View Full Version : New here and to Vintage TV.
Daave 11-07-2011, 09:08 PM Hey all, I just signed up here.
Ive always had an interest in early roundie colour TVs, and have been looking around for an early colour TV for a while and finally found one (in fact I haven't even taken delivery yet).
Anyways its a Zenith 5215 UD model with a 25mc33 chassis. Ive never worked on a tube TV, but have repaired many solid state TVs with the assistance of the Internet ;)
Can anyone tell me anything about this particular set?
Owner says its 1965. Im in Ontario Canada, and this would be one year earlier than colour TV broadcasts started (which also makes even finding these TVs hard here) but perhaps the close proximity to the USA border it was probably used to receive many stations across the lake at the time.
Thanks for your time!
Electronic M 11-07-2011, 10:03 PM Welcome!
The roundy Zenith sets were for the most part very well made and reliable sets. Yours may still work (though it is best to power it up on a variac incase there are any power supply issues). I have two 1964 monochrome Zenith portables that still run well on the original capacitors.
I believe that there are some here that should be familiar with your exact chassis. On Zenith sets with different models, but the same chassis the insides are usually electronically the same (plus or minus the occaisional extra of a HIFI amp or remote chassis).
kvflyer 11-08-2011, 04:07 AM Hello and welcome to the forum. I suspect there will be much help coming your way. This forum seems to be full of helpful info.
zenithfan1 11-08-2011, 07:40 AM Omedetou gozaimasu! Congratulations on your Zenith acquisition. The 25MC33 chassis seems to be one of the best for reliability IMHO. There won't be any wax caps in that one but there are a few of those black beauties in there, only like 2. The cans are easy to deal with on these too, they usually aren't even bad but if you plan to clock a lot of hours, I suggest changing them. Please post some pictures when she arrives. I'll be happy to share any knowledge I have on it. There are a few other Zenith guys that will probably chime in too.
benman94 11-08-2011, 10:41 AM Hey Dave. I wish you the best of luck on your restoration. I'm mid-way through my first. You're right, the color set would've only picked up color broadcasts from Detroit or Buffalo. Just out of curiosity, where are you located?
compucat 11-08-2011, 11:08 AM My Zenith roundie uses that exact chassis. When you get it I will be glad to offer any information. I have had mine in restored condition for four years now. When working right it is a great set but can be a little maintenance intensive at times.
Daave 11-08-2011, 11:36 AM Hey Dave. I wish you the best of luck on your restoration. I'm mid-way through my first. You're right, the color set would've only picked up color broadcasts from Detroit or Buffalo. Just out of curiosity, where are you located?
The set was from the Chatham area Ontario so likely Detroit stations, and possibly Buffalo with the right antenna. Erie PA perhaps if they were broadcasting colour at the time. Im in a small town about 30 minutes directly south of Hamilton.
benman94 11-10-2011, 07:38 AM Chatham you say?! Grandfather was born and raised Wallaceburg; moved to the US to work for WJR in the late 40s.
kvflyer 11-10-2011, 02:51 PM I bought a CTC-9 210CK875 locally almost a year ago. It sat for about 6 months and I decided to remove the electrolytic caps. I re-stuffed them and replaced the zero emission CRT and was rewarded with a raster! I used a variac that fed a Kill-A-Watt. That thing is great. You can monitor the voltage, wattage and amperage as you bring the voltage up. Excessive current becomes obvious immediately and gives you a chance to stop.
So, a good place to start. I suspect that if you do the electrolytics, you will be way ahead of the game.
Daave 11-14-2011, 09:21 PM Welp I finally got the set today. I normally wouldn't jump into powering up a set this old but the owner said he did only a couple weeks ago, so I figured any harm that was going to happen, would have happened already.
So it powers up, all tubes that I can see including the 21FBP22 picture tube glow a nice orange, and after some 10-15 seconds the HV winds up and I see all 3 guns firing to form a nice horizontal white line across the picture tube!! So Im excited, there is no vertical deflection, and I didn't hear any sound either, and the horizontal output tube has a blue arc after the HV started. Also heard some popping. I didn't leave it powered on past that. I think its a good start though. Some of the majors are working!
