Looked at the 6AL5 it was not lit.
Fixed the socket and it lights now.
Check the resistors leading to the Horz Osc they are good.
Still the same problem.
I did get my scope out of storage. Don't know what I am
looking for using it but thought it might help.
What does the signal look like that leaves the Horz AFC
and what does the signal look like at the input of the
Horz Osc?
Tom Guest
I would have thought you found the problem when the tube wasn't lit and you fixed that.
Schematics quite often show waveforms. Depending on where you look you will see sawtooth or pulses at a frequency of 15750. I could send you some waveforms but they wouldn't be exactly the same for your TV.
Norm
: Hello
: Looked at the 6AL5 it was not lit.
: Fixed the socket and it lights now.
: Check the resistors leading to the Horz Osc they are good.
: Still the same problem.
: I did get my scope out of storage. Don't know what I am
: looking for using it but thought it might help.
: What does the signal look like that leaves the Horz AFC
: and what does the signal look like at the input of the
: Horz Osc?
: Tom Guest
My scope too old to have freq markings. What I see on the output of the Horz AFC is a sawtooth.
I see the same type on the input of the Horz Osc.
I have not replaced 2 paper caps in this section. But with the meter
they show above 2 meg (finally ran out of caps).
Just thinking about the Mods that are in the Horz Osc section.
Could they be causing this???
At this point I don't know even what questions to ask.
Any help would be great.
Thanks in advance
Tom Guest
I know you mentioned mods before but I figured they were there before and the TV did work. You may be right, maybe it didn't work after the mods were added. Try going back to the orignal, nothing to lose.
Sawtooth would be a reasonable signal from the sync circuit. The frequency is right as the horizontal oscillator is close.
What you found, 6AL5 not lit, was a problem that, when fixed, should have made the TV work.
: Hi Norm
: My scope too old to have freq markings. What I see on the output of the Horz AFC is a sawtooth.
: I see the same type on the input of the Horz Osc.
: I have not replaced 2 paper caps in this section. But with the meter
: they show above 2 meg (finally ran out of caps).
: Just thinking about the Mods that are in the Horz Osc section.
: Could they be causing this???
: At this point I don't know even what questions to ask.
: Any help would be great.
: Thanks in advance
: Tom Guest
Can't seem to get a brake with this TV. Saw it has not lit and thought that would fix it.
I will go buy new parts tommorrow and see if the 2 caps are the problem.
I will draw out the mods and post on where I have 2 .1uf caps to ground.
Thanks for your help.
Tom
Tracked down the mods they are 2 resistor value changed in the Horz Osc(12AU7).
Where there should be 122k there is a 33k it leads from the Horz coil to the width control.
The other should be a 10k there is a 4.7k and it also goes the same width control.
How much voltage DC would you expect to be on the input to the Horz Osc from the Horz AFC?
I get about -.4vdc is this right?
Any other ideas on this one? I am almost stumped.
Tom
Those resistor values alone shouldn't be the problem. You had mentioned earlier an additional .1 mfd cap?
Each TV would be different but a DC level of .4 volts would be reasonable if the signal was measured at a grid of the horizontal oscillator. Can you scan this portion of your schematic? I may already have it but right now am not sure where..
The problem is in the sync circuit and the way it connects to the horizontal oscillator. You have replaced caps and checked resistor values..
Norm
: Hi Norm
: Tracked down the mods they are 2 resistor value changed in the Horz Osc(12AU7).
: Where there should be 122k there is a 33k it leads from the Horz coil to the width control.
: The other should be a 10k there is a 4.7k and it also goes the same width control.
: How much voltage DC would you expect to be on the input to the Horz Osc from the Horz AFC?
: I get about -.4vdc is this right?
: Any other ideas on this one? I am almost stumped.
: Tom
The cap was a wild goose chase.
It turned out to be part of the Horz Osc But placed far from it's orginal location.
Have checked most resistors in Sync and Horz Osc.
Most caps have been replaced. Just returned from Radio Shack with more to complete these sections.
Living in the 80's have no scanner. Can I mail or fax it to you?
Will replace the remaining caps and check resistors.
Tom
Hopefully the caps will fix the problem. There can't be many left in the circuit. Some circuits do have resistors that should be closely matched, 5% is ok.
If I can't find the schematic, mailing a copy might be a good idea. That way I could scan and forward it to others.
Norm
: Hi Norm
: The cap was a wild goose chase.
