Silvertone 113/110.700

[mr_rye89]

Back on the subject of HV. I can draw a decent arc on the output of the flyback, but after the HV rectifier I can barely get anything. HV rectifier is good. Could the 500 pf 15kv doorknob capacitor be leaky and pulling the HV down? Or should I just stop being lazy/cheap and recap the horizontal section?

[leadlike]

I had similar symptoms on an Emerson the other day and it was indeed a leaky doorknob capacitor.

[mr_rye89]

I noticed the HV rectifier filaments are not lighting up. I tested the resistance of the secondary "winding" for the HV rectifier and its fine (0 ohms). The HV rectifier works fine in a different TV. So the filaments for the HV rectifier are getting no power. I can still draw a healthy arc off the flyback output.

I'll look to see if there's anything goofy with the flyback's core where the rectifier filament winding is.......

[damen]

Check and see if the filaments light with the plate cap disconnected.

[mr_rye89]

Tried that, Nope.

[old_coot88]

Try getting rid of the doorknobby. If the CRT has a decent enough aquadag coating it may not need it.

[mr_rye89]

Took the doorknob out of circuit, still no filaments

[Jeffhs]

I'm curious. How can you tell if the HV rectifier filament is glowing or not? These tubes almost always have 1- to 3-volt filaments (typically 1B3 in b&w TVs, 3A3 in color sets), so there is ordinarily no way to tell if the filament is glowing. (In other tubes with 6-volt filaments, for example, the filament will light with an orange glow if the tube is working as it should.) I would also think if there is any kind of visible glow in a tube with a 1-volt filament, there would be a problem somewhere in the filament supply and the tube, of course, would not operate nearly as well as it should, if it works at all. If the TV produces a bright picture with no distortion, the HV rectifier is working, whether or not the filament appears to be glowing.

Edit: I just read one of your other posts and read you had tried the tube in another set; as you stated, the tube worked well. This eliminates (or at least should eliminate) the tube itself as a possible cause of the trouble you describe. If the problem persists even after replacing the doorknob capacitor in the HV cage, it is almost certainly somewhere else in the HV supply, possibly the flyback. I don't remember that much about how flyback HV systems in televisions are supposed to operate (I had to give up my workshop over 20 years ago when I moved to an apartment, so haven't seen the innards of a TV set since then, except in photos here on VK) so this is about the best I can do.

I truly hate to tell you the flyback may be bad, but since you seem to have tried everything else, this is almost certainly the last thing that could be causing your problem.

[jr_tech]

Are you certain that the horizontal oscillator is operating and running reasonably close to the correct frequency?

Do you have an oscilloscope?

jr

[ChrisW6ATV]

Originally Posted by mr_rye89

The HV rectifier works fine in a different TV.

Are you able to see its filament lit when it is in that other TV set? As Jeffhs mentioned, sometimes it is hard to see the filament glow from a 1B3GT or other HV rectifier tube.

[old_coot88]

In a darkened room, the filament should be visibly glowing dull orange. That is, assuming you have a clear visual up inside the anode.

[Yamamaya42]

Are you still running it with all those old paper caps in it?
if so you you are lucky you are getting it to do anything at all! :O

[mr_rye89]

Mostly original caps. Hv rectifier is 1X2B. I wanted to see if I could get a raster before doing a recap job. And I’m pretty sure the horizontal is running……

[jr_tech]

Is that an “air arc” , or is the nut driver grounded?

jr

[mr_rye89]

Grounded, should I get a good air arc if the horizontal is happy? I get a teensy air arc now……

Perhaps the horizontal too weak to make enough juice for the rectifier filament and it’s just time to recap