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  #46  
Old 12-12-2010, 08:28 PM
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That does look pretty good. Your CRT can't be THAT bad! :-)
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  #47  
Old 12-12-2010, 08:48 PM
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Looks good, how does it look with the Simpsons ? Do you get the red bleed? (thats my test now)
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  #48  
Old 12-26-2010, 04:55 PM
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left it on for a while, checking the CRT. after being on the CRT tester for about 45 min I rechecked the emissions and tracking all very good. I don't get it but I am not going to complain. I need to get this one in and just play it. The only issue I have now is the lack of range on the hue, guess it could be a pot, but will check the quad diode tube (think it has one of those) in the chroma circuit. the hue pot is very touchy, have to keep it full CCW and mess with it or its too green (never gets magenta, just right at max CCW).
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  #49  
Old 12-26-2010, 06:18 PM
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Damn, but that's good color.
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  #50  
Old 12-26-2010, 06:47 PM
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there is a coil that it says to adj for hue range, will be checking into that and see.
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  #51  
Old 01-02-2011, 07:02 PM
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ok decided to check into the hue issue, 1st check some caps and resistors around the phase detector, all good. I had the set on its side and was going to tweek the burst amp coil to see if I could get better hue range. so I had it on its side, powered up, no pic, I hear static, I look at the back and I see sparking at the filaments

I have no idea what happened, I layed it on its side very gently, no bumps etc.. I check the CRT with a CRT tester, I see one filament glow weakly them more sparks then nothing.

filament pins read 30k I tried checking the even went so far as to try to resolder, no joy, break away the socket to get at the filament wires, nothing.

I tap around the neck (not hard) and I see a crack around the neck. I hear nothing at all, on air leakage etc, and it is an open crack (I can lift the neck off). So somehow it was either cracked and gone to air, or had gone to air and then I cracked it. My guess is it had gone to air before I cracked it, the filaments just burned out, otherwiise I am sure I would have heard something.

Anyway the CRT was very weak, took a good 5 min to produce a decent pic.

I had a spare CRT that I had planned for another project, but since it was no where near being ready (a CTC 7 with a very ruff chassis, may be a lost cause anyway) I decided to go ahead and use it. It the kind with the separate lens (no cat to deal with ) after struggling with it for about 1 hour I managed to get it all in an buttoned up. I touched up the purity and did a real quick static convergence (on over the air broadcasting not the dot bar gen) just to get it in the ball park. I have some vert bars on the left so I will need to look into the HOT/Damper and will recheck all the setups, did a quick gray scale setup. it looks very good, the pic quality and brightness are much much better and the pic is good to go in about 30 sec vs the old CRT 5 minute deal.

Not sure what happened but all ended well. I will get some more screen shots later after I take the time to do a proper setup.

something I have not seen before, the brightness seems a little greater on the top of the pic than on the bottom, maybe its just a linearity setting but I seem to recall reading about this kind of issue and diodes in the blanking circuit but not sure about that.

My guess is the better CRT is allowing defect to be more noticable now.
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  #52  
Old 01-02-2011, 09:07 PM
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I am SO glad that a good thread on a Zenith of this vintage is here. I was posting before Christmas about finding a metal cabinet Model 5111, but I got sidetracked in going back to work on my 59 Space Command 24" B&W. There is so much good information here, a lot of which leads back to the same old same old, bad capacitors. Right now my Zenith starts smoking when the DC comes in; it's somewhere in the vicinity of the red hot horizontal output tube which I must keep the anode cap off of to eliminate the smoke. I already mentioned this in another thread, so I don't want to seem as if I am stealing the thread. When I get time to get into mine I think that I am simply going the route of pulling the chassis and replacing the paper and electrolytic caps and checking the resistors. I think with this approach I will find the road to a decent set a lot easier because I honestly don't know anywhere near as much about vintage color sets as I do black and white sets. There is a lot going on in an old color TV chassis, but I figure as long as the circuit components are in working order, then I should have a good old Zenith. I don't possess the equipment or the knowledge to worry about producing a perfectly aligned and pure picture, so I hope and pray that nobody has been in there adjusting things that shouldn't be adjusted. Actually, my set has all stock tubes, so I feel that it has been dormant for a VERY long time. I think that the last owner told the guy who gave it to me that it worked fine back in 1980. It's just been asleep too long to bring back to life without major surgery. If I tried to shotgun repair it, I would probably drive myself crazy with all of the problems constantly arising and end up hating the set. I say re-cap is the way to go, on this one anyway.
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  #53  
Old 01-03-2011, 07:08 AM
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Not sure of the vintage of yours, but there are not a lot of paper caps in this one. The whilte elmento tube caps are the ones that may cause trouble but chances are they are ok. They are rated 1000vdc think there are 4 in there total.