The cabinet top is rough shape, Quite dirty over all and does need some cabinet work. I think I have a guy that can fabricate new top/side panels for it. It has 45 years of dust in it, but from a non-smoking household. I think as suggested my first move is cleaning it, finding a schematic and the lytics. It is 100% complete though. So I think its a good find especially being in Canada.
miniman82 11-14-2011, 09:58 PM Recap the power supply filters at a minimum, as for the no vertical does this set have a setup switch? I had the same chassis in the house not too long ago, but didn't spend a lot f time with it so I don't remember. It's probably in the wrong position or just dirty, wiggle it if there is one and I bet vertical pops up.
Electronic M 11-14-2011, 10:12 PM You need to turn the brightness to the minimum needed to light the screen when running without vertical sweep or you will BURN the line PERMANENTLY into the phosphors ruining watchability of the CRT.
Phil Nelson 11-14-2011, 10:31 PM A raster and horizontal deflection are encouraging signs (arcs and popping sounds, not so much).
In addition to electrolytics, I think I see a "bumblebee" plastic-coated paper cap hanging off that convergence board. Those are as bad as wax paper caps -- highly suspect.
If I spied any other bumblebees, particularly in vertical & horizontal sections, they would be high on my list for replacement. Ditto for any plastic-coated caps in other clothing, like Big Chiefs.
Have fun,
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html
Daave 11-14-2011, 10:33 PM Recap the power supply filters at a minimum, as for the no vertical does this set have a setup switch? I had the same chassis in the house not too long ago, but didn't spend a lot f time with it so I don't remember. It's probably in the wrong position or just dirty, wiggle it if there is one and I bet vertical pops up.
After clearing off the dust on the vertical output tube, its getter is gone all white and flaking off the inside of the tube. Im gonna guess thats bad.
I only ran the set for a few seconds in this state as to not burn anything in.
bgadow 11-14-2011, 10:48 PM Correct diagnosis on that vertical tube. Was the arc inside the HO tube? I'd say replace that and the damper. I forget which tube it uses; if one of the really expensive ones, shop around a lot. Remember to post here if you need any tubes or parts as lots of us have a good stash.
Electronic M 11-14-2011, 11:03 PM When the gether turns white it means the tube has lost it's vacuum, and tubes can NOT function once the vacuum is lost.
That is a nice set!
I think I have the tuner and some parts off of a similar model if you need them.
Daave 11-15-2011, 07:22 AM Correct diagnosis on that vertical tube. Was the arc inside the HO tube? I'd say replace that and the damper. I forget which tube it uses; if one of the really expensive ones, shop around a lot. Remember to post here if you need any tubes or parts as lots of us have a good stash.
6JS6C is the HO Tube. Removing it the metal cap broke off the top.
Ebay shows them to be pretty pricey yap ;)
kvflyer 11-15-2011, 01:59 PM 6JS6C tubes do see to be expensive. But if you look at the completed auctions, some were gotten for $9 and NOS. Patience...
Daave 11-15-2011, 09:11 PM A raster and horizontal deflection are encouraging signs (arcs and popping sounds, not so much).
In addition to electrolytics, I think I see a "bumblebee" plastic-coated paper cap hanging off that convergence board. Those are as bad as wax paper caps -- highly suspect.
If I spied any other bumblebees, particularly in vertical & horizontal sections, they would be high on my list for replacement. Ditto for any plastic-coated caps in other clothing, like Big Chiefs.
Have fun,
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html
Do you mean the white cap on the convergence board? Im not familiar with what a bumblebee cap is. Also, How can I spot other plastic coated "Big Cheifs"? There are a lot of maroon caps and ceramic disc types.
I see about 5 of those white caps on the chassis, including one large one in the vertical circuit.
miniman82 11-15-2011, 10:05 PM The white ones are not to be trusted.
