Mits VS4506 "missing" video

J

JURB6006

Guest
Hi;

Got this intermittent video. Mitstips and repairworld were no help.

I have no print so you can imagine all the fun I'm having. I have the pinout
for the M52023 jungle IC and it says the video inputs are pins 43, 45 & 47.
There is no video on any of them. (set has OSD)

I went back to the tuner board and I see active video at pin 1 of the "RU"
connector. Is this where it's supposed to be ? It could be who knows, but it is
on a shielded wire and I can't find the other end of it anywhere. I looked at
the waveform on every shielded wire goi ng to the main chassis and I can't seem
to find video anywhere.

Question is, where is it supposed to be ?

I got no print on this one, but it actually has strong tubes and believe it or
not, no capacitor crap on it. Must have very low hours.

This thing has video for about the first five minutes of operation so I don't
think it's a broken wire, I just can't seem to find the other end of it.

Even if nobody has any bright ideas at the moment I would very much appreciate
some info on just where does the video come in to the main chassis.

Thanx in advance.

JURB
 
Jeff,
This is still a V11 chassis. Cap city.
Even though they aren't leaking they are bad or dried out.
The video (Y) is on pin 4 of connector AE/DE, chroma is pin 10 and sync is
pin 1.
Find DL2001 on the video board (flat board on the left) and see if you have
"Y" there.
This is basically half way in the circuit. You can start backtracking either
direction from there to find out where it is missing.

Good Luck,
Bill Jr

If you have a VS4007, 4506/7, 5005/6/7, 6004 or 7004 print they can be
useful.
There are only 2 different versions of V11 so one these should help.




"JURB6006" <jurb6006@aol.com> wrote in message
news:20040120175503.24678.00000418@mb-m16.aol.com...
Hi;

Got this intermittent video. Mitstips and repairworld were no help.

I have no print so you can imagine all the fun I'm having. I have the
pinout
for the M52023 jungle IC and it says the video inputs are pins 43, 45 &
47.
There is no video on any of them. (set has OSD)

I went back to the tuner board and I see active video at pin 1 of the "RU"
connector. Is this where it's supposed to be ? It could be who knows, but
it is
on a shielded wire and I can't find the other end of it anywhere. I looked
at
the waveform on every shielded wire goi ng to the main chassis and I can't
seem
to find video anywhere.

Question is, where is it supposed to be ?

I got no print on this one, but it actually has strong tubes and believe
it or
not, no capacitor crap on it. Must have very low hours.

This thing has video for about the first five minutes of operation so I
don't
think it's a broken wire, I just can't seem to find the other end of it.

Even if nobody has any bright ideas at the moment I would very much
appreciate
some info on just where does the video come in to the main chassis.

Thanx in advance.

JURB
Click to expand...
 
Thanks Bill;

I'm keeping my eyes peeled for the cap crap on the PC boards and believe it or
not there is none. This must have about the lowest hours on it as any V11 I've
seen lately.

Anyway, in the last few years there has been some remodeling done and I simply
can't seem to find a V11 print. I'll get someone to look for it this week.

Also I got an update on this thing- it <u>is</u> mechanically intermittent.
Everyone was tapping and it didn't respond, and it really did look like a
thermal component failure, however when I <u>flex</u> the board I can make it
come and go. The thermal component of this failure is still there though, when
the set is cold you can barely make it go out, when it warms up it gets less
and less likely to come back.

This reminds me of a similar repair in a Mits RPTV a year or so ago. I believe
it was video the set was losing and everybody at the shop was on their second
go at it. I finally nailed it down to a broken ground foil to the emitter
circuit to one of the myriad of video buufers. It was near a shield and we
figured thermal expansion probably caused it. Perhaps the board was also
cracked but we couldn't see it. I think it may have happened during
manufacturing but didn't manifest itself for about 8 (?) years.

Actually I don't remember if I had a print, for some reason I scoped the
emitter because I didn't know if it was actually grounded or what, then when
the it lost video, there it appeared on the scope. AHA ! is my usual
exclamation and the boss smiles cause he knows $$$ are coming, then the other
tech(s) need to have a look. (I dunno about other shops but we don't discourage
this)

Anyway I think this is going to turn out to b e something similar, the other
one was a bear to hunt down.

Thanks again and I'll let you know what it was <u>when</u> I nail it.

