good now check them in the service mode. I think it should be close to the 180v

Will have to flip her over for this one. The output transistors are TO39 casings and the legs were cut so they sit flush to the socket. I'll have to do it from the bottom.

Oh, never mind. Seems the test points I found are the collectors you mentioned. No need to flip her. :thmbsp:

I am a little behind you, try checking at those same point you found, should be close as I think there is only a 1k resistor between them and I doubt there would be a lot of voltage drop.

Okay, here's what I got from the output collectors at the test points in setup:

Red = 197V
Blue = 184V
Green = 192V

which line did you say you could get in the setup mode?

Both red and blue wouldn't come up. Green did, but it was very weak and only came on at maximum rotation.

well those all look a bit high considering the G1 in the mid 30's give you a bias of about 160ish neg which is prob cutting of the CRT.
you would want it bias off more than normal since you want to reduce the beam current when the vert sweep is disabled but not completely cut off. Sorry I just know know what the exact number should be.



I would check the voltage of the output transistors next, and if you can get a good bright raster in reg but the serv mode does not work, then I would check the resistors and that ties the emitters of the outputs back to ground AND that blanking signal from the fly. Now would be a good time to trace the flyback signal with the scope.

It looks like the emitters get voltage from the emittier of the video driver in reg mode, but in the service mode they are grounded thru a 1.5k and a 12k that gets the flyback pulse. look this over carefully on the schematic until you see what I mean.

Okay, I got the voltages of each base of each output transistor (both in and out of setup).

The first value is SM, second is normal and the third is in setup mode.

Red: 15.6, 15.9 and 16.6
Green: 15.6, 16.1 and 16.7
Blue: 15.7, 16.2 and 16.8

I see on the schematic the setup/normal. In setup I see a 1.8K and a 18K (not the 1.5K and 12K you noted). After that, I see it tie in somewhere in the vert/horz blanking and then it goes to pin 4 of J201 and also is connected to green of T207. I'm lost after that. I can see how switching to setup takes the voltage away from the emitters fed by the video amps. T207 is the horizontal output transformer, so I guess that's the source of power for the emitters in setup. J201 pin 4 goes to the convergence board and I don't see how that fits in.

Guess I'm not getting that much better navigating schematics. If you could give me a clue as to where the flyback signal for probing is to be found, that would be great. I don't know where along the circuit to probe. Is it the H Sweep of the horizontal module, or the base of the horizontal output transistor? Or...is it in a completely different location?

Sorry to be such a pain. I hope I'm not coming along too slowly.

Just noticed something...might be nothing...might be something....

As you know I haven't been able to converge the blue lines very well and in some areas they are way off on the left and right of the screen. Well in tracing this current circuit, I noted that the blue convergence lines right and left are coming off of pin 4 of J201. That's the one fed by the by the setup we've been tracing. Even when in normal, there is the signal coming from the vert/horz amps tied in with the two 100K, 33K and diode we've been eyeing.

Now it might not be connected, but I thought I'd toss it out here.

you read the base voltage, look for the emitter voltage this would be normal mode no signal (raster).

Yes I noted the connection to the convergence board, and no I do not know if that is related.

1st things 1st get that emitter voltage my guess is changing from normal to setup alters those voltages as a means to bias the transistor to cut off more when in setup mode.

as far as scoping I would start by seeing if the sam wave form matches, if it does then thats a dead end, if not then you would just start working back towards the flyback. That horz pulse at the convergence board will will prob look a lot like the one you see in my video which is also a flyback pulse for convergence. PP may be different but I suspect the shape will be about the same.

Okay, the emitters could only be measured at a point on the other side of the 180ohm resistor (unless I flip her over and removed the stand and cover). Measuring though the 180ohm resistor gave me 14.3V normal and 15.5 setup. Is going through the resistor okay, or do I need to go directly to the emitter lead?

I feel really stupid, but I can't get the scope to do what I want. I connected it to the S test point though a 10x probe in 1x mode and couldn't figure out how to adjust the darn controls to give me a usable waveform. If you look at the pic I posted in the thread asking if the scope was okay, could you step me though setting the main controls for it? The manual it came with is basically useless, at least it is for me. I'm sure if I can be pointed in the right direction for setup, I'll be able to adjust from there for other points.

Thanks!

Okay, this is the waveform I got off the convergence board's white/green wire. In the first pic is how Sams shows the waveform (it's the one on the right). In the second pic is what I managed to get on the scope. I know I must be missing something as I got two waveforms and couldn't merge them or make them bigger.

hard to say about the scope you should be able to increase the size with the vert amp and stretch it out with the sweep rate.

Don't know what to tell you bout testing the emitters. I would test the way the sams says to. We are trying to figure out why the setup does not work. Until you get that working I would hesitate to work on anything else.

I think the bias voltage are off, so i would concentrate on those transistor voltages.

Okay, I'll flip her over and open her up to test the emitters directly from the socket and not through the attach resistor. Also, if I were to pull the transistor, wouldn't this also allow me to test the resistor? It would be the same as cutting one let as without the transistor in the socket, there's nothing connected to the leg.

I think there's an issue with the scope. If I put the probe in the vertical input, I get a nice tall waveform. Only issue is, I need the horizontal input for what we're checking. Also, I noticed that when measuring the horizontal, the waveform distorts when I put my hand near the vertical input or sync amplitude knob. This poor scope has seen better days, I guess. I think it's over 50 years old.

Okay, I did the emitters and all of them had a normal of 15.7V and a setup of 16.2V. each of the 180ohm resistors on them were within tolerance (about 176ohms each).

