1966 GE PortaColor Restoration

[Dubis7]

Originally Posted by Electronic M

If the rectifier isn't the problem the cup it's socket is in might be

Okay, so I'm potentially on the right track that my HV rectifier might be suspect, then? I was more or less shooting in the dark, but I figured it's a cheap part and an easy swap, and worst case I have a spare I can access.

I've heard of something called "Bloom" Does that sound similar to what I'm describing?

[Electronic M]

Originally Posted by Dubis7

Okay, so I'm potentially on the right track that my HV rectifier might be suspect, then? I was more or less shooting in the dark, but I figured it's a cheap part and an easy swap, and worst case I have a spare I can access.

I've heard of something called "Bloom" Does that sound similar to what I'm describing?

What you describe is hard to understand...

If you had a blank raster or unchanging test pattern the set should not flicker of change brightness. What blooming typically manifests as is an overload of the HV supply. Less HV makes for dimmer picture and bigger deflection since less HV means slower electrons that hang out longer in the yokes deflection field. Blooming is typically either constant (beam current set far too high) or dependant on average brightness of the video image displayed.

I've never seen a set display something that looks like a tape artifact unless connected to a tape deck....there is a phenomenon known as retrace lines that occurs when screens and or brightness is too high....

You need to post some pictures.

[Dubis7]

Originally Posted by Electronic M

If you had a blank raster or unchanging test pattern the set should not flicker of change brightness.

The entire screen flickering is new. It does that when I hear a spark from the HV section. Before it was just the lines I was seeing.

Originally Posted by Electronic M

I've never seen a set display something that looks like a tape artifact unless connected to a tape deck....there is a phenomenon known as retrace lines that occurs when screens and or brightness is too high....

No, it wouldn't be that, then. These actually get more visible when the brightness is all the way down. They looked like lines when a picture was displayed, but when I turned the brightness down they appeared as larger blotches across the screen. I don't think the artifacts themselves were changing, I think the video signal was hiding it. It's almost as if these were electrical spikes going straight to the picture tube that had nothing to do with the rest of the circuity, which again makes me think HV.

Originally Posted by Electronic M

You need to post some pictures.

I'll plan to either Friday evening or this weekend. I won't get a chance to get to my workbench before then.

[jr_tech]

I would also check the condition of the external dag on the CRT to assure that it is not flaking off and is properly grounded to the chassis. Examine the operating set in a darkened room, with dark adapted vision, to look for the arcs.

jr

[Dubis7]

Originally Posted by jr_tech

I would also check the condition of the external dag on the CRT to assure that it is not flaking off and is properly grounded to the chassis. Examine the operating set in a darkened room, with dark adapted vision, to look for the arcs.

I'll give that a try. As far as the CRT goes, I didn't notice any obvious flaking, but I can definitely check whether it's solidly grounded.

[Dubis7]

Just to make sure we're on the same page:

When I started, here's what was wrong:

- Audio Hum from bad filter caps.
- The picture would grow larger when I turned the brightness down, and
smaller when I turned it up.
- After being on for a few minutes, lines that resembled tape artifact lines
would appear on the screen. With the brightness turned all the way down
(and the picture not visible) it appeared that these lines were actually
bright splotches flashing on random parts of the screen. These were not
impacted by changing the brightness.
- The vertical and horizontal hold was exceptionally touchy.

What happened when I replaced C1:

- So, I actually technically got this right the first time. I intended to
connect the negative end of my new C1 to ground, along with all the
ground connections that had connected to the negative lug of the can I
replaced. When I soldered it to the terminal strip, I miscounted and
ended up soldering the negative end of C1 and the connections that had
gone to the negative lug of the can to each other on a spare, ungrounded
terminal connection.
- At the time, I also replaced C67 and C105, which are paper capacitors on
the main board. I believe they're related to the vertical and horizontal
holds.
- I tested my C1 replacement and it worked (thanks to my faulty
connection.) I was able to connect a signal and tweak the horizontal and
vertical holds. They seemed much more stable than before. The flashing
on the screen and fluctuating picture size (when I fiddled with the
brightness) were still there at this point, but nothing had gotten worse.
- I recognized my "mistake" later and reworked the connection. I moved
the negative end of my C1 to a ground point, and connected the
connections that were meant to connect to the negative end of C1 to a
ground point on a different terminal strip. That was a mistake, but it also
meant that almost all of the chassis was cut out of the circuit.

Replacing C2:
- I replaced C2 at the same time that I "corrected" my "mistake" on C1. I
was very careful to label which wire went where, and have checked
repeatedly to ensure that I did not miswire anything. C2 should be
correct.
- After replacing C2, I noticed that I was getting filament lights, and
nothing else. It was then that I realized that I had miswired C1.

Fixing my "Correction" on C1:
- I then corrected C1 to match the schematic, but still saw no change.
Voltage measurements indicated that power wasn't even getting through
fuse M1, so I measured R119 and discovered that it had drifted millions of
ohms above what it should have been.
- To verify my hunch that R119 was the source of my problem, I bypassed
it with a pair of alligator clips. The set came back to life, but I began to
hear sparking from the HV section, and noticed that video was now
compressed from the bottom third of the screen. I didn't leave it on too
long like this, since I didn't want to run it for long with R119 bypassed.
- I replaced R119 (3.6 ohms at 7 watts) with a 3.5 ohm at 10 watt resistor.

Where I am now:
- C3 is still untouched. I prefer to test my set after replacing major
components so I know when a problem started.
- Since replacing R119 and C2 (and correcting C1, though that hadn't had
any impact before) the picture has been squished, and a raster doesn't
appear on the bottom third of the screen. There's sparking noises from
the HV section, but the flyback itself still produces sparks when I place a
screwdriver next to it.
- The picture flickers (and sometimes stretches to fill the entire screen, but
only for a moment) when I hear a spark.
- I need to see if the splotches are still present.
- The picture grows much larger, almost to the point of filling the whole
screen (it may actually, but at a certain point it's too dark to tell) when I
turn the brightness down.
- My audio hum is gone.

[jr_tech]

Excellent! I think that is a very good idea to periodically summarize the steps taken and observations made, especially when the thread starts to get somewhat long, to keep everybody on the same page.

jr

[Electronic M]

Originally Posted by jr_tech

Excellent! I think that is a very good idea to periodically summarize the steps taken and observations made, especially when the thread starts to get somewhat long, to keep everybody on the same page.

jr

The irony being the summary was the last possible post on its page, and in complementing it putting us on the same page the post being complemented is now on the previous page....