I have this monochromatic chinese television largely manufactured in the past decade, marketed under several brands (Coby, Curtis, Precision, etc). This one in particular have a external AC DC converter of 1.6A and 12v and AV out. His cover is like this one but silver.

In this photo as you can see, it shows several horizontal black lines along the image vertically expanded. I already opened it to clean (had small cockroaches living in with his feces). This photo was taken while plugged in with a alternative smaller and lighter ac dc adapter (1.5 a 12v). The original power adapter seems to be faulty, because in addition of this lines the screen becomes unstable, as if closing.

I wonder if someone could give me a answer or clue about this problem. Thanks.

Chinese CRT 5.5" horizontal black lines

enter image description here

  • 3
    \$\begingroup\$ It almost looks like the vertical deflection amplitude is much too large - it appears that we can see the individual, interlaced horizontal scan lines with the lines getting closer together towards the bottom - a sign of non-linearity. As usual, check for failed electrolytic capacitors around the vertical output stage / IC. \$\endgroup\$ Nov 3, 2016 at 0:54

1 Answer 1


The main board had some opaque solder. I just heated those to the melting point and now the TV displays the image with correct deflection amplitude.

enter image description here enter image description here

  • \$\begingroup\$ now you can use that flyback red wire to fry the Brazilian cockroaches ;) if you decide to retire the set. \$\endgroup\$ Nov 11, 2016 at 5:00
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    \$\begingroup\$ the expanded vertical indicated excessive vertical sweep voltage slew rate \$\endgroup\$ Nov 11, 2016 at 5:06
  • \$\begingroup\$ The cockroaches where four (very stealth ones), 3 crushed in flight and one fugitive. Brazilian... You saw the Globo logo for sure. \$\endgroup\$
    – K. Márcio
    Dec 2, 2016 at 16:06

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