Zenith Sl2773W
n3qxc
I have a zenith sl2773w system 3 27' stereo TV date of mfg. June 1993.
My problem:
Complete loss of green color.
Found:
I traced each color gun through the last stage of amplification all the way
back to the controlling IC. (LA 7672 color TV single chip signal processor)
Knowing very little about TV, (I'm a biomedical tech) I found that the green
color signal was greatly reduced in output from the LA 7672. I took a chance
and bought a replacement IC from MCM electronics. Same Mfg (Sanyo). I
replaced the IC. This did not cure my original problem. I was about to live
with the fact that I can't get the green gun working again. But... now I'm
plagued with a different problem. I have no sound, so I re-installed the
original LA 7672 hoping to recover the sound and forever watch purple
people. This did not correct the problem. It was then I also noticed that a
menu missing from my tv. I was once able to access a sound setup menu to
adjust for stereo/seq/mono and also adjustable bass treble and balance. I no
longer have this option.
What have I done? How can I correct the loss of sound. I have traced sound
to pins 1 & 5 of the la7672 but there is no output from pin 6.
To further justify my color issue.... I disconnected the signals going to
the last stage of amplification to the CRT. I swapped the blue signal to the
green gun amplifier. (on my color setup menu the letters R & G for the tint
control are lit up in red and green normally.) when I applied the blue
signal to the green amp the letter G lit up blue indicating that the gun in
the crt is still operating and not shorted. I also did this with the red gun
to further verify. Any where I connected the green signal e.g.. the red amp.
the R letter in the menu would remain black. I also increased the gain to
max on the green gun, this had no effect when the green signal was applied
as normal to the crt.
Is there a setup mode that I can use to restore my lost menu? Will restoring
my lost menu restore my sound?
Anyone willing to help this non-TV tech?
All help is appreciated. Please feel free to mention where I may have went
wrong in my troubleshooting. I'm still learning and would like to hear from
a seasoned pro.
Thank you
N3QXC
Radio tech / Biomedical tech & not a TV tech!
Andy Cuffe
>
> Hello all you TV techs....
>
> I have a zenith sl2773w system 3 27' stereo TV date of mfg. June
1993.
>
> My problem:
>
> Complete loss of green color.
>
> Found:
> I traced each color gun through the last stage of amplification all
the way
> back to the controlling IC. (LA 7672 color TV single chip signal
processor)
>
> Knowing very little about TV, (I'm a biomedical tech) I found that the green
> color signal was greatly reduced in output from the LA 7672. I took a chance
> and bought a replacement IC from MCM electronics. Same Mfg (Sanyo). I
> replaced the IC. This did not cure my original problem. I was about to live
> with the fact that I can't get the green gun working again. But... now I'm
> plagued with a different problem. I have no sound, so I re-installed the
> original LA 7672 hoping to recover the sound and forever watch purple
> people. This did not correct the problem. It was then I also noticed that a
> menu missing from my tv. I was once able to access a sound setup menu to
> adjust for stereo/seq/mono and also adjustable bass treble and balance. I no
> longer have this option.
I would check very carefully for a damaged trace, or solder bridge near
the IC you replaced. It's a good idea to clean the flux off the board
with rubbing alcohol after you remove a large IC before soldering the
new one in.
> What have I done? How can I correct the loss of sound. I have traced sound
> to pins 1 & 5 of the la7672 but there is no output from pin 6.
>
> To further justify my color issue.... I disconnected the signals going to
> the last stage of amplification to the CRT. I swapped the blue signal to the
> green gun amplifier. (on my color setup menu the letters R & G for the tint
> control are lit up in red and green normally.) when I applied the blue
> signal to the green amp the letter G lit up blue indicating that the gun in
> the crt is still operating and not shorted. I also did this with the red gun
> to further verify. Any where I connected the green signal e.g.. the red amp.
> the R letter in the menu would remain black. I also increased the gain to
> max on the green gun, this had no effect when the green signal was applied
> as normal to the crt.
Actually, by swapping the green and blue you just proved that it is a
dead CRT green gun, not the green amp. If it was the green amp, the
letter G should have still been black since the blue gun is now being
driven by the green amp. If the CRT was good and you swapped the G and
R lines, you would have a green R in the video manu. If you can't ever
get any green on the picture with the green and one other color's
drivers swapped, the CRT is bad. This is no surprise because the 1993
model year is well known for having CRT problems. The only thing that's
hard to explain is why it lasted so long. 3-4 years was normal for
these CRTs.
> Is there a setup mode that I can use to restore my lost menu? Will restoring
> my lost menu restore my sound?
>
> Anyone willing to help this non-TV tech?
>
> All help is appreciated. Please feel free to mention where I may have went
> wrong in my troubleshooting. I'm still learning and would like to hear from
> a seasoned pro.
>
It's time for a new TV. I have never seen an L line zenith with a good
CRT.
--
Andy Cuffe
balt...@psu.edu