[Marc] Today on the bench we have my Sony Trinitron color monitor,
which is apparently missing a color. So, fortunately, we have Mr. TubeTime,
who provided the replacement monitor in the first place, when we shot the color TV video.
If you followed our adventures on reviving the Apollo lunar TV microwave link,
the color Sony monitor that you have seen is not this one. After we found mine did not work,
TubeTime rescued us by bringing his, and that’s the one we ended up using for filming the video.
But we want to repair this one too.
And it's nicely made. So you can flip the board out.
Ohh - aah.
Made for servicing. You have already made some initial discovery on that one, and we believe,
actually, that the tube works - it's missing the green - but you were able to make some reappear
by readjustment. So probably the tube is good, but the amplifier might not be good.
[Eric] That's what I'm thinking, yeah.
So, we adjusted the gain controls to compensate,
but I have the game turned all the way up, and it's still not quite where it should be.
[Marc] Let's turn it on.
And you gotta wait!
Yeah, it's very red.
[Eric] Yeah.
[Marc] Did it lose another color?
[Eric] Let's try going to color bars.
[Marc] Yeah, no green. No green at all.
[Eric] This isn't really the right tool for this.
[Marc] Yeah, it reappears. So I hope the tube is not shot,
because then we would be in deep doodoo. But it looks like it's there, but just not enough.
[Eric] Yeah, this is with the gain all the way up, it's not right.
[Marc] Initial thought is, RGB amplifier, the G is not good.
And it's over here. It will be RGB or BGR, we don't know. One of those transistors. But we have
the schematics and everything. And fortunately this is from when Sony, like HP, like Tektronix,
was giving the whole schematics. Very well done instructions for repair.
But it's complicated. So, this is part of the blanking, and this is the RGB amplifier
right here. So, I blew it up. We have three times the same circuit, so we can compare.
And it's complicated because it has blanking in it. The blanking is doing the difficult things.
[Eric] 149 and 152.
152, 149, I think that's the middle pin here.
[Marc] Okay, you got something.
[Eric] Yeah. I'm wondering where all the spikes are coming from.
But let's switch to...
...here's a 100% field.
Oh I see, those are individual lines.
Yes, it looks like it's up around 4 volts.
And then...
So it's the same.
[Marc] Yeah.
[Eric] And then, let me check channel three.
[Marc] Ah, the input signal is there! So it doesn't make
it through the amplifier, or the tube is lazy.
[Eric] This is the current in each of these amplifiers that I looked at. And
each of these amplifiers stages, that's the same.
[Marc] This is annoying, because if the current is correct,
then the tube is receiving the correct thing.
[Eric] Well, not quite. I haven't gotten to that voltage yet.
So, this is interesting. If I go in with the probe...
[Philip] Yeah, that changed it.
[Eric] Yeah.
[Philip] So did that, but not as much.
[Eric] That's a clue.
[Philip] And that changes it a lot.
[Eric] So that was the blue and the red channels that changed it a lot, and the green channel
didn't change it very much. And I'm probing on the emitter, which is this point right here.
[Marc] So, cursory check of that transistor, transistor looks like it's good. And so, I'm
thinking, maybe one of these two, or D346. But D346 looked good from the traces on the scope.
Dang, we could find nothing wrong with the transistors,
diodes, everything. And then we are going back to the end of it.
And it looks like we have plenty of green at the output. So, which is the one you're moving?
[Eric] Yeah, so this is the green channel.
[Marc] We have tons of it compared to - can you move TO the blue for example?
[Eric] this is blue. So we actually have less blue going out through this final stage amplifier.
[Marc] Yes, than the green. So we have plenty of green signal. So, maybe it's good up to here,
and then there's not much... It goes from here back to the tube, right?
And look also, when you put your probe on it, it will affect the color of the screen
when you're on the blue and the red, but not when you're on the green.
Bad resistor back there?
[Eric] Maybe. Bad socket, bad wire.
[Marc] Bad soldering joint?
[Marc] Okay, that's the board for the neck. We're getting dangerously close to the tube. So
if it's not the resistor... Where's the green? This one?
Goes through one resistor, and one solder joint. So, if it's not that,
then it's the tube, and then we're hosed. All right, so... It's off.
Can you take it off? Probably.
[Eric] Yeah.
