tamal@cougar.ece.cmu.edu (Tamal Mukherjee) (01/13/91)
Hi, After coming back from a short vacation, I noticed that all of a sudden, spurious characters were cropping up on my Z29 terminal. When I type something over them they have a tendency to do one of the following: - display the typed character in correct case - display the typed character in the wrong case - display the char whose ascii value is 15 less than that of the typed character. - and so on... Also, these occur randomly all over the screen, making it difficult to use the terminal. I believe that there is something wrong with some RAM that stores the characters that are being currently displayed. Does anyone have any ideas about fixing this ? Thanks in advance, Tamal Mukherjee
hanavin@udel.edu (Chuck Hanavin) (01/15/91)
In article <1991Jan12.210223.19162@fs7.ece.cmu.edu> tamal@cougar.ece.cmu.edu (Tamal Mukherjee) writes: >Hi, > >After coming back from a short vacation, I noticed that all of a sudden, >spurious characters were cropping up on my Z29 terminal. When I type >something over them they have a tendency to do one of the following: > - display the typed character in correct case > - display the typed character in the wrong case > - display the char whose ascii value is 15 less than that of the > typed character. > - and so on... > >Also, these occur randomly all over the screen, making it difficult to use >the terminal. I believe that there is something wrong with some RAM >that stores the characters that are being currently displayed. Does anyone >have any ideas about fixing this ? Replace U440, character ram chip. It is a static ram chip 6116 which can be bought from jameco for 3 dollars. While we are on the subject of z29's, here are a few other common problems. Screen filled with strange characters (sometimes scrolling) Check U417. vertical sync off frequency, Check U407. Has curser but terminal serial port not communicating, check + and - 12 volts on 7912 and 7812. If ok check U401 and U403. the solder connection on the power supply board tends to deteriorate with age. Chuck (WB3FJJ)