TV free off the curb

[Th3_uN1Qu3]

Hardly ever thought i'm gonna see this day in this country. Admittedly, we're talking about an old CRT TV (heck it's prolly almost as old as i am) but at least it's a color one. It's a Goldstar CKT9902 chassis P04. I found it on the street in a large fabric bag - it was just waiting for someone to pick it up.

I first noticed a badly bulged cap near the flyback, which was also rated 200v when it was supposed to be 250v. I replaced that with a 250v Nichicon, and the TV started up but there was no picture, and the rail that cap was on was 270v instead of 180v!

I thought of a flyback fault and asked about it, i was told to shotgun replace all the caps in the SMPS and vertical deflection as they are most likely bad. And indeed, after taking the board out a very noticeable bulge could be seen on the B+ rail cap (which is why the other high voltage rail was so high - B+ is regulated, the others just track it). Albeit not so noticeably, the main filter cap was bulged too. I had a couple CRT monitor boards so i replaced them as follows:

47u 160v Samyoung -> 100u 200v Nichicon (B+)
120u 400v Samyoung -> 220u 400V HEC (primary). Yes i know HEC isn't the best brand but we're talking about replacing a primary cap which died of old age - now it's likely that the tube will fail before this cap does.
Haven't done the caps in the deflection yet because i didn't have appropriate replacements. There are two 10u 100v caps and one 25v 470u.

After these two replacements the TV started up fine. I also replaced a few more caps in the power supply afterwards, just to make sure. The colors were a little messed up but that's what trimmers on the neck board are for - i love things with trimmers. I also did the mod which enables 90 programs instead of 40, it works fine. Needs a little more alignment but so far it's looking good, the picture is better than the Samsung in the living room which is only half as old, and i had to fix that 3 times already.

I'm off to buy caps for the vertical deflection, because at the top of the picture i get some thin lines which disappear in the first two minutes - a clear sign of bad caps in that area. I'll also pick up a remote control for it, and that's about all.

[tom66]

Re: TV free off the curb

I get people offering me CRT TVs for free... even though they work perfectly fine people want the latest and greatest flat screen TVs.

That cap looks like it was right next to the HOT. The HOT probably runs quite hot so it toasted that cap.

Also I've never seen that Samyoung logo before. I knew Chemicon and Samyoung were in cahoots but did they actually use almost the same logo?

[mariushm]

Re: TV free off the curb

Wow... indeed rare in this country.

Give me a message if you can't find some caps - maybe I can source them here in Cluj or maybe I already have them "in stock" and can mail you some.

[randtek]

Re: TV free off the curb

If, after replacing the caps in the vertical circuit, you still have a few lines at the top that go away, look for a leaky diode in the vertical circuit. These lines are sometimes caused by a leaky diode.

[Th3_uN1Qu3]

Re: TV free off the curb

That cap looks like it was right next to the HOT. The HOT probably runs quite hot so it toasted that cap.

Nope... The HOT heatsink runs just warm. On the other hand the primary heatsink runs on the hot side. My theory is that the primary cap dried up first and from there on cascading failure due to high 50Hz ripple entering all the circuits.

Also I've never seen that Samyoung logo before. I knew Chemicon and Samyoung were in cahoots but did they actually use almost the same logo?

Remember this TV is likely almost 20 years old. I think they changed the logo by now... The other brand of cap found in this TV was Samhwa.

Wow... indeed rare in this country.

Give me a message if you can't find some caps - maybe I can source them here in Cluj or maybe I already have them "in stock" and can mail you some.

Had all of them handy, don't worry.

If, after replacing the caps in the vertical circuit, you still have a few lines at the top that go away, look for a leaky diode in the vertical circuit. These lines are sometimes caused by a leaky diode.

Thank you, in this case only the caps did it. I have replaced the two 100uF 35v caps (which i mistakenly read as 100v, and no idea where i pulled 10uF from) with 220uF 35v Chemicons. No more lines. I also found another dried lytic in the deflection circuit but it seems it was just a part of a snubber as replacing it did nothing. I had to change the 0.47uF cap in series with the H coil to 0.82uF to get the correct H-Size, upon adjusting the B+ to the value indicated on the schematic, 118v (was 115v) h-size was too large (stuff cut out at the left and right). Now everything is fine.

I've also finished tweaking the colors. Can't get rid of the green/blue hue on dark areas tho, tube is worn. Decided not to do convergence as center comes out perfect, and the edges are not only misconverged but also slightly blurry - this is simply an aged tube. It isn't all that bad anyway.