Electronic M 11-15-2011, 10:12 PM Bumblebee caps are in molded black plastic cases and the values are colore coded on them like resistors (some are much bigger than any color coded resistor which is a visual give away). I believe that "big Chiefs" are molded plastic as well but do not have the color code stripes. Plastic Molded paper capacitors come in many colors and trade names and are easy to spot once you know what they generaly look like (or by tracing the schematic if you are good at doing so).
I wish I had time to snap some photos of some bumblebees, and other types I've replaced to show you, but I'm sure the other will do that soon.
Phil Nelson 11-15-2011, 10:21 PM This article has basic info about recapping, with photos and descriptions of common capacitor types:
http://antiqueradio.org/recap.htm
I don't know what's in those old white tubular caps, but I agree, those are iffy, too.
Regards,
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html
Daave 11-16-2011, 09:30 AM Are the large electrolytic capacitors really that expensive?
I mean one filter capacitor 160MFD(uF) 250 volts at mouser or digikey is around 22 dollars?
I think since the set powers up, Im gonna replace the bad tubes first, and see how the picture tube is, if its OK I will start to replace the big caps and the other ones, I just won't run the set long or worry about picture problems until they are replaced. I don't have a CRT or tube tester.
There are many plastic coated paper caps underneath the chassis, I have the schematic but I guess it takes considerable time to cross reference all of them? What kind of time you guys spending doing that?
Phil Nelson 11-16-2011, 11:49 AM As noted in the recapping article, with electrolytics it's often OK to go up to the next common higher capacitance value. For instance, if the original cap is 18 mfd (an oddball value), then you can use 22 mfd (a common value).
Same deal with voltage rating. It's OK to go somewhat higher. For instance, if the original cap is rated for 160V, then you can use one rated 250V.
I don't know where you're looking on Mouser, but electrolytics are generally a few dollars each. Another good supplier is http://www.justradios.com/ , located in Canada.
If you look at their listings of what's available, you'll get an idea of what is a common value and what is not. 160 mfd is not very often used nowadays. To get that value, you could combine, say, 100 mfd and 68 mfd in parallel (again, read the article). You could also bump up to 220 mfd if that's the nearest common value.
Yes, color TVs are complex and it may take you a while to learn your way around that chassis and schematic. I don't count the hours I spend in a restoration because I do it for fun. Realistically, this is not something you can expect to polish off in one evening.
So, I would relax, take my time, and enjoy the process of bringing a great old TV back to life.
Regards,
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html
Daave 11-16-2011, 05:14 PM As noted in the recapping article, with electrolytics it's often OK to go up to the next common higher capacitance value. For instance, if the original cap is 18 mfd (an oddball value), then you can use 22 mfd (a common value).
Same deal with voltage rating. It's OK to go somewhat higher. For instance, if the original cap is rated for 160V, then you can use one rated 250V.
I don't know where you're looking on Mouser, but electrolytics are generally a few dollars each. Another good supplier is http://www.justradios.com/ , located in Canada.
If you look at their listings of what's available, you'll get an idea of what is a common value and what is not. 160 mfd is not very often used nowadays. To get that value, you could combine, say, 100 mfd and 68 mfd in parallel (again, read the article). You could also bump up to 220 mfd if that's the nearest common value.
Yes, color TVs are complex and it may take you a while to learn your way around that chassis and schematic. I don't count the hours I spend in a restoration because I do it for fun. Realistically, this is not something you can expect to polish off in one evening.
So, I would relax, take my time, and enjoy the process of bringing a great old TV back to life.
Regards,
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html
Thanks for the site/info! Helps a lot!
bgadow 11-16-2011, 10:04 PM Your new capacitors will look different than the old ones, since technology has improved and they are now a lot smaller. The linked article may explain it, but basically you can leave the old filter cans in place and mount the new electrolytics under the chassis. (don't leave the old ones wired in, though) You can get new can-type caps but those are expensive; maybe that was what you saw when you were shopping. Get electrolytics rated at 105c instead of 85c as they will last longer but won't cost much more.