JURB
 
damif it wasn't so . . . .

You were right ! I have found one leaky cap at the base of (I think) Q2015.

Something I do that alot of people don't is to use my DVM to turn on a
transistor. This transistor is common base and seeing the voltages I suspected
it as the culprit, but while it was out I got the video back by simply using
the DVM probes to bias it on. At this point either the pullup resistor is bad
or the bypass cap is leaky. Leaky it was in more ways than one, actually it was
the PC board that was leaky I guess. Same shit, black cap lead and a small area
of the PCB soaked.

The back board started rendering it's smoke believe it or not, and it turned
out to be a service switch located on the signal (not tuning/whatever) board.
(I can't seem to find it on the print, now that I have one) When that happened
I told them if they want it fixed we need a print. I was actually hopeful that
this might cure the video too, but no. Just one of those quirky things that
only seem to happen to techs. Go figure. Totally unrelated.

I know I said there was no crapacitor shit, there is <u>no</u> blackened foil.
This might be the first lytic that caused a problem in this set. I will
scrutinize it more closely as I fix the next problem.

Oh yeah, there is another problem. Like you said I get all the fun ones. When
it came in it would lose video after about ˝-1 hour of running, then about an
hour later you would get the sound.

It's losing the audio at IC 3001, and I have replaced it. Now I play a racing
game to Tshoot before it comes back. Pretty interesting, DC voltages at the
chip stay put, the output starts cutting in and has a wierd quality, cutting
in/out at a fast rate. It also seems to me to be driving the stereo LED at the
same rate. (yes there are square waves on the output pin for this, when it
doesn't work the pin is high, when it's distorted it has squarewaves in the
hundreds of Hertz, when the sound is clean, the pin is low)

Now if you got any ideas for that . . . . . .

Geez man I must owe you about a case of your favorite beverage at this point,
along with who knows. Again, let me know if I can ever send you something.
Preferably something legal. . . . . . . . . .

JURB
 
Like I said, you are chasing your tail until you deal with the leaky caps.
Heat the negative side of every polar electrolytic and smell. When you
sense that someone is cooking old tuna you have a bad one. I have not seen
one of these sets with less than 60 bad caps in years.

Leonard Caillouet

"JURB6006" &lt;jurb6006@aol.com&gt; wrote in message
news:20040127215747.04510.00000890@mb-m10.aol.com...
damif it wasn't so . . . .

You were right ! I have found one leaky cap at the base of (I think)
Q2015.

Something I do that alot of people don't is to use my DVM to turn on a
transistor. This transistor is common base and seeing the voltages I
suspected
it as the culprit, but while it was out I got the video back by simply
using
the DVM probes to bias it on. At this point either the pullup resistor is
bad
or the bypass cap is leaky. Leaky it was in more ways than one, actually
it was
the PC board that was leaky I guess. Same shit, black cap lead and a small
area
of the PCB soaked.

The back board started rendering it's smoke believe it or not, and it
turned
out to be a service switch located on the signal (not tuning/whatever)
board.
(I can't seem to find it on the print, now that I have one) When that
happened
I told them if they want it fixed we need a print. I was actually hopeful
that
this might cure the video too, but no. Just one of those quirky things
that
only seem to happen to techs. Go figure. Totally unrelated.

I know I said there was no crapacitor shit, there is <u>no</u> blackened
foil.
This might be the first lytic that caused a problem in this set. I will
scrutinize it more closely as I fix the next problem.

Oh yeah, there is another problem. Like you said I get all the fun ones.
When
it came in it would lose video after about ˝-1 hour of running, then about
an
hour later you would get the sound.

It's losing the audio at IC 3001, and I have replaced it. Now I play a
racing
game to Tshoot before it comes back. Pretty interesting, DC voltages at
the
chip stay put, the output starts cutting in and has a wierd quality,
cutting
in/out at a fast rate. It also seems to me to be driving the stereo LED at
the
same rate. (yes there are square waves on the output pin for this, when it
doesn't work the pin is high, when it's distorted it has squarewaves in
the
hundreds of Hertz, when the sound is clean, the pin is low)

Now if you got any ideas for that . . . . . .

Geez man I must owe you about a case of your favorite beverage at this
point,
along with who knows. Again, let me know if I can ever send you something.
Preferably something legal. . . . . . . . . .

JURB
Click to expand...
 
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