Thanks Electonic M and old coot88 for the ideas. I guess I know the right way to do such a job, but often there are 'tricks of the trade' that are guicker and/or easier, while being just as effective. I think old coot88's tip is one of those very ideas, for those without a meter at least, but like a meter the circuit still must be broken and the bulb wired in series.

As for me, I have one of the monolythic Hickok Model 209A "volt-ohm-milliammeters, which is primarily for show since I can't find the proper size lead plugs for the small leads which I may have one of, but I would need two for some functions. The lead that I have is brittle, but I could re-use the ends. I have the large screw in lead in good condition. I love the look of this unit and would like to put it to use some day, but that's likely another restoration in its self. I also have an old Simpson VTVM that needs calibration or something as well as a later solid state Simpson that works great. I like to take that one to work to confuse the 'super techs' and even engineers these days. That is what I will probably use for this horizontal output job since analogs supposedly do a better job at giving a good, steady readiing. Of course there is always a dime a dozen digital meter or two around. Mine is decent, but frankly I don't see a big difference between my KAL Equipment job and the ever so popular Flukes we use at work.

I think it is in another thread that this H.O. current is being mentioned and once I read to disconnect a pin that is grounded to the chassis and add a small value capacitor. Then someone else wrote that he didn't get a reading with a capacitor, but he did when he removed it. No doubt, with these threads you can't take every little thing to heart or you might never get a job done. There are too many variables like human and equipment error. But V-K sure a great place to get tips from the best of the best; many of whom were doing this for a job. That sure must have been a great time to be in the electronics profession as all of the home entertainment repair is gone. There are a few bench jobs in industrial equipment repair these days, but I will refrain from getting on that boring topic.

Thanks again folks! I'm feeling the Zenith exitement coming on! Once this coil is in place and with hopefully good results, I will probably be talking about getting the color back. I think I mentioned once before that someone sent me a crystal that is supposed to work as a replacement for the old type that supposedly often go bad. The new part looks almost like a blue disc capacitor. Hopefully this repair will be easy since the set had great color to be at least 20 years dormant, then it just went away completely to black and white, so probably not too difficult. I think its a capacitor frankly, but that's just because they are usually the problem with a long dormant set.

I had to remove the capacitor that is supposed to be added when doing the ma test on the cathode because the meter I was using wouldn't pass the current to ground with the capacitor there, once removed it went from the cathode to the meter to ground completing the circuit.

Tj,
If the HO cathode current was within spec before the eff.coil went springy, very probably it'll be within spec with the new coil once you dip it using the 'magic light bulb' method.:tongue: Does the HO tube look beat up with heavy black deposits inside the glass or other obvious 'burnt' looks? If not, it was probably running in the safe range.
RS still sells #44 bulbs (cat.# 272-1108).

Kramden66 mentioned using a cap with the meter causing an open-circuit condition (in the cathode leg). He mighta had the cap in series instead of in parallel with the meter.
I never used a capacitor with the meter or saw any need to, since the meter presents a very low (effectively nil) impedance. Like a near-dead short.

Back in the day, there was an adapter (Pomona?) you'd plug into the HO tube socket, then plug the tube into the adapter; it breaks the cathode leg, and two leads coming out of the adapter connect to your milliameter. Doubt if those adapters are still available today, though.

(EDIT) Just a thought.. i never done it, but it might be possible to use a
digital meter for cathode current by shunting it with a very large capacitor to smooth out the raggedy waveform. Several thousand mfd. might keep the meter from going nuts.

Hey kramden66, we have a good and valuable friend in old coot88! It's easy enough to tell that he did this for a living! I do it for a living as well, but I'm sure everyone has read enough of my soapboxing of the "dumbing down" of electronics. It's more or less a plug and play, or throw away world ever since the microprocessor was integrated into electronics. We don't really have a big need to know what used to be almost a given and really is just the fundamentals of electronics. Our knowledge base and training give us the capability and credentials to gain employment in the field; and yes I guess I take a lot of the knowledge for granted and I tend to forget that the average individual without some training doesn't know the difference between alternating and direct current.

