1949 Motorola 7VT5A ETF score, restored!

[zenithfan1]

I was lucky enough to get a good one, I plan on making a new one like Phil Nelsons general idea but am toying with other ideas as well. I spaced on an auction for a NOS one a few weeks ago, I remembered it about two hours after it ended. Oh well, more will turn up and I probably just use a home made one if I plan on using it more than I do now. (not much)
One of these days, I'll restore the ratty basket case that I won in the live auction. It is the same exact one as this and they were made about month apart. BTW, the one here was "born" November 4th, 1949.

[bandersen]

I missed out on that auction too

I'm currently restoring two more Motorolas - a TS-4H and TS-18 chassis. The TS-4H ballast has at least one dead element. The TS-18 is missing the ballast entirely.

I just received a bunch of power resistors from surplussales.com that I'm going to experiment with. I'll let you know how it goes.

[bandersen]

Do you have any tips for restuffing the caps?

Did you slide off the cardboard and cut the metal tube or work out of the bottom like a 'ship-in-a-bottle' ?

I'm about to give that a try for the first time

[zenithfan1]

I did slip off the cardboard and set it aside while working. First, I take close-up pictures of the area under the chassis at different angles so there can be no confusion of what hooks where, sometimes the cap is out for a day or two and it is easy to put one lead in the wrong place and have it "look right". I suck up all the solder on the terminals and tangs with a wick and carefully straighten the tangs that hold it to the chassis. Then it pops right off. There is that lip around the bottom that is knurled over, use a cutting wheel on a Dremel and cut that lip into little sections that can be bent outward like an onion blossom. Or, you can slice most of the lip off and leave no less than 4 tangs to bend over. Either way works, the second method is not recommended for tall caps because it is weaker. Pull out the terminals and fiber disc and save it. Then you can heat it up with a heat gun, while holding the hot cap with an oven mitt, stab some needle nose pliers into the electrolytic goo/foil wrap and pull it out, most of the glue that holds it is in the other end so heat the top thoroughly. If it don't come out tie a string around it on both ends to make a "handle" and hold it horizontally in a pot of boiling water for about ten minutes, it WILL come out after that. Make sure not to let it rest on the bottom of the pan. Then to start installing new caps, put any original terminals that came all the way out back into the disc, they will fit loose but there is usually some of the aluminum lead left on the inside part of the terminal from the old connection, bend that over to make it fit tighter. If the whole thing is loose when done assembling, use a small amount of epoxy on the inside to hold the terminals into the disc. All caps aren't the same inside so you have to just do whatever necessary to make it work. The last ones I did were on this set and most of the lead inside the cap was aluminum so I couldn't solder to it. I used a 1/16 drill bit and added an extra hole to put the new lead through on the OUTSIDE of the cap, it is soldered with the outside leads and cannot be seen after installation. The leads on the new caps slipped right past the terminal to the outside. I usually drill those holes on the part inside the can. Attach all grounds together and run a small wire outside the bottom of the cap, there is usually a handy little hole in the disc but just drill one if not. Tape all connections inside or use heat shrink. Check for fit in tube after each cap is installed and when done, bend the tangs over and reinstall on the chassis. Your ground wire goes to one of the tangs with a hole and then soldered in place, try to make the wire go the tang right next to it and the wire is then almost undetectable. Hook up all other connections as per the symbol chart on the can. Be really careful to put the correct value cap inside the can to the correct symbol or you are screwed. The first three are this set.



Below:This is from a '65 Admiral color roundie.




Below:These two pics are from a '65 Zenith being restored at the same time.


Let me know if I don't make sense I've been up 22 hours and it's 12:47am now.

[bandersen]

Wow - I didn't realize how tricky it was to open those up! I've only re-stuffed the old Philco bakelite blocks before. All you need to do with those is melt out the tar.

You just saved me loads of time and who knows how many mistakes.

It all makes perfect sense to me and I'm wide awake

Thanks for the detailed photos. I bet this will be a great help to others too.

Bob

[bandersen]

Did you end up replacing the selenium rectifiers?
Any thoughts on using a series resistor with a silicon diode and what value and wattage it should be?

[zenithfan1]

No, I never messed with it. I don't think I'll use the set enough to worry about it. It would take a 1N4004 or close and I'm unsure of the resistor. Hopefully someone will chime in that has done the mod to one of these.

[zenithfan1]

Here is the new ballast tube! Looks and works so much better than the ugly 'ol metal one. I'm just keeping that as a spare or for that crappy set I have like this. I'm hoping the seller will let me ship back the bad one for an exchange, I want a spare glass one. He seems nice so we'll see.

[bandersen]

Awesome

I'm glad you got it working in this set (one anyway).

Does it start up 'smoother' now i.e. the filaments warm up evenly ?

[zenithfan1]

Yes, it does. They used to come on with a bright flash when the current rushed in, now they tend to 'come up" all at once more like a transformer chassis set. Looks much safer for it. It also puts out less heat.

[bandersen]

Originally Posted by zenithfan1

Yes, it does. They used to come on with a bright flash when the current rushed in, now they tend to 'come up" all at once more like a transformer chassis set. Looks much safer for it. It also puts out less heat.

Excellent - that's exactly what I experienced.

[zenithfan1]

It's great, she's been on for over an hour and the area around the ballast feels about 20 degrees cooler, feels cold compared to what it did. I was burned on the side vent there a while back, now that is barely warm. The tubes are all lit very even and not a one too bright. Those metal tubes are for the pits, these glass ones are the cats ass. Get 'em while you can fellas, just make sure you leave him one to replace my dead one

[zenithfan1]

That seller is very nice, he said "throw out that ballast tube, another is on the way already" What a nice guy. The listing says buyer to pay return shipping on returns.

[bandersen]

I was just poking around my suitcase set and noticed several labels specifying the use of this ballast tube even though it's a TS-4J chassis which normally uses the 17A470303 tube. I wonder if they had heat issues back then too?

[Sandy G]

Question for you TV guys- I've read this thread & a bunch more like it here over the years, & it occurs to me that there were a fair number of "faults" w/the circuits of these early sets, that now, w/the benefit of 60 years experience, we can correct easily enuff... Was part of it inexperience w/the then-new medium of "television", and was it that these things were operating at the edge of what was possible to achieve then ? Or was it an attempt to use the cheapest parts possible, to keep the price low ? These things were fairly "big money" for back then, even at $175-200..., which is comparatively not much now. Seems like you always hear about how much trouble they gave...Like this heat issue, which seems to have been at least somewhat settled by a simple substitution of parts...Or am I talkin' out my hat, as usual ? (grin)