You must not be measuring hFE correctly. A transistor cannot test good with a hFE of zero.

If the driver transistor were dead, you likely would not have horizontal scan at all. The driver transistor is very unlikely to be the cause of intermittent sync.

Again, if some function is intermittent, you should applied mechanical tapping, pressing and jiggling to find an intermittent connection.

I double and triple checked with two different meters and both read zero. I also found my old horizontal board and pulled the 755 off and tested. it had an hFE of 82.

I've tapped the crap out of everything, but nothing changed. I pulled all boards and reseated, nothing. I took the horizontal, vertical and chroma boards out and checked all the resistors and transistors. I then remembered the video processor board. It gets the sync signals. I check the resistors and all but two are within the noted value. The others were so far out, I'm going to lift a leg for better testing. One is 4.8K out of 10K and the other is 6.8K out of 18K. But most concerning is the IC. The legs are black from some kind of corrosion and/or heat. I tried cleaning them, but it won't come off. It is has migrated down many of the legs. There a couple with bluing from heat.

I've uploaded a video of the problem. Maybe a visual will help. I really don't know where to look as there are multiple places the horizontal sync is processed (IF, video processor module and horizontal module). As suggested I have tapped on everything, wiggled all connections, removed and reseated modules and tested a number of components on the modules.

It no longer seems to be intermittent sync as I have not been able to get it back, even for a moment. Been working on it for about 7 hrs now.

I've ruled out the IF module. See attached pic. It is from test point C1, Detector Output. I see the section where blanking, color burst and horizontal sync take place, followed by the video information.

https://youtu.be/Ftj62sprzNY

The horizontal is running way off frequency. If the horizontal hold adjustment is a coil you might be able to bring it back in with that.

+1 Horiz osc is way off frequency. This is almost entirely contained on 9-57 Horiz Board, with the exception of the horiz osc coil/hold control and the attached capacitor that forms the circuit that determines the osc frequency.

+1 on the Q803 121-755 Horiz Driver transistor not being the cause. ECG 190 is a closer substitute.

The question is, can the osc run on frequency or is the AFC driving it off frequency.

Do you have a spare 9-57 Board?
Is the plastic stop still in place on the horiz hold control? Has it already been forced past the stop?
Have you replaced any other components on the 9-57 Board?
Re-examine and tighten pins and connectors A11, U4, T13, that connect to the coil.

Common problems:

R808 330ohm 1/2w replace and upgrade to 1w
R821 2.2k 1w replace and upgrade to 2w

Lead sockets for the transistors are always problematic, most people will either remove the pins and solder the xsistor directly to the board, or solder the leads in the pins. Every rebuilt board I've ever seen, Zenith or PTS, soldered the leads into the sockets.

From there you need to troubleshoot the board. At least its not intermittant anymore?

On the Video Proc IC, I've had luck gently scraping with an Exacto knife, also taking a small piece of green scotchbright soaked in DeoxIT or CRC Cleaner, held with a needlenose and gently scrubing. Be care not to over manipulate the pins.

The horizontal hold still has the stop on it and it hasn't been turned past it. The image does show slight change as I rotate the control.

I replaced the 755 on the current board yesterday, no change, so I have to agree, it's not the issue.

I have replaced all the transistors on the board in the past month, other than that, it is unchanged. Could a bad transistor in another part of the board cause it to loose synch? If so, I have all the original transistors. Maybe one of the new transistors is bad. I also have the original 9-57 board, but after 13 years I can't remember why I had to replace it. Guess I could swap it and see what happens.

The lead sockets on the current module have one crimped socket per transistor. I guess they did that to make sure they were secured.

I tested the resistors. R808 is 310 ohm and R821 is 2.4K ohm.

I was given a "new" video processor board years ago, but it never worked. Then I noticed the top corner of it had a red mark on it. I'm betting it was the bad one put back in the box and that mark was to let them know that. Somehow it got out. Never got around to finding out what was wrong with it, but I remember the board yesterday and took the IC out of it and put it in the existing board. Problems solved for that one.

