Aw, crapdoodles, here we go again... - Page 2 - Videokarma.org TV - Video

mbates14 · #16 05-07-2005, 01:45 PM

yea really.

mbates14 · #17 05-07-2005, 01:50 PM

Hell, I catch caps all the time that are bad, but doesn't look physically bad.

mbates14 · #18 05-07-2005, 01:56 PM

I heard sometime in the past nichicon screwed the dielectric electrolyte formula and been using it ever since, which is why the massive failure occures, not only on motherboards, but TVs, camcorders, etc... hell Ive seen a nichicon cap fail in the EFM section of a DVD player, and having the exact sympom of a bad laser.

ha1156w · #19 05-09-2005, 02:50 PM

I'll second that. I had a Toshiba DVD player with bad caps in the audio output section...the problem was so common that there was a "how-to-fix-model-X" tutorial on the web, a la the Sony TVs in the early 90's. By the way -- has Sony finally learned to solder, or are they still having bad joints these days?

HA1156w

Tony V · #20 05-09-2005, 06:22 PM

I've had a couple friends that have bought Sony tv's within the past few years and it seems that they are getting better with soldering as both tv's are about to hit their 3 year mark with no problems. That sounds good concidering that some of them werent getting even 6 months on them before going to the shop. The days of Sony producing a good picture as we were used to seeing seems to have faded away though.
-Tony

domfjbrown · #21 05-10-2005, 04:25 AM

My 1995 Sony 14inch portable had to go back after only 3 months due to a colour feed from the Teletext decoder on it having a dry joint... My 1996 vintage 25 incher's still going strong though, so they're not all bad!

jstout66 · #22 05-10-2005, 05:34 AM

Tony V, I hear ya about Sony. I've vented about this in other posts, but my parents had a 1979 Sony 26" console. That thing had the best damn picture and lasted almost 20 years until the picture tube went bad. It had the red smearing and started having internal arching. The tube was still available, but those 26" are expensive! In 2004 (thinking Sony was still "da bomb") I bought a new 24" Sony Wega. The set had an awful picture. Mainly it was waaayyyyy to dark, even with the brightness on MAX. I started looking at e-opinion posts and that was a common complaint along with power problems. Seems they like to go out within a few months. I had the store take it back and bring a new Toshiba flat screen. My 1979 Zenith System 3 I use in the bedroom has a better picture tho.

charliesheen · #23 05-10-2005, 08:33 AM

well my 21' maggie,i got it in 98 and havent had a problem yet.

veg-o-matic · #24 05-10-2005, 01:01 PM

Okay, here's my latest, uhm, debacle.

I pulled out the SAMS last night and (from something I read somewhere else, can't remember where) actually managed to locate the vertical circuit, the logic being that this is a vertical problem. So far, so good. I managed to find that there are two electrolytics that are in that circuit. I figured it would be one or the other that's causing the squashed picture/rippling sides problem.

Turns out I had already replaced one of the caps (C5, I think), but just for good measure I jumpered another cap over it and didn't make any difference. Okay, must be the one in C4 (C4B, if I recall) which is one of those really small ones, maybe like a 40uf/50V. It's so puny that I didn't think there was a snowball's chance it would help. But I jumpered it in and took a look. Squat change. Wellsir, I was done for the night. Yes, I give up easily

Plus, I was lying on my back under the set, and a certain weiner dog insisted on helping.

New day, fresh start. I thought I'd read over the posts from the last time this happened (similar, but slightly different problem) and came up with a couple of points that I'd like to clarify before I actually flip the set over.

Doug had said that if a cap is leaky, bridging over it with another cap won't tell anything; this only works with open or changed value caps. Am I understanding this correctly? So I won't really know what's what unless I desolder the lug coming off the can and then put the new cap in the circuit? Except for one, I don't think I bothered doing this with any of the other caps I replaced. This is not to say that I'm second-guessing Doug, I just want to be sure my feeble brain is understanding correctly.

Am I barking up the right tree with the two electrolytics that are in the vertical circuit? Or should I be looking elsewhere?

(Yes, I know I should be replacing all the caps, particularly since this is the second cap-related problem I've had. On the other hand, the more I do to a set, the likelier the chances of screwing something up totally. Believe me, I know my limitations!)

Sorry to be so stupid here. I just don't want to kill Laura! I was a perfect whiz putting in the new garbage disposer on Sunday. So apparently, I can do something!

Here's a pic as a reminder.

