Mighty Monarch of The Air

[vts1134]

Quick question to all of you. Are there any tubes that if removed from the set would do damage to the set if it's fired up without them?

[vts1134]

Originally Posted by roundscreen

Another check may be to see if the crt is your problem. Put the anode connector in a plastic or glass cup, Fire up the set and see if the problem goes away.
Ed

Tried this and it's not the problem.

[Electronic M]

"X" and "Y" are probably tube heater windings on the power transformer, look around the power supply on your schematic, and you will probably find what they are connected to.

Tom C.

[Phil Nelson]

Yes, there is a separate filament supply (Y and Z) for the damper tube and kinescope (the other tube filaments are supplied by connecting to the X supply and ground):



I think I read somewhere that a damper is given a separate filament supply to reduce the risk of heater-to-cathode shorts, when its cathode is at hundreds of volts above ground.

The schematic seems to show that C62 connects to ground in some models and to the +255vdc source in other models:



A note elsewhere says, "Dotted in parts are not used in all models. When dotted in parts are used, points marked X are broken." In other words, that leg of C62 would connect either to +255vdc or to ground, depending on model.

Referring back to the first picture, the +255vdc source is separate, not the same as the Y filament source that connects to pin 7 of the damper. So, if I follow this correctly, connecting C62 between pins 3 and 7 is not right for either model.

Here is a bigger chunk of the schematic showing other dotted-in stuff:

http://antiqueradio.org/art/temp/Majestic1600.jpg

There you see that C61 is like C62, connecting either to +255vdc or to ground, depending on model. Parts R95, R97, and C71 are also dotted. Perhaps if you check how all those components are connected in your set (and whether R97 and C71 are even present), that will give a clue how to connect C62.

Phil Nelson

[old_coot88]

Thanx for chiming in there, Phil. I had formulated a post saying essentially the same thing, but you beat me to it.

One thing's still puzzling- he says C62 was connected to pin 7 of the 6W4. That would put it from cathode (pin 3) to heater (pin 7), which would make no sense...

unless....

...the floating heater is clamped to the 255V supply via pin 7.

Otherwise, C62 has gotta go either to ground or to the 255V supply depending on model.

oc

[CoogarXR]

I keep checking this topic to see- "is this the post to say he got it working?"

I've been on the edge of my seat... Great work so far, can't wait to see a picture on it

[VintagePC]

Originally Posted by CoogarXR

I keep checking this topic to see- "is this the post to say he got it working?"

I've been on the edge of my seat... Great work so far, can't wait to see a picture on it

's what I love about AK - the restoration projects here aren't just one person's work - everyone takes part and can't wait to hear of or see the end result when it works.

Occupational hazard too - this feeling is contagious...

Fingers crossed- we've got the champagne sitting ready

[miniman82]

If the doorknob isn't causing the arcing, it could be the socket itself. Have you checked it yet? Carbon tracking on HV parts can cause shorts from seemingly nowhere, so make sure you inspect the rectifier tube socket and replace it if you're in any doubt.

[vts1134]

Originally Posted by miniman82

If the doorknob isn't causing the arcing, it could be the socket itself. Have you checked it yet? Carbon tracking on HV parts can cause shorts from seemingly nowhere, so make sure you inspect the rectifier tube socket and replace it if you're in any doubt.

Interesting thought. I'll inspect.

[roundscreen]

VTS1134. Try turning down the horizontal drive control and see if the arcing goes away or calms down. If it is a tuning cap that would be counter clockwise but try turning it in both directions. The sides of the screen should cave in and the picture will loose brightness. I thought I saw a drive control in the schematic. Also do you have a signal going into the set? Is the picture normal and has vertical and horizontal sync? If you are going to keep working on vintage TV a HV probe is a good idea. At some point you may want to restore a color set and a probe is a must.

[miniman82]

Just rob it from a newer set. I get mine from BPC stuff, just cut the anode lead off the flyback and discard the HV cup.

[vts1134]

Originally Posted by miniman82

Just rob it from a newer set. I get mine from BPC stuff, just cut the anode lead off the flyback and discard the HV cup.

Bingo. Never thought of that, we throw tube TVs away almost daily!

[vts1134]

Update.
I've replaced the filament loop wire with 50kv rated wire. I've also got a third 1X2. Those haven't solved the problem. I also now have a high voltage probe and am getting some interesting readings. The 16GP4 has a maximum anode voltage rating of 14kv. I can't get the input voltage on the set over 95v before I am above 14kv on the anode. Anode voltages above 14kv is also when I start to have problems with the 1X2 sparking and glowing.
I've also adjusted the horizontal drive as per roundscreen's suggestion. Turning the drive up increases the anode voltage and subsequently makes the 1X2 spark and glow when voltage reaches over 14kv. As long as I keep the anode voltage below 14k I can run the set as long as I want with no 1X2 problems.
Any thoughts on why my anode voltages are so high with the set on 3/4 power? Sounds like this might be the whole problem, but what could be the cause?

[ChrisW6ATV]

Yes, I definitely agree that you have found the problem with the rectifier. Regarding the cause, I would test other voltages in the power supply and horizontal circuits with the AC input set at 90 or 95 volts.

[bandersen]

The maximum peak inverse voltage on a 1X2 is 15kv so I think you found the rectifier problem too.

Are you measuring the HV with the 16GP4 installed ? If not, it might be to high because there's no load.