Okay, I'm going to put the old horizontal in right now and I'll post my results. I'll also retest the transistors I put on the current board and see if any have gone bad.

Well now I know why I replaced the 57 module. When installed, there is no image or raster on the screen, but there is sound. I hear the buzz of HV, but the CRT is not active.

Okay, I think I know what happed to the old 57 module. See attached pic. Back when I first got the set, I was told to check all the transistors to make sure they are seated. I guess I pushed too hard on this one as the emitter lead left the side opening of the socket and joined up with the base socket. I'm no expert, but I think they call that a short. :lmao:

I'm going to test that transistor, and possibly just replace it no matter what testing says. Then I'll reinstall the board and test again.

Okay, fixing the insertion issue with the transistor fixed it. I put the board in and it fire up. Slight adjustment of the horizontal hold and it's all good. I'm going to let it run for a few hours to make sure it has been fixed. Now to use the removed board to practice my troubleshooting and repair. This board is exactly what I need for that.

Appreciate all the help. I'm sure it won't be the last time I need it, that's for sure. When this is done, I have a B&W RCA 12" from '75 and a 13" Hitachi from '82. :smoke: Not to mention a Canon Monochrome computer monitor that has a weak CRT. The socket adapter I have for my B&K had a couple wires pulled from the socket. I asked the previous owner and they said something about that socket had the wrong wiring for many of the monochrome monitors and he said someone switched a couple leads. Now I'm uncertain of using it, so I need to find the wiring diagram from B&K and compare it to the connector of the tester to make sure they all line up. Once that is done, I'm sure I'll have to go the rejuvenation route with it.

I've ruled out the tuners being the source of the jailbars. I have a modulator that outputs to UHF and tested a laserdisc and VCR on channel 82 and the jailbars are still there.

The next step is the IF module. I found out why the new IF is over saturated. I need to adjust the detector output. I'm going to just turn it down by eye at first to see if the jailbars are still there. If not, I'll do the SM adjustment procedure. If they are still there, I'll put the original back.

After that, I'm not sure I have the ability, currently, to go any further in trying to find the source. I won't stop trying, but all the while I'll enjoy watching what I've been able to accomplish so far in making the image as close to factory new as possible.

Can ringing like what is causing my jailbars come from the 240V and/or 750V boost circuits? The reason I ask is I realize the diodes have not been changed. The 750V was cut and tested, but the 240V wasn't. I have one new diode, but need to get the second.

Also, the capacitors across these are 2KV, but the diodes are only 1.4KV. Since their voltage ratings are not standard, and I haven't been able to find them, can a voltage of 1.5KV be used?

Diodes themselves cannot cause jailbars. Jailbars could be gnerated in a circuit that happens to contain the diodes, but changing the diodes would not fix them.

Are you asking about replacing the caps or the diodes?

1.5 kV diodes can be used in place of 1.4 kV diodes.

1.5 kV caps should not be used in place of 2 kV caps. The rating may or may not be important for steady state operation, plus, it could be specified to tolerate temporary overvoltage due to CRT arcs or some other condition.

Just thought that if the specs of the diode(s) were out, then it might introduce noise in the circuit that appears as bars. Since I have one diode, I thought I'd replace a current one, most likely on the 240V boost, then the other one when I get its replacement.

I remember years ago when I first started looking at the jailbar issue I was told to put a capacitor of the same voltage in parallel with the B+ filter caps to see if it helped. I didn't, but was wondering if the same would apply to the caps across the boost diodes and damper diode. I have some 560pf 2KV caps an was going to see if they worked in place of the 600pf across the damper and boost diodes. But now wondering if I could parallel them to see if it has any affect on the bars. If not, I have one real 600pf 2KV on an NOS flyback that's instructions say if replacing my current unit I'm supposed to remove it. So if I ever need the new flyback, the capacitor isn't needed. But since it's only one, and my set has three, I'd like to use it where it's actually needed.

