KV-34XBR800 issues, first the 6/7 blink, then other troubles

[Auburn Boy]

KV-34XBR800 issues, first the 6/7 blink, then other troubles

by Auburn Boy » Wed Jun 24, 2015 1:37 am

Hi,

I'm a new user here, but this seems a lot like the right place to be talking SONY!

I have a KV-34XBR800. Purchased new in 2002. Yes! It is still up and running. It's the centerpiece of my living room home theater system.

In 2007 I encountered the diagnostic power shutdown 6/7 blink problem. I purchased MCZ3001DB replacements for IC6501 and IC8002 and installed them in sockets on the "D" board. Not a difficult operation, since I've been an electronics technician for 40 years.

Now, fast forward to 2015. Other things are happening to my XBR800.., Regardless of my experience with electronics, CRT Televisions are NOT my forte. I'm not even sure how to describe the issues, but here goes. (Maybe some pictures or a video might help later.)

First, when the system is powered on from a cold shutdown, the display has an odd pattern of moire-like bands in red and green that rotate around the screen, change width, and separation for a couple of minutes before the system completely warms up and they disappear. That started happening about a year ago.

Lately, the second symptom started creeping in. It may be somewhat related to the first symptom. After the set has warmed up, and we are happily watching a show or a movie, when an image comes on like an advertisement, where the background is supposed to be white, it doesn't STAY white. When objects or image segments come on the display, the background takes on a "hue" related to the new color object.., Red objects make the background somewhat pink. Green objects make the white go sort of green, and so on, with Orange, and yellow, and blue.

This has only been evident for about two or three months.

What makes me look around to see what might be done to fix it NOW? LOL!!

The dreaded Self Diagnostic Errors returned. 4, 6, or 7 blinks.., Luckily, I bought FOUR MCZ3001DB replacements.

So NOW that I have the set fully opened up again, it might be time to see if I can fix the new defects.

I heard a long time back that there were CAPACITOR issues in SONY sets. Could this be one of my problems? Any other suggestions? If I can get the major problems out of the way, meybe it's time for an ISF Technician to come in and perform some tuning magic on the set.

I would HATE to lose it.

Either SONY designed an inadequate circuit around the power monitoring chips, or the factory/designers blew it on the silicon!!

Any help would be appreciated.

Auburn Boy (A.K.A. Neil)

[jehill]

Re: KV-34XBR800 issues, first the 6/7 blink, then other trou

by jehill » Thu Jun 25, 2015 4:19 pm

I don't recall ever hearing of capacitor issues. If you have a capacitor checker, why don't you try checking what appear to be candidates to you? What you might do is study the schematics and compare the actual circuit voltage with a capacitor's rating. I would start out with power supply filter capacitors. Electrolytic capacitors that are pushed close to their voltage limit are stressed more than ones with ample head room and are the most likely to fail or degrade due to stress.

[Auburn Boy]

Re: KV-34XBR800 issues, first the 6/7 blink, then other trou

by Auburn Boy » Fri Jun 26, 2015 1:24 am

Hi jehill,

Would you recommend putting an O-scope on the power supplies and check their ramp up stability, and ripple during warm up.

I've been gradually learning the circuit through the manual, but I'm no TV tech..,

I had heard that some models of the XBR WEGA unit had inferior caps, and that they degraded rather fast. But I couldn't find that post. I think the post was over on AVR forum.

Do you happen to know which power supply would be most responsible for driving the color guns?

Thanks,

Neil

[jehill]

Re: KV-34XBR800 issues, first the 6/7 blink, then other trou

by jehill » Fri Jun 26, 2015 2:54 pm

Now that I have thought about it more, I don't see how a defective filter capacitor could cause the moire-like bands that you have seen. If the problem is a capacitor, it may well be a small capacitor. You said that you saw red and green bands. What about blue? Using a scope to locate the problem is a great idea. Comparing waveforms between the circuitry for the three colors (red, green & blue) may cause the problem to stand out. Obviously, the waveforms for the three colors should be similar. Years ago I remember doing that on a TV that a friend was having trouble with and quickly located a bad disc ceramic capacitor. I don't know if you have noticed yet, but most of the schematics include waveform drawings and tables listing the DC voltages that you should expect.

