I've made a bloody mess!

[Chad Hauris]

The only test equipment you need is a digital multimeter (or analog voltmeter, but I find the digital is easier to read). Skill and knowledge only comes through experience! The more you do, the easier it becomes.

Troubleshooting always moves from the general or obvious to the specific or concealed. You took care of obvious potential problems such as electrolytics or tubes...that is the first step.

Now you need to start examining the DC voltage readings, starting with the most general...the power supply input voltage to the stage (+405 volt B+). Also it looks like the boost voltage (usually +800 volts or so) comes into this stage. Check the supply voltages against your photofacts. If they are off, then you know that the trouble may lie in the power supply circuit delivering that voltage.

If the power supply inputs are OK, now start measuring the voltages at the 6GF7 tube...check against the photofacts. If you find wrong voltages here, then you know what part of that vertical circuit has a problem.

Do not do component substitution until you have really narrowed down the problem. Checking the DC voltages against the photofacts WILL help lead you to the problem.

[veg-o-matic]

Well, it's too late to do anything about the tubes 'cause I've already sent them off. On the good side, a lot of what I've read seems to point accusingly to that 6GF7A vertical output tube, so maybe getting a new one will do something.

Digital multimeter, eh? Well, I guess the budget will stretch for one. Plus, they're small and a reasonably fun gadget so I'll go shopping soon.

Frankly, though, I just can't see myself patiently testing all these voltages in a logical manner. I'm thinking 10 minutes tops, then I go take a nap.

As for gaining skill and knowledge through experience, well, I can easily see myself getting a really bad perm before any of that "knowledge" stuff sinks in.

Case in point: I got hold of a do-it-yourself TV service book from 1969 yesterday. Looking through it, I see a how to discharge the high-voltage anode (??-- suction cup thing on the CRT). Okay, you attach one end of a lead to the high-voltage cage, then pull the suction cup and poke the other end of the lead to the connector. I'm thinking that lead ought to be pretty heavy duty, but there was no mention of it. And here's the kicker: the picture illustrates the process with the guy's arm leaning on the HV cage while he does it.

Heaven knows I'm no expert, but isn't that kind of...what's the word I'm looking for...assholic?

Well, back to the drawing board. If you don't hear from me for a while, send flowers.

[veg-o-matic]

Well, no real progress, but there's potential.

Got hold of an old book--SAMS Photofact guide to TV repair, or something like that. Bunch of screenshots of problem pictures with associated components to check. Easily the best repair book I've come across so far. Gonna hate to return it to the library!

Anyhoo, there's a capacitor that could be the troublemaker for my "doesn't fill the screen" problem. Found it and pulled it last night, though I don't have a replacement yet.

Here's a stupid cap question--do they all have polarity? The one I pulled is marked .47 +/- 20% 200WV EM. There's a small line of yellow paint at one end. Does that indicate negative pole, or am I screwy?

The SAMS book also pointed an accusing finger at a number of resistors, all of which are buried and almost un-getatable. Should I decide to take the plunge and pull the chassis (not a decision I will make lightly!), how exactly do I discharge the HV anode without making myself dead? I've seen pictures of people just touching the connecter part to the HV cage without using gloves or anything. This makes me nervous!

Though I only have a partial screen's worth of picture, I sat around and watched some (you guessed it) cartoons the other night. Even with the lack of height and the misconvergence, I was impressed by the quality of the picture. Everything was nice and sharp with nice, bright (here it comes...!)

LOLLIPOP
color!

More updates as events warrant!

Hello Veg a Matic,

1. Just electrolytic caps have polarity. Most caps of the value you mentioned don't have any polarity.
2. To discharge the anode of the CRT- The way I usually do that on a tube set is to take a long flat blade screwdriver and attach a test lead to it. Attach the loose end of the test lead to the chassis ground. Then very carefully slide the end of the screwdriver under the anode cap until it touches the metal connector underneath the rubber insulator. You will most likely hear a snap when you contact the connector as the HV drains away from the CRT anode.
Good luck!!!

