Sony Trinitron tube - no red

[Carl Jenkins]

Hello,


I'm working on a colour set that
has a blue-green picture. I have
replaced the Red-drive transistor
on the CRT's socket PC board and
ran through colour temperature
and purity adjustments with no
change (still no red). I can't
proceed unless I know the CRT's
red gun is still functioning.
Is there a cheap and dirty way
to check if all the guns in the
CRT are emitting without having
to purchase an expensive piece
of test equipment?


Thanx for n-e help,

Carl

 

[Wild Bill]

A fairly simple solution that was recently suggested (by Andy, I think), is
to cut the traces from two colors and solder jumpers in place to see if the
other color will drive the red gun.

Cheers
WB
..................

 

[Carl Jenkins]

Thanx WB,

I have also read that if you turn the
colour (saturation) control down to
minimum and still see a true monochrome
(no colour cast or wash) picture then
all the guns are still functioning.
Is this correct?

Thanx again

CJ

 

[The Al Bundy]

Thanx WB,

I have also read that if you turn the
colour (saturation) control down to
minimum and still see a true monochrome
(no colour cast or wash) picture then
all the guns are still functioning.
Is this correct?

Thanx again

CJ

Yes, this is correct. A true monochrome pictures can only be made with all
the 3 colors, red blue green. (or you have a monochrome picture tube If
one of the colors are missing or bad then you dont get a white screen.

Once I tried to repair also a Sony trinitron that had the same problem.
After crossing the red en blue connection to the picture tube socket it
became clear that the red gun didn't work anymore.

Al

 

[Art]

Cathode voltages for each gun?? 10Kohm 1/2 watt to ground should cause the
respective gun to saturate and produce a single coloured raster, if the red
does not come on with the resistor to reference than you know for sure the
crt probably is at fault: or maybe a lousy connection in the socket.

 

[Carl Jenkins]

Hey Mr. Bundy,

Thanx for the confirmation.

CJ

 

[David]

You measure the crt cathode voltages to the tube and look at the
waveform on the o'scope to determine if the gun has a problem.

Another option is to put the tv on a signal generator with a blank
raster (sync MUST be present), then carefully take a 5 watt 500 ohm
resistor to ground on each of the cathodes and look at the relative
intensity of the color with retrace on the tube.

Both options require the minimal test equipment that would be expected
if one is going to succeed in doing even some of the most basic tv
troubleshooting. O'scope and signal generator.

David

 

[Carl Jenkins]

Thanx David,

I "invested" in a multimeter so
I'll be able to check the cathode's
DC levels (I think the multimeter
also has an AC RMS setting). If
I'm feeling brave I'll try your
resistor ckeck to bypass each
gun's raster contribution.

Thanx again,

Carl

 

[Jerry Greenberg]

The black and white tracking is adjusted with the colour control at
minimum, and idealy with a grey scale test pattern is put up on the
screen.

When the CRT is working correctly, and the colour ballance is
correctly adjusted, the set should be able to produce proper black and
white pictures. This is the basic way the set should be working,
before it can be expected to have the proper colour ballance for the
colour pictures.

Jerry G.
========

 

[Kevin]

Correct me if I'm wrong, there should be 3 distinctive filaments inside the
neck of the tube. If one is out, I'll bet it's the red one.

 

[Carl Jenkins]

Good idea!

I'll dim the lights and take a good look.


Thanx Kevin,

Carl