The three "guns" (cathodes) are controlled by the CH (Video Out) board which is driven by R, G & B signals from the B board and receives +200V and +12V from the D board. The CH board is attached to the CRT via the CRT socket.

I really have no idea what is causing the moire-like bands that you have seen. I am not a TV repair technician. I did take a TV repair course long ago that provided me with a Heath-kit TV to assemble. However, I have done a lot of electronics troubleshooting in the past. Did you Google moire-like color bands on tube TV? It might be worth the time it takes.

[Auburn Boy]

Re: KV-34XBR800 issues, first the 6/7 blink, then other trou

by Auburn Boy » Sun Jun 28, 2015 9:34 pm

HEATHKIT!!!

Wow, we must be of the same generation.

Healtkit: A.K.A. Bell and Howell Correspondence courses.

I built an oscilloscope, a digital multi-meter, a four channel audio amplifier, and a/fm tuner for an Entertainment Electronics course.

I tried to hit the moire bands on google, but didn't have any luck. Maybe I need to frame the query a little better. The reason I thought "power supply caps" or "filter caps" was the warm-up nature of the symptom. After about three minutes the banding goes away.

I have the KV-34XBR800 manuals here. I grabbed them in '07 before they disapeared. I wonder if anyone has a BILL OF MATERIALS for the "D" Board. That might help me identify capacitor sizes and values. Maybe even manufacturers part numbers..,

By the way, how does one add a picture of a video to the forum posts? (Activated after I've become a trusted poster??)

Thanks,

Neil

I'm going to try and borrow a 'Scope from somebody too.

[jehill]

Re: KV-34XBR800 issues, first the 6/7 blink, then other trou

by jehill » Mon Jun 29, 2015 7:37 pm

If you have the KV-34XBR800 service manual, you should find the parts list at the end. It lists the parts on each board.

[Auburn Boy]

Re: KV-34XBR800 issues, first the 6/7 blink, then other trou

by Auburn Boy » Thu Jul 02, 2015 9:32 am

Thanks! Wonderful.

[Auburn Boy]

Re: KV-34XBR800 issues, first the 6/7 blink, then other trou

by Auburn Boy » Wed Jul 15, 2015 1:52 am

I wonder if my "dis-colored" white fields are due to something called "Cathode Poisoning?"

Could cathode regeneration help? I've been reading a little more about CRT televisions and keep running into unusual issues..,

[jehill]

Re: KV-34XBR800 issues, first the 6/7 blink, then other trou

by jehill » Thu Jul 16, 2015 2:32 pm

I wonder if my "dis-colored" white fields are due to something called "Cathode Poisoning?"

Could cathode regeneration help? I've been reading a little more about CRT televisions and keep running into unusual issues..,

I have never heard of "Cathode Poisoning". Don't try cathode regeneration. I am wondering if your "dis-colored" white fields" are the result of your set being out of convergence. Take a close look at the screen. Are there any areas where the red, green and blue vertical lines don't converge? The most likely areas to see convergence issues are in the four corners. If this has nothing to due with what you are seeing, don't worry about it.

[Auburn Boy]

Re: KV-34XBR800 issues, first the 6/7 blink, then other trou

by Auburn Boy » Sat Jul 18, 2015 12:56 am

Hi Jehill,

Nope, the white fields get tinged uniformly all the way across the screen. I think it is likely either some power supply thing. (Bad caps) Or the cathode poisoning.

http://www.ke5fx.com/crt.html

I had found some other reference to brightness going south from that, and diminished color gun performance. WIKI has:

Failure modes[edit]
The emissive layers on coated cathodes degrade slowly with time, and much more quickly when the cathode is overloaded with too high current. The result is weakened emission and diminished power of the tubes, or in CRTs diminished brightness.

The activated electrodes can be destroyed by contact with oxygen or other chemicals (e.g. aluminium, or silicates), either present as residual gases, entering the tube via leaks, or released by outgassing or migration from the construction elements. This results in diminished emissivity. This process is known as cathode poisoning.

Cathode regeneration is supposed to remove any oxide coating or other contamination from the cathode filaments..,

Anyway, that's just a S.W.A.G., after all..,