Quote:
Originally Posted by Retro-guy
Well at this moment I don't have a spare one but the DY87 in the set seems to be OK ALMOST LOOKS LIKE NEW ...
it probably has bad EHT regulation,what components can I check ???
Also where can I found some lecture on how these things work,so I would know a bit more what I'm doing ??
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A tube can LOOK PERFECT and BE COMPLETELY DEAD....However if it looks dead (white getter, hole or crack in the glass, etc) it is dead. The only sure test of an HV rectifier is to get another HV rectifier and try it in the set. No tube tester made comes close to testing HV rectifiers under real world application conditions.
Also there is almost certainly NO HV regulation circuit in that set. Usually they design the horizontal deflection system, flyback, and HV rectifier system to produce varying, but acceptably varying HV output. However if the HV/horizontal deflection system is loaded beyond design (as I suspect yours is on the edge of, since increasing the brightness pushes it over the edge), or the oscillator/output is not preforming correctly it will vary outside the acceptable range.
There have not been lectures on this subject in decades. You can find some TV troubleshooting videos on youtube (Banderson has many good videos) which may be helpful, but you are best off getting some TV servicing books off the internet, and reading them. Also google searching this forrum and others like it will dig up some good info on horizontal troubleshooting. Unless you can find someone with the same set and issue the info will be general, and possibly not completely apply to your set.