four 1988-1990 at the Corporate campus in Tustin, CA. Really enjoyed working there. I've enjoyed reading these threads, looking at the pics
Welcome to the Forum Jeff. Would love to hear some stories from you.
 
Top