Mighty Monarch of The Air

[vts1134]

Originally Posted by Phil Nelson

The parts list has an asterix next to C70. "Not used in all models." Also a note symbol and dotted line in the schematic.

Phil Nelson

We'll there you have it. I guess my model is part of the exception.

[jeyurkon]

Originally Posted by VintagePC

My understanding is we're talking about the one above his upper yellow arrow. The one you refer to is part of the horizontal circuit, whereas we're diagnosing the vertical

Thanks, that explains my confusion. That one is actually 0.25 uF, or would be if it were used.

I should have paid more attention and noticed that the discusion was about the vertical.

[vts1134]

I took an early day at work to spend some time on the set tonight. I also read through this entire thread a couple of times to come up with a game plan of tests for this evening. Here is what I'm thinking.#
I'm going to recheck the vertical height control selector.#
I'm going to check voltages on v13 and v14. I will connect my lead clips to the set and to my meter, then fire the set up for a measurement. After taking a measurement I'll remove power from the set and move on to the next voltage measurement.#
I'm going to disconnect both primary leads on my new t2 and connect them to the two leads on my variac. I'll fire the set up and turn up the variac to line voltage or robust deflection, which ever comes first.#
If deflection does not occur I will move on to OC's next suggestion of driving the coils directly with the variac. On this test I'm a bit hazy on. There is only one lead from the yoke on the vertical side. What would I do with the other lead on the variac?
After completing those test if I have time I'll move on to more.#

[VintagePC]

There is only one lead from the yoke on the vertical side. What would I do with the other lead on the variac?

The other side of the vertical is connected to ground according to the schematic (most likely chassis ground somewhere.)

you _SHOULD_ be able to connect the neutral side of the variac output (Be careful that you do really have neutral!) to the chassis, and then the HOT side to your coil wire.

HOWEVER, before you do that, double-check that your chassis is actually grounded or connected to line neutral. If your set has the possibility of a "Hot" or floating chassis voltage (i.e you do NOT read close to zero volts when measuring voltage from chassis to neutral in the wall plug), DO NOT DO THIS - it could trip your breaker!

Since you know the transformer is good though, if driving it with the variac produces no deflection, you can be almost certain the coils are the problem... and the test you're unsure about will produce little extra information.

[vts1134]

Taking off early to spend time on the set turned into run errands time I was able to do a voltage test on V13 and V14, however.
My results:
V13 according to the schematics should read- Pin 1: 170 to 40VDC. Pin 4: 6.3VAC. Pin 5:170-40VDC. Pin 6: -40 to -2.4VDC.
V13 actual readings- Pin 1: 51 to 20VDC. Pin 4: 7.5VAC. Pin5: 51 to 20VDC. Pin 6: -1.21 to -.97VDC.
V14 according to the schematics should read- Pin 3: 260 to 230VDC. Pin 4: 260 to 230VDC. Pin 6: 215VDC. Pin 7: 6.3VAC. Pin 8: 30 to 8VDC.
V14 actual readings- Pin 3: 350 to 300VDC. Pin 4: 445 to 230VDC. Pin 6: 295 VDC. Pin 7: 7.5VDC. Pin 8: 49 to 12VDC.

V14's readings are a bit high, but could those be within tolerance? V13's readings are low enough that I can't imagine they would be within tolerance. V13's readings on pins 3,4, and 8 change with the adjustment of V4a(the vertical size control). Schematics call for resistance of 2.5meg which is right what it metered to. I mentioned before that I wanted to change V13(a 6C4) but I haven't done that yet.

[Phil Nelson]

I would check resistors around and downstream of the oscillator, R65 and R66 especially, also R67 and R68 while you're in the neighborhood. You have partial deflection, suggesting that your oscillator is working somewhat, but its sawtooth is attenuated. You have already replaced obvious capacitors in that area. There ain't much left but resistors, so I would check those to eliminate 'em from the equation.

Also, C48 is the coupling cap for the oscillator. With a value of 4700 pf, I suppose it is a mica, but micas do croak sometimes.

Phil Nelson

[vts1134]

I tested R65-R69 previously and they all passed. I'll look into C48.

[old_coot88]

Any chance somebody could post the schematic of the entire vertical section? I re-read the thread to see if I'd missed it, but dint see it. oc

[Phil Nelson]

Here ya go.

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

Grid and plate voltages of the oscillator tube are low. It would be interesting to sub that tube, or even look at things upstream.

Phil Nelson

[old_coot88]

Arr. Now we're cookin'. First assuming the output transformer and yoke coils have proved good, I wouldn't worry about the oscillator just yet, but first prove whether the output stage is working or not. Just inject some AC at the control grid (pin 5) of the 6V6. No need to disconnect anything, since everything 'upstream' is high impedance and DC-isolated by C50. Just run a jumper from pin 7 (heater) to pin 5. That'll put 6.3VAC directly on the grid, which should give a few inches of deflection (and it should vary somewhat with the linearity adjustment). If it does, that would indicate the output stage is working, and the failure lies upstream in the osc. area.
oc

[vts1134]

Originally Posted by old_coot88

Arr. Now we're cookin'. First assuming the output transformer and yoke coils have proved good, I wouldn't worry about the oscillator just yet, but first prove whether the output stage is working or not. Just inject some AC at the control grid (pin 5) of the 6V6. No need to disconnect anything, since everything 'upstream' is high impedance and DC-isolated by C50. Just run a jumper from pin 7 (heater) to pin 5. That'll put 6.3VAC directly on the grid, which should give a few inches of deflection (and it should vary somewhat with the linearity adjustment). If it does, that would indicate the output stage is working, and the failure lies upstream in the osc. area.
oc

Should I get a few inches of deflection total? or a few inches more deflection than I have already, which is already a few inches?

[old_coot88]

Originally Posted by vts1134

Should I get a few inches of deflection total? or a few inches more deflection than I have already, which is already a few inches?

A few inches total, since all the grid will be "seeing" is the 6.3VAC. Also, before doing this, try grounding pin 5. You should get a flat line. Then do the 6.3 jumper trick. How does this deflection compare with what you already had?

[vts1134]

OC- Grounding pin 5 did indeed give me a flat line. Jumping pin 5 to pin 7 gave me a lot of deflection as you can see below. The two pictures below display the range I got from adjusting the linearity adjustment.





Very exciting to see something different! Also kind of interesting to see 60hertz through the second picture, which I only noticed on the picture and not looking at the set itself. Thanks so much to all of you for all the help again, I'm having such a blast with this!

[old_coot88]

Hey cool. Now in one fell swoop you've proved that the output stage, transformer and yoke are all good, and the failure lies back in the osc. area. Basic isolation technique 101.

[vts1134]

I spent some time looking over the schematic to get familiar with things down stream from the vertical output stage. I traced each connection from point to point on the schematic and on the set itself and found my first mistake. I had connected the secondary of T2 to the wrong place. I connected it correctly and got this.

I also found the the ion trap was a bit out of place so I tried to align it as much as I could by site. I also adjusted the vertical controls to see if I could get an aligned picture but the picture above is as good as I could get it. I'm not sure if you can tell by the picture but the bottom of the picture is brighter than the top, and the left hand side of the screen is brighter than right. Any ideas on where to head next?