Re: 7613 Mainframe - Readout problem


Harvey White
 

If I remember the threads properly, the thermal compensation (dancing readouts) fixed a small wobbling problem.  This sounded like a much larger deviation, and the picture I was thinking of was, say, the character height or more (in both X and Y) rather than a fraction of it.  I have seen the readouts vary, but that was when the vertical amp had been overdriven.  Reduce that, and that particular wobble went away.

Very few designs are completely immune to power supply variations (unless great care is taken, IMHO, but I'm not an analog expert). My thought was that if power supply ripple is large enough, then that can couple to the output voltages, and make the readout (and all else, I might add) wobble on the screen.  If it's JUST the readouts, and the rest of the screen is steady (trace, hor sweep, etc.), then I'd be looking for another problem.

Harvey

On 1/4/2021 7:53 PM, teamlarryohio wrote:
and I must be thinking of another 7K frame as I couldn't find it in the manual I have. It's also been called thermal compensation, or it may not be there on this model. But the symptom was dancing readouts, usually
moving about as high as one of the characters. I'll keep looking.
-ls-




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