Thanks!

veg

blue_lateral · #25 05-10-2005, 09:44 PM

I'll bet youre barking up the wrong tree with the vertical. The horizontal is weak too, and probably the high voltage... from that picture you posted it looks like everything is weak.

I think the other posters had it nailed, its a low-voltage power supply problem. All Zenith roundies (as far as I know) have a voltage doubler power supply. Its the same circuit used in RCA ctc9 to 15, Silvertone, Philco, even Setchell-Carlson! (havent seen that one, only the schematic). It makes about 400 volts.

As I understand it it works like this, theres 2 diodes and 2 capacitors (160mf, 250v). When the current from the power transformer flows one way, it flows through one diode, and charges one capacitor (to 200v or so). When it flows the other way, it flows through the other diode and charges the other capacitor (also to about 200v). Because the capacitors are in series, you have about 400v output to the filters.

You can check this, just measure the DC voltage across each 160mf 250v capacitor with the set running. Each one should have about 200v. I'll bet one is really low. When you find the low one, substitute another capacitor (unsolder the old one). If the capacitor doesn't fix it, you probably have a bad diode.

Unsolder one side of a diode. Hold onto the lead with a needle nose pliers (diodes dont like heat). When you have one end loose, check it with an ohmmeter. It should measure really low one direction, and really high the other. If the first one is good, try the other.

Of course I might be completely wrong about this, but if both halves of the voltage doubler are ok, start going down the power supply chain, checking the voltages against the sams.

Gorgeous set

Hope you get it fixed.

John

P.S did you mean in that last post that the old caps are still in the circuit along with the new ones? I wouldnt do that except for a quick test.

roundscreen · #26 05-13-2005, 07:06 PM

On your post you said the sound came on normal but the picture was slo to come on.
If you have spare tubes, try replaceing the horz and damper tubes.

kc8adu · #27 05-14-2005, 01:57 AM

that is a case of low b+ due to a bad cap or diode.the ripple causes the waves.
everything that runs from it will be sick till its fixed.
forget everything but the power supply for now.

roundscreen · #28 05-14-2005, 07:28 AM

I am just wondering why is the sound ok. When he replace the caps the first time he had a humm in the sound. I have seen a bad damper tube can do that to the screen. If a cap was leaking that bad I would think something would over heat. Resistors or the bad cap. If the damper and caps are good then it must be the diodes.

jstout66 · #29 05-14-2005, 12:04 PM

I would assume bad caps on this one as well. Especially since many of them have been changed and perhaps something wasn't hooked in right the last time? I'm not "bagging" on veg-o-matic, as he has certainly shown more ability than myself in repair attempts. All I can do is diagnose and change tubes. I can't solder worth a crap, and I don't dig in anything too deep for fear of really screwing something up. My comment in general tho, as I've noticed this in other posts, and to a degree in this one, is why some freak out and assume the caps in mid 60's to 70's color sets are always a "problem" and must be changed, even when the set shows no symptoms of having a problem in that area? They use the "modern" caps and it's not like they are a danger or problem like in the 50's stuff. My repairman Uncle who I observed and worked with always found the specific problem and repaired it. He wouldn't mess around with future potential problems as he believed "If it ain't broke, don't fix it" as that could cause MANY worse problems. As for this problem, yes most likely an incorrect or bad cap, but I have seen the damper tube cause this, as well as a bad Yoke. You can't assume that just because the set may have had a bad cap before that this is the same problem now. It narrows your scope in getting this problem fixed. Veg, if you have anyone in your area that you can get to repair this I suggest you take it to them. I screwed my "roundie" up and had to take it in, and I hope all works out well for you on this set. From your posts it sounds like you really enjoy and appreciate what you have. Good luck!

stereofisher · #30 05-15-2005, 09:00 PM

Quote:

Originally Posted by veg-o-matic

Okay, so I fired up Laura and noticed that while the sound came on normally, it was taking a long time for the picture to show up.
Dang it, this is what I got.
Is this another capacitor that has to be replaced? Please, couldn't it be a tube this time? I'm good at those!

Funny thing is, she worked just fine last week. I haven't been watching much TV lately, so she only gets turned on once a week or so.
Any thoughts to help a poor fool like me?
Thanking you in advance!

My CTC 10 had bad caps. Replaced all caps in the power supply and the focus tube,horizontal output,horizontal oscilator, and rectifier. Brought here back from the dead

From memory the Zenith is easier to change them. Did my parents set back in 1973. A 1966 model. Square screen. Both sets came back nice. Great pictures. That is a nice set you have there! Its an easy fix!

Eric