Motorola VT-71 resto almost completed.

[Electronic M]

So on vacation a friend sent me a make offer listing for a mahogany Moto VT71 seeing knobs but not being able to evaluate the CRT or see if the back was present I offered $25, my friend picked it up for me and passed it along. CRT tested fine using the working chassis from my blond VT71 and the chassis had all it's original caps, the original back and metal ballast tube. I changed all the paper and lytic caps and all 3 diodes and it just came to life. What surprised me is the original metal ballast tube seems to still work fine....granted it cracked and popped like a yule log on fast forward for the first few minutes.
I recall hearing that the metal ballasts are always bad (and the glass ones are usually fine) anybody else have a VT71 still working with the metal ballast?

Right now I need to get a new CRT rubber mask, mount my new cheater cord, and apply some Howard's.

This set has started a kick to get my electrostatic sets going. I ended up going through my Halicrafters T54 and first then this and now a Silvertone.

[decojoe67]

All my working electro. Motorola's ran with the original metal ballast. I had about 5 all together and 3 now. Even my Teletone portable runs on it's original metal ballast. From what I've seen, I would say the chances of one bad is about the same with any old component.

[Kirk]

I have just finished a VT 71- and am starting on a second one. I learned a neat trick from a fellow restorer about the CRT mounting on these- I use a styrofoam pipe insulator that is available at Home Depot. With a little work from a blade you can form it around the inside of the cabinet where the goo used to be. Carefully knead the tube into it and there you go. Use a light grey one made for a 1/2" pipe. Looks ok from a few feet away, centers the tube, and saves 50 bucks. Just fine for a personal workshop heater such as this.

[compucat]

My Motorola 9VT1 ran for years on the original metal ballast. One day I was watching it and it just turned off as though someone pulled the plug. The ballast tube just burned out. I replaced it with a glass one and no problems since. They do last but run hot and can go bad. I like electrostatic sets. They work well and are an interesting part of early TV history.

[decojoe67]

Originally Posted by compucat

My Motorola 9VT1 ran for years on the original metal ballast. One day I was watching it and it just turned off as though someone pulled the plug. The ballast tube just burned out. I replaced it with a glass one and no problems since. They do last but run hot and can go bad. I like electrostatic sets. They work well and are an interesting part of early TV history.

So far mine have been holding up. I notice it's very tough to find these metal ballast tubes on eBay. A while back I saw a good tested one and just bought it as a spare.

[Electronic M]

Originally Posted by Kirk

I have just finished a VT 71- and am starting on a second one. I learned a neat trick from a fellow restorer about the CRT mounting on these- I use a styrofoam pipe insulator that is available at Home Depot. With a little work from a blade you can form it around the inside of the cabinet where the goo used to be. Carefully knead the tube into it and there you go. Use a light grey one made for a 1/2" pipe. Looks ok from a few feet away, centers the tube, and saves 50 bucks. Just fine for a personal workshop heater such as this.

Once this covid thing dies down enough that the folks will let me to home depot again I may try to implement that fix. It just left the old gasket too alone since I the gasket I found on ebay vanished. I would like to put a correct reproduction on if I could find one.

I think I completed 4 electrostatic sets after that one, and a few months later bought and completed a Philco electrostatic set. With all the time I was cooped up in the basement at my work bench I got a lot done and addressed parts of my back log in by category....the same way I did all my electrostatic sets at once I did a bunch of VCRs at once and several TVs color TVs one after the other...some how I still have projects left. I probably buy too much.

[Chris K]

Originally Posted by Electronic M

Once this covid thing dies down enough that the folks will let me to home depot again I may try to implement that fix. It just left the old gasket too alone since I the gasket I found on ebay vanished. I would like to put a correct reproduction on if I could find one.

I think I completed 4 electrostatic sets after that one, and a few months later bought and completed a Philco electrostatic set. With all the time I was cooped up in the basement at my work bench I got a lot done and addressed parts of my back log in by category....the same way I did all my electrostatic sets at once I did a bunch of VCRs at once and several TVs color TVs one after the other...some how I still have projects left. I probably buy too much.

Hi Tom...what diode did you use to replace the selenium rectifiers?

[Electronic M]

Originally Posted by Chris K

Hi Tom...what diode did you use to replace the selenium rectifiers?

The venerable 1N4007 without any added series resistance. Done that on 2 electrostatic Motorola's, soon to be 3.

I picked up a 9VT1 similar to compucats and refinished it. Once my Dumont Manchu is done (it's close) the moto is probably next.

I also picked up a better blond cabinet with a melted mask... I'm planning to eventually take the good mask in my lousy blond cabinet out, make a mold so I can cast replacements then transfer it to the other cabinet.

[Chris K]

Originally Posted by Electronic M

The venerable 1N4007 without any added series resistance. Done that on 2 electrostatic Motorola's, soon to be 3.

I picked up a 9VT1 similar to compucats and refinished it. Once my Dumont Manchu is done (it's close) the moto is probably next.

I also picked up a better blond cabinet with a melted mask... I'm planning to eventually take the good mask in my lousy blond cabinet out, make a mold so I can cast replacements then transfer it to the other cabinet.

In a search I've seen some use the 1N5408. Would either be appropriate? I've got a bag of 007s but none of the latter. Any advantage using one over the other?

[Electronic M]

Originally Posted by Chris K

In a search I've seen some use the 1N5408. Would either be appropriate? I've got a bag of 007s but none of the latter. Any advantage using one over the other?

Either should be fine. The main difference is the 5408 is 3A and the 4007 is 1A. IIRC the original seleniums are something like 0.3-0.5A so either one has plenty of headroom.

[Chris K]

Great thank you!

[Kevin Kuehn]

Originally Posted by Electronic M

I also picked up a better blond cabinet with a melted mask... I'm planning to eventually take the good mask in my lousy blond cabinet out, make a mold so I can cast replacements then transfer it to the other cabinet.

This sounds like an honorable endeavor. Please keep us informed and some video of that process would be fascinating.