Mighty Monarch of The Air

[vts1134]

Originally Posted by Phil Nelson

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

Phil Nelson

It did.

[old_coot88]

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 ?

That's the very first thing I thought of too, until checking the schematic. If a burn-through happened there, it woulda zorched R89, the 470K resistor in series with the HV lead. He says R89 is OK though.

[vts1134]

Originally Posted by 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

Pin 5 is empty in the socket, no connection there. On my picture I should have drawn the connection from pin 6 to pin 8 AROUND the flyback instead of next to it. It wraps around the flyback but it is not connected to it. All of those connections read infinite impedance to ground by my meter.
R95 is actually reading around 3.6 ohms which is right at 20%. Possibly this should be changed but could that little fluctuation in tolerance possibly be the entire cause of the problem?

[old_coot88]

Originally Posted by vts1134

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

You're using the highest ohms scale, and it's reading open circuit, right?

R95 is actually reading around 3.6 ohms which is right at 20%. Possibly this should be changed but could that little fluctuation in tolerance possibly be the entire cause of the problem?

No, not a chance.

[vts1134]

Originally Posted by old_coot88

You're using the highest ohms scale, and it's reading open circuit, right? Now how about from the 1X2 filament loop to ground?

All connections on the 1X2 socket read open to ground.

[Phil Nelson]

Originally Posted by vts1134

It wraps around the flyback but it is not connected to it.

Yes, the filament winding just wraps around the flyback.

Phil Nelson

[vts1134]

Originally Posted by Phil Nelson

Yes, the filament winding just wraps around the flyback.

Phil Nelson

Is there a reason for this? Or is it just something that's done?

[bandersen]

Originally Posted by vts1134

Is there a reason for this? Or is it just something that's done?

That's how the power for the filament is pulled from the flyback. One turn is all it takes.

[roundscreen]

If the door knob cap and other parts in the high voltage circuit check good, I would look to see if the horz osc is way off frequency. It is possible that the fly back is sending too much voltage into the 1x2 tube and over dosing the tube.
Do you have a hi voltage probe? If you do, Check and see it the hv is way to high. 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. Btw, Nice set you have there. You have done a good job on it.
Ed

[vts1134]

Originally Posted by roundscreen

Btw, Nice set you have there. You have done a good job on it.
Ed

You have no idea how good that is to hear.

[old_coot88]

Originally Posted by roundscreen

If the door knob cap and other parts in the high voltage circuit check good, I would look to see if the horz osc is way off frequency. It is possible that the fly back is sending too much voltage into the 1x2 tube and over dosing the tube.

I've seen cases of the horiz. being miles off-frequency, but never saw (or heard of) it causing the fly to put out 'too much' juice. The HV is not the product of the sweep frequency but of the fast "fly-back" spike of the sawtooth.

Just wondering if maybe the second 1X2 could be bad. This'd be one case where it would be handy to have a SS stick rectifier to sub in there. oc

[vts1134]

Originally Posted by old_coot88

I've seen cases of the horiz. being miles off-frequency, but never saw (or heard of) it causing the fly to put out 'too much' juice. The HV is not the product of the sweep frequency but of the fast "fly-back" spike of the sawtooth.

Just wondering if maybe the second 1X2 could be bad. This'd be one case where it would be handy to have a SS stick rectifier to sub in there. oc

Where might one procure such a thing?
The new 1X2B that I have was brand new in the box for whatever that's worth. I'll see if some one else I know has a known good 1X2 to test with.

[old_coot88]

Have you checked the 1X2's filament for continuity? Here's the data page with basing diagram..
http://www.nj7p.org/Tube4.php?tube=1x2

[vts1134]

Originally Posted by old_coot88

Have you checked the 1X2's filament for continuity? Here's the data page with basing diagram..
http://www.nj7p.org/Tube4.php?tube=1x2

Filament has continuity.
After much thought I decided that this latest problem happened after I changed 10 tubes and 4 caps. I thought I would take a closer look at the items I replaced before the problem. Following the schematic to each cap I replaced led me to C62. C62 is connected to pin 3 on V17 and ground according to the schematic (as far as I can tell). Can some one confirm this? On the set it is connected to pin 3 and pin 7 on V17. I know I replaced lead for lead of the old cap and can still see a small amount of the lead of the old cap to confirm this. The old cap was one of the black beauties I mentioned that I missed before. I tested pin 7 and it is not connected to ground. Maybe I'm following some one else's botched repair? Or maybe I'm just misreading the schematic?
One other question. The schematic shows pin 7 and pin 8 of V17 connected to "Y" and "Z." There are some other connections on the schematic labeled as such. What does Y and Z refer to?

[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.