The Family DuMont

[CaryLee]

Mystery Tube! That black metal tube center-left in first photo has all the numbers rubbed off..and the photos in the SAMS showed a small glass tube in that spot..6AH6 video amp tube.

Glad I got the "Production Changes Bulletin" with the old SAMS folder..it shows that tube was changed to a 6AC7 tube on chassis code "R" and later. If anyone needs the production changes bulletin, let me know and I can scan it and sent it to you.

There was a tube in the tuner that I thought was wrong too, and was ready to order the one shown on the parts list, then got to looking at the changes bulletin and saw that the "mixer tube", 6AK5 on the parts list, was changed TWICE during later production runs...first to a 6BC5, and then to a 6BC6...and the 6BC6 is what was in that spot. That's when I figured out that the letters stamped on the back of the chassis are "chassis codes" that coincide with production runs shown on the changes bulletin. Mine is stamped "AM", which coincides with the last change on the list. Seems to denote that my set is from the last production run, and has every single change made..now I'm going to have to look over my capacitor list and see if I ordered any wrong due to production changes! Live and learn!

Second photo is of tuner string squirrel's nest after I "unclogged" it from the gears..looking close, the middle gear on the shaft MIGHT be fiber! Glad it didn't get chewed up!

[old_coot88]

Cary,
I'm truly awed at this project, to be restoring such a rare heirloom handed down within one's own family.
Wonder how many here are old enuff to remember the dreaded fiber timing gear in the Model A Ford engine.

[wa2ise]

Originally Posted by CaryLee

Mystery Tube! That black metal tube center-left in first photo has all the numbers rubbed off..

You can usually find the tube number embossed in the metal part that surrounds the octal plug part of the tube.

[CaryLee]

Originally Posted by wa2ise

You can usually find the tube number embossed in the metal part that surrounds the octal plug part of the tube.

Thanks. I took a look but don't see any number there. It's a JAN military surplus tube, apparently Ken-Rad..Ken is visible, "Rad" is worn off. The only numbers on it are a "V4", and "SC961A", but I haven't found any cross-reference to that number. There is also a barely visible "2" like it's the end of the a number, and cross reference to a 6AC7 is an 1852, so that's a possibility. Visually, it does appear to be the correct 6AC7, and the heater pinouts match, so I'm going to figure that's what it is for now since I don't have any reason to think someone would have put the wrong one there. It's the only metal tube in the TV, and apparently the 6AC7 is only available as a metal tube. I've now seen photos of the embossed number like you mentioned, and this tube definitely doesn't have one.

[CaryLee]

Recapping has begun! No turning back now....

[David Roper]

Originally Posted by CaryLee

apparently the 6AC7 is only available as a metal tube

A vanishingly rare 6AC7GT was produced. There is at least one vendor selling them for a very reasonable price; it's tempting to get one or two for experimentation to see if they are at all suitable for use in TVs.

[ChuckA]

Originally Posted by CaryLee

Thanks. I took a look but don't see any number there. It's a JAN military surplus tube, apparently Ken-Rad..Ken is visible, "Rad" is worn off. The only numbers on it are a "V4", and "SC961A", but I haven't found any cross-reference to that number. There is also a barely visible "2" like it's the end of the a number, and cross reference to a 6AC7 is an 1852, so that's a possibility. Visually, it does appear to be the correct 6AC7, and the heater pinouts match, so I'm going to figure that's what it is for now since I don't have any reason to think someone would have put the wrong one there. It's the only metal tube in the TV, and apparently the 6AC7 is only available as a metal tube. I've now seen photos of the embossed number like you mentioned, and this tube definitely doesn't have one.

Military tube then the number missing is VT-112


Chuck

[CaryLee]

Originally Posted by ChuckA

Military tube then the number missing is VT-112


Chuck

a-HA! Thank you!

[CaryLee]

Yesterday was a marathon recap day! I'm not a very fast solderer, I have big hands, a 30 watt iron, and can't friggin' see close up through my glasses anymore (I'm resisting bifocals). And some of those caps are in VERY tight spots, particularly the two that were in the metal box in one corner of the chassis..it took forever to finagle those out and then in again.

I still have the HV section to tackle today, but I feel I'm on the downhill side!

Here's a couple noteworthy events:

The parts list in the SAMS photofact appear fairly accurate. In general, in replacing the paper caps, I ordered one or two spares of each, in case I screwed up and ruined some, and that's about what I ended up with. EXCEPT the .05 value. I ordered 11 of them, and I'm pretty sure I ordered at least two spares and maybe three, because it uses far more of them than anything else..and I only have ONE spare left.

I will say this: I didn't take into account the productions changes bulletin when I ordered caps, primarily because I didn't think of it until after the order was placed, so that could account for coming up "short"...glad I ordered extras!

There are a couple other values that I have extra leftovers of, and that might coincide with the "shortage" of .05's.

MOST notable is that I came up one short on 10uf 25 volt electrolytics. There is only one listed on the parts list (I didn't order any spare electrolytics, primarily because of expense, and not being familiar enough to know what I might use in the future, and I might lose them down the road anyway...you should see my shed..I figured they're a tad more durable with their aluminum housings, too) Turned out there's one in the "main chassis", and there there's another one "hidden" inside the aforementioned metal box in one corner of the chassis. The SAMS photofacts photos show it there, with the cover off the box, but there is nothing at all denoting it's existence. None of the usual arrows corresponding to SAMS location numbers point to it. Seems it was missed somehow. I didn't find it in the production changes bulletin either. Luckily it's a value that our local Radio Shack appears to stock, for a couple bucks, so I'll go get one today and get it in there.

Evidence of prior replacement caps: In one case, location C2 on the SAMS, calls for a 50uf 150 volt electrolytic. What was actually there was a 16uf 150. It's listed as a "filter". Don't know the result of such a change, but it's back to the value as listed in SAMS. I'm sure it was an early replacement, as it was soldered to a cut "pigtail".

There was also a couple older plastic caps in there. A HUGE Mallory .5 "Plascap" and a plastic Sprague.

Pretty much every old paper wax coated caps was "gooey". I saw in a previous write up by someone that they had to get the residue off their hands with Boraxo. I keep Boraxo around too! Works wonders!

I did not "restuff" any of the old cardboard or aluminum caps, but did leave them in place for aesthetics. Frankly, I'm not completely confident in my abilities, I've never worked with multiple can caps before, and figured if something goes haywire in the power up, I wanted to be able to see, smell, and hear what was going on...and having everything out in the open will make replacement in that case easier.

Here's a photo of what appears to me to be a couple of obvious failures:

[ggregg]

Been my experience that some of the worst looking caps still work. You just never know.

You didn't leave the old caps in circuit, did you?