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CRT Troubleshooting - Blue Bleedthrough on black.


Nov 17, 2021
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I could use guidance on further troubleshooting a hidden fault that is leading me into circuitry and voltages I am not entirely familiar with. Given the voltages involved I decided it best to seek proper support before taking my most expensive tool, my multimeter, to it haphazardly. Below is the model, the symptoms it’s suffering, the steps I have taken, and my theory of where I need to go next with it. If someone could point me in the proper direction, my tools are limited to a high-quality multimeter, fine tipped Pinecil soldering iron, and a -mostly- similar Samsung service manual.

Curtis Mathes model CM 19022S
Circa 2001 - owner since 2004
Samsung based budget 19” CRT with Composite Stereo and RF inputs.

Symptom: faint blue phosphor activation across entire screen in a “trace pattern” zig-zagging from right down to left, wiping horizontal and repeating; stays fairly static, with a more subtle rolling “noise” across whole effect. Appears unaffected by any user or technician serviceable adjustment to Brightness, Contrast, Tint, or even SC

Steps taken:
1: replaced all large-dimension electrolytic capacitors with matching or slightly higher voltage/temperate tolerance capacitors
2: rotated neck-board trio of transistors to see if symptom changed color.
3: inspected main PCB and Neckboard for any solder defects; took advantage of opportunity to practice desoldering/resoldering most joins, transistors, IC’s as a matter of practice with my tools.

I can say image brightness and stability has improved and I even got a crash-course on convergence/purity upon discovering those rings were not factory cemented; but instead thumb-tightened. But the primary symptom remains.

I’m concerned this MAY be due to heater/cathode short, but until would be willing to use this opportunity to learn more about the circuit pathways driving the voltages to this mad-science in an over-sized bottle I’ve loved since child-hood.


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