Redless screen

Sillygirl I thought I would pass along a little tip on crt testing I learned many years ago. You take a 470 Ohm resistor and ground on end with a cliplead and touch the other end to the collector of the drive transistor. If the crt is good it will glow that color of the drive xixtor so you can simply check all three guns in a easy fashion without draging out the old crt tester/rejuvenator. Now this is only to see if the tube is working on that gun and wont tell you how much gain the color has..

If still under warranty or if you have no electronic repair experience you should take the set back to the shop or to a repair person. Some of the solutions described below can be dangerous, TV's and CRT monitors are very hazardous to service. Even when plugged out, they can store very high, deadly voltages.

How old is the picture tube? If there's lots of phosphor burn on it, chances are the red gun inside the picture tube is out.

A sure-fire way requires an oscilloscope. Check the voltages on the three color guns at their corresponding pins on the CRT's neck board.
You can see their levels change as you tweak their adjustment pots on the neck board. If the red voltage is present and at the same levels as green and blue, then the gun inside the tube is shot. If the red voltage is NOT there, then you can work backwards and find out where you're losing it.

It could be a bad buffer amplifier (transistor or I.C.), bad solder
joint, or even a broken wire in the cable harness.

check for cracked solder joints where the RGB, Grd Sync connector is.

check the pins on the molex power supply connector, could be that the pin for the red is pushed back and is not making contact.

Try swapping the red and green inputs if you see red on your monitor and no green, then it is NOT the tube. If you see no red still but still get a green where red should be I would suspect a bad chassis.

The white lines on the darker backgrounds are more than likely retrace lines. Usually caused by a leaky capacitor in the horizontal sync circuitry.

If the red comes and goes it's probably a dry joint in the red drive. If you're handy with a soldering iron try resoldering the solder joints on the CRT neck board. If that doesn't do the trick then perhaps the drive transistors are on the motherboard. Just look for 3 transistors usually in a row and somewhere very close would be adjustable pots with the letters R.G and B printed near them. Even a simple gentle tapping with a plastic end of a screwdriver around that area may make the red flash on and off.

Just resolder around that area and you'll know it's fixed when the red stays on. Just make sure the power is unplugged when working on the set and stay well away from the EHT and power supply areas. They can give you a nasty shock even if it is unplugged. Actually with live chassis TVs it's always best to use an isolation tranformer.

If any of this is over your head the say hello to the repairman :-)


BMW

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