[Marc]
I hope there is a bad solder joint or a bad resistor, because if not...
[Eric] Did you say R702?
[Marc] R... Yes.
[Eric] Looks like it's directly beneath the connector. I'm gonna try to measure it.
[Marc] Okay.
Well, you should be able to measure continuity, right?
[Eric] Let's go down here out to this pin on the socket.
[Marc] And... 2k! Which is what it should be?
[Eric] Yep, 2.2k.
[Marc] Then, oh man, then we are at the last bit. And if that bit works,
then it's the tube. And then we are hosed.
No, 2k now.
[Eric] Yeah.
[Marc] Now we have 2K. So it makes it (to the tube).
Then it's our tube.
Do the solder joints look good?
[Eric] They look okay.
[Marc] Ah dang, then it's the tube.
[Eric] There's one other thing that we
haven't checked yet, [Marc] Which is?
[Eric] The filament.
[Marc] It's true.
[Eric] They're all wired in parallel inside the tube.
[Marc] Yes, so there's nothing much we can do about that one either.
[Eric] I suppose we could try wiggling this neck board.
[Marc] Well, it's a free Sony monitor, so if we can get it to work... Well, nope. Still very red.
[Eric]
Yeah, it's not flickering at all.
[Marc] And you can check that it's getting its signal, we can check right at the board, right?
[Eric] In other words, after the resistor?
[Marc] Yeah.
[Eric] Okay. Yeah, signal is there.
That's after the resistor.
Yeah, I think we have a weak gun.
[Marc] Ah, dang.
[Eric] That's too bad!
[Marc]
Is there an experiment we could make with your (monitor) - cross connecting the two tubes?
You could get me less blue, and less red.
[Eric] I don't think I have any control of the red.
[Marc] Oh, really?
[Eric] Yeah.
[Marc] Red is a reference.
[Eric] One of them is the reference, yeah. So I have blue gain, green gain,
and I don't think I have any red.
It doesn't look like it.
[Marc] Okay, we're hosed.
We could artificially lower... Yeah, we have a little bit of green.
We do have green, we just don't have much. We have too much red.
[Eric] I cranked the gain way up on green, that's why. Normally it's going to come out like this.
[Marc] Right, crank it up.
If we had a way to lower the blue...
[Eric] And the red. I can lower the blue. I just can't lower the red.
[Marc] Well this is not good news, everything points to the CRT tube being bad. The electron
emission of the green cathode is likely too low, probably from a contaminated or just too old of
a cathode. Which is not too surprising, as this free monitor was rescued from a dumpster pile.
We still have a little bit of green though,
so the green filament is still working. Which further points to a low-emission cathode,
which electron emitting barium oxide coating has been poisoned, or just evaporated due to usage.
So we are thinking to do a cathode rejuvenation using this B&K Model
440 tester, which manual promises to fix everything under the sun with your
CRT. But tube rejuvenation is retro snake oil. It might damage your tube even more.
And even if it works somewhat, effects are usually temporary,
and the tube will revert back to its previous state in a matter of hours.
But hey, this is a free dead monitor, and I have never tried a rejuvenation. So, for the good of
science and our own electro-education, let’s give it a go and see what happens.
[Marc] Whatchama got here?
[Eric] This is our B&K CRT tester. It's really designed mainly for black
and white tubes, but it does support apparently one type of color tube.
[Marc] Really?
[Eric] And we don't have an adapter to get to the CRT in our little PVM monitor here,
so I am manually wiring it up.
[Marc] Yeah, and it's only, what, kilovolts?
Nah, you don't need to do a kilovolt.
[Eric] Yeah. For rejuvenation,
it just runs the electron gun. So you don't need the final acceleration.
[Marc] Oh, you don't even need to turn this thing on.
We won’t review how CRTs and electron guns work here, but if you feel like learning about it,
and what all the electrodes do, we explain all of it in our previous CRT video. Complete with
an extended elevator music section. I will link it in the doodly-doo.
[Marc] Okay!
[Eric] All right, so let's go ahead.
So I got 4 volts in here, which is closer to the correct filament voltage of 4.5 volts.
I'm probably going to have it set to emission at first on the red gun,
and then I'll cycle through and see what there's to be seen.
[Marc] So what did you connect?
[Eric] I connected the grids, and anodes, and cathodes, and filament.
