Westinghouse TV no picture : Strip or fix?

[JesusJones]

There is a "trimmer" (adjustable capacitor) at the back of the tv. For horizontal I think.

What does it do?

C-433

page 4 schematic.

P.S. If i Recap this tv, should I use orange dips or axial caps(Metalized Polyester Film "Tubular axials").

[Old1625]

Originally Posted by JesusJones

This sounds like it could very well be the case. But like I said before I have no Idea what the agc loop is. Could some one tell me where this is? what it is?

If you look at the control grids of each pix IF stage in a typical set you will see that the grid receives a negative bias which should grow stronger with stronger signal. Because it is the practice to use "remote cutoff" pentodes in the IF stages the increasing negative bias with stronger signal causes a cutback on total IF string gain, preventing overload. The AGC line feeds off the video detector as a rule, and supplies this negative bias. A shorted or leaky bypas capacitor from the line to ground may kill the AGC action altogether.

Sometimes it is simply that in fiddling around with a set that an actual AGC trimpot may have been disturbed, knocking the AGC out of adjustment, meaning that you could probably solve your problem with a simple tweak. These AGC level adjustments are usually found only on the higher-priced more elaborate sets, while most other more basic sets usually don't have such an adjustment.

[electroking]

Hello again,

Be sure to check your e-mail, I sent you some more documentation including a
discussion of the AGC circuits. Taking the time to read all this carefully should
be helpful. Good day.

[JesusJones]

Ahhhh thank you very much

The Tv shut itself off. Or screwed up wild it was turned on. I went to the back of it and noticed the fuse. That hooks up directly to line voltage was rather hot. Something is shorted out. Or a cap is open. I have no idea where. and it's making me mad. I wanna order capacitors but I don't have a large enough of an order to even do it. (And a man here sells the capacitors I need but at 4.50 a peice! for a .0047!)

I saw smoke come out of the tuner once also. I checked all the resistors in the area I saw smoke. They all seemed ok. But in this tuner are many "short" looking resistors(but I don't think they are resistors) They all check closed letting no current pass. What are these?

And as for the shorting problem(heating up fusible resisto) Would faulty caps cause this? Or something else.

And I don't have (Like i said before) a large enough order to get the caps I need. Unless I were to buy caps for my nordmende isabbella C console stereo. But I have no idea what it requires. Might anyone have a schematic for such a console or have done a similar one? Or will I have to rip my nice stereo apart.


And the Tv did not shut itself off. Luckily it unsoldered itself Where the b+ soldered to the diode I put it. And no real harm was done

[JesusJones]

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I'm sorry for hitting my keyboard
I just needed to do it.
listen to this and see why.

The antenna was connected to a tab. With three points. The middle point was grounded. From the middle 2 large value resistors went to the two outer points. The 2 outer points had the antenna hooked up to it. From these two outer points. The antenna signal was sent to the first tube via 2 capacitors then a transformer of sorts.

THIS FREAKING TAB WAS BENT. This bend it had. Made the signal from the antenna go directly to the capacitor then ground!!!!

I BENT IT AND THE PICTURE WAS 10x's better. And other channels showed up.

And I am rather annoyed by this simple fix. I was spending alot of time checking things and starring at the schematic to look for things to check. But thank God it's working. I just wish I found/thought of it sooner. I can't even beleive

[bgadow]

It is ALWAYS something simple...the hard part is finding that simple thing.

I think the fusible resistor would get a little warm but I don't know what is normal.

Are you using justradios.com for your caps?

[electroking]

The bright side of it is that while you were doing all that troubleshooting, your mind
was absorbing more and more information about the principles and practice of TV
receiver design!

Don't worry too much about things being warm in tube type equipment. You said at
some point that you had added a resistor somewhere to drop the voltage. If the
DC supply voltages (+264 and +132) are reasonably close to the values shown on
the schematic, then the power supply is probably operating correctly. If those
voltages are too high, then a small resistor in series with each of the two diodes
would be the right thing, making sure that those resistors are correctly installed
to prevent any kind of shorting.

Bye for now.

[JesusJones]

Yes I am using the Justradios website for capacitors. They require 15$ minimum purchase as your probably know.

I will check the voltages of the power supply momentairly. I hope it is slightly higher. A resistor is a pretty easy fix!

And yes The learning is what it's all about really. Being 17 my brain just takes it all in. And by the time I'm older I'll be Pro.

Just like you guys

P.S. If any one wants to see that nordmende I have for better reference. Or just veiwing purposes check this out http://www.audiokarma.org/forums/sho...light=isabella

[JesusJones]

Ummmmm.... I tested the voltages. From the + ends of both the 200mfd capacitors to ground. The results scared me.

From the first cap connected to ground (The 136+v) Was 250volts!
And the other cap was 475!!!!

How much extra radiation was I exposed to. Haha ha (I'm only half kidding there).

And Is this still just a fix with a resistor? If it is I'll be glad.

Maybe I tested it wrong. But I think not.

[radiotvnut]

Originally Posted by JesusJones

Ummmmm.... I tested the voltages. From the + ends of both the 200mfd capacitors to ground. The results scared me.

From the first cap connected to ground (The 136+v) Was 250volts!
And the other cap was 475!!!!

How much extra radiation was I exposed to. Haha ha (I'm only half kidding there).

And Is this still just a fix with a resistor? If it is I'll be glad.

Maybe I tested it wrong. But I think not.

Silicon diodes have a much lower voltage drop than a selenium diode. It is usually necessary to place a resistor in series with the diode to drop this excess voltage. Something between a 22 and 100 ohms should work. You'll just have to experiment with different values to see what resistor yields an output voltage close to what the schematic calls for. Just make sure you use at least a 10 watt resistor. Anything less will likely overheat and burn itself open.

[electroking]

Hello,

Be sure not to operate the TV until this has been fixed. I attempted to compute
the resistors required, but this is no simple problem. I will ask for some expert
advice from folks who have done it. Just look for the new thread.

[JesusJones]

So I need a resistor after the x-501 diode?
or Both?
I put a 25 ohm in originally but I guess it's not enough.

And I can post pictures now. Gimmi a while though

[JesusJones]

from before

I also have a large adjustable wire resistor. Goes up to about 200 ohms.
Should i give it a shot with it set to 100 ohms?

[electroking]

Be sure to drop the B+ voltage close to 264, otherwise you will fry something!
And I told you to leave it off in the meantime...
Good luck.

[JesusJones]

I did leave it off.

I know that 500 volts is near the maximum value of the tubes, (most likely) and you don't want anything like that. It actually made me sad when I found out I had been testing the Tv at 475 volts. I'm amazed it stayed alive for 30 seconds.

It wasn't until I put my 25 ohm and 150 ohm resistor in that I tried it.
The Voltage was actually too low. I've been paraleling resistors since then to try and get it up.
Voltage doesnt go anywhere near 400 anymore though. Which is a big releif


I only really have 2 problems now.
The screen is too wide
And the top looks a incy bit stretched. Other than that all seems well.