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.

Horizontal line means loss of vertical deflection and vise versa.

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

The "vice versa" condition (vertical line) cannot occur in modern TV deflection systems.

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.

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.

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.....

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

sylvania

Join Date: Feb 2015
Posts: 12
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

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

.

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.....


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.

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

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

If you can, please post the vertical circuit section of the schematic . That will help us see possible causes of the problem. You have replaced all caps that are not micas or ceramic in the circuit which is good...But have you tested the vertical stage tubes, and the resistors in those stages? If not, then that is the first step to take in moving forward.

Yes I checked the tubes and resistors that were out of tolerance replaced. I hope the attached file helps. I know its hard to diagnose something over a forum.The image cut off tube identification on right is 6L6GA tube on left is 12AU7

this is the continuation of schematic from the vert osc transformer

If you have confirmed the vert output stage transformers are ok, simply
by checking the resistance across the windings that are printed
in the schematic, then it's possible the osc is just not running....
Don't forget the vert. yoke winding too...

The timing cap and resistors with the red dots are pretty critical,
you should be sure these parts are in good shape. New or
at least checked, and you know they are good... and correct values.

Do you have plate and screen voltages on the vert output tube...?
Around 300V ???

Also the vert lin. control pot, and that r111 I think it is that goes to
ground after the pot, please check it too....

.

Yes I had over 300v on Vertical output tube will check again what you show. I know oscillator is not running I can not hear it.Thanks

The vertical buzz is most often caused by the output transformer. I'd do the variac test on the output, then if it shows deflection go back to the oscillator.

If you're squeamish about the variac test, then here is another idea connect pin 2 of the 12AU7 to the non-grounded heater line through a large film cap (something like .047 to .47 should work) and see if you get any deflection. If you do it proves the output stages are working, if not then you need to work on the output stages first.

Everything before (read left of) C87 should be ignored for now. That stuff is part of the synch separator, and you should have vertical oscillation and deflection even if C87 were to be cut out of the circuit.

Thanks Tom I will do that, I checked everything Squirrel Boy suggested everything was to spec.I checked the deflection coil vertical and horz ohms were to spec.

Tom, I did as you instructed jumping the pin 2 no deflection

Okay that tells us that there is no functional signal path between the grid of the second stage of the 12AU7 osc tube and the yoke which is a problem...Since if we assume the oscillator is working (or is later made to work) in the current state of the circuit any osc. signal there is not able drive the yoke as it should.

Try pin 5 on the output (the grid). This test is supposed to be a signal injection/ substitution test. It uses 6.3V@60Hz from the heaters to approximate the oscillator drive signal (which is assumed to be absent). This signal injection may not yield much deflection, and it will not be synched or linear, but it should let you know if the output stage is working. If there is no deflection achieved from driving the grid of the output tube, then you will want to do the variac vertical output transformer drive test I outlined in a previous post since either the trouble is at the tube or in the transformer/yoke system if grid drive does not yield deflection.

If you have ever trouble shoot a AA5 radio with no reception problems using a RF-AF generator, then you can think of this as the same basic idea only with different signal characteristics.

Tom I found the problem, I kept looking at a resistor from the vertical output transformer that had been replaced in the past thinking it seemed small for the load 315v, Because my voltages were wrong in that area.I checked the photofact and sure enough it was supposed to be a 3300 ohm but a 330 ohm had been inserted, I replaced it and my deflection came back.When i got this set I never had a picture because CRT was bad.I have a replacement CRT but it has electrostatic deflection.

Are you SURE the tube is bad? Likely it is just ASLEEP...after many decades of non-use. Unless it has gone to air--I would NOT give up on the tube yet. Give the fil. about 7.5 volts for maybe 10 mins...and see if that wakes it up some.

I have repeatedly stated and will continue to do so...at LEAST 2/3 of old CRT's I come across are at least uesable. This includes a 7JP4 tube, and a predicta 21" tube I recently acquired. It is not perfect....but IS useable. both emissions and cutoff are good--after a wake-up. lfe test does NOT hold long though...but that may improve after time.....and good 21" predicta tubes do NOT come along a dime-a-dozen.

They are NOT makin 'em anymore--NOR rebuliding them either--AFAIK--so we MUST do our very best--to use the CRT'S we come across.