Even we tend to forget aspects of the two types of current and their effect on capacitors as was proven by old coot88's reminder of a capacitor's behavior as an open circuit if placed in series with an ammeter and a DC supply. I hadn't really thought of it (or remembered), but it makes sense. With DC a capacitor is charged to its full capacity and then behaves like an open circuit with AC because of polarity reversal this charge and discharge cycle continue and the current continues to flow in the external circuit. There is no frequency with direct current, so there can't be capacitive reactance. X sub C = 2 x pie x frequency x capacitance if I remember right.

My HO tube doesn't look burned up, but when I first brought the set home there was no HV and the tube was red plated. It's been so long I don't remember all the specifics, but I think one of the tubes was damaged, maybe cracked. Seems like it was one of the tubes inside the HV cage. I replaced that and I think one other tube extenal of the cage that's related to sweep and gained HV and no red plate. It wasn't long before I discovered this coil and haven't had much power up time at all on the set. I didn't want to risk any flyback damage since I have read so much about it with these color sets which I typically never mess with, so my knowledge on a lot of the particulars of these sets is very limited.

OK, I installed the Efficiency coil finally. No real change, but there wasn't really a problem other than knowing that there was a broken part in the set that could cause damage to the set that could be avoided. I didn't work the set long as I still haven't wired in an amp meter and checked the cathode current.

I did notice a bit of hissing in the H.V. cage that led me to play with the slug a little. I could adjust a little and it would go away along with the on screen jitters that come with corona discharge. The discharge is very light; not a loud hiss or snapping like I have heard. I turned the H.V. adjustment down a little and it didn't make any difference. I need to get a meter on this puppy.

I have heard of moisture collecting in long dormant sets and noise from the cage being an issue until the set works long enough to dry out well.

Lacking a meter, at least get #44 bulb to dip the K current. Is there a RS store near you?
The dip point is very sharp, and if the coil is off dip, the current can be dangerously high and you'd never know it, even if the tube isn't red plating yet.
You're right about letting moisture cook off to see if the hiss goes away. But get the K current dipped first.

I agree 100% on getting that current right. My Simpson meter should do the job fine. Or if I chose to use a bulb, isn't a #44 a standard pilot lamp bulb for vintage radio and TV? I need a source for a few of them, but I never would have thought about Radio Shack. I wouldn't think anyone would know what a bulb is that works there frankly! LOL! Again, thanks for REAL words of wisdom and good advice. It would be easy for many to overlook such an issue, but since I have addressed a real issue with replacement of the broken coil (which was floppy like a slinky), I may as well do the job right.

I never knew how important that cathode current was till I started working on my set and then was given the advice to make sure its ok , it was at 220 or 225 or something like that , I'd have to check my notes but it running like that was causing the fly to get hot after a while , now that I have it running at 200ma the fly doesn't get hot , I don't even think it gets warm , if it does its so low that it is tough to tell and is negligible , so get that bulb hooked up or even better the meter and make sure its not high , I was told I could probably take mine lower but the schematic shows 200 and the instructions say no higher then 210 , I didn't want to go to 180 as was suggested because the proportions are just barely right now , if it gets reduced anymore the only way a circle will still be a circle would be to adjust so theres is a gap at the top and the bottom and I don't want to do that.

is this cathode current issue important for the black and white sets too I wonder .

mike

The H output tubes in color sets (like 6JE6, 6JS6 etc.) are run at their absolute heat limit with no 'headroom' for overcurrent. That's why it's imperative to dip the current. Highest 'safe' current would be around 210 ma, with 200 preferable for good longevity. Much below 200 and you start getting width and regulation issues.
Tubes like 6KD6 etc. are beefier by design and can take more overcurrent, a requirement with the feedback-type HV regulation used in some Admirals.

B&W sets normally don't have these issues since the HO tubes run with adequate 'headroom'.

RS still lists the #44 bulb..
http://www.radioshack.com/product/in...ductId=2102798
Incorrectly listed as "flashlight bulb".
Also listed is #47 which is more commonly used for dial lights, and is half the current. Cat.# 272-1110

These are foreign sourced junk but better than nothing.

I think I will use my Simpson 260 on this and go ahead and make a permanent and eventually fused connection point. Sounds simple; break the conductor grounding the cathode pin and run two pieces of wire to put the ammeter in series with the circuit.

I have a digital meter with the current fuses blown out of it, so I suspect someone without training in properly using a meter got a hold of that one and checked some amperes in parallel. I was on another thread last night and someone was talking about checking current with a volt meter hooked in parallel. There are quite a few fundamentals of using meters that perhaps we should do another thread on. I think it would be a good thread where the right people could explain the often superior nature of the analog meter. An elaboration on the further pros of the VTVM would be good too.