The jail bars frequency is in the 100 kHz or so range. It takes significant inductance to resonate at that frequency with the caps that are across the diodes. Take your spare cap and connect it across an existing diode cap and see if there is any difference. You don't have to remove the existing cap to see if the capacitor across the diode is having any effect on the jailbars. If you do see an effect, you have a starting point for investigating from there. If you don't see any effect on the jailbars, you can stop wasting your time and look for some other cause.

This advice is based on the caps in question being across the diodes as you describe and not from one end of the diode to somewhere else.

There are two that fit the criteria. The one on the damper diode and the one on the boost rectifier for the 240V.

The damper diode will have to be done from the bottom, but the boost can be done from the topside. The diode and cap for boost are across connection 13 of the terminal strip by the flyback. I can just connect the cap to those for testing.

Can I use clip-on leads to them? The damper diode is from collector to ground and the SM has the collector at 125V and the boost is 240V.

I find it interesting that the new flyback is one revision newer than current, has the same resistors, capacitors, etc..... Yet, it says when replacing my current version, I need to remove the 600pf 2KV capacitor. The capacitor on mine is on the FB side of the boost voltage to ground. Guess they figure since the supply line going to the diode has one of those capacitors across it, thing the supply side of it to ground isn't necessary?

"Guess they figure since the supply line going to the diode has one of those capacitors across it, thing the supply side of it to ground isn't necessary?"
A cap across a diode and a cap from one end to somewhere else serve different purposes. One place doesn't sub for the other. There must be something different about the flyback transformer itself to require removing the cap.

Re clip leads: keep leads short and be very careful about accidental shorts, as the diodes would not like that.

If there is something different with the flyback, I can't find it (visually). The capacitor only stays in if you're replacing the -02 with this -02. The original -00, -01 and -03 deletes the capacitor. Not going to put anymore thought into it. Just glad I now have a 2KV capacitor. If I do find that one of the current ones is not up to spec, I have a replacement.

The leads I have are 10" and rated for 600V. Clips are insulated except for the bite section.

Voltages in some parts of the horizontal section can exceed 600V, so i would play it safe.

I only plan on testing on 240V boost and the damper diode. According to the SM, the collector on the HOT is 125V. And of course no connecting/disconnecting while set is on. :nono:

Okay, curious results of parallel capacitor on 240V Boost.

I remembered I had a 560p 2KV capacitor, so I decided to use that in parallel to the 600p 2KV across the boost diode. The results were noticeable, but didn't eliminate the bars, but did reduce them. Don't know if it reduced the ringing or the overall brightness of screen. I'm assuming it hasn't done anything to eliminate the bars, just made them dimmer, which might mean an overall dimmer screen? If the original cap is in spec, then I upped it to around 1160.

Anyway, I also measured voltage. On the supply side from the flyback, it's 131V. On the other side of the diode, it's 249V. I'm assuming that is within specs for the 240V boost circuit.

I've attached a couple of pics. They look similar, but the one with cap is dimmer. I figure the bars should have changed in other ways, narrower, less of them, etc.

Tomorrow I'll try across the damper diode. Need to put the set on its side and remove the base and access panel for that.

In my experience with fighting jailbars (so far), eliminating the bars is often related to smoothing out them out. Doing so tends to make the picture a little softer in the process.

After duplicating the test, I determined that it was the bright logo from the DVD player's screen saver that created the difference it bar intensity, not the capacitor. So the boost section capacitor is doing what it's supposed to be doing.

I'm about the flip the set on its side and remove the bottom and parallel the damper diode.

You wouldn't happen to know if removing the Automatic Brightness Limiter's transistor would disable the function and leave the set running without the function? The reason I ask is that of all the places I've scoped, the ringing is most visible on that circuit. I also remember last time I worked on it, just getting the scope's probe near the focus lead gave a ringing pattern. Is it possible for jailbars to come from the tripler?

Well paralleling the damper diode didn't get rid of the bars, but it did something I didn't think would happen. It reduced the overall brightness. I guess the added capacitance did that?

It's all buttoned up and proudly showing off her amazing image. Jailbars don't show up on dark scenes where I'm assuming it's below the level of black. For instance, I put on Buck Rogers TV show from '79 and all the space scenes were perfectly black. The only time the bars showed was during scenes with low light, not the absence of it.

