[Ron Ramirez]

Here's my next case:

[Image: http://www.philcoradio.com/images/phorum...e00001.jpg]

That was a quick and dirty photo. Here's a better picture:

[Image: http://philcoradio.com/images/phorum/tro...720T-1.jpg]

The Philco Tropic 42-720 was introduced at mid-season 1942 (January). You can read more about it here:

http://philcoradio.com/gallery2/1942b/#M...1T_42-722T

http://www.philcoradio.com/phorum/showth...?tid=15028 (scroll down to 42-720T, 42-721T, 42-722T)

I could not find a schematic for the 42-720. The chassis, however, appears to be very similar (if not identical to) the 42-724.

Now that I have this radio on the bench and partially disassembled, I have found that this seems to be a bit of an oddball.  There are no labels, no rubber stamps on the chassis, nothing. More on that later.

Let's take a look under the hood.

[Image: http://www.philcoradio.com/images/phorum...e00002.jpg]

Did you notice the writing on the electrolytic caps?

[Image: http://www.philcoradio.com/images/phorum...e00003.jpg]

[Image: http://www.philcoradio.com/images/phorum...e00004.jpg]

Production samples, made by Magnavox for Philco and dated 4/4/1941.

Another sample part - the two-section trimmer condenser which is just right of center in the under-chassis photo above:

[Image: http://www.philcoradio.com/images/phorum...e00005.jpg]

It is marked "TELERADIO SAMPLE".

I am wondering if this radio is a preproduction sample?

Well...if it were in better shape, I would just leave it alone and let it be a "shelf queen." But this radio was obviously used - and used a lot. The brown flocking on the backing plate behind the dial glass has turned black and is in bad shape; it will need to be reflocked.

Someone drilled a few holes in the side of the cabinet, for some strange reason.

The original Tenite escutcheon is gone, replaced by a wooden escutcheon that is OK but just not quite the same as an original. I can tell the wood escutcheon is much newer by the crude pieces of metal attached to the back that are holding the glass dial scale in place.

Worst of all...the glass dial scale is broken. And it's one of those dial glasses that is painted on the front and back.

Because of all this, I decided to proceed with the rebuilding. It is going to need a lot more than just a recap and recarb, so it won't be finished right away. I'll have to find out how to reflock the metal backing plate, and figure out what to do about the dial scale. And, of course, those lovely rotten rubber-covered wires.

So...I've already removed all of the paper and electrolytic capacitors and have melted out and removed the original innards from all of them. This set, too, will receive new caps restuffed in the original sleeves.

[Ron Ramirez]

If you want to see the schematic of a 42-724, which appears to be identical to the 42-720, you can get a copy here (warning for those on slow connections: this file is 774 KB in size!).

[Arran]

 That set reminds me of a few Canadian model Philco sets I've seen, both in the cabinet and the knob layout, unfortunately I never owned them so I have no idea what models they were. Whomever made that wooden escutcheon did a fairly respectable job, if it were not for the open grain of the wood it would almost look original, at least from the outside. One saving grace is that it looks like it shares the same dial scale as a model 42-724, which would make sense if the schematic matches up. Apparently there are some outfits that can make you a one off reproduction dial, radio daze is one, but there was another that I saw mentioned on the barking dog forum that made signs for windows.
Regards
Arran

[NostalgiaRadioTime]

Those production sample electrolytic caps are fascinating! It's always an added bonus to find a component...any component...in a radio that has a date stamped or written on it. And the fact that these are in fountain pen handwriting is very cool!

I had a thread on reflocking the turntable on my 47-1230 a few years back, and you might be able to do the same for your dial backing plate: http://philcoradio.com/phorum/showthread.php?tid=5231

And, with such a grapic-intensive dial glass, I would think a Radio Daze reproduction would be the way to go. I inquired with them about the dial glass on my little AA5 Crosley a couple of weeks ago and they told me it would cost $39 (a larger dial like yours may or may not cost more) and take at least 4 weeks out because of backlog. Since I only paid $10 for the radio, and since it's not really a very valuable radio even in restored condition, I opted to scan my dial instead. Todd on this phorum (tab10672) did some amazing restoration work on it. Then I just printed it out on ink jet clear decal paper, and applied it to a freshly cut piece of plexi-glass (or lexan) and installed it in the cabinet.