DaveWM 11-16-2011, 10:59 PM you can also save by using radial leads vs axial leads, a lot cheaper. I generally get nichicon's 105c rated. Check voltages, often you can get a 350v for the same as a 200v so if you need a 200v just get 350's that way you have them when a circuit requires a 300 or 350v. the also come in a variety of sizes, I like the tall skinny radials since they fit inside the old cans (I prefer to restuff the cans vs putting them in under the chassis). I have a method that I use when not too concerned about cosmetics. I have what I call a bone saw which has a receiprocating blade about 2" long. I 1st cover the chassis with paper around the can, then use the saw to cut if off just above the shoulder (about 1/4 inch from the bottom). the paper is there to catch the alum chips from the saw action. cutting at the shoulder leaves the phenolic base (which has the terminals of the can embedded in it) intact. then drill from the bottom side right along the term strips. with a center hold drilled for the common negatives. A little planning here can help to make sure the leads from the caps are in a position to allow all the caps to fit inside (up to 4) the can. Care needs to be applied to make sure the leads are next to terminals and not shorting to the chassis, there is not a lot of room for error, but its not hard. Triple check the polarity and the correct cap the correct term on the can.
by doing the above you can leave the lead dress alone as well as any parts soldered to the lugs (like resistors). I find that alone worth the effort as you don't have to spend time removing the old can and all the attached wires and parts. a typical can cap can be restuffed in about 5-10 min tops after you get the hang of how to use the saw and how to align the caps. The tall skinny ones make it much easier since they fit so easy inside the can.
for the common neg I just pig tail some solid copper wire, slide it over the common leads in the center, solder, then solder the wire to one of the already solder cap twist lock lugs. I leave the insulation in place just so its not as critical to make sure the wire does not brush up against term on the cap. again rechecking work catches this stuff (I have a very bright shop light handy for that).
after all that is done I will do a slow start with a variac, monitoring the B+ voltage and current. slowly ramping it up will make sure there were no reversed caps or shorts to worry about.
if all good then I will use a large threaded hook screw into the old cap guts, pull them out, clean the inside bottom edge of the can with some solvent, scratch it up with some 150 grit sand paper, smear some 5 min epoxy around the inside edge, positiion the can over over the base (with values pointing out so they can be read) and let gravity pull the epoxy downward and flow around the base. the 5 min is good since it's pretty thick stuff.
I will also cut some alum tape (used by hvac folks) into strips about 1/2 wide and use that to join around the shoulder, just in case some of the epoxy manages to seep out the seam.
again this is not cosmetically the best but it is fast, and IMHO the least disruptive to the overall chassis (since the bottom terminals are left completely alone, but for the new cap leads solder to them.
I take the same approach on recapping hand wired chassis, leaving the existing leads alone where they attach to tube sockets, just pig tailing the new parts in. The main reason is to properly remove the old solder and unwrap the orig leads can be some what stressful to the terms, esp on old wafer style sockets. the pig tailing done well does not look bad and certainly is a lot less stressful.
now if I was doing a museum quality restoration then I would no doubt take a different approach, but for daily drivers, esp if they do not belong to me, I go the do no harm approach even if it is not as pretty.
DavGoodlin 11-17-2011, 07:27 PM Daave: "Are the large electrolytic capacitors really that expensive?"
Another source for electrolytics are BPC's (90's TV's) and monitors. I recycle them at the county "dump" facility, BUT only after i snip leads and pull out the chassis. Monitors have a few 160 volt caps from 47 to 200 mfd and I hide these under many a radio chassis. Junk black box Tv's get the same treatment and there are usually caps up to 350 volts. Your Zenith will need some in the 450 volt range and those do cost some $$$. Check the schematic to see what voltage is really needed rather than going by the OEM cap.
