Mighty Monarch of The Air

[jeyurkon]

**I forgot about the recent progress and was commenting about an earlier state.**

[old_coot88]

Um.. just to reiterate what was suggested back in post# 62, the plate load resistor of the
V.oscillator is a very common failure point and should be double checked if you haven't already done so. Now that we got the schematic to look at, that would be R66, 470K (half a megohm +/- 10% or so).

And does the V.size control (R4) measure correctly at 2.5 meg or so?

How about the voltage at the bottom of R4? Since it's supplied from B boost, it should probably be somewhere around 400-450 V.

oc

[vts1134]

I think I might have found my answer... Well let's all cross our fingers and hope so . Being a rookie at this restoration business I mistook black beauty capacitors for resistors. I missed five of them in the set including C49- the vertical discharge cap. I have the replacements on order and I'll let you know if that's the solution.

R66 is good to go btw.

[jeyurkon]

Sounds promising. They look pretty but are evil.

[vts1134]

But they're so pretty!

[old_coot88]

Originally Posted by vts1134

I think I might have found my answer... Well let's all cross our fingers and hope so . Being a rookie at this restoration business I mistook black beauty capacitors for resistors. I missed five of them in the set including C49- the vertical discharge cap. I have the replacements on order and I'll let you know if that's the solution.

R66 is good to go btw.

Yeah, C49 could sure as heck be pulling down the 6C4's plate voltage if it's leaky. Just for the heck of it, try disconnecting C49 and see if the plate voltage goes up. That resistor in series with it (R67), what does it measure? It's kinda hard to read from the print but it looks like it says 8K.

With C49 disconnected, what happens to the sweep?

oc

[vts1134]

Originally Posted by old_coot88

Yeah, C49 could sure as heck be pulling down the 6C4's plate voltage if it's leaky. Just for the heck of it, try disconnecting C49 and see if the plate voltage goes up. That resistor in series with it (R67), what does it measure? It's kinda hard to read from the print but it looks like it says 8K.

With C49 disconnected, what happens to the sweep?

oc

I know R67 reads good, I checked that off of my list. I'll disconnect C49 and and report results but I can't do it tonight. I've already started and I made a rule, no TV time after beer .

[Electronic M]

Aww, but that is when it is the most fun! Last new years(or was it christmas) I had a couple, and droped a Color chassis on my foot. It took me a while to realize that it cut me!... the little bugger.

Back when I encountered my first set with those bumble bee caps(it was a zenith transoceanic) I made the exact same mistake. To this day it still has those caps in it.

Tom C.

[old_coot88]

After you get the C49 thingy sorted out, take another look at the 6V6 output stage and see if it's "version 1" or "version 2".

With the revisions shown in the schematic, the output stage itself has seen a fair bit of engineering fudgery, probably to optimize linearity.

In "version 1" the plate and screen (pins 3 and 4) were simply strapped together. Kind of unusual.

In "version 2" the screen is supplied from B boost (again kinda unusual), through added-in resistors R96 and R97. Cap C69 is added from the plate to screen, probably to tailor the waveform. And bypass cap C71 is added to filter the boost line.

If your set has "version 2", those two caps should definitely be replaced if not already. And the two resistors checked for value. oc

[vts1134]

Because I'm not afraid to look like a rookie here, and in the hopes of teaching some one else, I'm going to tell you what I didn't do. I didn't test the tubes in this set (except the two vertical tubes, and even then I don't think the tester was good) until today. I know some of you will be thinking , I am thinking . My new rule is tubes will be tested before I even begin recapping. Ten tubes were shot... 10! I came home to replace the tubes in question and found two things. #1- my set uses V10 and I don't have a 6AT6. I had a 6AV6 left after replacing all of the other tubes. I'm not sure if I had a mix up at the shop when I was replacing tubes, or if a 6AV6 was in V10 in the first place. At any rate I simply left V10 out and fired the set up. #2- When I give the set more than 90volts I start to hear a sound in the high voltage cage that I don't like. The sound get worse as I cranked voltage higher. It kind of sounds like a very faint snap...snap...fsst...crackle...fsst..snap...crackl e. It could just be a different sound and I'm paranoid but it sounds like something is eating itself. I don't know how to test such a thing as I can't tell exactly where it's coming from. I'd rather not "test" by waiting until what ever it is to finish eating itself and whatever other components around it that it wants to take with it. Any thoughts on what the noise could be?
BTW the vertical is now full height.
Sorry to all of you here for wasting trouble shooting time by not completing step one.

[old_coot88]

The 6AT6 and 6AV6 are interchangable. if the 'V6 is good just leave it in.

Do you smell anything burning, or smell ozone? Is the aquadag (conductive coating) on the CRT securely grounded?

Hey, you didn't waste anybody's time so don't feel bad We all enjoy the heck outa this stuff no matter whut.

[vts1134]

Originally Posted by old_coot88

Is the aquadag (conductive coating) on the CRT securely grounded?

Where is this connection?

I may not have wasted any ones time, but it was a forehead slapper for me that's for sure. It sure has been a learning experience on my first set.

[Phil Nelson]

When the CRT bell is coated with aquadag (black graphite-looking stuff), there is usually a pair of thin wiry springs (sometimes one spring) that push onto it when it is fully installed. These connect to chassis ground, often through the metal yoke housing.

If the sound is a sort of faint hiss or fsst noise, it might be corona (high voltage arcing) somewhere inside the high voltage cage. Did you ever open that cage and clean the stuff inside? It's often covered with very fine, sooty dust. Rubbing alcohol cleans it off easily.

If the inside of the cage is clean, you could open it up and briefly power up the set with the room dark. HV arcs look bright blue or blue-white. If you see any, note the location and power down immediately, then investigate.

Phil Nelson

[vts1134]

Originally Posted by Phil Nelson

When the CRT bell is coated with aquadag (black graphite-looking stuff), there is usually a pair of thin wiry springs (sometimes one spring) that push onto it when it is fully installed. These connect to chassis ground, often through the metal yoke housing.

If the sound is a sort of faint hiss or fsst noise, it might be corona (high voltage arcing) somewhere inside the high voltage cage. Did you ever open that cage and clean the stuff inside? It's often covered with very fine, sooty dust. Rubbing alcohol cleans it off easily.

If the inside of the cage is clean, you could open it up and briefly power up the set with the room dark. HV arcs look bright blue or blue-white. If you see any, note the location and power down immediately, then investigate.

Phil Nelson

I remember reading this from your 630ts. When I first heard the sound this is what I thought of so I took a look at the area through the bottom of the set with the lights out and couldn't see any arcing. I'll try looking at it from the top of the set tomorrow and see if I can't pinpoint any arcing.

[vts1134]

Found the source of the noise. It is V18, the high voltage rectifier. The base of the tube is sparking bright light blue. Could this be a bad tube itself, or possibly a fault elsewhere causing the problem? R89 and R95 are both reading right on.
I'm sorry to be such rookie but I'm still don't quite get the ground connection for the aquadag. I've google searched the spring connections and saw a couple of examples but my set doesn't have anything like that that I can see. The only connection that I can see is a rigid wire connected to ground with a u shape around the high voltage wire. Is this supposed to be making a connection for the aquadag, or is it just to hold the high voltage lead in place? I've tried to show as much as possible of the tube in the three pictures below.


This next picture you can see the high voltage lead and the wire I mentioned with it.