Are these things I should consider bad

[jr_tech]

Another *very* long shot, but I gotta ask... Is the external dag coating on the CRT ok and properly grounded? Any shielding around the CRT or Yoke that is not properly grounded?

jr

[TinCanAlley]

Originally Posted by jr_tech

Another *very* long shot, but I gotta ask... Is the external dag coating on the CRT ok and properly grounded? Any shielding around the CRT or Yoke that is not properly grounded?

jr

Okay, I don't know about the coating other than there is a small scratch from where the metal shroud around it must have touched it at one point. The metal shroud has a ground from chassis to it and two from the CRT socket connected to it. How do I go about checking for proper CRT grounding?

[TinCanAlley]

Originally Posted by zeno

Service switch kills vertical also kills video & gives the 3 video outs a
constant voltage. On this chassis it also adds a crude blanking pulse.
If all the DC voltages are correct you should get very bright service
lines. At that point its 99% the CRT. Sometimes the CRT can look
& test good but be a little weak.
Good news ! Since I was a bench man & only did about 25 of these
sets I ran it by our old road man over a beer. He did a repair on
one once & it had the exact same jailbars. Bad news is the set was
very old & they didnt want to pay to pull the chassis. At least you
know this wasnt self induced & a real failure, possably common.
Just for kicks remove the wire from service switch that go to
jcn of R295 & R297. See if they go away.

73 Zeno

Okay, Sunday is the day to disconnect the wire from the junction noted to the switch. So I am to leave it in normal mode without that lead in order to see if the switch has a bad connection and might be allowing current from that lead from the setup side to the normal side, right?

[TinCanAlley]

Just thought I'd post a pic of the switch. I don't know if this could cause any problems, but it looks like terminal two of the setup side of the switch is wired to ground, but also the T2 of the AGC pot is also connected to the same terminal on the setup switch. I've circled the ground side in yellow and the power side in red (the lead to be disconnected on Sunday).

[jr_tech]

Originally Posted by TinCanAlley

Okay, I don't know about the coating other than there is a small scratch from where the metal shroud around it must have touched it at one point. The metal shroud has a ground from chassis to it and two from the CRT socket connected to it. How do I go about checking for proper CRT grounding?

So is there any connection between the shroud and the dag coating? It sounds as if the shroud and I'm guessing perhaps spark-gaps at the CRT socket are grounded to the chassis. Might want to ohm check the ground connection to make sure.

jr

[zeno]

Originally Posted by TinCanAlley

Just thought I'd post a pic of the switch. I don't know if this could cause any problems, but it looks like terminal two of the setup side of the switch is wired to ground, but also the T2 of the AGC pot is also connected to the same terminal on the setup switch. I've circled the ground side in yellow and the power side in red (the lead to be disconnected on Sunday).

Its OK they are using it as a tiepoint for ground.
Yes run it in normal for the test.
The CRT dag usually grounds through a few paths. The DGS shield
has fingers on it touching the CRT, usually a spring mounted wire
across the bell under the shield, sometimes the ground straps
touch the dag. Then usually straps run from the shield to the
chassis, tuner assy, & convergence assy. If it were floating you
should hear hissing, used to happen to B&W's sometimes.

Lead dress keeps me worried here also. Be sure the CRT harness
is well away from any HV or large hoz pulses. Focus, yoke,
and the 2 HV leads. IIRC its pretty hard for that to happen on
this set.
Also bad caps may have caused it. Every S cap that opens
brings up everything from the HOT on up 10%. In the olden days
it usually stressed the divider then the F terminal of CRT
socket arcs. If a bunch of them go it starts tossing lightning
bolts like you read about ! Quite a show........
So over time things may have been under stress.

73 Zeno

[TinCanAlley]

Here are a couple of pics of the CRT and the shroud w/ground leads. You can see the two from the CRT socket and the one that goes from the shroud to the chassis. If you look closely at the left side of the neck you'll see the scratches, but I don't think they went through the coating. They appear more as surface scratches.

As for the setup switch, I'm gong to use some Deoxit on it first to see if it needs a little cleaning. I figure that being in the same position for so many years and the fact it's an open design, it might be dirty/oxidized.

[old_tv_nut]

You should not need to spend much time on the dag connections. The dag appears intact, as do all the wires. Just look for obvious mechanical problems, and wiggle the connections a bit to see if the problem you are trying to fix shows intermittent effects.

[TinCanAlley]

Originally Posted by zeno

Service switch kills vertical also kills video & gives the 3 video outs a constant voltage. On this chassis it also adds a crude blanking pulse.

So is the horizontal still there when in setup? Reason I ask is that the bars go away.

Also, don't remember if I checked the voltages on the G2s and G1s when in setup mode. Maybe that is a next move.

[DaveWM]

the bars go away cause the vert is collapsed.

[jr_tech]

Originally Posted by old_tv_nut

The dag appears intact

I must be missing something... I don't see any external dag on the tube... is there just a little area of dag on the lower part of the tube where the grounding strap wraps under?

jr

[TinCanAlley]

Originally Posted by jr_tech

I must be missing something... I don't see any external dag on the tube... is there just a little area of dag on the lower part of the tube where the grounding strap wraps under?

jr

Here's a pic from when I first got her and hadn't been cleaned yet. This metal shield goes all around the back side of the CRT. It had ground straps from the CRT socket and chassis on it.

[jr_tech]

So what area of the tube does the external dag cover... I am still not sure that I see it. Note the highly visible pattern here where the external dag can be clearly seen *almost* to the yoke: http://upload.wikimedia.org/wikipedi...17px-Crt14.jpg
jr

[TinCanAlley]

Originally Posted by jr_tech

So what area of the tube does the external dag cover... I am still not sure that I see it. Note the highly visible pattern here where the external dag can be clearly seen *almost* to the yoke: http://upload.wikimedia.org/wikipedi...17px-Crt14.jpg
jr

In the picture you'll see the metal (bronze colored) shield connected with springs and other screw type adjusters/fasteners (you can see a long screw that is used to pull the sections together for a tighter fit). That's the part that in contact with the painted on DAG of the CRT and then connected to the chassis via a yellow ground connector.

[Electronic M]

The CRT shields on Zeniths of that era almost completely hide the dag. I should know I have at least two Zeniths that use that CRT shield.