Found a working 56" RCA P56930BL Tv that needs some slight adjusting.

[MRX37]

Got this TV off Craigslist. The guy said that the picture would be fine for a few minutes but then curve inward. I ran this TV for 3 hours and the picture remained stable. The picture is pretty good, but the corner converghence is just a bit off, and the image kind of bows a bit at the top. Look at the pic below to see what I mean.




I have the remote for it, and there is a convergemnce menu, but that only has the cross in the middle of the screen. Is there a menu I can access to touch up the corner convergence?

Oh and of you're wondering about the grid displayed on the TV screen, that's something I drew quickly in paint for convergence purposes.

[MRX37]

Actually, I just found a service manual for this chassis (CTC 195).

Is there anything special I need to know about this TV, like do caps tend to fail on it?

[avionic]

That really does't look that bad at all.Corner convergence on those large projection's is a challenge sometimes.I do believe there is a large convergence board inside the unit for a more detailed alignment.

[MRX37]

According to the manual, I need some software called "chipper check" to do major convergence touchups, but it says that I can adjust geometry.

I wonder if it would be a prudent move to replace all the large capacitors inside the TV? There's no evidence of them being bad, but the TV is 10 years old, though apparently it's only seen about 6 years of use.

[radiotvnut]

On some newer big screen sets, there are several low ohms fusible resistors on the convergence board. I replaced the convergence IC's in a later model Akai; but, there were parts of it that would not converge. I found a couple of, IIRC, 3.9 ohm resistors that were open. These probably opened due to the shorted convergence IC's.

[MRX37]

Ah. I know what fusable resistors look like, and I'm certain that the convergence IC's work fine, because I get the convergence menu and according to the service manual, that menu would not be available if the convergence IC's were shot.

EDIT: Someone definitely replaced the convergence IC at one point. I pulled out the board that that IC is on, and the soldering was different. It was done well enough, but not factory. None of the resistors around it were touched though, so I'm gonna test each one and replace any bad ones I come across.

[andy]

000

[rcaman]

replace the stk730-130 on the convergence power supply and you will be good to go. the powewr supply is mounted about the conv. outputs there is a red and black wire going to it from the main chassis. have fixed a ton of these for your symptom. steve

[MRX37]

Originally Posted by andy

Is that your cross generator, or is there a major vertical linearity problem near the top?

Yes that is my grid pattern. Yes I know it doesn't look right... I downloaded a test pattern DVD with better patterns...

I found a resistor that I'm certain is bad... because it reads as 0 ohms on my multiumeter.

[andy]

000

[MRX37]

This resistor is red, black, silver, gold, which if I recall calculates out to be 0.2 Ohm's. On my multimeter, it reads exactly 0.000 Ohm's. 0.001 ohms if I wiggle the leads a bit.

And yes this resistor is out of circuit.

[MRX37]

So, here's what I'm wondering:

0.2 Ohm is such a low value, and this resistor does read 0.000 Ohm's. Does it really matter that this resistor is essentally just a dead short or does that 0.2 Ohm matter?

The resistor is located in an area on the board where several 4 pin cables connect to.

[radiotvnut]

It shouldn't matter. Often, these very low ohms resistors will read like a short on an ohm meter. They are in the circuit for protection and are designed to open in the event of an overload.

[MRX37]

So, even though it reads no resistance whatsoever, it's fine cos if there's an overload, it will open?

In that case, why isn't it a fusable resistor?

[MRX37]

Okay, since this post is already here I might as well use it for something.

I decided to put the resistor back in and put the board back in the TV.

I thought I had screwed up the TV when I reconnected the convergence board. The convergence and deflection were TERRIBLE. The problem turned out to be the only 3 connectors on the board that are not keyed. They're 4 pin connectors and they go to the control boards for each of the 3 CRT's. I think these are the yoke connectors.

EDIT: I found the digital convergence menu, which displays a grid and allows convergence at all of the intersections of the grid! I can probably fix all the picture issues using this.