View Full Version : What could cause this?


SpaceAge
07-24-2017, 07:22 PM
I have a Sony TV-VCR combo model KV-13VM30, manufactured 12/96. It was a $1 garage sale purchase about five years ago, and it has had problems since the day I bought it.

When I first power it on, the picture appears too bright, with poor contrast. I played the opening sequence from Star Wars on it, with the text scrolling up the screen. The background is black space and should be completely dark, but instead appears gray and washed out. In addition, there is a bright band on the far right edge of the screen, about a quarter inch wide, top to bottom. After about 15 minutes of use, the picture will begin to shake side to side very noticibly. Turning it off and then immediately back on will not fix this, I have to leave it off for a while and let it "cool down." Given enough time, I can turn it back on and the get back to where I started. After 15 minutes, the shaking will return. The issue happened regardless of the input. The VCR seems to work fine.

I opened it up today to take a look, and a few things stand out. Several large caps seem to be held in place by blobs of white silicone. Someone must have used the silicone to hold the caps in place, and then turned the board upside down and soldered the bottom. I doubt this is original, since the silicone blobs at least partially cover neighboring resistors. No way do I believe it was like that when new. Also to note is the label on the tuner is printed "NOV 09", I assume that's a date code. So apparently this thing has been worked on relatively recently.

If anyone can advise, I would appreciate it. This thing isn't vintage or particularly interesting, but I want to at least give it a chance and try to fix it. I could post a video of the problems on YouTube, if that would help. Thanks :thmbsp:

SpaceAge
07-24-2017, 07:37 PM
Some pictures:

http://imgur.com/Vppy9j2.jpg

http://imgur.com/v8wV2er.jpg

http://imgur.com/OL25YUw.jpg

Findm-Keepm
07-24-2017, 09:46 PM
I opened it up today to take a look, and a few things stand out. Several large caps seem to be held in place by blobs of white silicone. Someone must have used the silicone to hold the caps in place, and then turned the board upside down and soldered the bottom. I doubt this is original, since the silicone blobs at least partially cover neighboring resistors. No way do I believe it was like that when new. Also to note is the label on the tuner is printed "NOV 09", I assume that's a date code. So apparently this thing has been worked on relatively recently.


Sony famously used silicone to fasten large items to the board - vibrations in shipping would work the part loose otherwise. After the late 80s/early 90s IF solder fiasco/money maker (out of warranty work), Sony never took another chance, and passed the bad solder problems on to JVC and their vertical chips. The RTV on some large screen CRT sets did come back to haunt Sony.

That tuner is original - The tuner's final inspection fell on 11/9 of whatever year. I have some NOS OEM tuners with Oct 23 on them, so if 2023 ever gets here, or if Marty Mcfly brought them back, well....

As to your lack of contrast, I have several guesses - guesses they are. AKB on some Sony's gets wonky - might have to chase the G2 and cathode voltages to see if any change dramatically and work back from there. Related, Sony had a problem with the CRT sockets on your model sets - but the gripe was Picture dark, not what you are seeing. Is there a possibility that is was dark, someone cranked up the G2 or Screen voltage, got a picture and left it?

Lastly, your set is famous forregulator issues (http://vdoko.tripod.com/tvs/faqs.html) - a 6V three terminal regulator would cause a dead set, and the solder around all of the IC18XX regulators could be bad as well - all seen on at least a couple of sets.

And lastly - ZD1504, an 11V Zener, will get leaky, cause an all-white screen, perhaps with retrace, and shutdown the set. Replace the original with a 1N4741A, available at Mouser, Digi-Key, or use an NTE5074A.

That's really all I have from our Sams, a brief Google search, and some thinkin'

Electronic M
07-24-2017, 09:58 PM
That silicone looks factory original to me. I've seen plenty of unopened electronic gear with it inside. It had various uses, preventing adjustments from being tampered with, preventing large (otherwise) poorly secured parts like main lytics from wiggling in transport, etc.

If I was in your shoes and happened to like it enough to bother I'd touch up and suspicious solder joints (and the ones on the high power stuff like PS and sweep sections), then hit the caps with an ESR meter to look for bad ones.
Maybe ~10% of my SS gear I like well enough to give that courtesy upon death/failure, the rest I scrap without a second thought....Life is too short to waste on garbage...If it proves obstinate chuck it, grab another off the free section of craigslist and move on with yur life.

StellarTV
07-25-2017, 02:51 AM
It's probably a filtering problem. I used to repair hoards of video poker monitors for the casino industry and these typically ran 24/7 for years at a time. All various makes but one problem in particular- washed out screen with a bright band off to one side was always a bad B+ filter capacitor.

I'd first try checking or replacing the higher voltage electrolytic off of the B+ line near the HOT or flyback. They were always just dried out, but visually looked fine. Probably a 250v cap, 10 to 22uF, but I just don't know for sure on your Sony.

zeno
07-25-2017, 08:56 AM
First thing to check is the 200V filter cap. Its one of the most common
problems on all brands of TV's. It will cause the symptoms.

