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 Post subject: Zenith 14E Table Radio
PostPosted: May Sun 06, 2012 5:40 pm 
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Yesterday I got an early Zenith table radio. The plate on the chassis, the tag on the cabinet, and the power supply (a ZE-9) all indicate that this is a 14E, which, along with the 11E, is one of their earliest AC sets.

The thing is, I can't find any reference to the 14E ever being made as a table radio. Info from the web and the Cones & Bryant book lists this model as a console only. But the cabinet tag clearly indicates that the cabinet was used for the 11E, 14E, and 18E.

Anyone ever seen a 14E table set before?


Attachments:
Zenith Power Pack Tag.jpg
Zenith Power Pack Tag.jpg [ 197.06 KiB | Viewed 1429 times ]
Zenith 14E Chassis Tag.jpg
Zenith 14E Chassis Tag.jpg [ 193.68 KiB | Viewed 1429 times ]
Zenith Cabinet Tag.jpg
Zenith Cabinet Tag.jpg [ 219.06 KiB | Viewed 1429 times ]
Zenith 14E Table.jpg
Zenith 14E Table.jpg [ 179.46 KiB | Viewed 1429 times ]
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 Post subject: Re: Zenith 14E Table Radio
PostPosted: May Sun 06, 2012 6:03 pm 
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Why your chassis has 14E on the tag is a puzzle. Perhaps the chassis was replaced early on?

The table cabinet you have is definitely the 11E

Very nice radio indeed! Probably the first Zenith to use AC tubes. The model 27 was Zenith's first AC set which was a retrofitted Super Zenith VII and used battery tubes. It (as well as the model 17) used a panel meter to properly adjust filament voltage on the battery tubes.

-Steve

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 Post subject: Re: Zenith 14E Table Radio
PostPosted: May Sun 06, 2012 6:37 pm 
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azenithnut wrote:
Why your chassis has 14E on the tag is a puzzle. Perhaps the chassis was replaced early on?

The table cabinet you have is definitely the 11E

Very nice radio indeed! Probably the first Zenith to use AC tubes. The model 27 was Zenith's first AC set which was a retrofitted Super Zenith VII and used battery tubes. It (as well as the model 17) used a panel meter to properly adjust filament voltage on the battery tubes.

-Steve


Thanks, Steve. Do you know what the difference between the 11E and 14E was? They have the same schematic.

Speaking of which, here's another mystery. The ZE-9 powerpack has a big honking 70 ohm wirewound resistor in series with the power transformer primary, and this could easily get hot enough to fry up your dinner on.

It's not shown in the schematic. Why would they put a resistor in series with the primary winding? Did somebody believe it would cut down on the hum?


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Zenith Resistor.jpg
Zenith Resistor.jpg [ 175 KiB | Viewed 1412 times ]
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 Post subject: Re: Zenith 14E Table Radio
PostPosted: May Sun 06, 2012 7:07 pm 
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Hmm, very interesting... Perhaps it was added to reduce line voltage or provide better regulation? I'm not really sure.

Where exactly is that resistor located?

My 11E has a stack of resistors immediately to the right of the 80 in the power supply, but I believe they are the DC voltage dividers.

The 14E is a floor model with the same chassis/power supply. Here is a picture I found on line.

http://www.radioatticarchives.com/radio.htm?radio=3775

As well as the battery version model 14 with a couple after market battery eliminators stashed in the battery compartment.

http://www.radioatticarchives.com/radio.htm?radio=3774

-Steve

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 Post subject: Re: Zenith 14E Table Radio
PostPosted: May Sun 06, 2012 8:28 pm 
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azenithnut wrote:
Hmm, very interesting... Perhaps it was added to reduce line voltage or provide better regulation? I'm not really sure.

Where exactly is that resistor located?

-Steve


Mine has those power resistors on the right of the 80 rectifier too, but this resistor is on the other side, to the left on this photo.


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ZE-9 Resistor.jpg
ZE-9 Resistor.jpg [ 209.56 KiB | Viewed 1395 times ]
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 Post subject: Re: Zenith 14E Table Radio
PostPosted: May Sun 06, 2012 8:43 pm 
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Very odd indeed. I cannot explain that one.
Mine has nothing in that location.

-Steve


Attachments:
zenith11e-supply.jpg
zenith11e-supply.jpg [ 85.81 KiB | Viewed 1394 times ]

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 Post subject: Re: Zenith 14E Table Radio
PostPosted: May Mon 07, 2012 1:55 am 
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Yeah, it is strange. It doesn't look like an owner modification to me- looks more like a factory thing, almost like an attempt to make up for using a the wrong transformer.

In any case, the radio isn't working and the power pack looks like a nightmare to try and repair. I hope it won't end up being the problem.

Bob


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 Post subject: Re: Zenith 14E Table Radio
PostPosted: May Mon 07, 2012 6:18 pm 
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Early AC radios frequently had transformers that were maybe 90V on the primary, and you used a series ballast to compensate for the difference between the design voltage and your line voltage. (110-120V)

Early power generation systems weren't terribly consistent, and user-replaceable dropping ballasts were the solution to make it work in as many coverage areas as possible.


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 Post subject: Re: Zenith 14E Table Radio
PostPosted: May Mon 07, 2012 6:33 pm 
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Quite true!
though, nothing of this is on the schematic of the ZE-9 power unit and mine doesn't have the ballast.