I put this on my 465 for a day it barely raises the needle on emissions and when I found this set it had a brightener on the tube. I would love to have a new one for sure. The Magnavox tube I have has good emissions same voltage it is electrostatic deflection instead of magnetic.I am going to hang on to the old CRT for a while and hope some day it can be rebuilt somewhere.

What tube # is it? I might have something here in somethg..

Tube is 27RP4

It has to be this resistor..... in the pic attached....
I almost included this one in my list to check because of
your grid voltage on those two tubes..... But I didn't
because my book made that timing cap just look more like
a better starting point......
Sorry.....
Sorry I was out for most of the afternoon.....

Good to see you got it working ! !

.

Thanks for help, I have to make adjustments to video and its pretty messed up great sound. Can not get picture to focus enough to see it clearly

I have got the picture on a test CRT, seems the picture not very bright.Have I got used to new LCD tv's and forgot how much dimmer pictures were on old B&W tv?

I don't have a feel for the relative brightness, but the max available brightness depends on the amount of HV you have and the CRT emission capabilities (ie how good the CRT tests), and how well the circuits driving the neck are working (and position of the ion trap if present). On most sets made after 1952 you should be able to watch the set in a sun lit room (pix may not be optimal in this case) as long as the sun is not directly shining or reflecting onto the screen....Less brightness than that indicates significant miss-adjustment, wear, or correctable defects.

It looks like you have very weak contrast. Is the contrast control maxed and have you adjusted the AGC control properly?

I have the contrast turned way down, it washes out the pic if I go higher. The AGC pot does not seem to be working because when I adjust it I see no difference,

If you crank the AGC from min to max you should go from blank raster to weak contrast to strong contrast to wildly excessive contrast/loss of synch to negative video and or useless chaos on screen. If you don't have that then the AGC circuit is not properly functioning.

More contrast should not wash out the picture, less should. More should make the darks darker relative to the brights areas. The brightness control should normally be able to washout the image when maxed out.

Have you ever put that test CRT you're using through a proper CRT test using a CRT tester? If it is in bad shape it could be contributing to things.

I have the contrast turned way down, it washes out the pic if I go higher. The AGC pot does not seem to be working because when I adjust it I see no difference,

Hi !

Before going into any further guessing about a possible cause of your problem.....
I think we should clarify what you are seeing..... You say you have the
contrast turned way down, (to the left) but to turn it up, washes out the
picture.... To me washing out the picture means almost no contrast, as if
the picture were almost all gray, no sharp black and white....

This action is almost the exact opposite of what we expect when turning
either the contrast knob to the right (up) or turning the AGC knob up.....

Turning either of those knobs should produce an almost "overloaded"
picture, too much light for the bright areas, and too much dark for the
dark areas.....

When you turn the contrast "up" would you still say that the picture gets
even less contrast...?

.

What I am seeing is if I turn contrast up (making it brighter) it washes out picture.If I darken it (less bright) I can see it clearer. The AGC does not seem to effect picture adjusting to right or left. The test CRT was supposed to be new old stock and I tested it and it showed good emission. I do think the AGC circuit my not be functioning properly very little response from adjustment on back of chassis.

Ok, well the AGC is a kind of Automatic signal amplifier adjustment, so with
no response from that control, you most likely have - or possibly have some
signal loss along the IF section..... But before we go there, what is the quality
of the sound....? Good full tone, loud, or is it also kind of washed out, and
have some noise in it.....?

First, you should leave the set on, and locate the tubes in the tuner, and IF section
and first, second Video IF and wiggle these tubes in their sockets, tap with a wood
stick the circuit board, or chassis near these tubes, and look for any noise, or
jumping in the picture..... Possibly a momentary better picture....

.

You sure you don't have the brightness and contrast controls mixed up?

Contrast should not change the average brightness.

I could of done that, I am using sound control pot to make it brighter which washes out most of pic i can still see it but very dim so I turn brightness all the way down. Contrast adjustment helps a little.Definitely AGC not responding I can turn it all the way right or left just get a little flicker at end of travel of pot. I have very good sound quality. Possible AGC
pot is bad it feels like it has no resistance when turned.

I could of done that, I am using sound control pot to make it brighter which washes out most of pic i can still see it but very dim so I turn brightness all the way down. Contrast adjustment helps a little.Definitely AGC not responding I can turn it all the way right or left just get a little flicker at end of travel of pot. I have very good sound quality. Possible AGC
pot is bad it feels like it has no resistance when turned.