First go to CRT socket & find the 3 larger resistors all the same value.
One end of all 3 tie to the 200V follow this back to the chassis, it
may go through a choke or low value resistor on the way. You will
come to a diode thats off a FBT winding. The cap is off the cathode of
the diode. Typical value is 4.7mfd 250V, Use at least a 350V.

73 Zeno:smoke:
LFOD !

BTW this cap will cause any of the following symptoms in
any combination.

Jail bars
Normal pix one one side, too brite on other.
Too bright
Washed out
Streaking like a weak CRT
pix "not right" but usable
bright vert line(s) on right
too bright then shut down
other I am not thinking of !!

SpaceAge
07-25-2017, 01:15 PM
Brian, you're right about the tuner. It dawned on me right after I posted, it's probably November 9, 1996. Makes sense, the rear plastic shell is stamped 10/1996 and final assembly in 12/1996.

The silicone is interesting, not something I've personally seen before. That said, this is the newest tv I've ripped apart, and the only Sony to date.

Thanks for the suggestions, we'll see what happens.

Jon A.
07-26-2017, 12:15 AM
It's probably a filtering problem. I used to repair hoards of video poker monitors for the casino industry and these typically ran 24/7 for years at a time. All various makes but one problem in particular- washed out screen with a bright band off to one side was always a bad B+ filter capacitor.

I'd first try checking or replacing the higher voltage electrolytic off of the B+ line near the HOT or flyback. They were always just dried out, but visually looked fine. Probably a 250v cap, 10 to 22uF, but I just don't know for sure on your Sony.
+1.

I'm re-capping my daily watcher. Picture had poor contrast, long nasty streaks to the right of bright images, would get brighter toward the right side and the colors were pretty bad. Swapping out the 22uF 350V filter near the fly wiped all this clean.

SpaceAge
08-07-2017, 01:04 PM
Some progress... I found the 4.7uf 250v cap Zeno and Stellar were talking about, replaced with 4.7uf 400v. The bright band on the right side is now completely gone, so that cap was definitely toast. But there are still problems here.. The picture is still flickering and shaking, but the on screen display does not seem to be affected. Something wrong in the video processing circuit??? I posted a short video demonstrating the problems on YouTube yesterday, but can't find it now. I had it playing some random DVD, I wonder if the video got canned for copyright reasons? :scratch2:

zeno
08-07-2017, 03:32 PM
Some progress... I found the 4.7uf 250v cap Zeno and Stellar were talking about, replaced with 4.7uf 400v. The bright band on the right side is now completely gone, so that cap was definitely toast. But there are still problems here.. The picture is still flickering and shaking, but the on screen display does not seem to be affected. Something wrong in the video processing circuit??? I posted a short video demonstrating the problems on YouTube yesterday, but can't find it now. I had it playing some random DVD, I wonder if the video got canned for copyright reasons? :scratch2:
Well done.
Next most common thing on these is cold joints at the vert output IC.
Resolder them even if they look OK. I will look at the utube when
you find it.

73 Zeno:smoke:
LFOD !

SpaceAge
08-07-2017, 04:06 PM
Not sure why I couldn't find it earlier, but here's the video: https://youtu.be/LuEMdIfrEok

zeno
08-08-2017, 05:11 PM
Not sure why I couldn't find it earlier, but here's the video: https://youtu.be/LuEMdIfrEok
That a tough one ! Try turning the G-2 down a little ( on FBT ).
Not the vert for sure, either video or G-2.

73 Zeno
LFOD !

old_tv_nut
08-08-2017, 05:29 PM
Is this while playing a tape? If so, I would try a separate input device and see if it's still there. It would help isolate between the tape player and the display.

SpaceAge
08-08-2017, 08:22 PM
Is this while playing a tape? If so, I would try a separate input device and see if it's still there. It would help isolate between the tape player and the display.

This was with a DVD player. Been a while, but I did try a tape and it looked exactly the same. So I guess that means the VCR is actually functioning well???? Connecting a cable box to the RF input got the same result as I recall, so it's not an issue with a particular input. I actually remember watching the World Series with the infamous Will Middlebrooks obstruction call on this tv. I thought running the set for a few hours might fix the issues. Obviously it did not, and that may have been the last time it was powered on before last week. Anyways, I'll mess around with the G-2 and try some other things. This will keep me occupied until I can get started on some tube projects. Those are on hold until I have access to a decent tube tester, which will happen in a few months. :thmbsp:

old_tv_nut
08-08-2017, 09:39 PM
It seems to be at a somewhat regular rate, like power supply motorboating or some similar oscillation in the beam controls. I'm guessing there's still a bad cap (or cap connection) or two somewhere.

EDIT: poking around the video supply with a scope or a fast-acting DC meter may lead to the problem.