Mighty Monarch of The Air

[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?

[roundscreen]

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

Dug out this Zenith { Chassis14Z33 } from the B@W room and connected the HV probe to the to the anode of the CRT. I picked this set because it has a vary stable tube horizontal oscillator/output circuit and a coil for the horizontal hold control. Turned on the set and let it warm up, With a normal picture the HV reads 19kv on the probe. Then I turned the horizontal coil one and a half turns counter clockwise. The picture went out of sync and the HV went up to 22 KV. What else was interesting is when I turned the coil one more rotation counter clockwise the HV went back down to 19KV and the picture was a horizontal mess. This proves that there is a direct connection between the horizontal oscillator and the high voltage. I guess I just do not know how to explain the problem properly. All I know is I have seen this type of problem before in the 1950"s set's and they are hard to track down. Also the horizontal circuits are not as stable in a 50's set as the horizontal circuit in a 1969 zenith.
I am not a big fan on installing solid state diodes in place of a diode tube. I tried it once with a ctc 15 chassis damper tube and it increased the horizontal output tube current. Plus it looks funny on the chassis.
Ed

[old_coot88]

That's an interesting observation, Ed. To tell the truth, I had never tested the correlation between sweep frequency and HV level. But it stands to reason that changing the sweep freq also changes the duration of the retrace/'fly-back' spike from which the HV is derived via resonance (or near resonance) with the secondary winding (the 'tire').
But as you demonstrated, there's only a moderate peak as you tune through it, not a continuous ascent.

Re. the SS stick, I was referring to the HV rectifier type, not a damper. Replaced enough of those in CTC-22s. Gaak. oc

[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?

[old_coot88]

Originally Posted by vts1134

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

Oh yes indeed. The horiz. oscillator. If for any reason the H.output tube loses drive, it loses the negative bias voltage* on the control grid (G1). The plate current goes through the roof and if there were no fuse the output tube could be destroyed in short order, possibly cooking the fly also. That's why there's usually a fuse there for protection.

Removing either of the vertical tubes would kill vertical sweep, which could burn a line across the screen if allowed to run that way. oc

*This voltage is developed by the G1-cathode diode action rectifying the drive signal.

[vts1134]

The reason I asked is I thought I would check back through the tubes to make sure I didn't mix some of them up when I reinstalled all of them. I noticed two things. V10 is a 6AT6 on the schematic and I have a 6AV6 installed. I mentioned this before and was told it was ok but thought I would mention it again. V15 (the horizontal output) on the schematic is a 6AV5GT and I have a 6AV6GA installed. Are these interchangeable or is this no good? Also I replaced C40 with a .022mf cap because that is what the capacitor list called for, but the alternate schematic (which is actually what I have) calls for a .002. Is .022 too much for a replacement? If the horizontal tube isn't the whole problem in a nutshell (I'm sure it's not, that would be too easy), I think I'll look back through the set and make sure I didn't replace other caps with the wrong capacitance because of the parts list being different from my set.

[VintagePC]

The 6AV6 and 6AT6 have identical specifications and pinouts.

Originally Posted by vts1134

...schematic is a 6AV5GT and I have a 6AV6GA installed.

A quick google shows me that the filament pins for these two tubes are not the same, so immediately I would say they are NOT compatible. It also looks as if one is a 7-pin tube and the other an 8-pin tube.

Can you trace the 6.3v filament line to the pins on the socket? The place they come out should indicate which tube is correct.

6AV6 specs - Filament pins 3 & 4
6AV5 pinout - Filament pins 2 & 7