TTI LA3200 LA4800 logic analyser fault finding - Halts at first menu

[rh100605]

I thought I would share a fault found in an LA4800. On power up the screen test passes but it halts before showing the main menu.

The NiCad battery on the small CPU board had leaked and fluid was on the Flat cable that connects the upper and lower boards. After replacing the cable and cleaning the pin headers the problem still remained.

The 6303 on the lower board was not responding to the serial link from the 6303 on the CPU board. Checking the crystals on the lower board found 3 failures !

Hope this helps someone revive another LA3200/4800. The service manual is at http://www.ko4bb.com/getsimple/index.php?id=manuals and then search for Thurlby Thandar la3200