Please Help? Vacuum Tube TV

[Yanni10]

Hi All

I have a vaccum tube tv. When I turned on the tv, the screen had a thin white line across it. Now the when I turn on the tv, the on switch button light just flickers and the tv screen doesn't come on.

What could possible wrong with my vacuum tube tv?

Please help?

Best regards James

 

[Gryd3]

Sounds like more than one thing unfortunately...
The image on your TV is created by scanning a beam across the screen... 4 coils are responsible for that in the back of the TV. They are a form of electromagnet that rapidly change to direct the beam in a scanning pattern across the entire screen. If there is a white line... that means that 2 of the coils are not operating. This in itself could be caused by a couple of things. The direction of the line might help.
Now that all you get is a flickering power light... it is apparent that there is an additional problem, or that the initial problem got worse.

In order to scan across the TV fast enough, the voltage fed to the coils is incredibly high... Dangerously incredibly jump through the air and hit you high. The coils are driven in pairs, if one of the coils is bad, it could cause the circuitry that creates and controls that high voltage to fail as well. It could be any part of that circuit down the line. The fact that you had the line in the first place though makes it seem as though at some recent point in time some of the circuitry worked.

Now here's the kicker. I won't help you fix it. I won't give you tips, or recommend tools. I would suggest you don't even open it.
Remember that oh so very scary high voltage I was telling you about? It's not 110-220V that goes into the TV... there is a transformer inside that pumps out 1000s of volts, and this is the deadly scary sir gap jumping voltage that is incredibly dangerous to work around/on/with.
Go buy a new TV, or pay a qualified repair guy to take a look for you. It's not worth the risk to save some cash.

Best of luck
~Jerid

 

[KrisBlueNZ]

A horizontal line is called frame collapse. Loss of drive to the vertical deflection coils in the yoke on the shoulder of the picture toob. In a toob set most problems are due to failed toobs. If you provide a make and model number, and we can find service information for it, we may be able to suggest the toob to replace, but you may have trouble finding a replacement.

Dead set could be a whole lot of things. I think you'd be best to bin it.

 

[shrtrnd]

Yeah. The first thing you'd have to do is pull the vacuum tubes and test them, which isn't easy to do these days. Very few tube-testers around.
Then you'd have to get replacement tubes, which aren't all that easy to find these days either.
Then you'd have to troubleshoot the TV to find out what else might be wrong with it.
With the price of new TV's as low as they are, it's more cost efficient to get a new one, rather than try to extend the life of an old vacuum tube model.

 

[liviuadam]

First verify suply video.Arround 180-200V.Something electhrolitic 4,7-10uf/250V.

 

[Yanni10]

Thanks all for the information!

It is actually my girlfriend tv, she keeps in our bedroom. She only paid R300 for it second hand. It is not worth fixing it.
We have a flat screen tv in the lounge. The people that repair flat screen tv's here in Cape Town, South Africa have indicated to me that they don't fix vacuum tube tv's anymore.

 

[Thirantha]

A single horizontal line means that you have lost vertical deflection. High voltage is most likely fine since there is something on the screen.

This could be due to:

1. Dirty service switch contacts. There is often a small switch located inside on the main board or perhaps accessible from the back. This is used during setup to set the color background levels. (On some sets, this is located on the CRT neck board and may be a jumper plug or other means of selecting service mode - not an actual switch.)
   When moved to the 'service' position, it kills vertical deflection and video to the CRT. If the switch somehow changed position or got dirty or corroded contacts, you will have this symptom. Flip the switch back and forth a couple of times. If there is some change, then replace, clean, resolder, or even bypass it as appropriate.
   
   
2. Bad connection to deflection yoke or other parts in vertical output circuit. Bad connections are common in TVs and monitors. Check around the pins of large components like transformers, power transistors and resistors, or connectors for hairline cracks in the solder. Reseat internal connectors. Check particularly around the connector to the deflection yoke on the CRT.
   
   
3. Bad vertical deflection IC or transistor. You will probably need the service manual for this and the following. However, if the vertical deflection is done with an IC, the ECG Semiconductor Master Substitution guide may have its pinout which may be enough to test it with a scope.
   
   
4. Other bad parts in vertical deflection circuit though there are not that many parts that would kill the deflection entirely.
   
   
5. Loss of power to vertical deflection circuits. Check for blown fusable resistors/fuses and bad connections.
   
   
6. Loss of vertical oscillator or vertical drive signals.

The most likely possibilities are in the deflection output stage or bad connections to the yoke.

 

[davenn]

Bad vertical deflection IC or transistor. You will probably need the service manual for this and the following. However, if the vertical deflection is done with an IC, the ECG Semiconductor Master Substitution guide may have its pinout which may be enough to test it with a scope.

Thirantha

the TV is an old tube based one, not semi conductors --- read the thread title

to the OP ... what is the model of the TV ? if we could identify which tube or tubes are for the vertical output, that would help lots

Dave

 

[Colin Mitchell]

It's simply the vertical output valve

 

[davenn]

It's simply the vertical output valve

yup we know that, Colin

We are trying to identify the TV make and model so we can possibly identify which tube is the vert O/P one

Dave

 

[Yanni10]

Thanks all for the Help! The tv is working now. It was the plug. Best regards James

 

[HellasTechn]

Thanks all for the information!

It is actually my girlfriend tv, she keeps in our bedroom. She only paid R300 for it second hand. It is not worth fixing it.
We have a flat screen tv in the lounge. The people that repair flat screen tv's here in Cape Town, South Africa have indicated to me that they don't fix vacuum tube tv's anymore.

In Greece we dont even bother to take them in to troubleshoot them. No one does nowadays i think. Also factories have ceased production of some key parts also like HV transformers.

 

[Yanni10]

Once you change one part of a vacuum tube tv which is old, you find that another part of the tv breaks a little while later. If you bought the second hand tv for R300 in Cape Town, it is not worth spending R600 for example (R300 for Labour and R300 on parts to fix it.)

My girlfriend's tv is working fine now, so she can use it in the bedroom until it one day eventually packs up. We have a flat screen tv in the lounge and my girlfriend has a tablet she can watch movies on as well.

 

[elebish]

Glad to see the tv working!
Ed.

 

[errol-smith]

Thirantha

the TV is an old tube based one, not semi conductors --- read the thread title

to the OP ... what is the model of the TV ? if we could identify which tube or tubes are for the vertical output, that would help lots

Dave

I think it was actually a solid state cathode ray tube TV from what the SA guy was saying.

 

[davenn]

solid state cathode ray tube

no there's no such thing

 

[BobK]

Yes there is. The later model TVs with picture tubes use mostly semiconductors and even ICs for other parts, in fact they were advertised as solid state.

Bob

 

[davenn]

Yes there is. The later model TVs with picture tubes use mostly semiconductors and even ICs for other parts, in fact they were advertised as solid state.

Bob

not what I meant