20 inch GE CTC166CS chassis red smearing but strong CRT

[zeno]

First off he is using S-video so the chroma & video are separate already.
SO tuner, IF, video amps, comb filter, delay line are OUT of the pix.
IMHO the problem is a failure NOT inherent in the set. Its just too damn
obvious. This is a CTC166 not a cheap red China product. It was as good
as any at the time. Problems were few. I just remember some bad tuners,
bridge rects & the 9 V sense. The set uses a lot of SMD's for resistors &
transistors so that complicates things a bit. The order things get done
depending on the price of the IC is......
Change all chroma & VCC electrolytics.
Measure all IC voltages & scope all VCC's & GND's.
Pull IC & check all SMD's before replacing IC.
Replace IC
Call RCA TA ( they were very good ). If still no joy send to RCA service.

If you just decide to get an other RCA of this vintage add the CTC169 to your list. Its the top of line at the time & IMHO the best RCA ever built. I loved
working on them cause they always came out so good.

73 Zeno
LFOD !

[JohnCT]

The

Originally Posted by zeno

If you just decide to get an other RCA of this vintage add the CTC169 to your list. Its the top of line at the time & IMHO the best RCA ever built. I loved
working on them cause they always came out so good.

73 Zeno
LFOD !

Here's a true (and truly boring) story:

Back in 1991, the 169 was first introduced as a high end chassis in the 31" and 35" table and console models. These chassis featured Invar mask CRTs, twin focus, digital pix in pix, and a digital comb filter.

I sold three of these and hated the picture. It's hard to describe but they just had a "dirty" picture to them. One of my customers constantly complained about it and I made several house calls (he was close to my store) and I adjusted the two focus controls and set the customer adjustments best I could. I blamed it on the "blown up" picture on the big 35" tube.

Next year, RCA changed the chassis a bit (there's probably two dozen variants of the 169) the picture on these were drop dead gorgeous. Smooth video very well detailed. No hard edges, no ringing - just sharp detail and smooth as well. I ordered two more, and brought one home and gave the other to my dad.

I pulled the schematics and noticed that RCA had replaced the digital comb filter sub board for an analogue one. About this time my customer with the 1991 called again and this time I called RCA about procuring a 1992 169 chassis to swap into my customer's TV - no dice.

I had my customer call RCA customer relations and RCA called me back. I explained what happened and how this guy called at least half a dozen times, and I never billed RCA for the calls because there was nothing wrong. RCA ended up having me field-scrap the whole TV, and they shipped a 1992 model in it's stead. I had to send the chassis back to RCA along with the model/serial tag cut off the back cover.

My customer loved the new model. My point of is that anyone looking to get a 169 must watch out for that first year.

Some more boring stuff:

About 5 years later I pulled a 169 in for repair that had the original digital comb filter, and I had a later 169 scrap chassis. I ended up swapping in the analogue comb filter for the original digital, but this was a bigger project than I thought. There were probably 10 or more SMD parts that had to be added or removed on the main board to get the comb filter sub board to work, but the picture was great when I finished.

Lastly, I took the original TV that RCA had me field scrap home to store in my basement. I figured I'd run into a chassis someday and have a perfect low hour (8 months) CRT in a beautiful oak cabinet, or use the tube if my 35 upstairs ever got weak. It did finally get weak, but but the time my original 35 tube went bad, we were into the flat screen era, so I never moved the chassis to the console.


So, if anyone in the Connecticut area wants a mint 35" Invar dual focus tube with the bonded yoke, you're welcome to come get it.

John

[MRX37]

Boring? Not so much to me. Might explain my set's issue. This set is much plainer, and cheaper looking than an equivalent RCA Colortrak 2000, so maybe the video quality is just not as good. My set is technically a CTC 166CS chassis. No idea what the differences are between a 166 and a 166CS, but were I to guess, they're cost saving differences.

And Zeno: I have an RF modulator coming in the mail, which will allow me to compare the image to other TV's and rule out a problem with the video source.

[MRX37]

Okay I have an update:

Today I finally received my RF modulator. It has enough output to transmit a signal several feet. This absolutely, certainly, without a doubt, gives me the ability to rule out video source and cables.


It has been a long time since this Chromacolor II pulled in anything over the air...


Now lets see how the CTC 166 looks with the same signal:



Hm. That's actually not that bad. I can still see the smearing, but it's better.

[MRX37]

So I have something of an update here. I found a CTC 146 chassis that does not power up. It appears to have the same U1001 IC and a CRT that is almost identical.


The CTC 166 has an A51ACG14X01 CRT in it.

The CTC 146 has an A51ACG14X02 CRT in it.

So I'm trying to find out of I can either swap the IC or the CRT and rule one or both out.

[JohnCT]

I'm betting the jungle IC will fix it, but I did on occasion run across a CRT that had a smear that did not show up on the tester.

If it affected all three guns I would be thinking a bit of heater to cathode short, but not on one gun.

In any case, you can eliminate the tube as the problem by swapping the red input wire for the green right at the socket.

The grey scale will shift and the color will be wrong (it will look like bad purity), but if the smear moves to the green, the tube is OK.

John

[MRX37]

Hmm. Would have tried that earlier if I knew that.

But all 3 colors smear far as I can tell.

