RCA XL100 portable with a dark screen
 

Hello. I am new to working on Tv's, but I have a few years experience working on vintage audio gear, so I know most of the principles. I need some advice on this RCA portable tv I got for free. The tv powers on, and I can see snow, but there is no light coming from the tube. I have messed with all the controls and have had no luck. The flyback transformer sounds normal and the tube is certainly getting voltage, so I'm not sure what to do about this issue.

Thanks for any advice!

How can you see snow if there is no light coming from the CRT of a solid state TV?

It's just barley there, but everything is dark. With the lights out the tube emits no light, but with the lights on you can see the snow.

Get the chassis number (a lot of totally different chassis wore the XL-100 badge) it should begin in CTC- , use it to get the sam's photofact, then measure the voltages on the CRT and compare those to the listed voltages in sam's and check back.

There are a lot of things it could be. knowing for sure which voltages are wrong will point you down the right path and reveal any other issues.

Given the tube brightens with the room there is probably an auto-brightness sensor that senses room light and compensates for it. To confirm put the set in a dark room and shine a bright flashlight all over the case (but not the CRT it's self), if the screen gets bright then there is a sensor. The sensor or it's circuit could be bad, the CRT could be bad, the HV could be weak, etc. Hard data will reveal the truth.

Do you hear the crackle of high voltage on the screen when you turn it in? You should also be able to feel the static effect if you put your hand near the screen.

Are the heaters in the neck of the CRT lighting up?

Yikes, one google search showed a million TV's with that badge. Never knew a company would keep using a model number over and over like that. The chassis number on this one is EC-338w according to the sticker, and the tube model is 13vaup22. I looked up sam's photofact and unfortunatly $22 is something I can't swing, especially for a Tv I'm learning on. That causes a lot of issues with figuring out voltages but I can still poke around for anything obviously bad.

Yes Eric H, I hear the crackle of high voltage on the screen and get the static effect on my hand. Last I powered it up my friend noted that the heaters were not lighting up, but we didn't turn the lights out (we have a habit of watching for smoke when putting anything on a Variac). We did find that the pins on the back of the tube were getting voltage though, so that may be good.


I started looking at the board attached to the neck and found this part that I don't really know what it is, but if the bands are the same as resistor bands it is certainly bad. The part reads 10ohms and makes the meter squeal. Years of working on audio and I've never seen a part like this, but that's why tv's are an adventure. A picture of the part is attached.

One of the confusing things about this part is that it is beside a 2700ohm resistor. Both parts are going to and coming from the same place, so why would a near shorted part be next to a 2700ohm resistor? When looking at the board and how it's built it's hard to see how this part missing or bad would change much of anything, but a bad part is a bad part.

That might be some kind of coil, possibly a peaking coil in which case 10 Ohms would be about right.

If the tube heaters are not lighting up that's where you need to start looking.

I think they may be powered from a winding on the Flyback which is why I asked if the set had high voltage, no HV no heaters, I could be wrong however and they are powered from a transformer.

The part is a coil.
Try adjusting the G-2 control.
Measure G-2 use a meter good to 1KV. Normal is abt 400VDC.
Measure the cathodes. If they are up to 200 VDC the set
has a video problem. If apx 120-150 VDC video is normal.
Longshot, pull & check the CRT socket for overheating. Some
early RCA in lines would get a poor fillament connection.
Last is a dead CRT, more on that later.......

73 Zeno:smoke:
LFOD !

Sorry about my lack of experience regarding Tv's (I mostly just repair audio), so a lot of that went over my head. Where is the G-2 control and what is it?

The cathodes are the pins on the tube, correct? When poking around with a meter I can only get a few volts off those. The neck board seems to be receiving low voltage. So far nothing on the main board has stuck out, and the power supply seems to be alright.

This Tv is just so attractive looking when sitting on my bench that I have to keep messing with it. Hopefully it'll live again.


Also, earlier in the thread I mentioned seeing snow. Must have been my eyes playing tricks because I can't see any snow at all, though the screen does put out some static.

G-2 usually on the HV transformer or a seperate white block that
plugs into the CRT socket. Almost always its near the focus control.
Sometimes its called "SCREEN".
Be sure you have a good ground. Use either the CRT shielding
or the shielding around the IF stages. There also should be a
layout chart in the back to help you.

73 Zeno:smoke:
LFOD !

OK gents its a CTC87A. RCA's 1st non modular SS 13". Remember
those boxy ones with all the FBT's ??

Anyhows the G-2 A.K.A. screen control is on the right rear by the
horz & vert hold controls.

CRT voltages
pin 12 G cathode 133V
pin 3 B cathode 128V
pin 8 R cathode 128V
pin 9 G-1 19V
pin 10 G-2 350V
pin 1 focus 7.5 KV !! HV probe only !
Look for a way off voltage.

73 Zeno:smoke:
LFOD !

pin 12: 131v
pin 3: 100v
pin 8: 90v
pin 9: 14.5v
Pin 10: my meter freaks out so this pin is too powerful

I tried touching pin 1 and got a sound that made me jump so I didn't get a reading. I also tried adjusting the screen control with no luck.

Pin 3 and 8 are weak so I guess that's why the scree doesn't come on, so is the tube bad in this tv?

On any modern set the lower the cathode the brighter that
color will be. So the green is normal & the R&B are set lower.
If the G-2 is OK you probably have a bad CRT.
Can you see any effect when you turn the G-2 ???

73 Zeno:smoke:
LFOD !

When turning G-2 nothing happens at all.

I did notice someone else worked on this and gave up. There are melted wires that could only be melted if someone removed the neck board and worked on it. Unfortunately they ended up giving up on it without leaving any notes like most of the units that came from this place.