I've fixed hundreds of those Sonys, and my guess is that you will have to replace that MCZ chip soon.

One of the tricks we used to identify a bad MCZ chip was to simply heat it with a heat gun or a wide blade soldering iron across the top of the chip. If it started, I changed the chip. Heating them would sometimes restore them for a short amount of time. While it's certainly possible you had a bad connection that you fixed by soldering, I can honestly say that I never saw bad solder on the power board.

Some info from the field for site posterity:

There are two board versions - the brown and the green. The brown may have been in the DA1 and the green in the DX series, but I don't trust my memory like I used to.. The brown board is a single side board and it's very easy to replace the chip conventionally. I normally would put down a little liquid solder flux and use Chemwick to clear the pins.

The green board is a double sided affair and the solder goes through the lead holes and stops on the component side. It's a lot harder to replace the chip on the green boards. I used to add some chipquik to the original solder along with flux, then hot air the chip out of the board. It could also be wicked out but I preferred the hot air. I wouldn't use a spring loaded solder sucker on these as the recoil could damage a trace.

I never did this, but some guys would clip the pins of the chip from the top of the board with a *high quality* pair of angle cutters, then heat and remove each pin individually. Alternatively, you could also use a Dremel (if you have the swing room) with a cutoff wheel to cut the pins at the chip's body. Don't rush the cut lest you snag the pin and pull it, and don't go too deep!!

Towards the end of the Sony DTV era, there were TONS of counterfeit chips around. At the end, the only place I would trust to buy any Sony chips is B+D https://www.bdent.com/. I don't know if they have any originals left. The counterfeits would either not work, fail shortly after power up, or trash other parts around the chip. Careful with sourcing the MCZ chips.

Lastly, 98.136 percent of Sony TVs that came in for repair that had a power supply problem only needed the MCZ chip closest to the flyback, so I would only install the one chip - not both.

John

My set hasn't had the MCZ fail again but the grey scale will shift red then the entire screen will go red and trip a shutdown. Sometimes I can slap it before it gets too red and it will go back to normal....It got real bad a few months ago and I reflowed some solder on the neck board ICs/heatsinks and it was fine for months, but it is slowly coming back.... Anyone got a more precise/lasting repair method?

CRTS on Sonys can get cranky. If the grey scale shifts, the AKB will mute the screen or causing blinking, but if the cathode goes too low, it will draw too much current and shut the chassis down.

Try gently flexing the neck board of the tube and gently tapping the neck of the tube itself. Sometimes, there could be a piece of wayward cathode material that gets caught between the other tube elements. If flexing the board seems to change things, take a close look at the IC mounted to the heatsink (some have one IC for each gun, others have one larger drive IC to cover all three). These ICs run hot and could develop cold joints.

If the tube was the problem, I used to use my modified B&K 467 to try to clean the out by pushing the shorts clear button repeatedly while tapping on the neck. If that didn't help, I'd put the B&K on clean setting and repeat while tapping the neck.

John

Mine is the 1 IC per gun version.

If flexing the IC doesn't change behavior (IIRC it did and the heat sink ground joints were the worst last time) I'll try my B&K 466 on it as a last ditch (ISTR hearing most Sony CRTs die if you try rejuvenation).

Going bright red could also indicate a heater to red cathode leakage/short. These shorts can't be blasted because the heater would be damaged, but the heater can be "floated" as a workaround. The heater voltage is provided from a winding off the flyback that provides 6.3 volts but it's anchored to ground.

So, if the heater and any cathode make contact, the cathode will be pulled low towards the heater's ground reference. The lower the cathode voltage, the higher the current drawn and the brighter the screen goes.

What I used to do is to wrap three turns of ordinary insulated wire around the core of the flyback and feed it to the CRT socket at the filament pins. Often, a trace would have to be cut in order to get the CRT filament away from ground.

If done properly, you'll still get 6.3V**, but it will now be a floating ground supply. If the heater and cathode short again, the floating heater supply will get pulled up to the cathode potential of 200 plus volts above ground, but it will still maintain the 6.3 between the pins. Because the filament is no longer anchored to ground, a heater cathode short can't pull the cathode low.

Heater to cathode shorts usually will respond to gentle tapping on the neck of the tube, but not the circuit board flexing.

As far as Sony's blowing up on rejuv, I've done a bunch without issues, but any rejuv on any tube is a last resort option. If you need to, there's nothing to lose.

Sometimes, the clean setting will heat the cathode enough to either burn off any crud that's causing the runaway red condition or even melt the cathode and stabilize it.

If the tube is cranky and it's not a filament issue, then try a cleaning.


** With regards to wiring a floating ground supply: you must be careful not to exceed 6.3VAC filament voltage as even a couple of tenths will shorten the balance of the tube's life considerably, and this goes for all CRTs, not just Sony. Also, because the filament supply is sourced from the flyback (15Khz, not 60hz), cheap meters will give false readings of the voltage. A True RMS meter will read the high frequency AC voltage accurately. This is important.

Once you wrap the wire around the flyback core, zip tie it into position as moving it up and down will "tune" it and affect the voltage. Add an appropriate low value 5 watt resistor in series to get the voltage to 6.3 or just under.

John

I'm the one who originated this thread. I have a KD-34XBR970 set as the family daily driver in the living room. On average, every ~4 months, I've had the "blinking light issue" on startup that I originally posted about. I've been able to solve it by unplugging the set for a short time, then plugging it back in.

I have the genuine replacement chips on hand, but haven't swapped them yet.


Recently, I've observed a new behavior when the set starts up, and I'd like feedback from the experts on it. When the CRT is initially coming up, I see horizontal "streaks" in the lower 1/6th of the screen, as well as the R/G/B colors not aligned in that area. After several seconds once it's warmed-up, these issues go away and the picture looks normal.

What are probable causes of this? Is it repairable? I'll try to remember to capture a picture or video of this.

Thanks!

Recently my KD-34XBR970 set has had the faintest green tint uniformly over the whole screen. It’s most noticeable when the picture is all white or very light colored, and it seems to improve after the set has been on for awhile.

Are there any thoughts on this and what to do about it?

Slow imorovement points to the CRT being a little weak.
The set almost definately has AKB so it adjusts itself. There may be
a way to tweak it in the menus BUT if its OK after warm live with
it.
BTW if you go into the service menus ALWAYS write down the
parameters & save them. Also be sure to exit properly to save the changes.

73 Zeno:smoke:
LFOD !