Jeff

[Carmine]

I've been shocked a couple times from discharged HV (never while on!). Discharged HV likey wouldn't kill you, assuming you're in good heath.

However, it will make you do other things...

Once when I was shocked by a Zenith roundie, my legs tried to stand-up while I was crouched inside a console. Needless to say, I banged my head HARD I didn't know whether to feel pain from my head, or my hand which received the shock, so I just did a lot of cursing!

[jstout66]

You never forget a shock like that!!! I got shocked once by a Sylvania Hybrid set and I will NEVER forget that. I got thrown back into the wall! I had been discharging sets the same way for years and never once took a "bite" from any of them. I don't know why that damn set had such a high build up. Anyway.... I am such a wuss I have never discharged a set again. While in the shop I always made my grandpa do it! (now how nice is that????)

[drh4683]

Did you ever get zapped when picking up a CRT thats not in the cabinet? When I did catarac repair on my zenith roundie, I almost dropped the darn thing right on the floor! The HV well touched the side of my arm when I was aligning it to fit back in the set. I too always did the screwdriver wire trick and it worked good, however if I didnt hold it long enough, there would still be a good zapping charge. Now I use my HV probe, as I can watch the voltage drop to zero, telling me its safe to touch!

[Chad Hauris]

The charge will re-accumulate on the CRT after the first time you discharge it...if a CRT anode lead is disconnected, the button on the tube should always be discharged again before touching.

I disconnect the test lead from the multimeter and connect the end that would plug into the multimeter to an alligator clip lead connected to the CRT ground strap...then I touch the end of the meter probe to the CRT anode to discharge it. The test probe seems to offer good insulation from the HV...have never got shocked using this method.

The only time I have gotten shocked from the HV was when I was removing the 3A3 from a Zenith set years ago...I touched the metal cap of the 3A3 (with the set unplugged) and the HV charge came back through the 3A3 tube somehow...should have discharged the CRT first.

[Richard D]

I think it is safe to say that we who have been in this "hobby" for awhile, it's not a matter of if you will get a hv gotcha! but when. My 2 cents worth
Richard

[veg-o-matic]

Originally posted by Richard D
I think it is safe to say that we who have been in this "hobby" for awhile, it's not a matter of if you will get a hv gotcha! but when. My 2 cents worth
Richard

All righty then!

I'm already nervous just poking around inside the set--this discussion ain't making it any better!

I think mayhap I'll leave the chassis in the cabinet for the time being. At least until I can teach CPR to my weiner dog!

[Richard D]

Hi, veg-o-matic, I did not mean to alarm you unnecessarily, you have a healthy respect for what you are working on and I would be very unhappy if because of my post you quit working on your gem. I think you will be fine, it's the person who trys to blindly charge into a tv chassis without asking for help that really scares me. You seem to be doing everythig right so please continue. Just think of how you will feel when you get it working perfect, and you will!
Richard

[veg-o-matic]

Just so y'all don't think I'm totally inept...

Mom expressed interest in having her bathroom painted. Took care of that and while I was at it, figured it was time to do other stuff it needed.

So, over the weekend I painted, ripped up the old toilet (generic, builder-grade) and replaced the white (!!) ceramic tile floor with good old-fashioned vinyl tile. Yeah, I know the ceramic was supposed to be something of an upgrade, but it was impossible to keep clean, especially the grout.

Oh. Installed a new toilet, too. Kinda important!

It looks quite lovely, if I do say so as shouldn't. Paint might be a bit too shiny, so I'm considering applying a matte glaze to tone it down a bit. Mom's happy with it as it is, but it's my house, as I keep reminding her!

My bathroom next.

No progress on the Dumont, though. Went out and bought some of that PB Blaster stuff to spray on the convergence controls but they're still frozen (though it did help me loosen the supply line for the terlet). I'm about ready to give up on this sucker. Anyone want to give it a good home? Just come on by!

Oh, and I won that Heathkit with the horizontal hold problem on ebay. Glutton for punishment? You betcha!