Anyone familar with scopes?

Anyone familiar with repairing scopes? I have a watterman pocket scope made in the 40s. I replaced all the wax and can caps in it. The tubes tested good. I plugged it in and at first I could see a line at times. I could tap the pot controls and switches to get the line. So I sprayed some spray cleaner in the controls and now I get at least a dot the size of a pencil eraser all the time. If I put a signal in the line goes all the way across. Before I sprayed them I could adjust the focus good but now I can't get it less than a width of a pencil. The scopes tube size is about 3 inches wide. Thinking it may have been the tuner cleaner I sprayed I used another cleaner that evaporates. It had no effect. I can put in a signal on the horizontal and the line goes side to side. If I put in a signal to the vertical it will go side to side as well. But with no signal I get a dot in the center. It seems like its not as bright as it should and I can't focus. Otherwise it looks like it is working. I also adjusted the voltage on the horizontal and vertical circuits as it said in the book and got it like it needed to be. I do think after letting it set all day it seems better. I am more audio than I am video. I wasn't the best at TVs and scope repair as I didn't do as much as that. I was wondering if anyone had any suggestions on what to check. I have a diagram below.

I have a Tektronics 532 that I do not use much. Other than dirty controls, which you have already checked, the biggest problem with mine is dirty tube sockets. With plug-ins, it has 77 tubes. The biggest offender is a 6AL5 that hangs upside down and really needs a new socket. My suggestion would be to wiggle the tubes that you can safely and see what that does. Scopes are not my strong suite, either. Good luck, Willy.

Regards

WC

Thanks wildcat! I would love to get this one going. Its a neat little scope and a small size. It actually has good response the best I can tell as when you move the Hozizontal and Vertical centering it works good. I checked and I used GC electronics Jiffy bath on the controls and I am wondering if it has set up some kind of capacitance between something that is getting it off. I sprayed some evaporating cleaner and it did seem to be better. The biggest problem about it is what makes it nice, its size. Its small and compact which means its almost impossible to get in there. I did go around and resolder all the solder joints I did.

I would have another look at the intensity and focusing pots and their associated resistors. From what you describe, I would think that would be the affected area. Do a good linearity check for the pots, and make sure the resistor values are as close as possible. Sometimes cleaning materials can cause temperature shifts in component values also.

I went back through it this morning. I wiggled the tubes and nothing happened. I then took the scope tube out and cleaned it and cleaned the pins. It looks like a wax cap went bad in this thing and left wax residue all over it. The pins had wax on them even. I also looked at at resistors and they seem to ohm out properly from what I can tell. I got to thinking about the suggestions and I took some evaporating cleaner and sprayed into the controls. This was different from the jiffy bath as it removes residue and evaporates. After doing this and letting it run for a minute or so the focus began to work fine.

So with this in mind this scope may be fixed or close to being fixed. Here is what I have now. I have a horizontal input and vertical. If you input a signal into the vertical the scope will have a line up and down. If you input a signal into the horizontal it will have a line left to right. But if no signal is input it has a single dot in the center. It has a switch that you can put it on internal sync and it will have a line all the way across. If you put the switch to horizintal input it will have a single dot in the center until a signal is injected then it will be all the way across. I also noticed that the waveform doesn't have too much height but that may be due to me not being familiar with the scope setup.

So here is my question at this point. Is the last paragraph normal on older scopes with only having a dot until a signal is injected? I am use to newer scopes,made in the 70s and above. Do these older scopes made in the 40s only have a dot in the center until a signal is injected. I am thinking if it still has issues it may need to set a few days to dry out from the cleaner.

Yes. That was the case with the old OS-8 scopes we used in the military as training units. The older units didn't have timing circuits that gave a trace before having a signal put to it. Now you need to make a nice lissajous trace on your pride and joy and post a pic for us.   

75X11 wrote:Yes.  That was the case with the old OS-8 scopes we used in the military as training units.  The older units didn't have timing circuits that gave a trace before having a signal put to it.  Now you need to make a nice lissajous trace on your pride and joy and post a pic for us.    

thanks for the info. I was wondering if it was ok. It sounds like it is from your info. I will see if I can make a lissajous pattern this weekend and post it. I have it running some to heat the rest of the jiffy bath off.

Update. after 75x11s post about older military scopes not having timing circuits I went over to youtube and found a 40s Navy training film on scopes. I set it up with a signal injector like it showed about 15 minutes into the film and I was able to get it to show a waveform all across the screen like the tracer produced. So this one is working now for sure. Thanks for all the input as it helped me to get this old scope working. I will try to get a lissajous pattern on it this weekend and post it. If anyone has a older scope watch this video to see how it works.

Thanks again for the help.

Here is a later version of the scope I got my first training on. This one has a sweep oscillator, though. The one I used had few controls and 4 binding posts for the inputs.
http://www.ebay.com/itm/Vintage-US-NAVY-Oscilloscope-mod-OS-8C-U-Carol-Electronics-Div-U-S-A-/181325657599?pt=Vintage_Electronics_R2&hash=item2a37d9f5ff

I couldn't get a lissajous pattern as I don't two good working signal generators. I have a few of them but I need to go through them as well. But I do have a signal generator I hooked up to it to get a nice pattern on it. Here is a video of it.




Here is a picture of it on from the top





This is one straight in the screen.



I am happy with it. I still may look for a newer one though. But this little one will be neat to use and display. I need to make a new handle and tuck the wires in. I also need to put on the post for the leads. One was messed up and I have made a plastic piece to fit it. I also need to put the sides on it again.

Looking good!

Wow...what a sweet little unit!

Nice going Willie!   

Thanks folks, I am glad to get this little unit going.  I have a sencore sc61 I think it is,a heathkit from the 70s,a leader stereo test unit with a scope and none of those work. I would pick one up if one died or acted up. I never got the time to really work on any of them. And then not doing too much work on stuff at home other than computers over almost 20 years I let it go. I might can get the others working now as this simple one really helped me to understand the workings in these scopes.

Go, Willy!   

You are the scope guru!

Regards

WC

Wow. Neat 'lil scope!