5116+5D10 intensity problem

Yeun-Jung Wu


Today I dig out my 5116+5D10 to display signal from FG501 and FG501A. I used "channal addition" to display added signal from two oscillators tuned to nearly 7kHz sine wave. At equal amplitude the expected envelope was beautifully displayed on the screen. Switch to X-Y mode display a dotted Lissajous pattern. Read out and cursor all function as expected.

After operation about one and a half hour the intensity gradually decay. It was accompanied by the expansion of horizontal and vertical graticutes. Now one dotted horizontal and vertical division expanded to include four real inner CRT divisions. Read out information was pushed outside of screen. Pushing the "Beam finder" button display a image filled out the entire screen (save + Power on), instead of a scaled down version of display. The intensity of the pattern was barely visible. Weak wave forms were still displayed on the screen; mostly with a red LED warning: possible under-sampling.

I had tried to adjust intensity range R245 on A3 board with little effect.

Should I go further to poke the wave forms at 21 and 26A/B? Was the problem in Z-axis amp or HV (pin 2 of CRT socket)?
Q222, Q234, Q226 all located in a hard to reached region so I had not checked their status yet.

Any suggestions? Thank you in advance.

Yeun-Jung Wu

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