RCA TV with a Problem

[Console User]

I have noticed of late since I got Dish Network that my RCA TV is doing something strange. When a commercial comes on with a white background and big black letters I get a Zig Zag and the black letters wobble. It's not all commercials with these backgrounds.

It may do it some with the Converter Box, but I don't think as bad though.

What is causing this?

[rcaman]

your zig zagger is going out. we need pictures.

[jbattles]

oh man that's funny.

[Console User]

Originally Posted by rcaman

your zig zagger is going out. we need pictures.

I can't provide any pictures as I do not have a digital camera. I can take pictures with my cell phone though, but can't download them to a computer.

Not funny at all!!!

[Kamakiri]

Actually, it is kinda funny, I have to admit

How about I PM you my cell phone number and I'll post the pics for you?

[Jon A.]

Hm, perhaps you could email the pictures to yourself? That's assuming that you have a regular computer to log in on.

[DaveWM]

fine tuning.

http://www.youtube.com/watch?v=RAk9l...CVtyRrqXVtll-g

[Console User]

Originally Posted by DaveWM

fine tuning.

http://www.youtube.com/watch?v=RAk9l...CVtyRrqXVtll-g

Very interesting you tube. Thanks for the information. It looks exactly like the problem I have is with the Fine Tuning. Do you know where that adjustment is on a 1986 RCA Model#GLR689PR? I have a push button pad for on/off & channel numbers.

Thanks.

[DaveWM]

that's a newish TV to me, don't know if there is fine tuning.

[zenith2134]

That's a great channel DaveWM
I hate to say this, but I had a number of RCAs from the mid eighties with tuning issues.. bad coils and delay lines...odd failures but my '80 RCA had a bad delay line and my '84 RCA had a bad sound discriminator coil. On other sets, I could get the sound out of the pix by adjusting that coil but not on 1 that I had. And on the other I used any old delay line and it actually fixed it(I usually avoid 'shotgunning' parts) but in this case the number of turns was close enough I suppose. How about the CTC-121 and 130 with the MTT control module for the OSD and electronic tuning..Not very repairable when they go, but luckily it is usually poor soldering on the ground connections.
Hoping it is just the fine tuning.

[zeno]

Assuming its fine tuning there is no fine tuning on the set.
Try changing the CATV-NORM switch on the rear top or
antenna board usually.
Next would be resoldering the tuner & MTT conectors.
If they havnt been done they need it anyways.
Then it could be either the 4.5 trap or AFT tank coil
needs tweaking. If you havent done that before come back for advice !!!

73 Zeno

[NoPegs]

This is a fairly common thing on mid-range sets. (Not the $130 paperweights, but also not quite a $299 "quality" set, using a 27" tabletop circa 2005 for pricing reference..)

There's a feature they came up with where the horizontal sweep ramp is varied so that it runs slower over high intensity elements and speeds the hell up over dark or black areas. This is combined with some "clever" electron gun modulation and results in a seemingly sharper picture with better contrast, but when certain patterns are displayed, resonance points in the H-yoke do some weird things.

This usually shows up on scenes that aren't composed of "normal" items. So a mountain vista is just fine, but if you're looking at something with lots of vertical elements things go a bit wobbly. Text is a big thing there. I know Toshiba specifically designed their sets around that problem when displaying closed captions by disabling the fancypants circuit when the beam entered the CC draw area. Most others didn't care and left it on, or just altered the font a bit...

Back in 2006 I could have told you which manufacturers (ab)used this technique specifically, but detailed knowledge like that has little use outside of retail CE sales, and I repurposed that bunch of brain-cells about 3 years after I took a running jump off the deck of that sinking ship...



Edit: I lubricated some of those brain cells and managed to extract the following from them after some careful forensic analysis:

The feature I refer to above is "officially" known as: Scan Velocity Modulation, but may go by other unremembered names depending on the manufacturer... Turn it off, if its not in the user menu, get the codes to access the service menu (Be careful, only change things that you know what they do, it is possible to change things such that you can't see the menu to fix them.) and disable it there.

Basically it was a flashy feature that made them appear better on display in the store, but turned out to be terrible in your own home.







vvvvvvvvvvvvvvvvvvvvvvvvvvvvvv: Forget everything I said. I don't think they had SVM in 1985, or if they did it wasn't over-used. Is the plug polarized? If not try flipping it over.

[Console User]

Originally Posted by zeno

Assuming its fine tuning there is no fine tuning on the set.
Try changing the CATV-NORM switch on the rear top or
antenna board usually.
Next would be resoldering the tuner & MTT conectors.
If they havnt been done they need it anyways.
Then it could be either the 4.5 trap or AFT tank coil
needs tweaking. If you havent done that before come back for advice !!!

73 Zeno

I had some soldering done on this set about a year ago. I assume that yes the problem is in the tuner. When the set warms up I get vertical lines in the background when I use a certain make of converter box. It doesn't do this with all converter boxes, rather just one brand in particular. I tried using RF#4 and the vertical line interference is way worse. I have also noticed a little hiss noise in my picture. I guess I can't expect miracles as this set is 28 years old. These vertical lines with the use of the converter box can give you a grayish or grainy looking picture.