Re: 7613 Mainframe - Readout problem


Look for a signal called x/y shutdown. It originates on the readout board (J2138), goes via coax to the horiz amp (J503), then a 2-pin ribbon (P504) to the main interface board (P38) and then pin BC to the vertical interface board where it actually shuts down the vertical while a character is drawn. Check Q238 on the vertical interface board. If the characters are only moving vertically, the signal is getting lost after it goes through the horizontal amp.

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