: It turned out to be part of the Horz Osc But placed far from it's orginal location.
: Have checked most resistors in Sync and Horz Osc.
: Most caps have been replaced. Just returned from Radio Shack with more to complete these sections.
: Living in the 80's have no scanner. Can I mail or fax it to you?
: Will replace the remaining caps and check resistors.
:
: Tom
FIXED THAT PROBLEM !!!!!!
Feel stupid but it was the Horz Osc being 5 turns off!
I have only moved it about 1/2 turn when I adjusted it. Might have been a harmonic?
I was begining to think I was losing it.
Now on to the next problem.
Have a locked Picture and white retrace line thru the whole screen.
Contrast is low (deosn't seem dark enough) but brightness is fine.
Screen jitters some.
Any guess on what area to look in next.
Tom
Great!
The retrace lines show because the brightness is turned up high. Contrast being low can be Video IF's but is usually the Vidio Amp circuit. What is your Video Amp tube? Someone recently mentioned having a 6AU6 for video amp, 6AH6 would be better. The contrast control is usually in the cathode circuit of the video amp. Be sure you have high plate voltage on the video amp. The closer the cathode comes to ground, the more contrast.
The picture tube emission could also be low. If it is, detail in faces will wash out. These older TV's may also require viewing in a darker room.
Norm
: Hi Norm
: FIXED THAT PROBLEM !!!!!!
: Feel stupid but it was the Horz Osc being 5 turns off!
: I have only moved it about 1/2 turn when I adjusted it. Might have been a harmonic?
: I was begining to think I was losing it.
: Now on to the next problem.
: Have a locked Picture and white retrace line thru the whole screen.
: Contrast is low (deosn't seem dark enough) but brightness is fine.
: Screen jitters some.
: Any guess on what area to look in next.
: Tom
My video amp is a 6AH6. Video IF's are 3-6BH6's & 1-6BJ6(4th vid IF)
The details in faces don't seem to be washed out. Hopfully the CRT is OK because I don't have any 12" tubes.
I will check the voltage on the video amp and adjust the brightness down.
Tom
The voltage on the video amp is 203vdc.
The retrace lines are the last thing to leave the screen when the brightness is
turned down. Just before the screen turns black I have white dots.
Replaced the last few paper caps in the video section.
Anything else to look for?
Tom
This is a long thread and I may not be able to cover things in as great of detail as I might otherwise try, but here are a few other things to look at.
The dim picture may be caused by either inadquate High voltage, or the low voltage rectifier may not be up to snuff. It would not hurt to double check the condition of the horizontal amplifier and damper too. The caps may be okay, but I would verify the resistor values, and if you can get a voltage for the primary to the high voltage, check that to verify it is where it should be.
Is there any evidence of a "corona discharge"? This may indicate where some of the voltage is getting lost as it is being given a path to ground.
The white line "may" be simply interference from a switching type power supply in close proximity to the set. It may very well be another tv set, or VCR, or perhaps someone is charging their cell phone nearby. It may also just be a trace that sometimes gets revealed when the brightness of the tube is not as high as should be.
Is the line present on all channels, or just the ones with a signal? If it is just present on those with only a signal, the IF's may be just slightly out of tune from where they should be. These would not be adjusted for maximum signal, but rather best picture quality. TV's use a different approach to the bandwidth provided for them.
It may also be a situation where your set is particular about which tubes it has in the IF section. As tolerances add up, perhaps yours was one that requires you to try several tubes in the IF until you find the right one for the ciruit.
Is there a problem if someone walks across the room? If so, tap the tubes gently to find the one that may be harmonic.
If all of the tubes check out okay, process of elimination leaves the picture tube. If the voltages are in the normal operating values for the tube, the tube is probably at the end of it's useful life.
I hope this helps. I have found that TV's can be aggravating when one problem shows up right after another.
: Hi Norm
: The voltage on the video amp is 203vdc.
: The retrace lines are the last thing to leave the screen when the brightness is
: turned down. Just before the screen turns black I have white dots.
:
: Replaced the last few paper caps in the video section.
: Anything else to look for?
: Tom
: Hi Norm
: The voltage on the video amp is 203vdc.
: The retrace lines are the last thing to leave the screen when the brightness is
: turned down. Just before the screen turns black I have white dots.
:
: Replaced the last few paper caps in the video section.
: Anything else to look for?