I checked my manual the white green should be 22v pp close enough to sams 20v.

you need to calibrate the scope use a 9v battery if there is no calibration point on the scope (more modern ones have a 5v pp square wave generator to test to). put a 9v battery and note how far a trace deflects, adj the vert amp to get a size that is easy to work with and will nearly fill out the screen on the scope if it was 22v (so make the 9v move the line little less than 1/2 the screen that way a 20v spike will nearly fill it. There are markings on the screen if you try to use those to represent 1v each.

increasing the sweep rate should let you see fewer spikes. I dont know much about scopes only the one I have, so not sure how keying works on yours.

This might be a stupid question, but should the probe be plugged into the vertical input or the horizontal? I am unable to get a decent size display with the horizontal input, but with the vertical input I can expand to fill the screen. Only issue is, I believe I need the horizontal input because we're aiming to check the horizontal circuit, right? If that's the case, I think this old thing is in need of repair.

Now on to the setup issue. I decided to check the red G1, G2 and screen voltage both in and out of setup from the pins on the CRT. I figured that if the line wouldn't come up at all for the red, it was the best to check. Here's what I got.

The first number is in normal mode and second is in setup mode:

G1 = 161, 192
G2 = 605, 612
Scr = 33.6, 34.3

Now the G1 is supposed to be 140V and the G2 should be around 590V. The Screen voltage is supposed to be around 36.4. Except for the G1, all numbers are pretty close. I don't know how much voltage difference is allowed for G1, but if I understand things correctly, it's voltage varies in conjunction with the G2.

cathodes are 6 2 11 180v in setupmode
g1 are 12 3 7 40v
g2 are 13 4 5 I dont have it but think sams is around 600v

terminology is

Cathode
G1 is the control grid
G2 is the Screen grid
G3 (listed that way on data sheet) is the focus pin)

in some sets the luma is from cathodes and the chroma is from the control grid, the mixing of the Y and B-Y/G-Y/R-Y takes place in the CRT on this set its done at the video out transistors (base for chroma, emitter for luma)

According to the Sams, wht/grn should be 170v. I think I got a better setup this time. I'm attaching a pic of the pattern I got. Other than the distortion of the wave (not sure if that's the signal or my settings) it looks kind of like the waveform in the SM.

Never mind the last post about the waveform. Seems it was generating that even after I disconnected the probe. I'm going to give it back to my brother and see if there is somewhere around here that rents them.

yep, with tvs you can only go so far with voltage readings, wave forms are were its at. put it back together and get some screen shots showing brigtness and the jail bars again.

Scopes are handy but expensive for a good one, you can get decent later models for around 100$ but you risk it not working, case in point my scope just took a dump on me so now I have to fix it.

You may just want to try your hand at fixing that scope, its prob pretty simple.

You do need to get a straight trace that reacts as it should.

Yeah, most of the scopes I've found listed for a decent price are either broken or untested (untested=broken most of the time). I can't really justify spending a decent amount on something I might use one or twice. I have a closet full of stuff like that already.

I'm attaching a pic of the jail bars and brightness. The brightness is greatly improved with much more available range, so that seems resolved. The jail bars, however, are still there and quite noticeable (even in lighter scenes). I've replaced the two 100K resistors, the 33K and the diode. None had any effect.

I have the scope's build instructions and I can go over it. If I'm not mistaken, this thing has tubes in it. I'll take them out and test them.

This scope has 10 tubes in it! Where to begin. :scratch2:

Well my brother built it, I'll have to enlist his help.

if the scope has not been recapped it may have issues there.

the fact that the horz convergence is not responding (I think that is what you said) and the horz blanking may be causing the jail bars sure points to a problem there. Is the width ok? not too wide?

It's been recapped, but I don't know how long ago. I see a combination of electrolytic, film and those "orange drops" in it. I'm seeing my brother tomorrow, so I'll get more info on what's been done to it. He said it worked the last time he used it, but I didn't has how long ago that was.

The horizontal convergence for the blue moves quite a bit, but just not in line with the other colors on the sides. There is the coil and two pots that move around the blue, but no combination of them will get the lines where they should be on the sides without messing up the top and bottom horizontal lines (center convergence stays put).

I've gotten used to no overscan, so this set's image seems too wide. I believe, though, that the overscan is about 6%. I can just see the edge of the 5% line on the overscan pattern.

I may be missing something here, but why is the scope thought to be in need of repair... the waveform posted looks reasonable, and perhaps the 10 or so "ripples" at the bottom of the waveform might indeed correspond to the 10 or so bands "jail bars" seen across the TV screen?
jr

If you scroll up to post #53 you'll see a waveform I posted. The waveform for the 170V in the pic is what supposed to be on the scope. I thought I had it, but that waveform didn't go away when I removed the probe. So it most likely isn't from the circuit, but from the scope itself.

I recalibrated the scope per manual and I was able to get both of those waveforms in the picture from the SM. However, all other attempts to scope out other points has given me garbage on the scope. I think there might be a short in the 10x probe.

I really suspect that the probe could have been picking up the waveform without direct connection to the test point... a sensitive probe held near the horizontal section can easily do that. If you turn the TV off, does the waveform on the scope stop?
jr

I managed to get to good waveforms from the convergence section (easiest to get to and many test points). The forms matched almost completely. Then things went wrong. I think there's a problem with the 10x probe. It's a heathkit, so I'm going to take it apart and see what might be going wrong.

if you are getting good wave form the 170v pp then trace on through and see if you can see it getting to the base of the blanker

I think the 10x probe is defective (it is 57 years old). I found it difficult to not only get the signal with it, but to keep it. Tapping it caused glitches. I looked over the schematics and it's pretty simple, but I don't like how the tip is designed. It's just a screw-in tip and the wire to it just hangs out the end of the probe and then the tip is attached. The wire just sit loosely in the tip, not soldered or attached in any way.

I've ordered a new probe and the BNC to banana plug converter. It should be here on Wed and I'll be able to get more done.