Mighty Monarch of The Air

[miniman82]

That's a lot of bombardment, I'd look for a short. You can temporarily remove the doorknob and see if that cures it, you won't do any harm to the set.

[vts1134]

Originally Posted by old_coot88

Holy mackrel. Possibly a dead short either in the doorknob cap or from the 1X2 filament winding to ground. oc

Maybe that's what was wrong with the problem with the other tube.

[VintagePC]

Originally Posted by vts1134

Fired the set up and got this.

Fired her down immediately. Is this normal? Just a burn off process or a symptom of another problem?

It can be a bit normal in POWER tubes... but you shouldn't see that in a rectifier. (Especially not that much- I assume that was a normal exposure.) Here's a 30 second exposure of the output tubes in my radio... and this was at a good volume for comparison.



To echo the other folks, look for a dead short. Keep the old 1X2 on hand-- it might still be good!

(EDIT: Ninja'd:

Originally Posted by vts1134

Maybe that's what was wrong with the problem with the other tube.

)

--> Though I do have to admit, that _is_ a very nice blue colour to see for real. Cameras don't do it justice.

[vts1134]

I'm sure glad my first project has had so many problems with it. Gives me more experience in what it's not supposed to look like on my future projects.

[VintagePC]

Honestly though, would you really have had as much fun, or appreciate the end result as much if you only had to replace a handful of caps?

For most of us nuts, the more challenging it is, the better - it's all that much more satisfying to wind your own coil and have it work than just drop in a generic replacement.

[vts1134]

R89 and R95 both read good. C66 is the doorknob cab, it is not shorted and removing it still gives the same results when I fire it up. Other components in the area are B3 (horizontal size control), C64 (horizontal sweep coupling), and T3 (the flyback). Any other components I should look at? I'm off to work but I'll be home early to spend some time on the set tonight.

[old_coot88]

There's a quickie way to verify whether (or not) the fly is putting out. Remove the 1X2 and using a well insulated screwdriver, bring the metal tip of the screwdriver close to the plate cap connector. You should be able to draw a hefty RF 'air arc' a quarter to half-inch long onto the screwdriver. If you get the arc, that tells you everything 'upstream' is working.

I was thinking maybe a hard-leakage path from the 1X2 filament winding to ground mighta developed, based on your earlier statement of hearing a sizzling noise. Just for the heck of it (with the set off), using the highest ohms scale on your meter, measure from ground to the 1X2 filament winding. It should read infinity (open circuit). If it reads anything at all, it would indicate an insulation breakdown that's lugging down the HV.

oc

[bandersen]

Perhaps the stiff wire that supports the HV lead going to the CRT has dug through the insulation and is shorting it out ?

[vts1134]

Originally Posted by bandersen

Perhaps the stiff wire that supports the HV lead going to the CRT has dug through the insulation and is shorting it out ?

Good thought but not the answer.

[vts1134]

Originally Posted by old_coot88

There's a quickie way to verify whether (or not) the fly is putting out. Remove the 1X2 and using a well insulated screwdriver, bring the metal tip of the screwdriver close to the plate cap connector. You should be able to draw a hefty RF 'air arc' a quarter to half-inch long onto the screwdriver. If you get the arc, that tells you everything 'upstream' is working.

Simultaneously the coolest and most terrifying test I've ever done. It's a yes on flyback output.

Originally Posted by old_coot88

was thinking maybe a hard-leakage path from the 1X2 filament winding to ground mighta developed, based on your earlier statement of hearing a sizzling noise. Just for the heck of it (with the set off), using the highest ohms scale on your meter, measure from ground to the 1X2 filament winding. It should read infinity (open circuit). If it reads anything at all, it would indicate an insulation breakdown that's lugging down the HV.

oc

Sorry for the ignorance but where can I measure/where is the filament winding on the 1X2?

One more thing. Even without the 1X2 in place I can hear the "voltage spitting" sound but unfortunately I can't get a visual on any arcing. I only fire the set up for a few seconds at a time, however, and even then not to full line voltage. If I can get confirmation that I can crank up to full voltage for a longer period of time- 15 to 20 seconds or so, maybe I can get a visual.

[vts1134]

I did a little drawing (I know don't quit my day job!) of the area in question. It differs a little from the schematic. I'm not sure if the answer is in there but here it is.

[Phil Nelson]

The schematic shows pins 5 & 6 connected to a loop on T3, the flyback transformer. That is the filament winding that Bill mentioned. Pin 8 connects internally to pin 5, so either of them could be used for this purpose. If the 486K resistor in your diagram is R89, then your hookup looks normal.

Do you see anything at all connected to other pins on the 1X2 socket? Pins 3 and 7 are not used for anything, so they would be free to use as tie points for unrelated stuff, although I don't recall seeing any such things on a HV rectifier socket before.

Phil Nelson

[miniman82]

My money is still on a shorted doorknob, if the filament winding on the flyback were arcing you'd likely see that as well as the intense glow from the rectifier. I say it's time to sub in a doorknob cap.

[Phil Nelson]

I thought he had the same problem when the doorknob cap was disconnected.

Phil Nelson

[vts1134]

Originally Posted by miniman82

My money is still on a shorted doorknob, if the filament winding on the flyback were arcing you'd likely see that as well as the intense glow from the rectifier. I say it's time to sub in a doorknob cap.

Shorted to ground? It doesn't read shorted. I don't have a capacitor tester so I can only test if it's shorted.