I'm leaning towards the IC myself. Question is... I have a CTC 146 chassis with that same IC, but that chassis doesn't work. I have no idea if that IC is good or not. Also no idea if the CRT is good or not.

You know, unless a red flag comes up I might just swap the CRT's tomorrow, and just see what happens. If it fails it fails, but at least I'll know.

After that it's probably a smart idea to hunt down a NOS u1001 IC.

and if that doesn't fix it I might just throw it in the trash and wait for another one to come along.

[MRX37]

Hoooo. Okay. Okay. First CRT swap I ever did, and the other CRT works.

And my god was this a nailbiter. I have never changed a CRT before, and I really do not like messing with things that could implode if handled carelessly. However this swap was very easy.

I typically don't like RCA bonded yokes because if the picture is tilted, welp you just have to live with it, but it makes purity and convergence setup a non issue. All I needed to do was just plug in wires, and the connectors are all keyed so it would be hard to screw it up.

Apparently the only differences between the A51ACG14X01 A51ACG14X02 CRT's is different connectors for the degauss coil and dag ground assemblies. So I reused the ones from the original CRT.


And... No change. The color smearing is exactly the same.


I believe this rules out the CRT once and for all. This CRT seems to be in good shape, and since the yoke plastic is not as yellowed and not as dirty, I think this CRT has fewer hours on it. Though the brightness seems to be about the same as the original CRT, so I am not sure.

In any case I highly doubt two different CRT's from two different chassis would have the exact same smearing issue, so the problem has to be on the chassis.

Can I do some kind of test to confirm it is the u1001 IC before I attempt to change it? Because that is a big IC with a lot of pins, connected to a lot of solder traces that could lift up and end this adventure.

In fact if I can confirm it is the U1001 IC then the adventure ends right here, because the one source I can find wants $40 for that IC, and cost exceeds value of TV.

[Electronic M]

By the mid 70s you pretty much had to try hard to get a CRT to implode. It's the earlier stuff that is more dangerous. Newer stuff you don't gotta be tense just don't rush or loose focus and you can't screw up bad enough to cause harm.

[MRX37]

Oh I know about removing the cataracts from older CRT's. The rectangular ones from the 60's especially like to implode because the pressure isn't equal on all sides.

I know full well that newer CRT's have very, very thick glass in the front and an implosion band.

I know all this. Logically I know all of this. That's why I even did the swap.

But tell that to the instinctual part of me that still fears an implosion or a 25 KV shock from that anode lead.

I mean I pushed past it. I got it done, and logically I know there is little real danger, but still. First time and all.

[Electronic M]

Once you've had half as many accidental 25KV shocks as I have it just becomes an annoyance like a bad static shock (some household static shocks have higher voltage and comparable charge involved). The biggest danger of an HV shock from a flyback/CRT, assuming you don't have a heart condition, is the shit you might slam into if you allow it to trigger your reflexes.

[MRX37]

Well right now my concern is that u1001 IC. I'd like to know if there is a test I can do, maybe a voltage I can check or something I can measure with a multimeter that will tell me if that IC is bad. If I can at least get a concrete diagnosis then I can put the issue to bed.

[JohnCT]

Originally Posted by MRX37

Well right now my concern is that u1001 IC. I'd like to know if there is a test I can do, maybe a voltage I can check or something I can measure with a multimeter that will tell me if that IC is bad. If I can at least get a concrete diagnosis then I can put the issue to bed.

Response to an earlier post: First, no way two CRTs would act exactly the same (unless it was mine). So we're talking power ball odds here. Also, I've never seen anything but a perfect picture on an RCA pre-yammed (their term) yoke with regards to purity, convergence, or tilt. Every one was damned near perfect. I only saw one yoke fail in all the years I was an RCA ASC.

The problem with this type of issue is that often our eyes are far better instruments than a scope would be. In other words, you may not even see the problem with the scope. This is one of those times when a parts swap is the best option.

If it was in my shop, I would have replaced the jungle chip, but then, we used to stock parts when these were in their heyday. If you've never worked on surface mount stuff, it can be daunting.

What is the number on the chip? Sometimes RCA just left the original Toshiba or Sanyo numbers on them, other times they were stamped with a partial RCA drawing number. If I have one, you're welcome to it.

John

[MRX37]

The number is A23-1101-01A

But here is the problem.

I tried removing the chip from the CTC 146 donor chassis as it uses the same IC. I literally do not have the dexterity to get that chip out without damaging traces.

The problem is RCA bent several of the pins, I guess to hold the chip on the board, and trying to desolder them wiped out the traces on the donor chassis.


So... If I can;t make a concrete diagnosis, and I can't compensate for the bad IC, then my only recourse is to put it back together and wait for another chassis to come along.

I now know the CRT is good. I also know it can work with other chassis. It will likely work in any 20 inch Colortrak 2000 set from 1991 to 1992.

So if I find another one with a bum CRT I have options.

[zeno]

$40 is ridiculous for that IC. Look in the Sams & see if they list a sub.

ONLY use high Q solder wick. We used chemtronics in the day.
Use a pick to pry up the bent pins. Working to slow will lift etch.
Use enough heat ! Just watch out for the SMD's nearby. My hands
shake like a paint mixer but I can change them fast. Its all in the
technique.......

73 Zeno