Good luck, Dave
DavGoodlin 11-18-2011, 02:53 PM Oh, i almost forgot: One of the most important things I learned about capacitor voltages involves the fact that AC voltages on the plate feedback circuit of vertical output tubes can far exceed the DC voltage. On most schematics, it says "do not measure", yet an OEM 600volt cap is feeding back to the vertical in a multi-vibrator configuration. These caps should be 1600 volts minimum. Many a Philco BW recap and subsequent vertical collapse taught me this lesson.
Daave 12-07-2011, 09:03 PM OK well I finally got a couple new tubes for this TV, and well, not sure the CRT is much good. It does have a full raster now, but no sound, VHF and UHF tuners work, but for the life of me I can't get it to tune a colour picture.
The G2 controls have to be almost all the way up to get any brightness, and the focus control won't dial in a sharp focus. All the filter electrolytics are still original and are cold after even a few hours of running.
The contrast control doesn't do anything, brightness as well has 3/4 of its control that just produces a black picture. So not terribly excited right now. Does anyone think I have any hope on a CRT rebuilder helping this tube? Its never had a brightener installed.
Some pics.
DaveWM 12-07-2011, 09:27 PM with that briight a red raster I think your CRT is prob fine. You should go thru the setup procedure, serv switch to serv, CRT bias fully CCW, no signal to set, turn up the G2's one at a time until you just see a horz line, turn up each color until you just see each, all about the same. Return the serv switch to normal. if any one color fails to produce a line, then slowly turn up the crt bias until that line is produced with the G2 at the max, then adj the other colors down until they are all the same, just visable lines.
If you dont have enough brightness, suspect the video out tube. If its weak it causes the cathode of the CRT to be to high, thus cutting off the tube. A quick check of the CRT pins voltages will confirm this (the cathodes and the G1).
Lack of contrast is prob due to an open bypass cap (large value 50-100uf) on the video out tube cathode, follow the contrast pot lead it should connect to it, prob a section of a multisection can cap.
Lack of focus is prob a focus rectifier (tube or Se stick), but the seeming lack of focus may just be the lack of gain from the video out tube (that 50-100uf cap above). Try bridging a new cap over that and see if the contrast and focus improves. If the contrast control is doing very little then its most likely that cap.
with that much red the prob is def not the CRT.
DaveWM 12-07-2011, 09:38 PM also since you are getting a B&W pic then all the guns are working. No color, I would start with the obvious, clean the color control, clean all the tube pins and sockets with your fav contract cleaner. Wiggle the chroma tube (burst amp, osc,demodulator tubes). if still nothing you can use a scope and check for waveforms with a sams, or just get some new tubes (I would suspect the 3.58mhz osc 1st). replace the color killer tube. Some times the color crystal will be bad, you may seen barber pole colors, sometime just a purple overall color, depends on just how far out of whack the osc is running. again a scope is best also voltage checks and tube replacement of the chroma tubes.
Daave 12-08-2011, 06:34 AM Thanks for all that info! What should the cathode and G1 Voltages be? Or is that on the schematic? Im new to this and will learn :)
The red raster in the picture exaggerates its brightness, but when I did a quick setup as you described above, the line is sharp and defined and well focused much better than the tuned picture is so you are probably right the problem might be somewhere else.
DaveWM 12-08-2011, 07:29 AM yea if you can get a sharp bright line with the bias all the way down, then you are good on the CRT.
The voltage are on the schmatic, pins 4/13/5 around 300v (cathodes) 6/12/2 200v (G1) 11/3/9G2 around 700
Daave 12-08-2011, 07:35 AM Awesome thanks! I did notice though that the green line dims out at the left edge, the other 2 colours didn't do that, but all 3 lines are bright with the bias all the way CCW.