One more part of the video chain eliminated.

The IF module is not the source of the bars. I installed the new IF and after adjusting the detector output to proper level, the bars are still there. Put back the original IF.

Next in the chain are the ABL, Blankers, 3rd Video Amp and then 4th Video Amp.

So far I've eliminated the tuners, IF, horizontal module, subcarrier module, B+, damper diode/capacitor and 240V Boost diode/capacitor. With all the electrolytics replaced with exact parts noted in SM as well. Transistors on the chassis and horizontal module have been replaced with factory correct.

There is a zener diode on the 4th video amp (emitter to collector/ground). Since this is acting as a voltage regulator, I don't think it can create the kind of noise to cause bars.

I also have checked all soldered ground points on the terminal strips to chassis, shielded cables and on the boards I've tested. I have tried a number of different routings of leads and isolated the yoke leads from all others.

If I never get rid of the bars, I'll still be very please with the overall image quality I've been able to achieve. The bars will be a very small price to pay to have an amazing set.

Best compromise between no jailbars and light jailbars. The overall level of brightness and contrast is too low when set to remove the bars. Then they are way too distracting when set to proper levels. So I have set it below where I where I normally view, but above where the bars are too distracting.

A few pics of the journey so far.

Looking at these pics on my laptop, I can't see jailbars in any of them. Have to try on the desktop monitor, I guess.

Yes. The tripler is part of the flyback circuit, which can be the source of the bars. When this journey started, I recommended shielding all of that to see if it went away. Did you ever try that?

Sometimes the bars can couple into the video just from proximity. One test I've done in the past is to make long extension leads between my flyback and the PCB and physically move the whole circuit away from the set and put it inside of a big steel can covered in thick plastic to prevent anything from shorting together. This is really the only foolproof way to eliminate proximity as a source for the bars coupling into the signal. It's dangerous though, so be very careful if you actually try it. I don't know how having an external tripler would effect the situation though. That's lots of high voltage parts to juggle, and the risk of arcing would be high

The important distinction here is that the bars can be one of two things. Either they are a function of the deflection, or they are a function of the video signal (ie they are modifying the actual video information before it gets draw by the deflection system).

The way you see the pulses on the probe is normal in a TV, and they will always be there. The problem is only when they are either coupled into the video signal, or when they are present in the deflection process during scan time. The bars will always be in the deflection during the blanking period and that is normal. Seeing those pulses on a probe is expected and doesn't tell you anything about where the bars are coming from.

Yes, it's normal that adding capacitance across the damper diode could cause a change in brightness. That was only to see if the bars went away, not a permanent fix.

They are there, but the settings I use on my camera to get decent pictures seems to diminish them at bit.

I don't know if it's the way I've adjusted things, but I swear the bars have a more defined edge to them. Almost perfectly smooth and uniformed. I'll have to do more low light scenes and make sure.

I have not figured out a way to shield things without shorting something out. Unless there's a material that can be used as shielding that doesn't conduct, I just know I'll kill something. Is it safe to wrap the anode lead in foil all the way down covering the tripler? The connections on the tripler have black RTV on them, so I don't see an issue on that end.

Would ferrite magnets be of any use? I need one years ago and had to buy 20 of them. They are small and would fit up to 10 ga wire.

As for the tripler, I have an NTE replacement, but that would require ditching the divider and I'm not sure if the NTE is better used as an emergency replacement. I haven't been able to find and OEM one.

Tomorrow I will be scoping the 3rd and 4th video amps. Now I know the settings for the test points from the waveforms in the SM, but if I'm looking for something outside of that, what should I be looking for? AC? DC? Certain time/div? The reason I ask is I've noticed a couple test points that have two different waveforms and each one has a different time/div and produces different forms. I figure it safer to scope all leads on the transistors, but not sure if that's necessary.

I wouldn't go putting magnets around the place, sounds like a bad idea to me.

You can get pieces of steel and double bag them inside of ziplock freezer bags to prevent them from shorting out on anything. Good enough for a test.