[Marc] So the first anode, the grid,
the filament? So you just exercise the electron guns through the first anode?
[Eric] Correct. So it's just G1 and G2.
[Marc] Okay.
And then you're going to see if you get any current, right?
[Eric] Yeah. Is the filament lighting up at all?
[Marc] Well, it's buried in there, it's hard to see.
[Eric] Oh, there you go, I am getting...
[Marc] There you go. Okay!
[Eric] So this is for emission.
[Marc] Do you have three guns in there?
[Eric] Yep.
[Marc] And so, you're on the green?
[Eric] I'm on red.
[Marc] On the red. So that's one that's working fine. Can you change to the green one?
And then, you see if the emission is different?
[Eric] Yeah, it's different, it's lower. And then blue is higher again.
[Marc] Oh, okay. Oh, that's great! We can actually tell that
there's something wrong with the green, right?
[Eric] Yeah. Let me crank up the filament voltage, because we're running it a little bit low.
So, here's 5 volts.
[Marc] Okay. Which is close to 4.7V. So it's barely good.
[Eric] So, emission is reading the current.
[Marc] And I cannot see the filaments in there. It's buried. But it's filamenting!
[Eric] So here's green, which is way, way down.
[Marc] Okay, which is what we had seen.
[Eric] And then blue is a little bit down, but not too bad.
So I set it to dynamic low. We have the green selected.
[Marc] So, this is a very blunt tool. If you look at the schematics, all it does is apply
rectified 1 kV or so to the first anode. This will form an arc with the cathode,
hopefully vaporizing the contamination and exposing some fresh barium oxide on the cathode.
You can do that at 3 filament voltages. Low is the normal filament voltage,
and medium and high apply progressively higher over-voltage to the filament, making it hotter.
So, this one might arc it.
[Eric] Yeah. So, I just basically push it and then release it.
[Marc] Okay. Oh yeah, I saw it arc!
[Eric] Oh, you saw a flash?
[Marc] Yeah, I saw it flash.
[Eric] Okay!
[Marc] Okay, let's see if it did something. And then if you do it in the medium.
[Eric] Oh, look at that! Emission is much higher now.
[Marc] Oh!
[Eric] That's, that's pretty cool!
[Marc] Wow!
[Eric] Look at that! See, now it's in the good range.
[Marc] It's the same as the other ones?
[Eric] Green is slightly better. Blue is like a little low. But green looks - now it's much better!
[Marc] Yeah! We'll see how long it lasts though. But unfortunately it's falling
It's going back to where it used to be.
You want to give it another whoosh, and then I try to capture it on the neck of the tube?
Except, okay, well, I don't have the best angle. But that's the best we can do so far.
Go on medium...
[Eric] I'm
supposed to wait 15 seconds before I push the button.
[Marc] Oh yeah, now that I turned the light down, I see the filament.
[Eric] Okay, you are ready?
[Marc] Yep.
Yeah! I saw it arcing big time.
[Eric]
Okay, so that's plugged back in. I need the pattern generator and the power cord.
[Marc] Okay, that should be on the other table.
[Eric] All, right it's time to look at that screen.
[Marc] All right, go for it.
See if we've got some white.
[Eric] And I just realized that the trimpot is probably cranked up.
[Marc] Yeah, it's a little bit better.
Yes, we have white! We do have white. Yeah, that's much better!
[Eric] It's pretty decent.
[Marc] It's much better than before.
Yeah, that's not too bad.
Oh yeah, the black and white is black and white now. It used to be completely purple.
This is great!
The little tube rejuvenation worked.
[Eric] Yeah.
Let me pull this off out of the...
[Marc] This is such a huge camera.
[Eric] It's quite heavy too.
[Marc] Okay, we should have the 70s music.
[Eric] I know, right!
[Marc]
Oh yeah!
[Eric] Got to get it into focus, but...
[Marc] Here we go, we have some pictures.
Yeah. From the completely red monitor that we had before, this is totally acceptable. Works for me!
Hello!
It's still slightly red, it's still very dim, it lacks contrast. So, it's a tube
at the end of its life, basically. But thanks TubeTime, I think you repaired it!
Very, very good.
Excellent. Where's my thumb? There you go! The other thumb.
There! It's a good camera - it's a good monitor!