DaveWM 12-08-2011, 07:45 AM would not worry about that green yet.
do not compensate for dim pic with the crt bias, if its dim and the setup shows the lines then you need to look elsewhere, your set is trying to tell you something is wrong. My guess is a weak video out.
there is also a brightness range pot on some zeniths that limits the action of the user adj brightness. It is set by adj reg brightness to full then turning the range to just before the pic blooms out. there are some resistors to check as well just look aound the brighness circuit. check the voltage on the screen of the video out. this is where a scope is handy since you could look at the PP of the signals and see if it looks good.
Daave 12-08-2011, 08:21 PM I took the measurements and compared to the schematic.
Cathodes
Pins 4-13-5 Schematic said 275, I read between 275 and 280.
G1s
Pin 6 Called for 230, I read 171
Pin 12 called for 230, I read 176
Pin 2 called for 220, I read 165
G2
Pin 7 Called for 475, I read 750v
Pin 11 Called for 425 I read 763v
Pin 3 Called for 445, I read 776v
These could all be easily adjusted to the specific voltages by adjusting the gain pots. but my picture disappeared :(
These were all read with the simple setup performed and a signal to the tv. I read the filament voltage and it reads on my meter at 6.09 volts, not sure if this is just a variance in my meter or the actual voltage and/or if that small amount would make any difference.
If I understand any of this, the Low G1 voltage combined with low brightness isn't a good thing., as well as the higher g2 voltage required to produce any image. Im still new, but all of that points to a weak CRT to me? Im really open to being corrected though ;)
DaveWM 12-09-2011, 07:23 AM I took the measurements and compared to the schematic.
Cathodes
Pins 4-13-5 Schematic said 275, I read between 275 and 280.
G1s
Pin 6 Called for 230, I read 171
Pin 12 called for 230, I read 176
Pin 2 called for 220, I read 165
G2
Pin 7 Called for 475, I read 750v
Pin 11 Called for 425 I read 763v
Pin 3 Called for 445, I read 776v
These could all be easily adjusted to the specific voltages by adjusting the gain pots. but my picture disappeared :(
These were all read with the simple setup performed and a signal to the tv. I read the filament voltage and it reads on my meter at 6.09 volts, not sure if this is just a variance in my meter or the actual voltage and/or if that small amount would make any difference.
If I understand any of this, the Low G1 voltage combined with low brightness isn't a good thing., as well as the higher g2 voltage required to produce any image. Im still new, but all of that points to a weak CRT to me? Im really open to being corrected though ;)
why does that point to a weak CRT, you keep saying that. Sounds more like maybe a HV issue IF by the pic disappeared you really mean it bloomed away.
IF its blooming I would check out the HV. The pic is dark because the CRT is being cut off by the low G1 voltage and the low screens. If you can get a red raster like you had then the CRT is fine.
if you really think its the CRT you should get a CRT tester. Just dont be tempted to rejuvenate it. the LAST thing I worry about is the CRT get everything else working, even a VERY weak crt will produce a watchable pic, not great but you should be able to get everything sorted out as far as color, image, sync, etc....
oh and voltages should be checked with NO signal.
DaveWM 12-09-2011, 07:42 AM checked my zenith color service man (RL goodman) shows 290/175/640 for K/g1/g2.
check your HV and focus voltages. you will need a HV prob for this.
if you have not already, you should try a new 1v2 AND 3AT2. I generally sub out all new HV tubes when HV is not right. (damper,hot,shunt,hv rec, focus rec). If that fixes it I leave the new rec tubes in, and try the old HOT and Shunt to see if the HV holds. the rec tubes are cheap so I leave the new ones in.
Daave 12-09-2011, 08:05 AM Yea I guess Im not sure what happens when a CRT cuts off. It can produce relatively bright rasters on all 3 colours. If the tube is weak I am ok with it if I can get it to make a watchable pic. Its not going to be a daily watcher.
Im limited in my testing equipment, I don't have a HV probe or a scope, and have no issues getting something, if it will help me fix it.
Is there ways to work on checking some of the HV out without the HV probe? What are they worth? Or is it just easier to get new tubes and try that first.
