Yet Another Motorola VT-71 Restoration

[kvflyer]

Here is what one of the members suggested. At this time, I did not know where the diode was. I was thinking it was in the round can. To my relief, it was in the rectangular can. Here is how it went...

Originally Posted by bandersen

I opened up one of those cans on a very similar TS-18 chassis. The can was held on by two nuts from below.

Here's what it looked like inside. The diode is the cylinder between the coils on the right and the capacitor to it's left.

Do you have access to a B&K 1077 TV Analyst ? It will allow you to inject a signal at any point in the IF stages modulated at the correct frequency.

[kvflyer]

(I snapped a couple of pictures before I ran out the door that night.)

Here is the Diode just as you all had described:



And the lead (or tin, it is very, very soft) cover:



"Tune In Tonight At 6 For Breaking News!" Yeah, Right! :wink:

[kvflyer]

(Those guys are just too much! I asked for help, they came to my rescue and sent me directly to the problem.)



Yes, it was that diode and it was a 1N34. I do remember seeing them as a kid in that same plastic sleeve. It measured "Open" and that was the problem.

I still have work to do. I don't have enough width but that will be another project in about two weeks. I can't tell you how pleased I am to have this little guy working. It was made in the same year that I was born. You can see the dark spot in the center of the CRT. This is my weakest CRT; the one that came with this set. I have another one that is much better. I have been using this one for testing so that Heaven forbid, something should drop on it and destroy it, it would not be the "Good" one.

Now, after refinements, the cosmetics of the cabinet will be addressed. For what it's worth, I really did not have a lot of time into the restoration, only about two days. And the price of the capacitors was very low.

Thanks a million, I really do appreciate it! "You Done It!"

[kvflyer]

I found this CRT in my assortment of Picture Tubes. So, now I have a "Test Tube" to use. Since I can't see the number on the tube, I didn't know what it is used in. I suspect an Oscilloscope. But I did "Go For It" and tried it. It works. So, I have a green phosphorus tube that I can use for testing purposes.





It does have a different current of the filament, something like 150 ma instead of 300 ma. So if I use it, I will have to bridge the filament with maybe an 18-20 ohm 10-watt resistor when I use it for testing.

It was suggested that this CRT would be good for a gardening show or horror movie

[bandersen]

Originally Posted by kvflyer

More progress. Coming down the home stretch... as far as capacitors. Every resistor that I randomly checked was pretty close. I paid attention to the high values and they were still within 10%, some even 5% when marked with the silver stripe....

Interesting. I also found very few (if any) high valued resistors in these sets that were bad. I did however find some low valued ones (< 1K) that were way off.

Originally Posted by kvflyer

I found this CRT in my assortment of Picture Tubes. So, now I have a "Test Tube" to use. Since I can't see the number on the tube, I didn't know what it is used in. I suspect an Oscilloscope. But I did "Go For It" and tried it. It works. So, I have a green phosphorus tube that I can use for testing purposes.





It does have a different current of the filament, something like 150 ma instead of 300 ma. So if I use it, I will have to bridge the filament with maybe an 18-20 ohm 10-watt resistor when I use it for testing.

It was suggested that this CRT would be good for a gardening show or horror movie

Very cool

You might get a kick out of this thread I posted a while ago. I tried hooking up a 7VP1 and a monstrous 12FP7 to a VT71. http://www.videokarma.org/showthread.php?t=247145