Now all i have to tackle is a slight buzzing over the sound with certain scenes, but that's for another day.

[weirdlookinguy]

Re: TV free off the curb

Let us know what the buzzing in the audio turns out to be, I have a 19" Sony of similar vintage with the same issue. The amount of buzzing changes according to how bright of an image is on the screen.

Tube is tack sharp and bright as fuck on that one though Made in USA. Puts out a better picture than any CRT TV made in the past 6~7 years.

It is full of Samyoung/Korea Chemicon caps, and they have the same logo as the ones in your LG. Korea Chemicon/Nippon Chemicon must have been very closely related back in the day if Sony was using them.

[lti]

Re: TV free off the curb

I want to fix my mom's old RCA TV now. The picture is good, but it has pincushion, red streaking (red text looks like a big red blob), and the tuner doesn't switch from 75 ohm to 300 ohm properly. There is a jumper on the back to select the input impedance, but there is no difference in the picture when I move the jumper.

[weirdlookinguy]

Re: TV free off the curb

I could be wrong, but "bleeding" on a tube (which is what you are describing) usually is a sign of a weak or overdriven gun, and red usually goes first.

[Th3_uN1Qu3]

Re: TV free off the curb

Let us know what the buzzing in the audio turns out to be, I have a 19" Sony of similar vintage with the same issue.

It's something in the sound converter and it'll likely involve careful tweaking of some coils. I just have to dig deep enough to find where exactly.

Been watching it until now and there's another issue - a clicking noise comes from the back along with a slight twitch of the picture, at seemingly random intervals. Could be as often as a few minutes, could be half an hour. I guess it's just some cold joints, i've been moving that board around a lot. However it started after i replaced that cap in the H deflection, which makes me wonder whether it could be done in another way. Because essentially that cap is in the power circuit, and making it bigger likely increased the load on the HOT. Methinks this can be done in the signal section as well, before it hits the HOT... off i go to read some datasheets.

[kb48]

Re: TV free off the curb

Buzz in audio is tweak the last stage of IF in the set coil that seperates out the audio, or could be aged out, but considering it all may just be sloppy design. Red blotch is purity. Either the degauss coil got unplugged or where it has been tossed around part of the CRT is magnetized. Take a soldering gun, place it at center of tube, turn on and slowly rotate it in circles and slowly move it away from the tube at the same time.
Turn it off when your at least 2 feet away. You will see the red go away or change a little at least. If that dont work then your going to have to play with the rings, around the neck of the CRT but this can result in convergence, red.blue.green go out of alignment.

Snapping noises are usually High Voltage issue or sign of the guns about to fail and arcing internally. You can tell in a dark room you see blue sparks. Or the flyback is about to die, and is arcing over.

Well if you can get a few more years out of it, the investment paid off.

They make large ring coils to do this also, but the end result is losing the blotches. Just dont turn off the soldering gun while doing this or you will make it worse.

[kb48]

Re: TV free off the curb

Red or blooming is sign of weak CRT. You have 2 choices. Cut back on the G2 bottom knob on the flyback, which will lower the brightness to where it no longer bleeds out, or replace the CRT. Last solution obviously not worth the effort. Years ago you used to be able to try to restore the guns, but that was only a band aid solution that could also blow out the tube. Some people can adjust the blue and green drive and cutoff trimmers on the CRT board, to sometimes get a little more life.

Considering the time to spend doing all this stuff, you could simply go to your local Salvation Army or Goodwill store and probably find a better, bigger and reasonably priced CRT set, to replace it. May have to invest in a universal remote, but you may end up with a set that is Stereo, has video inputs, and so forth.

I get most if not all my vintage stuff from GoodWill. I snagged a DVD/VCR recorder combo. (DVD recurds as well as VCR) and the only thing wrong with it was simply had to clean the belt on the DVD unit, as it was sticking and the tray would not open.
I bought a Harmony 300 remote at Target so for $40.00 I have a very nice unit to use as my DVR so to speak, with the purchase of $10.00 worth of DVDRW discs, to use with it. This is all cited as an example of where to find bargains only. The good thing is that with GoodWill they are willing to take it back, if it does not work, so even the non techie person can find bargains.

[Th3_uN1Qu3]

Re: TV free off the curb

Snapping noises are usually High Voltage issue or sign of the guns about to fail and arcing internally.

It does indeed appear to be coming from the tube. At least to me it sounds like the discharge is in the neck - so it appears that one of the guns is responsible. I tapped on the neck and it snapped multiple times in a row, then stopped and it's not doing it anymore.