I already have a new HOT, and damper. But the focus and HV rectifiers look to have been there since the set was new. The old HOT was making a blue arc internally. I do appreciate the help guys maybe Im just a pessimist.
DaveWM 12-09-2011, 08:18 AM if you can get decent rasters on all colors the CRT is not weak.
replacement those tubes. HV probs are not expensive, should be able to find one on ebay for 10-15$, very handy esp for discharging the crt (some use a grounded flat blade screw driver, but if you have the prob its just easier).
if it blooms out that is prob the ones. Have you checked the current thru the HOT? if its blooming its not being cut off but rather the HV is going away, either because the CRT is drawing too much current (incorrect CRT bias pot setting or some other defect in the drive circuits) OR the HV is simply not up to the job of providing the required current at the needed voltage.
Daave 12-13-2011, 11:52 AM How can I power up the chassis with no CRT/yoke ?
Daave 12-23-2011, 10:47 PM Ok I got it recapped, and that bought me the contrast control and sound back. I replaced the focus rectifier tube and that got me colour back (not sure how that works). But I tried to replace the shunt tube and the rectifier tube in the HV cage with NOS tubes and that got me very low HV and the pic kept blooming away, The shunt tube was a 6el4, and the new one was a 6el4a.(I had a few of these and none worked) So I put back the originals. But as a whole a huge improvement, watchable picture, good sound, but still won't go that bright (the first 3/4 of the brightness control is a black screen). I don't have an HV probe yet so not sure if the HV is still low? or possibly something else.
Some pics!
DaveWM 12-24-2011, 07:29 AM Besides G2 settings (screen pots) and CRT bias setting, the video out tube can cause low brightness. Most of what I read on proper setup is to NOT compensate for low brightness by cranking up the bias or screens (above the normal setup procedure using the setup switch). If there is low brightness AFTER the setup procedure is complete, then some more work needs to be done, unless of course expectations are just too high.
I would hold up any further work and get the HV checked out and setup (correct hv, and shunt tube current).
IIRC the problem with a weak video out tube is the plate voltage ends up being high due to a lack of V drop, and since the CRT is directly coupled the CRT cathode voltage ends up higher than is should be, cutting off the CRT.
Daave 12-24-2011, 08:17 AM I am working on an HV probe and yea don't plan on doing much else until I have it. I was very excited to have this picture on it, Im still a noob.
I do have another NOS video out tube I can sub in. The only setup Ive done is with the service switch on, Adjusted Pots just until I got a line on each gun, with the CRT bias all the way CCW. The focus adjustment is also all the way CCW to get a decent focus (but still could use more focusing)
DaveWM 12-24-2011, 09:54 AM focus can be a problem. On some of my sets it seems to be at an extreme end others is fine. On one I had to have the coil turned all the way in (coil used not a pot) and it was still soft, then replaced the focus tube and it was the other way. Same with deal with focus sticks. If you have a supply of focus tubes try subbing in others. Your setup sounds good, so try subbing the video out tube. The pic looks good, if it gets much brighter you will prob start to have some retrace line issues.
dieseljeep 12-24-2011, 10:42 AM One of the things I would do is replace that 6EL4 with a 6BK4. Also check or replace the dropping resistor for the 1V2 filament. You're making good progress on that set.
Daave 12-24-2011, 11:41 AM I did notice on the 6el4 thats in there, it never lights up, or is so dim I can't see it thru the dark glass even with the room black. As I understand this one only lights up when it needs to?
I don't have full vertical either, Im missing the bottom inch or so, the vertical output tube gets very hot I can't even touch it during operation.
dieseljeep 12-24-2011, 11:59 AM I did notice on the 6el4 thats in there, it never lights up, or is so dim I can't see it thru the dark glass even with the room black. As I understand this one only lights up when it needs to?
I don't have full vertical either, Im missing the bottom inch or so, the vertical output tube gets very hot I can't even touch it during operation.
