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I'm sorry it may not be the right place to post this but i'm not familiar with CRTs and old electronics so... here's my question:

This crt made a loud noise so i opened it and found this when i tried to discharge it, and it seems that the anode has some treeing. Does that mean that it suffered breakdown or something?


closed as off-topic by Leon Heller, pipe, iMohaned, Voltage Spike, ThreePhaseEel Mar 18 '17 at 17:21

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the repair of consumer electronics, appliances, or other devices must involve specific troubleshooting steps and demonstrate a good understanding of the underlying design of the device being repaired. See also: Is asking on how to fix a faulty circuit on topic?" – Leon Heller, pipe, iMohaned, Voltage Spike, ThreePhaseEel
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  • 1
    \$\begingroup\$ Loud noise? Like a spark / arcing? Snap? Crackle? or Pop? \$\endgroup\$ – Misunderstood Mar 17 '17 at 18:35
  • \$\begingroup\$ If the arc occurred there, then cleaning off all that dust and dirt likely will prevent future arcs. Let it dry before plugging the TV back in. And while you're at it, blow the dust out of the rest of the set because it can block airflow and cause overheating. \$\endgroup\$ – Mike Waters Mar 17 '17 at 18:55
  • \$\begingroup\$ it's more like arcing \$\endgroup\$ – iMohaned Mar 17 '17 at 18:56
  • \$\begingroup\$ You are treading on extremely hazardous ground - high voltage (yes, with the power unplugged, still - the tube is a serious capacitor) and flying glass shards if you break the tube and it implodes. The narrow end is quite fragile. Please pay attention to learning about the hazards before diving right into one of these and hurting yourself through a lack of what used to be common knowledge. CRTs demand respect. \$\endgroup\$ – Ecnerwal Mar 18 '17 at 4:13

The large "hat" over the connection is supposed to be pliable, so that it seals against the glass and provides a long "creepage" path that's free of dust, moisture, etc.

The problem is that the plasticizers used in the rubbery material either leak out or break down over extended periods of time, leaving the cap either very brittle or "glued" to the glass — which seems to be what you have found.

Yes, the loud noise was probably an arc-over of some sort.

The best fix would be to make sure the tube is completely discharged. Use something sharp that can push directly through the insulating cap to the terminal at the center. Then, scrape off the old cap to the best of your ability and clean the glass with alcohol in order to remove any remaining contamination. Replace the rubber cap with a fresh one.

Only then will you be able to determine whether the high-voltage power supply was damaged by the arc.

  • \$\begingroup\$ It's easy to lever off the anode cap by pulling up and sideways on the cable. Once off, the CRT anode can be easily discharged to the aquadag or the springs/whatever that ground it. Yes, one discharged, all that 'fur' has to go, and it may be possible to re-formate the plastic cap with careful use of a heat gun:) If it's still arcing, the EHT supply is almost certainly OK. \$\endgroup\$ – Martin James Mar 17 '17 at 19:24

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