Good luck with this new project, Ron. Always fun following along with your progress...you take great photos!

[Ron Ramirez]

Thanks, Greg! I already have the 3M Super 77 spray adhesive...looks like all I need is a bottle of brown flocking...

I may go the RD route with the dial glass, unless someone has a better suggestion. I would assume I would have to furnish the graphics, which I can do - I can scan both sides and clean it up where needed.

[NostalgiaRadioTime]

One thing I learned with the ink jet clear decal paper, it does not print the color white. Which worked well for me, because all of the white areas of the dial scale needed to be clear for the dial pointer to show through. But I understand the decal paper is also available in white, which may work for your scale where the numerals are in white / cream color. If you can scan and clean up / restore your scale yourself, it might be worth it to try the decal paper to save yourself some $$. When I was doing my Crosley scale, Eric Adams here suggested having a sticker made at Kinkos...put the scan on a thumb drive and have them print a reverse image on a sticker. He said it cost around $15.00 to have 3 printed (in case of screw-up).

[Ron Ramirez]

Yes, I recall reading about that.

Today's progress:

[Image: http://www.philcoradio.com/images/phorum...e00006.jpg]

I had mentioned previously that I removed all of the paper and electrolytic caps yesterday. This made it easier to replace the rotten rubber-covered wires, and I have the vast majority of those replaced now.

As you can see in the photo above, I had to remove two of the coils from where they were mounted just to get to the wires and components soldered to the various pins of the 7J7E tube socket.

All but two of the resistors have been replaced. Both IF transformers have been removed so that they, too, may be rewired.

[Ron Ramirez]

Paper capacitors, restuffed, sealed with hot glue and ready to reinstall in the radio:

[Image: http://www.philcoradio.com/images/phorum...g00007.jpg]

I will have to purchase some of those Nichicon CS series electrolytics - the electrolytic caps I have on hand are too large to fit in the original paper sleeves.

[Chuck Schwark]

Wow, those wax-paper caps really look crappy.  8) 
Good job preserving the "patina."

Chuck

[Ron Ramirez]

Thanks...I think.

[Ron Ramirez]

Moving right along...

[Image: http://www.philcoradio.com/images/phorum...g00008.jpg]

As you can see, most of the paper caps and the 2nd IF transformer have been reinstalled. I still have two more paper caps to put in, as well as a couple more resistors and the 1st IF transformer. Oh - and I still need to rebuild that bakelite block with new X/Y safety caps.

I might work on it a bit more this evening, but not much more. I have plans at 8 pm EDT - GO Royals!

[cewrightiii]

Since my teams both choked!

+1 Royals!!

[Ron Ramirez]

All paper caps that go under the chassis are now in place.

1st IF transformer has been reinstalled.

Coils are back where they belong.

Bad news: I turned the chassis right side up and noticed, for the first time, that a winding on the antenna coil appeared to be burned. I did a resistance check and, sure enough - that one winding is open. I am hoping I can rewind it. It is the primary winding for the AM band, so (hopefully) it won't be too difficult.

Well, game time is in half an hour. I'll be back later, probably tomorrow rather than later tonight.

[Arran]

 I found that when you have a dirty looking capacitor the best thing to do, before melting out the contents, is to wipe the dirt off with a paper towel soaked in mineral spirits, that way the dirt can't work it's way into the cardboard. But if it does you can remove it with some lacquer thinner, which is also useful for removing residue from that hard, dark brown wax, they use to plug the ends.
It sounds like another lightning strike victim, I'm working on one right now, but unfortunately the donkey who worked on it last pulled out the original antenna coil and wired in an external ferrite bar antenna, so I need to see if the substitute I found will work. But before I can do that I have to finish overhauling the rest of the chassis, I've never seen so many open resistors in all my life, not drifted but completely open. Like your 42-720, this radio must have had a lot of hours on it, not quite run into the ground but still.
Regards
Arran

[Ron Ramirez]

Thanks, Arran, good advice.

I like how my caps turned out - they have that patina of age.

Yeah, whether this 42-720 was a preproduction sample or not, it was definitely run almost into the ground.

No progress today, but I did remove the AM/SW1 antenna coil yesterday morning. I will attempt rewinding tomorrow or Saturday.

I need to get those electrolytics ordered, too, along with some flocking material to reflock the dial's backing plate.