Sylvania 336mu
 

I powered up this chassis today new problem, I have a thin bright line acroos the screen no picture, I checked HV its there my voltages to tube are ok, Have I lost the deflection circuit?

Horizontal line means loss of vertical deflection and vise versa. Check the caps first.

The "vice versa" condition (vertical line) cannot occur in modern TV deflection systems. The only way a vertical line could ever appear on the screen would be in a very old TV (pre-war to about 1950), if the set used an RF high-voltage system; the flyback HV system, used in all TV sets from the '50s on, is set up so that if the horizontal sweep fails for any reason, the high voltage to the CRT 2nd anode goes with it.

You are correct, however, as to the vertical sweep. Failure of the tube or of any of the components in the vertical sweep stages will stop the vertical deflection, resulting in a horizontal white line across the width of the CRT screen. Turn the brightness all the way down to prevent burning the phosphors.

You are correct as far as TUBE sets go....but in a SOLID STATE deflection system...it IS possible to get a no horizontal condition WITH a vertical line DOWN the screen...for a short time--before the H-out transistor WILL blow, from unbalanced loading without the yoke.

Thanks that is what i thought, on the hunt again

In some tube sets it is possible if the horizontal yoke is disconected most need the yoke to tune the circuit to work properly, but some can still muster a line

I think i checked that but will look again, strange thing day before ok next day no raster.

sylvania deflection loss
 

I am giving you a update and hope i am replying correctly, This set is Sylvania 336m. I am supplying chassis with 117v line load is 2.56 amps.I have sound and a horizontal line across CRT, I checked the voltage on tube 12AU7 which if I read the print correctly is the oscillator section. Pin number 1 on the photofact shows 235v, on that pin I am reading 333v.Photofact shows pin number 6 at 135v, my reading on pin 6 is 113v. This is with line voltage at 117v which the photofact refers to when checking voltages. This chassis has been recapped and new electrolytics, I checked the electrolytics again and they show good. After I had recapped this set I had deflection and then is slowly went to horizontal line only. Thank you

Don't worry too much about voltages within 20% of correct (such as the pin 6 reading) those should be within tolerance.

Which stage is the 12AU7 in? A horizontal line on the screen is a symptom of Vertical deflection failure...So you should be scrutinizing the voltages and components in and around the the Vertical multivibrator/oscillator, output tubes.

Here is a quick test that can clear the vertical deflection transformer and yoke (the most rare/costly parts). If you have a variac disconnect the primary of the vertical output transformer, and connect it to the variac. With the set on slowly crank up the output voltage of the variac, and if that line expands vertically before you hit max output, then your yoke and output transformer are functional....If the line don't expand disconnect the vertical winding of the yoke connect it to the variac, and repeat.

Really....? On the surface I think it would work.... But I can't see going above
20V..... Anywhere near max output with only the unit's fuse could put
2 - 3 or more amps into it.... Cooking it for sure I would think....

Have you actually done this....?

At the 20V I would be looking for just a small deflection, not full screen.....

-------------

A higher voltage on the plate usually means the tube is turned off.... not working....

.

Not direct to the yoke, but the primary of the transformer should be able to take it since the output tube should create a few hundred volts AC across it. The goal is not to hit max variac output, but rather to get 1-2 thirds deflection to confirm the transformer and yoke work....Once decent deflection is obtained more voltage serves no purpose.

sylvania deflection loss
 

The 12AU7 I am referring to is the horz oc and horz discharge section, I had thought the voltage being 100v higher on that pin was causing a problem elsewhere in the set, I will check the vertical section next. I know the Vertical output tube pins read correct voltage.

Not to be insulting, But you have been intermixing Horiz, and Vertical
issues, or tv parts. Just to be clear, look at the picture, and tell
everyone which line type you are having.... Then lets go on from
then......

.

Thanks I miss read

sylvania deflection loss
 

ok the Vertical section tube 12AU7 which is vert osc and vert disch pin 1 photofact shows 160v I read 112v. Pin 2 on photofact shows -74v, I read -12v. Now the vert osc side of tube 12AU7 pin 6 of photofact shows 05v I read 155v on pin 6. Pin 7 on photofact shows -74v I read -12v on pin 7