DuMont RA-103 Doghouse lives . . . kinda.

[Polaraligned]

Originally Posted by bigaudioal

A few folks on one of the FB forums said that there are tuners that tune counter-clockwise versus clockwise. But the counter-clockwise ones (like the dials you sent me)are rarer. LOL!

I just purchased a set that is in need of both dials that tune counterclockwise. Please, please, please sell them to me....

[Tom Albrecht]

Well, let's see if we can make this one of those nice VK moments. I have these two wonderfully pristine counterclockwise dials, and I would like to replace them with two (supposedly more common) clockwise dials. If anybody has one, I'll be delighted to forward these to you!

Another option would be if someone would send me a counterclockwise Inductuner, which I can retrofit on my set -- then there will be a clockwise one available.

[bigaudioal]

I just traded my brown counterclockwise dial with a collector that is getting me a clockwise brown dial. However, I am still hunting for a clockwise clear dial. Please PM me if you have a clear clockwise dial that you can part with.

I scanned both brown dials that I have before packing the counter-clockwise one for shipping. Hi-res photo below.

[Polaraligned]

Originally Posted by Tom Albrecht

Well, let's see if we can make this one of those nice VK moments. I have these two wonderfully pristine counterclockwise dials, and I would like to replace them with two (supposedly more common) clockwise dials. If anybody has one, I'll be delighted to forward these to you!

Another option would be if someone would send me a counterclockwise Inductuner, which I can retrofit on my set -- then there will be a clockwise one available.

I can't offer you the ones you want, but if you would like to sell, I would be happy to purchase.

[Tom Albrecht]

Time to resurrect this old thread -- we were previously discussing here about how the Inductuners in the Dumont RA-103 and its clones seem to come in two flavors -- one with a dial that has channel numbers increasing in the clockwise direction, and one with numbers increasing in a counterclockwise direction. Very strange!

This appeared to suggest that Dumont had Mallory make two different types of roller inductors with opposite helix directions, for no apparent reason.

Finally figured out why. The basic Inductuner roller inductor is identical in both types of tuners, but the shaft gearing is different. Here are the two variants:

Version A has a direct shaft from the roller inductor out through the front panel, with a reduction gear for the slower rotating of the two concentric dials. Version A looks like this (from my Crosley 9-407, photographed several years ago). Note the side-facing tubes on the right side of the tuner chassis.



In the above picture, the shaft is actually broken off (more on that later). In the picture below is the Inductuner after it was repaired several years ago, and with the cover removed. Direct shaft clearly visible.



Version B does not have a direct shaft out the front panel, but instead has a gear drive, which reverses the sense of rotation and is the reason why the two versions have clockwise vs counterclockwise dials. Note that this version has upright tubes on the tuner chassis. This is from the Dumont RA-103 I'm working on now.



Here's a closeup with the dials removed, showing the reversing gear.



What's interesting here is that to get the shaft location to be the same for both models (the cabinet is identical for both, with the same dial and tuner shaft position), the whole mechanical layout of the tuner chassis has been redesigned! The reversing gear moves the shaft to the right and higher, so the chassis was modified to move the whole Inductuner subchassis down and to the left.

Why in the world did they do this? I have a hunch it relates to the broken shaft. With the shaft of the Inductuner sticking directly out the front of the set with a big knob on it, the ceramic Inductuner shafts were getting broken in shipping and handling by pressure being put on the big tuning knob. So eventually they redesigned it so that the Inductuner shaft did not protrude directly out to the big knob, but rather a sturdy shaft driving a gear did so instead. This probably helped prevent damage to the Inductuners.

I don't know if that's really the reason, and I don't even really know which model was first and which was second, but now it's clear how the two designs differ. The roller inductor is the same in both models, but the drive shaft arrangement and tuner chassis design is very different between the two.

Mystery solved.

But, to finish restoration of this set, I still need either:

- nice set of dials for the gear-drive tuner in the set, which needs a dial which shows numbers increasing in the clockwise direction when looking at the static dial (turning dial clockwise goes towards channel 1), or

- tuner with direct shaft (like the Crosley set above) that can use the nice dial I have, which shows numbers increasing in the counterclockwise direction when looking at the static dial (turning knob clockwise goes toward Channel 13).

[Polaraligned]

Thanks for posting this Tom.

I am still in need of the clear dial that increases counterclockwise. Bigaudioal has one that does not work on his set, but he is not responsive to my PM's.

I would be happy with a scan so I can make a clear transfer to a fresh piece of acrylic.

Until then, the set sits...

[Tom Albrecht]

I'll make you a high quality scan this evening or tomorrow. If I manage to come up with the correct dial (opposite of what I current have and what you need), I'll be happy to pass along this really nice dial I have to you. But for now I will keep it, since an alternative that will work for me is to get the other type of tuner (the one with the horizontal tubes and the direct shaft out the front).

[Tom Albrecht]

Here are two files with scans of the FM and 7-13 (rapid turning clear) dial.

You'll note that these look "backwards" but that will make no difference when you print on clear material -- simply flip it over to make the image correct. Since the disk has a shaft bushing on one side, this was the only side that could go down flat against the scanner.

Took me a few tries to get a nice scan of it. What worked best was to have strong backlighting on white paper against the back of the disk. This helped reduce the amount of shadow from the scanner's own light projecting through the lettering to the paper backing.

I've attached one file with the raw scan and one that I processed to remove as much of the remaining shadows as possible. These have been reduced to much lower resolution by the bulletin board software. The .png files I uploaded are much higher resolution, and I can send them to you by email if you provide the address to me (send a PM if you don't want your email publicly displayed).

I also have .TIF uncompressed versions of both available which I can send by email (but cannot attach here because the format is not allowed).

[Electronic M]

Originally Posted by Tom Albrecht

I also have .TIF uncompressed versions of both available which I can send by email (but cannot attach here because the format is not allowed).

.ZIP files are allowed, and ZIP is a container format. You can get a ZIP program such as JZIP and use it to losslessly compress the .TIF to ZIP. then attach the file, and those that download it can unZIP the file and get the original .TIF out.

Over on AudioKarma it is common to see audio files such as .MP3 .FLAC .WMA etc. attached to posts as ZIP files....

[Tom Albrecht]

The allowed file size is still very small, even after zipping. So I've attached one of my processed files here, which is actually a pretty good one. Can't attach the raw scans unfortunately. I've sent the whole set of original scans to Polaraligned by email.