Is the 'sound control' still wired as a sound control or has it been substituted in another circuit?

If it is still wired in to only the sound system, then that behavior is both a significant problem and a clue......A large number of sets used what IIRC is referred to as stacked B+. Basically they connect the audio output plate to one of the highest B+ rails and use the tube as both a power amplifier and a power supply voltage divider resistor. The tube draws a fixed range of current (and variations within that get filtered out) and has a fixed plate and transformer impedance so it acts like a resistor. A lower B+ rail likely is supplied by the cathode of the audio output tube, and that rail likely feeds the video output tube, brightness control, and possibly the AGC circuit. If the audio output and driver circuits are not working just right then it can upset the cathode output voltage of the stacked B+ and disturb the circuits driven by the lower voltage rail it supplies....Troubles in the circuits driven may also cause problems. IMHO before you go after the AGC and brightness/contrast issues it would be wise to fix the 'sound control'/picture interaction (assuming the assumption made in the beginning of this paragraph are correct).

What he said....... Yah!

.

Thanks

I guess it was cheaper to wire the sets that way out the door more production at lower cost.So it would be best to supply a different path to supply voltage to that section.I could understand what a load is being put on that tube.

Stacked B+ ain't a bad thing and worked well (otherwise it would have been a short lived design), but it is a bit more involved to trouble shoot than a traditional resistor based B+ divider.

Stacked B+ ain't a bad thing and worked well

You're making use of energy (some going to the audio speaker) that would have been wasted as heat in a power resistor. And the audio tube acts a little like a voltage regulator, after some filtering to remove audio.

I was reading post from Electronic M. Checking my audio output tube 6W6GT is shows immediate short on my tester but under load on tester it is showing in good range, this could be some of the problem with set. I had checked these tubes twice before.Guess it went shorted under load.

The set could be damaging the 6W6, or it could have just been a problem tube that got worse from use. I'd look for voltages out of speck on that tube. One thing to beware of is autobias on the tube (don't know if it is used in your set or stacked B+ sets, but suspect it is). If it is off the tube could be conducting too hard and get worn out prematurely, or conduct too little and have other issues.

Autobias basically uses a lowish value cathode resistor to 'ground' (in your set its a lower B+ rail) and connects the grid to the 'ground' through a high value resistor. The resistor is chosen so that if a specific current flows through it it will create a voltage difference between cathode and the grid that makes that current flow....Basically it's a feedback loop with all static values dependent on the cathode resistor value (assuming no defects elsewhere).

One thing comes to mind assuming a modulated channel with no sound or significant noise if the 'sound control' is volume and drives the grid of the output, but is isolated from that grid with a cap the cap may have failed and the control may be skewing the no sound bias of that grid outside of the designed range.

I checked voltages and I suspect that is causing wear on tube. Sams shows pin#3 is supposed to be 150v my reading is 287v. Pin #4 Sams shows 140 my reading is 274v

Audio output tube voltage is wrong, Pin 8 shows 125v which checks correct. But on pin 3 I have 287v Sams shows 150 and pin 4 I have 274v Sams shows 140.What would cause this? I have checked resistors and wiring and can find nothing wrong or out of spec any ideas? And this is set at 108v if I raise it to 117v I am getting over 300v on these pins. On pins 3 and 4 shows large dot Sams say this is measured from 125v line

what are 5 and 8 voltage? the screen and plate are prob high due to a dead tube or incorrect bias (5 and 8).

What is the voltage on the 125V line? There are a few possibilities that come to mind....Such as the audio out transformer could have a shorted primary, or the tube could be conducting much less than it should be (which could be caused by a few things).

I checked pin 5 voltage is 105v pin 8 122v my 125 volt line is 132v.I checked this tube 6W6GT it shows good no shorts. the old one had a short. I have a very dim picture and sound is ok some interference using my DVD player I can tune most of it out with fine tuning.