A new 6BK4 is perfectly clear. If that tube is that dark, it's pretty well spent. New 6BK4's are very reasonable at ESRC in Florida. They show a 6EL4 for $40.00 USD. Why, I don't know. ???.... Is the vertical output a 6HE5? It's a fairly hot running tube. Probably a lot of faults in that set that have to be sorted out, one at a time.
DaveWM 12-24-2011, 12:18 PM yea you should see the 6Bk4 glow all the time, just brighter when there is less beam current thru the CRT (dark scenes), should be clearly visable glow near the base of the tube. The 6EL4 from what I understand is just more X-ray shielded, leaded glass perhaps. I routinely replace some of the large ceramic tube caps in the vert circuit of zenith, .1 1kv I think. My cap tester only goes to 450v so I cant really test them well. They are prob ok, but I change them anyway. like the other poster said, often there are a lot of minor problems, just need to work them one at a time.
Make sure your pic is centered, do this in the setup mode to see where the horz line is. then you can adj the V heigh and V lin. get that and the purity all squared away before touching the convergence.
miniman82 12-24-2011, 12:24 PM If you mean the blue tube glow, it should only do that when the screen is dark. If it's lighting up strongly all the time, you probably need to do the HV regulation performance check. It involves placing a 1ma current meter in series with the regulator cathode, turning brightness all the way down, then adjusting the HV pot for a .8ma reading. Any more than that and the regulator is dragging down HV too far.
DaveWM 12-24-2011, 01:27 PM I was meaning the reg orange glow of the filament, I have seen some ghastly green glow on some shunt tubes, perhaps that is a gassey tube. I generally will set up the HV to about 23kv, which works out to about 1-1.5ma shunt tube current with the CRT cut off, and the current on the HOT at specified amount (185-210ma generally). With full raster, the shunt is around .3 to .5ma with very little flux in the HV 23kv.
I have read that if if the shunt current drops below the low amount on the full brightness, then turning the horz eff coil CW 1/4 turn will bring it back up (and increase the current above the min dip amount in the HOT). the idea being if the current thru the shunt drops too low it will be less able to regulate the HV. But the HOT current should still be within the specified max. If all that does not work then there is a problem somewhere in the HV circuit.
I know there has been some discussion on what the HV should be set at, I like to keep it no higher than 23kv, the idea being its less likely to arc over in the HV section of the FLY.
Daave 12-24-2011, 02:34 PM I'm gonna have to check again but I'm certain I don't see a filament glow on he shunt at all either in the original or the NOS replacements I've tried.
Daave 12-24-2011, 04:28 PM Ok feel kinda stupid
The shunt tube was dead. I stuck in a NOS one and it works.
All the adjustments had to be done again. Now the HV adjust pot actually does stuff. Pic is sharper and odd blue glows from the 1V2 and the damper are gone. But the shunt does glow blue. (along with a red filament now)
Does that mean the HV would have been going full tilt all the time?
Electronic M 12-24-2011, 04:49 PM Yup! I once disconnected the shunt on an Admiral and turned down the brightness, and the HV shot up from 25 to around 30KV and there were lots of new arcing sounds.....Needless to say I did not run her that way long.
miniman82 12-24-2011, 05:54 PM The first color sets had very strong HV sections, both my 21-CT-55 and CTC-4 will make upwards of 40Kv is the regulator is disabled. The later sets were a bit weaker, I once had a CTC-9 that would only make 32Kv with the reg disconnected and my current CTC-7 project won't make much more than 25. I've heard the CTC-5 is the worst of the lot, most schematics show 19.5Kv as the anode supply.
julianburke 12-28-2011, 01:01 PM Some of the "popping" may be coming from the old dried out anode cup on the CRT. Zenith used rather small ones that when cracked would arc to the surrounding area of the anode button. These did deteriorate and be sure to look at it. Possibly you may want to replace all of it to the 3AT2 HV socket with a quality cup. Taking a air hose and blowing out the set is a good idea and wiping down the CRT with Windex esp around the anode button helps too. All of that dust/dirt attracts moisture.
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