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.

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

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.

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.

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

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.

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. :thmbsp:

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. :thmbsp:

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:D....

Unfortunate but true, I am so embarrassed and sorry.

https://live.staticflickr.com/4867/3...2567b4_w_d.jpg

jr

Okay, I finally had a chance to do some tests.

I have a video coming. It's a bit long since I tried to document everything I could.

Actually there's two videos, and I may have confirmed my issue. The first has the ringing, some sparking, and shows the "tape artifacts" that I mentioned before. In the second, I removed the HV rectifier, and the sparking etc went away. Obviously some of that will be because there's no power to the tube, but the ringing was definitely around the flyback and that also disappeared when I removed the HV rectifier, so I'm leaning towards that.

One other mystery: Should the HV rectifier tube hold static electricity? I removed it from the tv while wearing gloves (the set was turned off, but I didn't want to risk anything) and put it aside. Later, I went to pick it up without gloves and it sparked when I touched it. Could that be confirmation?

https://www.youtube.com/watch?v=dgot...ature=youtu.be

That's the primary overview. Sorry for the length, I was trying to make sure I caught everything.

https://www.youtube.com/watch?v=MQcN...ature=youtu.be

Here's when I removed the HV rectifier.

The ringing is probably mechanical vibration of the ferrite core of the flyback. It's usually curable by tightening those two nuts on the big C clamp that goes around the core (not too tight as the core can crack easily).

Your HV rectifier tube is good (if it was weak the raster would 'bloom' and fade out when you turn up the briteness).

The blue arcing when you touch the screwdriver to the glass and top cap of the HV rect is quite normal.

Insufficient height is usually a bad electrolytic coming off the cathode of the vert.output tube (although GE portacolors might not have this cap; other more knowledgable folks will chime in).

“Insufficient height is usually a bad electrolytic coming off the cathode of the vert.output tube ”

That would be c-2, which was replaced.... possible error? :scratch2:

jr

I checked C2 again. Still not finding an error.

Is there a specific section of C2 I should be looking at?

I did a few measurements by the way. I noticed my HV is hoving around 12KV when it's listed as being between 15 and 18KV. Also, my 670V boost voltage coming off of pin 3 on the flyback is measuring around 650V. Not sure if any of that could be related, but maybe that's a clue?

I tightened the core a bit. Ringing is gone, at least so far.

Does anyone have any thoughts on this?

I'm going to try replacing C1 and possibly C2D. I wonder if they didn't get damaged when I installed them incorrectly.

Any lytic that has seen reverse polarity should be immediately round filed and unless you have equipment to test for leakage current at rated voltage.

Hm. Well now I'm wondering if that's my issue with the height. C2D is definitely a potential culprit.

I had figured that if an Electrolytic didn't explode or smoke, it was fine. Obviously that's not true with the older dried out ones, but these are new. Perhaps I'm wrong?

I've got those parts on order. I'll see what happens when I swap them in. The rest of C2 should be okay.

No! That is not a rule-of-thumb.

Noted. Then I may be on the right track. Recalling that I:

- Attached the line going through R119 and M1 to ground, and attached the negative end of C1 to ground

and that I

- Swapped the polarity of C2D

At the same time. I'm thinking it's very likely that I damaged C2D at that time, which could explain my height issue.

Parts are on order. I'll see what changes once I swap everything in.

Still waiting on C2D to come in. I was doing some work in the power supply tonight.

I've got a new issue. It's my fault. I won't get too into it, I did something stupid trying to check a component and learned my lesson. Blew out R119, M1, C1, and X1. X2 still looks okay, but X1 is now measuring 0 ohms regardless of the polarity. The set blows M1 immediately upon power up. I disconnected the 270V line between C2A and L34 and it still blows, so I know the problem is in the voltage doubler circuit with X1 and X2.

R119, M1, and C1 are now replaced. R119 is now 3.9 ohm 10 watt, and M1 is a 2.5A 250V fast blow fuse. I also took the opportunity to install M2 as it's listed in the schematic, so I'll have that extra protection.

I'm not sure what diode to get to replace X1. Any suggestions? I'm trying to decide if I should go ahead and replace C103 while I'm at it.

