Feb 252016
 

Another Rainbow Islands PCB to repair.

This one had issues with the sprites which were broken up and seemed to be repeating, looked very much like a stuck bit on the sprite addressing;

IMG_20160224_112137583

IMG_20160224_112142174

All tiles and background graphics were fine, so I knew it was something to do with the sprite circuit.

The first thing I did was to look at the area where the sprite data is read from the two eproms.  The two 74LS244 buffers checked out fine, but one of the 74LS373 Octal Latches had an output pin stuck HI (pin 9);

IMG_20160224_112155598_HDR

So I desoldered it;

IMG_20160224_113645345

I confirmed the Octal Latch was bad in an IC Tester.  So I soldered in a socket and replaced with a fresh Octal Latch;

IMG_20160224_114050662

PCB sprites now restored;

ri_pcb_2

ri_pcb_3

  2 Responses to “Rainbow Islands repair log #10”

  1. great repair blog.
    pcb repair is new to me and the fact you said buffer and octal latch makes it easier for me to understand as a pcb repair noob.
    i see the fault on screen and see the possible cause too.
    🙂
    i don’t need to look through data sheets to see what the fault chip does which means i can spend more time on the board.
    free pint for Equites