> Hi Tony, > > I have checked the horizontal signal from the MDA using an > oscilloscope. It is pin 8 like you mentioned. I get a regular 18KHz or > so signal out of that. Pin 9 gives the vertical signal at roughly > 50Hz.
OK. Your PC and MDA card seem to be OK. Now trace through the horizontail circuit in the 5151. IIRC there is a driver transistor, the collector load of which is a transformer which couples to the base of the horizontal output transistor (sorry, I am doing this from memory, I don't have the techref in front of me). Do you get the 18kHz on the collector of the driver transistor? Are both transistors good? -tony