The idea is to completely cover the parts that are making the oscillation you're seeing. If it's coupling into the video in that way, you should notice some difference. Might not cure it, but it would at least tell you that you're on the wrong (or right) path.

What if I put several layers of foil inside freezer bags? Would that provide good/decent shielding? I have some 1 and 2 gallon bags. The 2 gallon would be large enough to wrap over the top and sides of the flyback and the 1 gallon over the tripler. I could also lay it on top of the chassis between it and the CRT.

Well I'm just about finished with all the connections this set is going to have. I do need to finish the trim on the table next to it, but my access to a brad nailer is gone, so I might just use wood glue. Also need to redo the carpet on the riser.

Oh, and I'm still confused about adjusting detector output level. I posted earlier the instructions. So I've figured out that I'm supposed to be on the highest channel without signal. I'm then supposed to connect 7.2V to E and ground, then a DMM from C1 to ground. The set is supposed to be one for this connection and adjustment and this is where I am confused. The circuit already has DC and and AC signal on it. Is me just connecting my power supply and injecting voltage all there is to it? Is the AC signal bad for my supply? What is my injecting 7.2V going to do to the DC already on it? And lastly, once this is done and I disconnect, the DC voltage on E will drop back to what it was before, so won't the adjustment I made change as well? As it stand s now, the voltage on C1 is around 7V.

Since there were untrained hands in this set before I got it, I'm checking all I can and this one is off, but not sure if the amount matters in the end.

It has to be pretty thick steel I think, not foil. There are calculations you can do, and if you wish to explore that, you can read up on Lenz's law and how it is contained in the equations of Faraday.

There are other kinds of metal that have been used by TV manufacturers that work better, the most well known of which is mu-metal.

What determines horizontal position in this set? I'm assuming it is something on the horizontal module as after swapping back to the original module after the failure of the upgraded module, the image is now off center horizontally. It was never centered perfectly with the newer module, but it was about 1/2 to the right. With the original module reinstalled, the image has move another 3/4 to 1" to the right. The horizontal control is all the way to the stop. If I rotate it away from the stop, the image moves more towards the right.

If a module swap is enough to mess with horizontal centering, is that because of something on the board out of spec, or the way it is interacting with the horizontal control? Really would like it at least back to where it was previously.

So, is my tripler 53 years old? Is the date code 7314? Other than part numbers and "YARO" or "VARO", the only thing that looks like it might be a date code comes out as 14th week of 1973. Does that seem correct?

I'm going to install the NTE526A in the set Friday. It's another test to find the source of the jailbars. When I replaced the focus divider years ago, the wires were long and I cut them to length. I have enough of the black to go from the new tripler to the focus connection on the flyback, but not enough of the white to reach the pot. I found some 18AWG 30KV wire in white and it should be here tomorrow. I really didn't want to cut the wires off the divider as I might end up keeping it and the tripler if the new one doesn't fix the bars. This way I have the OEM back and the NTE as a spare. If it fixes the bars, is there some kind of tests I can do on the OEM? Resistance? Diode check?

And of course a question. Is it okay to run the new tripler without RTV on the connections for testing? I want to be able to quickly swap it if it doesn't solve the bar issue. If not, is there something else less permanent I can do for testing to protect from arcing?

I got my hands on the plans to gut a 9-57 horizontal board and piggyback a 9-90 so I can use my old RCA VCR without the waving at the top of the screen. Only issue is I don't know how the B+ 125V is going to like/not like it. Since the B+ is passed module to module and the horizontal module is the last in line, does the B+ line care if it is cut at that point? With the 57 board, it goes in and out, but isn't used by anything on the board. If I gut the board so I can just use it as a base for the 90, the return path for the B+ will be severed.

About to install the new setup switch. I got the old one out and opened it after testing. Testing on the new switch showed no resistance. On the old switch, it showed resistance, mainly in the "setup" position. Upon inspection of the contact pads, I can see where the resistance is coming from.

Took plenty of pics to make sure I get the wiring on the new switch correct. Sure wish there was more play in the wires for easier install and soldering.

I've attached a pic. Can you guess which pads are for "setup"?