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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?
Last edited by sylvania; 03-13-2015 at 04:38 PM. |
#2
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Horizontal line means loss of vertical deflection and vise versa. Check the caps first.
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Quote:
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.
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Jeff, WB8NHV Collecting, restoring and enjoying vintage Zenith radios since 2002 Zenith. Gone, but not forgotten. |
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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.
Last edited by rca2000; 03-13-2015 at 08:23 PM. Reason: mistake |
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Thanks that is what i thought, on the hunt again
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Audiokarma |
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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
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
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I think i checked that but will look again, strange thing day before ok next day no raster.
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#8
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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
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#9
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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.
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
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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..... ------------- Quote:
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Yes you can call me "Squirrel boy" Last edited by Username1; 04-09-2015 at 06:10 PM. |
Audiokarma |
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Quote:
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#12
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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.
Last edited by sylvania; 04-09-2015 at 09:02 PM. Reason: more information |
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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...... .
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Yes you can call me "Squirrel boy" |
#14
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Thanks I miss read
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#15
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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
Last edited by sylvania; 04-09-2015 at 09:25 PM. Reason: more information |
Audiokarma |
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