The can caps are often fine. If the HOT is red plating the most likely cause is no grid drive since that is how it gets its neg bias. As a min you should check the cathode current, should be around 210-220ma(I use a socket that plugs into the socket, and has leads where the cathode is for connecting a meter) of the HOT, AND check the 6BK4 cathode current (there is a test point for connecting a volt meter so mearuse the voltage drop, should be around 1vdc drop), AND check the HV with a prob, should be around 22-23kv.

all those are related, if not working then I would start by checking the horz osc tube, its a triple triode compactron, if its defective there will be no drive to the HOT and red plating will occur. Sometimes you just need to wiggle the tube around some.

For general checking out of B+ I pull the HOT out of the circuit completely. I read somewhere that just disconnecting the plate lead is not a good idea, cant recall why.

With it pulled you can check the B+ current draw, should be very low. I generally do this with a metered variac, I pull the hot out, and the vert out, then do a very slow powr up. the variac I have has a voltage and currrent meter so I can see whats going on. Start slow and watch for current. I start out at 10vac just to see if the PT is shorted, then slowly ramp up to about 60-70vac over a period of time, again watching the AC current, again with out the HOT in it should be very low, around 500ma IIRC by the time I got to 70vac. I stop there since with no HOT load the B+ will go higher than the rated voltage of the can cap (I monitor the B+ voltage as well with a DMM while doing this, stopping when I get to about 375vdc, which will be well below line voltage). If you are just pulling the lead from the HOT and plugging it in to full line voltage, then the B+ will surely overshoot the voltage rating of the can caps, not good.
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  #54  
Old 01-03-2011, 01:07 PM
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RCA CRT HV Survey

Miniman82 states “Maybe I'm wrong here, but 22kv sounds fine for HV. All my RCA sets run at 22.5, so you can't be too far off base...
These round tubes were meant to be operated at 22.5kv, so there's no good reason to put 24 on them.

CT17 states “ yep sams says 22.5-23.5kv. I have to scan the sams, do it tomorrow. Got stuck exploring the abandon prison and got home late. C17”

Sams RCA 21CT55, CTC2B says “..set HV to 25K. HV Reg 6BD4 cathode should read .7ma”

RCA Field Service Guide CTC2B schematic shows 25KV, RCA Service Clinic says…
“…6BK4 regulates HV voltage to 25KV which is required at the ultor of the 21AXP22”

My CTC2B uses a 21FBP22 which RCA max specs at 27.5KV. I now use the OEM flyback used in the CTC20 which also uses a 21FBP22.

CTC4 with 21AXP22 schematic shows 25KV, CTC5 with 21AXP22 shows 19.5KV!!, CTC7 with 21CYP22 shows 23.5KV, CTC7 with 21CYP22 shows 23.5KV, CTC9 with 21CYP22 shows 22.5KV, CTC10 with 21CYP22 shows 23.5KV, CTC11 with 21CYP22 or 21FBP22 shows 24KV, CTC15 with 21FBP22 shows 23KV, CTC16 with 21FBP22 shows 25KV and finally the CTC20 with 21FBP22 shows 25KV.

The only good reason to use an ultor greater than 22.5KV is to produce a better picture.
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  #55  
Old 01-03-2011, 01:42 PM
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Quote:
Originally Posted by Tomcomm View Post
The only good reason to use an ultor greater than 22.5KV is to produce a better picture.

Really? You're still hung up on this?