Also, I got a chance to evaluate types of capacitors on this (for my collection) newer set. I wanted to see what I might immediately want to remove as far as commonly known to fail types like bumble bees for instance. I didn't see any of those. Mostly I saw the old reddish brown drops which I hear are ok in most cases. The paper-foil is what I think needs to go and what I saw was several black plastic coated paper caps. I wonder if these are as bad as the bumblebee type, or even remotely as bad.

I think for now I will leave the multi-section cans alone as they are pretty tough old parts and sometimes I think they might be better than what you get from China. Anyway, what about those black beauties?

if in doubt check those black capacitors for leakage if you have such an instrument to test them, wouldn't hurt to replace them, they could be causing your color issue too.

as far as electrolytics go i've given up on trusting 40 year old or more electrolytics even multi section , I do have one set running on one original electrolytic in a multi can , its a 58 zenith and the reason is its a 475 volt cap , I didn't have any 500 volt ones to put in so I chanced it and it seems to be holding up , its tough to test the voltage because the set can only be removed by disconnecting the tuner with the two plug in plug out connectors running to the tuner and I really didn't want to remove the tuner just to test the voltage on that one electrolytic just to see if it has a higher then 450 volt running voltage and running wires from it would have been a pain too , down the road I may just replace it , its in the focus circuit.

awaiting the post that tells us the cathode current.

Bad luck with meters lately. My digital junk has the current fuses blown. It was that way when I got it. I just forgot to get some more. Then yesterday I got out the Simpson analog; meter of choice and the batteries are dead.

Worry not, I will get this done eventually.:D

I want to clarify this procedure before I go further as it keeps being mentioned, but I'm not seeing specific connection points for the meter or bulb. I am assuming that if I read the schematic and find the cathode connection then I can simply break the circuit at the solder terminal and connect one lead. The other lead should be going to chassis ground. Is there something that I am missing or is this OK?

Yup you got it. :yes:

If you use a bulb then inserting it between the top cap and the lead that connects there is a better idea as a series cathode resistance from the bulb could throw off the grid bias.

This is true. But the 4V or so dropped by the bulb would be negligible and probably not noticeable except for a slight width reduction. For convenience doing 'dip checks' in the field, we put the bulb in the plate lead, using a little made-for-purpose adapter.

Looks like pins 4 and 10 will be the two potential places that I can break the connection and run two wires out to an eventual fused terminal. Then I can easily monitor this in the future by opening the two wires and placing the amp meter in series.

I saw a video where a guy showed two ways of checking the current on the tube. He was lucky enough to have some adapter that was made just for the purpose of cathode measurements. Also, he took measurements off of the much more easy to access plate cap, but he specifically used a stand alone milli-ammeter and stressed the dangers of doing it that way due to the extremely high pulses present there. Not sure why the old stand alone meter was any better to use than a normal analog meter, but that is what he used.

I did it. I ran the two wires and connected my Simpson meter. At first the current was about 210 or even more. I was surprised at how much I turned the slug to get what I consider to be a small reaction, but I was able to get it down to about 200.

What I battle now (maybe moisture related) is some corona arching, or really more of a hissing. You can see it inside of the rectifier. This gives an interference of course on the picture which by the way is stable and linear. Sound is good. Just missing color now and the hissing. I have more than once been tweaking the efficiency coil or the HV adj and made the hissing go away, but it comes back every time.

My final concern is heat. I'm not used to color sets, and I don't know what is an acceptable amount of heat to have coming from the fly and the power transformer. In a perfect world they should stay cool, or cooler than other things like tubes. I kept shining a flashlight into the H.V. cage and looking at the fly for signs of melting wax or plastic. The metal around the cage was warm to the touch. I wish I had my laser temp gun from work! Now the power tranny was to me hotter than I prefer one to run, but then again I know these color sets pull a lot of current from the wall. I could put my hand on the power tranny, but after maybe 30 seconds it was getting a bit too warm. None of the lytic cans were warm at all, so that's good.

There was one of those brownish/reddish drop caps over in the horizontal section that to me felt slightly warm. I hope it was actually. Maybe it has something to do with my hissing. Oh, and there was one bumblebee in there. Need to get that out quick.

