Zenith 15U270 - Printable Version
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Zenith 15U270 - rfeenstra - 05-31-2020
I bought this radio at the Stanton auction for $700. I knew nothing about it at the time other than it was a 15 tube model, a shutter dial and I liked the cabinet. I always thought I should have a shutter dial just because and I like high tube count radios. Plus it had a tweeter! So I bought it, not knowing its value. I have since found out that this model seems to command a higher price than I paid - a good thing. Anyway, the chassis is almost complete with just a couple of details to take care of. Best of all, it cranked up first shot out of the box, all bands. I like that kind of good fortune.
This radio had been worked on (the cabinet has been refinished) and should have played except that it blew the added fuse as soon as I turned it on. One of the 5Y4's flashed a beautiful blue just before the fuse went. I decided to clean up the restoration a bit. All the caps had been changed with a real hodgepodge of brands. All of the lytics had been changed with 4 section twist lock. 2 had been disconnected but at least were still on the chassis. I bought one Zenith painted can type on ebay and another stud mount from Mark Oppat. Kim Herron (w8zv at goldenradioservice.com) supplied me with a whole bunch of Zenith tubular caps to restuff and with a multi-section, strap mounted, cardboard electrolytic that I could stuff with 3 x 10mfd at 50v caps. many of the original resistors had been changed out so I decided to do a complete resistor job. Only 2 sections of the candohm where still in use. I disabled all sections and strapped on replacements. I hope the candohm insulation doesn't fail! There is a part of me says why stuff capacitors but put in modern looking resistors? It's a quandary in my mind, but there is something about Chinese yellow I don't like but I can look at new resistors and feel good about it. I just can't bring myself to molding all of those resistors!
Here are some cabinet pics and some before pics.
RE: Zenith 15U270 - rfeenstra - 05-31-2020
And here are after pics of the chassis. You will note an extra transformer next to the choke. I decided to install a bucking transformer under the chassis (Zenith gave plenty of real estate in this chassis). It brings my 121 volt line voltage down to 115 volts. I've heard from multiple sources that Zenith undersized the transformers and they run way too warm at today's voltages. I could drop it another 6 volts using the 12 volt tap for 109 volt operation. Any comments? I'm looking for advice on that issue! The radio will work at that voltage.
Oh, and one more question. You can see that the previous tech installed 2 caps in line with the antenna leads. For now, I left them in. I presume they were put in to isolate the radio from the antenna from some sort of voltage build up on the antenna. Any ideas?
RE: Zenith 15U270 - morzh - 05-31-2020
Gorgeous cabinet.
RE: Zenith 15U270 - rfeenstra - 05-31-2020
Yes, it caught my eye at the auction. It does have a bit of a problem with the curved burled walnut on one side.
I did lower the line voltage to under 110 volts and the transformer still runs quite hot. It's been on now for a couple of hours since I did that. I'll leave it that way since it works fine. I did an alignment. The BC band lined up good, some of the others not as much. But still very acceptable. I get a kick out of the motor drive. Quite necessary as the tuning knob takes a lot of twisting to get all the way across the dial. I think it's going to perform very well. I'm not a big fan of the preset tone control. I would prefer separate bass and treble.
RE: Zenith 15U270 - morzh - 05-31-2020
Zenith transformers are known to be undersized and so running hotter. Lowering voltage dies them good.
RE: Zenith 15U270 - Eliot Ness - 06-01-2020
You have it looking good. I'm with you about the capacitors vs resistors. I'll re-stuff capacitors but haven't molded or made resistors yet. Maybe I'll experiment on the 12 toober I'm working on.
RE: Zenith 15U270 - rfeenstra - 06-04-2020
Two 15 tubers side by side! Tonally, with a hifi transmitter, the 37-116 has the advantage. Better extended treble even though the Zenith has a tweeter. Interestingly, if I detune the Zenith slightly, the high frequency response improves. I think I'll put it on the spectrum analyzer and see if I can broaden the IF by stagger tuning the transformers slightly. The analyzer gives a good picture of what is happening. I'll also analyze the tone control circuit to see if I can change a couple of values to improve response. I'm not overly impressed with Zenith's system! Ya gotta love the dial though. Only problem is the dial light does a nice job of lighting the black trim but not the dial.
The curved veneer problem that I need to deal with is obvious. (Oops! That photo is upside down). Any experts out there with advice?
RE: Zenith 15U270 - sdradioman - 06-05-2020
Do you have your dial lamp slid all the way in? I had the same issue with a ‘39 shutter dial, found out the dial lamp needed to be slid in further so it shown on the numbers, not the back of the panels...
RE: Zenith 15U270 - rfeenstra - 06-05-2020
I'm quite sure it's all the way in but I'll check again when I take the chassis out. The problem is that it is a very tight fit and you must be careful not to short the socket to the chassis. It comes very close to the gear mechanism. Perhaps I can find a lamp where the filament is closer to the end of the bulb.
RE: Zenith 15U270 - morzh - 06-05-2020
I wonder if the veneer is not stifking out, maybe some marker would do it?
RE: Zenith 15U270 - Phlogiston - 06-06-2020
You can make the crack in the veneer look better for a while, but, in most cases, it will return after a year or so. The only sure thing is to stabilize the structure and replace the veneer. (This issue often arises from structural issues under the veneer)
RE: Zenith 15U270 - rfeenstra - 06-06-2020
the veneer is actually cracked and slightly lifted. I understand that this is not an uncommon issue with these radios. I'm thinking I need to get some hide glue - something that will activate the original hide glue - down into the crack and then clamp it down. I could then fill with lacquer and and smooth it out. I know Russ has said that repairs on curved veneer are rarely permanent. I may talk to Jean Goller of John and Jean Antique Radio Collectors. She has a lot of experience and training in the art of refinishing.
RE: Zenith 15U270 - rfeenstra - 06-06-2020
Russ, as far as I can tell, the wood under the veneer is a solid piece that has been shaped. I looked at the possibility of a joint under the problem but, as I said, it appears to be a solid piece.
RE: Zenith 15U270 - Phlogiston - 06-06-2020
That is good. Then you should replace all of the plywood on which that layer of veneer is applied (as opposed to replacing just the top layer of decorative veneer). It is likely that most of the layers of the plywood are split.
Doing a touch up is not wrong. Just saying, if you are like me, you will look at that spot every time you walk by. And when the crack shows up again - - you will be annoyed.
RE: Zenith 15U270 - rfeenstra - 06-06-2020
Thanks, Russ! I would be annoyed!! What you are suggesting is, perhaps, beyond my current level of skill. This cabinet was refinished before I purchased it. It was not a bad job and I don't relish the idea of doing it over cuz of some new veneer. I would have to do both sides as it is matched. I may just do the best I can and live with it!