Like I already told you in the other thread, there are better ways to get a better picture on the screen than stressing the already taxed HV section. Stripping out the matrix and replacing it with something modern like component video is one, installing a modern IC-based video section having a comb filter is another. Increasing HV only attracts the electrons from the gun 'harder', and puts stress on irreplaceable components like the flyback. I won't discuss this any farther on this thread since it's OT, either post about it in your thread or PM me.
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  #56  
Old 01-03-2011, 02:03 PM
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over lunch I pulled the replacement CRT yoke and replaced it with the orig yoke that came with the set. I orig did not do this since it was stuck on pretty hard and I REALLY did not want to end up breaking another CRT two in one day would have been pretty hard to take. The Yoke that was on the spare CRT (both zenith) had a different PN. I had some jail house bars showing on the CRT and was thinking maybe there was a different anti ringing network in the yoke, plus I would rather have the orig yoke in place. I did not get a chance to run in and look for the vert bars, hope this takes care of it. wil of course have to re do the purity and setup again.
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  #57  
Old 01-03-2011, 03:19 PM
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Quote:
Originally Posted by DaveWM View Post
Not sure of the vintage of yours, but there are not a lot of paper caps in this one. The can caps are often fine. If the HOT is red plating the most likely cause is no grid drive since that is how it gets its neg bias. If you are just pulling the lead from the HOT and plugging it in to full line voltage, then the B+ will surely overshoot the voltage rating of the can caps, not good.
Hey thanks for the tips on this one! My 5111 is supposedly a 1964 model. I don't have a Variac, as well as a lot of other needed professional equipment. However, initially I used the 100W incandescent lamp method for at least a chance at a slow start. The reason that I disconnected the anode cap of the HOT was due to the smoking which started before any recognizable HV was produced. I knew that it would disable the circuit so I could see what might be going on in the rest of the circuits as far as overheating transformers, cans, smoke, etc. I had no idea that it could hurt my electrolytics. Seems like they would have engineered the voltage ratings higher if an open in that area could cause such damage. Luckily, I have never applied line current for more than a few minutes, and only a few times.

I'll tell ya, some of you guys blow my mind with your extensive knowledge of what is more or less a lost art. There is really no school that you can go to in order to learn what some of you guys know! Miniman82 made the following comment concerning video, "Stripping out the matrix and replacing it with something modern like component video is one, installing a modern IC-based video section having a comb filter is another." I was very impressed with someone knowing what it would take to improve or perfect antiquated circuit designs. I am an electronics student (at 41) in my final semester, and they just don't teach what I call REAL electronics! Thank God my dusty trail goes back to HS electronics back when we used Simpson analog meters and were taught at least rudimentary understanding of oscillators, detectors, etc. Now we learn the extreme basics of the full wave bridge rectifier using low voltages and current, controlling electromechanical relays, and lighting LEDs. I am scared to apply for a job based on that! Now we will possess the valuable knowledge of PLC programming and three phase applications. I guess that is their main focus to market us for employment.

I love bringing in old stuff and watching everyone but the asst. professor watch me work as if they were not even an electronics student. Even one of the few remaining Simpson meters will confuse everyone. I am just guessing that some of you guts have just been around long enough to have worked in electronics when it was truly electronics and less solid state, IC, riddled junk. Either way, I am glad to have contacts like all of you here and this great site. When I find a good job in the industry I plan on being an official member!
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  #58  
Old 01-03-2011, 07:21 PM
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the most likely reason for the smoke was lack of drive to the HOT, you should be able to get a DMM reading on the grid of the hot, think it should be around -70v (neg to the chassis, positive to the control grid of the 6JS6).

My guess would be a bad horz osc or some cap in that circuit. The main thing to do is to monitor the HOT cathode current, if it goes over 260ma then you have a problem, no need to try anyhing else until that is under control.

Yes the caps have some over voltage in the ratings, but they are 45 years old so no need to test that rating

Just go slow, read read read, get some old manuals off the net.
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  #59  
Old 01-03-2011, 07:24 PM
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using the old yoke took care of the jail house bars, got the dot bar out and did a better convergence and set the lineairity. Looking pretty darn good. the convergence board still has on of those hard white caps (.056 10%) and a couple brown drops, and it still has the old Se quad rectifier pack, but I had to put it all away so the wife could have the garage back (tucked the TV over in a corner for now).
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  #60  
Old 01-03-2011, 07:48 PM
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Thats interests me why the yoke caused that unless it was a total impedance mismatch or if there is a cap in the yoke thats bad. The impedance is a definite possibility as the set that crt came out of had a totally different style chassis.

Tubejunky, I would avoid the shotgun recap at first, you may cause more problems that you have. First thing is find were the smoke is coming from and go from there. It could be anything from the flyback arcing to the no drive because the pins in the drive tube are not making good contact in the socket. Some pictures would help too, good ones of the chassis and where the smoke is coming from.
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