Say hey.:banana: if you got the K down to 200ma., great. The dip is usually much sharper than you describe, but if it holds at that value, what the hey. It wouldn't hurt to keep the meter on it for a while. Gotta luv the Simpson 260 huh?

It doesn't sound like you have any heat problem to speak of. The power xfmr will run pretty hot to the touch. The fly will get fairly warm. Sheet metal will warm up from radiant heat off the hot tubes.

The hiss sorta remains a work in progress.

Indeed I love the 260! I have a Simpson 303 VTVM as well, but I need some new leads and the calibration is off. I tried calibrating it once, but something was still amiss. That's OK because the 260 is bullet proof. A few years back I was finishing up my electronics degree and one night while staying late the troubleshooting instructor came and got me and asked if I could help with a meter.

A fellow tech had sent his wife to class with his old meter to save a buck or two. Not even the instructor knew how to use it, but they figured out enough to set it to resistance and had gotten the manual out and found out that they had to zero the meter. Well, the meter wouldn't deflect but about half way. I knew that the batteries were dead. I told her that I had a digital meter that would suit her needs for the class as well as any other (which was true) and that I would trade her even. I told her that I was pretty sure that it was the batteries, but I wouldn't know until I changed them and I would take a chance on it in a trade. She was happy; I was VERY happy! Yellow case and all; like new.

Anyway, thanks for all the info. I feel better about a lot of things except the lack of dip point that you mention. I knew that there should be a more profound effect on the current while turning the slug. Actually, it was pretty close to begin with and turning the slug only brought it down a bit. On the hissing, I might double check the H.V. rectifier and regulator.

try moving the HV filament leads around. The insulation may be breaking down on them, and they run right next to the cage.

I turned the lights off to look at the source of the corona arc and all I could see was a blue glow inside of the rectifier tube. I don't recollect rectifiers glowing blue inside. I was thinking that they are normally dark. But I don't spend a lot of time looking. Anyway, I was just looking through the slots in the bottom of the H.V. cage since I have the set on its side.

Hope I can get it to stop. It's not an actual arc or loud snap, but more like a hiss which is still an arc of some sort, just not the really bad kind.

Do you smell any ozone from the HV area?

Maybe you have already done this, but I always clean the inside of the HV cage -- and everything inside it -- with isopropyl alcohol. Great for removing any grease or black soot. Even if it doesn't magically cure your hiss, it might make it easier to see what's going on.

Phil Nelson

Good job , now like stated make sure everything is clean including the pins in the tube sockets , also post when you start tackling the color issue.
btw the glow inside my rectifier is blue/green in color.
mike

No, can't say that I smell anything. Just hear the hiss and see the blue glow inside of the rectifier, and of course the resultant interference on the screen. I only mention the blue glow inside of the rectifier because I expected to see something when I turned out the lights, but that is all that I saw.

Perhaps it just wasn't in a viewable area. I have had a number of sets through the years to have sharp solder joints or whatnot causing arching, not a hiss, but actual arching. Seems like a long time ago I had an old color set like this that was doing this and it was just moisture around the H.V. lead to the C.R.T. Perhaps I should check that just to be sure. They are in close proximity, so maybe I mistook the sound's origin.

If you have a length of flexible plastic tubing, you can use it as a sort of stethoscope to track down the source of the noise. Sometimes it's surprisingly difficult to pinpoint a noise source.

Phil Nelson

A HV Rectifier tube that is glowing blue is getting gassy. 3AT2's are cheap and hopefully you have some spares to compare. Gassy rectifiers will take out flybacks!

If the HV rectifier is gassy it will run hot. See if it feels inordinately hot (after you discharge CRT of course).:D

oops on my end I was referring to the 6BK4

I seem them give off a ghastly green around elements on those when shunting a lot (dark screen).

Just a side note, I have had my eye on a certain notorious for failing "bumblebee" capacitor for a swap out just for general purpose. But before doing that I wanted to see what circuit that it involved. Turns out that it is a .01 600V cap (C117) that looks to be in parallel with what looks like 3 grids maybe inside the c.r.t.

So, I'm missing color but I don't think that this is the cap that would be one that would take it out leaving behind a good black and white picture. I probably still should get rid of the cap just based on the failure rate. I guess right now I am in the stage of repairing the set as opposed to just jumping in there and replacing every cap with no regard for actual troubleshooting. But even when I get it right I do plan on replacing most of the caps. I may keep the multi section cans as I have found them to be pretty darned tough.

