Advice about repairing an IBM 5151

tony duell ard at
Mon Aug 31 23:54:15 CDT 2015

> Hi,
> I traced the 18Khz signal all the way from the moment it enters the
> logic board until the video board (attached to the neck of the CRT).
> The signal is there (it has different shapes but it is 18KHz). The

No, that is a different 18kHz signal. That is the video, which will
have a significant component at the horizontal frequency. It 
starts from pins 6 (intensity) and 7 (video) of the DE9 connector

You need to trace on from pin 8 to transistors on the main board,
right up to the flyback transformer.


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