Oh boy, don't you love tackling something that's already been futzed
with?

I'm lucky thus far, everybody who worked on it was competent. I know
them. Nobody has any more ideas. They didn't give up easily, and
neither will I, but I'm here now and it's in my lap.

I did say the EPROM looks like it's been changed, or at least the
solder does. Not bad but it's shinier. I wonder just how many sets can
run with no EPROM. Last one I can be sure of is a CTC140. Maybe a
CTC169.

It's very interesting you bring this up, here's a true anectode for ya:
One day I got your typical tuner grounds and EPROM job on an RCA.
However it happened I changed the EPROM with the set plugged in. Fired
the set up and it was exactly like it was before. I expected the H freq
to be out etc., until I realized that I hadn't unplugged the set.

I'm getting close to thirty years in this gig, and that has happened
more than once. More than half of the times no damage ocurred (though
I'll never be able to explain why for sure)

It's got to be a combination of luck and my soldering technique. I can
change a 64+ pin IC maybe ten times without collateral damage, but I
don't think that's special. I think most techs should be able to do it.
In some cases maybe the thing was dead shorted anyway so nothing I
could do could zap anything, except me of course.

This is what happens when you get called away from the bench for other
matters.

I will figure out a way to stop data from getting to the jungle IC, I
need to prove I'm on the right track now, or back up.

Of course at this point I have eliminated or checked so many things I
really don't know what exactly I should back up to !

Even if interrupting data to the jungle stops the symptom, now could it
possibly be any chip on the bus ? Micro, jungle and EPROM ruled out,
then what, take the tuner out ? Find the audio processor, closed
caption and possibly even XDS ?

What a game. In coming years I can see we are going to need drastically
better methods.

I need to know for sure if it's digital, but I'm not going to attack
the EPROM yet because it has no problem storing parameters.

Hmmmmmmmmmmmmmmmmmmmm

Just thought of something. What if it's set to 50Hz sweep ? Could it be
triggering the vertical alright but runs out of range and blanks when
it THINKS it's resetting the sync countdown ? It is not though, the OSD
is perfectly stable and remains interlaced, but maybe it THINKS it's
out of sync ?

I will try what we have discussed, but first I think I'll have one more
look at the service menu.

I might have to temporarily turn this job away, but I am by no means
scared of it. Remember I'm the one who had to adjust vertical centering
to fix a problem with greyscale, and had to reconnect a speaker to get
high voltage.

While I like the challenge, there is a customer out there waiting.

Thanks again, I'll let you know how the results of what I do next turn
out.

JURB