I will try to make this clear as I can, The audio tube 6W6GT pins voltages are wrong. I have over 300v on pins 3 & 4 Sams shows It should be 150 & 140v. Pin 8 Sams shows 3v I read 125v. Pin 3 Sams shows -11 I have + voltage on that pin. My audio was not sounding clear until I lost high voltage while troubleshooting voltages then it cleared up, so the high voltage was causing interference with sound. Upon checking why the high voltage quit I found the two damper tubes 6V3A and one horz output tube 6BQ6GT went bad. I check voltages on all other tubes and they were to spec and checked resistors have not found but a few out of tolerance. I had a dim picture and sound until high voltage quit, but as time went by picture got worse. Now have sound only. Until I get voltages correct on tubes what is the best way to protect the high voltage section? I see a lot of different theory's on how to protect the high voltage section.

is there anything in the sams legend about the large dot next to the voltage readings?

Sams says large dot reading taken from 125v line, I have 125 volts on that line.

so when you read those you are reading from the pin and the 125v line NOT the pin and the ground, correct?

Yes that is correct, I assumed that was what I was supposed to do.

Well i found part of problem, a resistor was going open when warmed up. Now try to figure out what happen to HV section.

I will try to make this clear as I can, The audio tube 6W6GT pins voltages are wrong. I have over 300v on pins 3 & 4 Sams shows It should be 150 & 140v. Pin 8 Sams shows 3v I read 125v. Pin 3 Sams shows -11 I have + voltage on that pin. My audio was not sounding clear until I lost high voltage while troubleshooting voltages then it cleared up, so the high voltage was causing interference with sound. Upon checking why the high voltage quit I found the two damper tubes 6V3A and one horz output tube 6BQ6GT went bad. I check voltages on all other tubes and they were to spec and checked resistors have not found but a few out of tolerance. I had a dim picture and sound until high voltage quit, but as time went by picture got worse. Now have sound only. Until I get voltages correct on tubes what is the best way to protect the high voltage section? I see a lot of different theory's on how to protect the high voltage section.

so when you connect the postive of your meter to pin 8 and the neg to the 125v line you get 125V so you are getting a voltage drop 125v across that 68 ohm resistor?

yes that resistor tested good with set off after power applied for a few minutes the resistor was open.I never had that happen before. I thought once it was open it stayed but this one acts like a current limiter in reverse. Now have to trouble shoot high voltage and interference with sound. I replaced that resistor and voltages returned to near the specs shown in the Sams. Doyou think that resistor would of taken out both damper tubes and a horz output tube? They tested good before this happened picture was dim, then high voltage quit, I found those tubes showing bad.

without a full schematic its hard to say if a defect in the 125v supply from the stacked b+ was used somewhere in the horz sweep circuit.

So you replaced the 68 ohm resistor in the cathode circuit of the audio out and all the voltage are reading correct for the audio out tube now?

Loss of HV generally starts with subbing new tube, horz osc, horz out, damper, and HV rectifier, and if used HV regulator.

I prefer tube subbing over tube testers, esp in sweep circuits.

I generally will uses a my BK 1076 analyst next to start with a plate drive signal to clear the damper/yoke/fly, if that works then I move to the grid drive signal, that will check the horz out tube, if that works then move on to the horz osc tube and check for voltages at the plate and screens.

Dave, thanks that is what i will do, thought it was strange that I had three tubes go bad all at the same time, Yes my voltages are with in 20% of Sams specs on that tube.

I was checking the chassis voltages and the high voltage shut down, the damper tubes 6V3A, Horz Output tubes 6BQ6 filaments are on. The HV rectifier tubes (2) 1G3GT filaments are not . Could this be fly failure and what is the safest way to check tubes in the HV cage without damage to a circuit or myself?:scratch2:

tape a neon light to a plastic straw, hold it near the plate lead of the horz out, it should light up when near (1/2") same with fly, anywhere near the fly and it should light up.

give it a try

I took off the cap to the HV rectifier tubes and removed them, checked the dc voltage from the fly I am measuring 400v. Both tubes not working (1B3GT) have checked other voltages all tests normal so far. Still no HV to anode lead.

If anyone out there would like to know, here is up date. checking thru this chassis again found the regulator tube 40B4 filament burned out. Waiting on replacement and see if that was the problem.

I finally have this set working, but I can not get picture to fill out screen on right side as seen in picture and it seems the picture is not as sharp as it could be, I have the picture pot adjustment maxed out ,adjusting the the picture pot I run out of adjustment.

Anyone know if the Halolight florescent tube can be removed from the front of a wood cabinet with out having to remove the CRT? I have a book showing one removal, but it only shows it being removed from a metal cabinet thru the front