Unless, it was an undocumented change, which is entirely possible.
It does look to be factory in Bob's power unit.

but, boy is it going to be HOT in that corner with both the ballast resistor AND the 80 rectifier. :shock:

-Steve

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 Post subject: Re: Zenith 14E Table Radio
PostPosted: May Tue 08, 2012 5:02 am 
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This is really interesting! I hadn't heard about early AC sets using transformers meant for 90V. Seems like my collecting interests are gravitating toward early AC sets, so thanks both for sharing the knowledge. There's another old thread on this forum that seems to indicate the same sort of thing:

viewtopic.php?f=1&t=46743

Anyway, I had put an 80 rectifier in to measure output voltages and after slowly cranking up the voltage on a variable isolation transformer, after only a couple of minutes it filled the garage with that "hot metal" smell to the point that I switched it off and haven't tried it again. Talk about HOT! (electronics-wise, anyway...) If I do use it in the future I may just plug in a shunt and be sure to run it off of only 85-90V.

Bob


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 Post subject: Re: Zenith 14E Table Radio
PostPosted: May Tue 08, 2012 1:12 pm 
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Does it get as hot with the 80 removed? If that lets it run much cooler, then I would look for shorts or leaky caps causing excessive current draw.

RCA's early AC sets have a HUGE ballast resistance bulb in the power supply. These things run EXTREMELY HOT! They put a chimney around the bulb to protect not only the bulb, but keep it from burning anything that may come in contact with it.

Other manufacturers used the same concept. Brunswick 81, Zenith 103. The resistance will change with temperature and current. It will be low when cold and high when hot. It therefore helps regulate the current flow through the transformer while the AC line voltage fluctuates keeping the voltages in the radio relatively constant.

-Steve

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 Post subject: Re: Zenith 14E Table Radio
PostPosted: May Tue 08, 2012 11:53 pm 
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Once you've checked the power supply out a bit more, I'd throw a multimeter on the primary of the transformer after the ballast and see what it has knocked the AC down to, then find a suitable bucking transformer to wire in and eliminate the ballast entirely. No reason to create a ton of extra heat unless you need to!


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 Post subject: Re: Zenith 14E Table Radio
PostPosted: May Thu 10, 2012 5:16 am 
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Well, it looks like the real problem is that the power supply has been completely rewired, and incorrectly. 230V going where 45 should go, 5V going to a 1.5V filament (burned out that 26), etc. May just be better to disconnect all of the wires under the power pack and rewire it again, hopefully the right way.

Under the chassis the good news is that the parts (except for most of the wires) are original and the transformers are good. But this too has been rewired, so who knows?

Not blaming anyone here- I'm sure they gave it their best and I will say the soldering is good, but now I know why I was able to afford this one. Will be quite a project!


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 Post subject: Re: Zenith 14E Table Radio
PostPosted: Feb Mon 04, 2013 3:09 am 
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hello, I was browsing posts for Zenith 14E info and found this, may I briefly comment/ask question?
The past few months I've been working on a console 14E with the ZE9 power supply for a friend of mine. The wiring was shot and it was obvious someone had worked on this in the past. I rewired the unit and replaced the caps. I also rewired the ZE9, repaired the molded plug end (plasti-dip is our friend here!), rebuilt the multicapacitor, etc.

The speaker cone was perfect but the speaker was non-functional. One of the posters to this forum noted a speaker that looked like the RCA 100 - the speaker on this example is exactly identical to the RCA100 (I have one and compared them)

When I powered the unit up the voltages were wrong and/or changed each time I checked them. Found that the ground lead to the multiplug had a bad solder joint to the chassis. Fixed that and now the radio works!

One thing I find odd is that the change in volume as you rotate the knob is delayed. Is this normal for these types of volume controls or is there a problem somewhere? Also, if you rotate the knob far enough the sound will drop out.

Thanks in advance for any assistance,

Mark


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 Post subject: Re: Zenith 14E Table Radio
PostPosted: Feb Mon 04, 2013 3:25 am 
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Hello and glad to hear you got it up and working!

I have been working on a Zenith with a similar chassis (model 37A). The volume control varies the B+ on two of the RF amplifiers. There is a 1 uf cap on the controlled B+ line which does cause the volume to be slightly delayed in reaction as it must charge and discharge with the changes in voltage.

As the volume is increased, it reaches a point where the gain is high enough it will drop into oscillation. This will of course, cause a drop in sound. Perhaps this is what your experiencing? I don't have the 11E/14E schematic handy to see if it has the same volume control, but it is probably a very similar scheme. The chassis these models use Zenith called the "E" chassis. Each with a few variations in circuitry.

I hope this helps. To me, it sounds as if it is working properly. :D

-Steve

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 Post subject: Re: Zenith 14E Table Radio
PostPosted: Feb Mon 04, 2013 3:46 am 
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Steve,
Thank you for the information! This is the first radio of this age and type I have repaired. Usually I work on more "modern" 1930's radios and up. I have only been doing this since summer 2010 so I'm still a novice I think.

What you explained makes sense to me and I believe would account for the oscillation I heard through the speaker just before it drops out. The schematics were themselves a challenge especially since the copies I had were void of values for caps, resistors and transformers.

I've been bitten by the radio bug for sure and really enjoy collecting and working on them (over 200 in the collection!). I am thankful for folks like yourself who are willing to share their knowledge. Thank you again,

Mark


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 Post subject: Re: Zenith 14E Table Radio
PostPosted: Feb Mon 04, 2013 4:31 pm 
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Your welcome, Mark. I'm glad I was able to help.

The Zeniths of this series used triodes in a TRF design without neutralization. Therefore it is not hard to turn up the gain and have them drop into oscillation.

-Steve

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