Would this replace X1?

https://www.ebay.com/itm/5pcs-1N2071...UAAOxynhFRBp5P

No... the diode you listed is a zener diode, you just need a common rectifier diode like a 1N4007.
https://www.amazon.com/MIC-Silastic-...s%2C358&sr=8-4

not affiliated,
jr

Good thing I asked, then. I'm sure the codes in the service manual match specific products that are long out of production.

Part ordered. I needed to pick some of those up anyway. Fingers crossed this fixes my power supply issue.

X1 is replaced and I have life again. Out of circuit, it tested completely open.

Still having the height issue. I'll update once C2D comes in and I do the swap.

Okay,

C2D has been replaced. I'm not seeing any change.

For good measure I also swapped in a new vertical output tube. Also nothing.

I measured the ohms on R5. It peaks just around 2K, which I belive is what it's supposed to be. When I measure the voltage output coming off of R5, which is listed at 15V in the schematic, I'm seeing it maxing around 22-25V and brushing at 15V at the lowest.

Any suggestions for what to check next?

Shouldn’t the cathode go to zero volts when the pot is at one end? :scratch2:

jr

Let me double check. I know it looked like it dropped off right at the tail end.

I'll grab a video of the voltage and resistance readings today. Maybe you'll be able to interpret it better than I can.

I'm wondering if my issue isn't in R5. I have no idea how likely that is, but could I have damaged that?

Portacolor sets are somewhat prone to tin whiskers in the pots...I had one which had the AGC pot dead shorted to ground via a tin whisker. The set had ZERO reception and it took some time troubleshooting the dead IF to trace it back to the AGC and then the pot...if a whisker developed on a pot connected to B+ or boost it could make the set really unhappy.

Here's a video where I took some measurements on R5. https://www.youtube.com/watch?v=aBqK...ature=youtu.be

Could this be tin whiskers? How would I go about correcting that?

That jumping near the end of the pot travel looks highly suspicious... have you tried cleaning the pot with deoxit?

jr

I did, but I'm not convinced I did it right. I'm thinking I'll take another crack at it.

That being said, if I do need to replace this, does anyone know what replacement part I'd be looking for? Obviously I'll check Moyers with the part number first, but assuming they don't have a replacement.

My standard process for tin whisker infested pots is to remove, and dismantle the pot take a toothbrush then fine sandpaper to the metal parts clean everything with a good control cleaner and paper towels, reassemble the pot, check resistance and range with rotation between all terminals and also case metal, and if all is good reinstall.

Okay. I'll give this a try. I'm going to just remove the pot, disassemble it, and deep clean it.

One thing I am sort of wondering about, and I can get pictures of this if you need it: I'm noticing that the pot doesn't have the standard three lugs. Instead, it has one that goes to C2D/the main PCB, and two that connect to ground. That matches the schematic just fine, but since this is unusual, is there anything I should be watching out for as I disassemble?

That just means it is configured as a variable resistor instead of a variable voltage divider...One benefit of this configuration is if one of the end lugs is open but center never goes open you can make the open end lug the grounded one and continue to use it(max and min vs rotation may swap).

Okay, well I really went at it with the deoxit on R5. Not seeing any change.

Are we sure this can't be a HV problem? Or maybe a voltage problem? My HV to the CRT is still measuring between 7 and 10 KV. It should be around 15 per the schematic.

I may have something here.

I'm noticing that my voltages are consistently 10 or so volts higher, except the HV which is several KV too low. I traced it back, and discovered that C103 has 0 volts when measured against ground.

I've ordered a replacement. Could that be related to my issue?

Also, if L34 is measuring 36 ohms, could that be an issue?

No.

Also re-check your C-103 reading, it can’t be 0 volts, if it is wired correctly and supplies are normal (or slightly high).

What does your boost voltage measure?

jr

C103 should be measured in VDC, correct?

Okay, I think I measured C103 wrong. I was measuring from the ground end of C103 to another ground point, and that was 0 VDC. I measured across C103, and it came out as 152VDC

Boost voltage (from pin 3 of the flyback against ground) is 664VDC

HV is still hoving around 10 V using my high voltage probe. I'm noticing that the image is somewhat dim, and I have to have brightness up above center to see it.

In its present condition what does the picture look like? Can you connect it to a signal source and take a picture?

jr