Kaypro 16 character issues

[Wolfman9291]

Hello all recently picked up some kaypros and started working on a model 16 which is a 8088 pc compatible unit. The main issue I’m having is it’s displaying a bunch of “garbage” characters on the screen. I’ve already started to reseat all the ic chips. Wondering if there might be a bad tantalum capacitor. The other issue is drive b needs the head realigned but that’s not a big issue. Anybody have any tips on the garbage character issue if a general cleaning doesn’t work? Other than that it boots fine.

 

[ldkraemer]

Looks like your Video RAM Bit 2 is stuck the problem.

C  o  p  y  r  i  g  h  t
C  k  t  y  v  i  g  h  t
   |  |     |       
   |  |     |_____72         vs   76
   |  |           0111 0010       0111 0110
   |  |                                 X
   |  |_____70         vs   74
   |        0111 0000       0111 0100
   |                              X
   |_____6F         vs   6B
         0110 1111       0110 1011
                               X
 
M  y  c  r  o  f  t
M  y  c  r  o  b  p
               |  |
               |  |_____74         vs   70
               |        0111 0100       0111 0000
               |                              X
               |
               |_____66         vs   62      
                     0110 0110       0110 0010
                                           X

Larry

 

[Wolfman9291]

Thanks Larry pulled the chips and reseated them, I also checked for any shorted caps. Looks like the video ram issue is well known problem with the xt’s and clones. The manual calls for 6665ab15 ram chips on the cga card. I see a lot of 6665bp20 chips marketed for the older systems. Kaypro calls for 64k x1 150ns ram chips