: Tom
The picture I have is bright and will go from total black to total white. The problem is that with or without a signal I am seeing vert retrace lines. I can't seem to see where in the set it feeds the vert blanking pulses to the picture to remove these lines.
Any help on where the vert blanking is on my set would be of great help!
I believe the HV power supplies are ok and see no corona discharge.
I have tested all tubes in the set and replaced the weak or defective ones. I have also tested the CRT on my B&K CRT tester and it indicates good usefull life with no plate short in the tube. I hope its not the tube only have 1 12" tube.
The only other problem I have is a popping of the sound and loss of sync for a moment but I believe that when I clean all the tube pins that should fix it (this works for my radios).
This TV is being pretty good so far (other one I had on the bench for 6 mo. without getting anywhere close).
Just takes time to learn TV's
Tom Guest
Your actual circuit may differ from this slightly, but it should be approximately the same. and will connect to the CRT in that same points.
If brightness is fine, the Ion Trap is probably okay.
I would check the last IF tube for a gassy condition. If you have a spare, try that once as sometimes gassy tubes don't show it.
Also double check the connections of the brightness control, as well as that pot. There should also be a resistor between the picture tube cathode and the brightness control wiper. See if that has shifted value.
Also check and resolder all of the connections in the video and HV sections. They may look okay, but once in a while there may be a contaminated conection, loose connection, cold solder joint, or a solder joint that is just degrading from an alloy contaminant.
At this point, if all of the above have been checked out and found fine, and there is still a problem. The CRT is the only thing left.
: Hello John
: The picture I have is bright and will go from total black to total white. The problem is that with or without a signal I am seeing vert retrace lines. I can't seem to see where in the set it feeds the vert blanking pulses to the picture to remove these lines.
: Any help on where the vert blanking is on my set would be of great help!
: I believe the HV power supplies are ok and see no corona discharge.
: I have tested all tubes in the set and replaced the weak or defective ones. I have also tested the CRT on my B&K CRT tester and it indicates good usefull life with no plate short in the tube. I hope its not the tube only have 1 12" tube.
: The only other problem I have is a popping of the sound and loss of sync for a moment but I believe that when I clean all the tube pins that should fix it (this works for my radios).
: This TV is being pretty good so far (other one I had on the bench for 6 mo. without getting anywhere close).
: Just takes time to learn TV's
: Tom Guest
All paper cap except for those in the audio section have been repalced.
I have swapped tubes thru the video IF sections and have seen no difference.
I have not check the values on the brightness circuit but I will tonight.
Looking at my schematic I am tring to find the R/C circuit your described.
What I have is the Picture tube cathode connects to a 150k to gnd and a 100k with a .1ufd across it. Going thru the 100k next is a 22k with a adj cap across it and an inductor across the 22k. Going thru the 22k you hit the 6AH6 video output tube.
The first grid of the Picture tube connects to the wiper of the brightness pot and a .1ufd cap to gnd . The pot then goes to gnd and to a 47k. Going thru the 47k you connect to the 2nd grid.
The second grid looks like it is connectedto the b+ feed to the video IF amps(all 4).
I was looking for a connection from the vertical section to the picture tube grid to cut off the picture when the vert retrace occured.
I know this is a tough question to answer but per my description which of these parts is the R/C blanking circuit?
Thanks in advance
Tom Guest
The only other thing I could think of before swapping the CRT, would be rechecking the tubes, caps, solder joints and resistors between the tuner and the video output at the CRT. It is very possible too that the IF's are not alligned properly. "peaking them" as you would a radio IF is not correct for them. It is possible if you purchased the set from someone, they might have tried peaking the IF's in that manner. They are designed to be tuned off of the peak.
: Hello John
: The picture I have is bright and will go from total black to total white. The problem is that with or without a signal I am seeing vert retrace lines. I can't seem to see where in the set it feeds the vert blanking pulses to the picture to remove these lines.
: Any help on where the vert blanking is on my set would be of great help!
: I believe the HV power supplies are ok and see no corona discharge.
: I have tested all tubes in the set and replaced the weak or defective ones. I have also tested the CRT on my B&K CRT tester and it indicates good usefull life with no plate short in the tube. I hope its not the tube only have 1 12" tube.
: The only other problem I have is a popping of the sound and loss of sync for a moment but I believe that when I clean all the tube pins that should fix it (this works for my radios).
: This TV is being pretty good so far (other one I had on the bench for 6 mo. without getting anywhere close).
: Just takes time to learn TV's
: Tom Guest