Yesterday I turned the set on to see if I could find a lower dip point than the slightly over 200mA (more like 210) that I measured. To my surprise I looked at the screen and the color had come back, nearly perfect. But it didn't last long and then it was gone.

At least I know that whatever is going on is probably something pretty simple. I cleaned all of the tube pins and sprayed the sockets when I first brought the set home, so it may not be THAT simple. I need to check the color related tubes again for shorts and also that H.V. Rectifier for gas since I still have the aggravating hiss reeking havoc on an otherwise crystal clear picture.

And B.TW. I disconnected one end of that .01 bumblebee and it measured dead on with a D.V.O.M. capacitance tester, so I just tacked it back in place. I know that it along with the other brown drops need to go if I am to use the set regularly. As I stated before, I sort of like doing the repairs and learning something rather than shotguning a bunch of new caps in. Indeed, my way is probably much more trouble than the shotgun method of repair by luck. Especially with the lack of some useful equipment like a very badly needed oscilloscope.

Well, tonight I went ahead a got rid of one of the two "bumblebee" caps. It's the .01mfd @600. that I mentioned previously. If anyone has a schematic, it's C117 and looks to be in parallel with Red, Blue and Green G2s. Like I said, the old one measured fine, but I don't trust digital capacitance testing, so I just got rid of it with a spare .025. I hope the value change is not a problem.

I'm still wondering where the "hiss" and related picture distortion are coming from. It's in the cage for sure and it goes away periodically and the picture smooths right out. I haven't done a lot like test the tubes which is the obvious next move, but I just don't think it's tube, but Lord knows I could be wrong on that. I wish I knew what the fly should run at temperature wise. I can get a laser thermometer & check that out. I might luck out and find a sharp solder joint or something inside that cage.

OR, could this be moisture? Anybody ever heard of that? I know that moisture causes temporary problems with flybacks. Is this one of the symptoms?

First thing is first on a HV corona/arcing issue (or a restoration for that matter) clean the inside of the HV cage including all parts inside as good as you can without breaking anything(conductive dust and gunk can cause all sorts of arcing/corona). After the cleaning if the issues continue run the set with the HV cage open and or partially dismantled and look for arcing/corona in a dark room with the set on. Once you locate it a picture of the area it is coming from will tell us what it is and how to advise you to fix it.

Thanks E.M., that sounds like the logical thing to do. I am sort of jumping the gun I guess as I have the set in a tight spot in the kitchen sitting in the floor on its side doing all the work I can do without being able to move it around much. I guess the good thing about a corona/arch issue is that you can see it in most cases. Removal of the cover and testing the H.V. related tubes will be the next step.

I want to be sure that the fly is running as cool as it should. The ammeter remains connected to the cathode of the H.O. tube, so I can watch for any issues there. I need to run the set for a long enough duration to let things sort of stabilize as they often do. Flys are supposedly notorious for collecting moisture, but I don't really know the symptoms of moisture in a fly.

This set is so unpredictable! I was pleasantly pleased when one day I hooked up a VCR/DVD combo and actually had a clear picture WITH color which had disapeard early on. Next go around or two I used once a stand alone VCR and also an RF converter to try a stand alone DVD player.

Now I have this awful blurry picture with no color at all. The picture has about 4" missing from the top and oddly it will periodically and slowly fade to almost black making you think about HV problems (as I still have the HV hiss and related interference line that it creates on the far left of the picture, top to bottom). However, you can switch to an unused channel and the raster is bright and full as any TV should be.

So I am thinking something in the video or AGC circuits. Any other suggestions? Really this is all dumb when it all could be avoided by replacing the caps and probably having a good running set. Just don't have the time and I hear of so many of these Zeniths more or less working as found. Really, this set is real close to working all things considered. Good sound, full raster etc. Just the HV hissing, video issues, and color. The color can't be far from working fine as I mentioned the one day that everything was dead on pretty much with the DVD/VCR combo.

You really should track down that HV hiss. If it has bad enough arcing or corona it can affect HV stability and cause things like the flyback to die....

If you can't see the problem then get some rubber or plastic tubing, put one end in your ear and probe around the HV cage listening for strongest hiss.