Sonora RDAU-209 - Videokarma.org TV - Video

jeyurkon · #1 04-11-2009, 11:05 PM

I picked up a Sonora RDAU-209 at an antique shop today. The first time I've bought anything at an antique shop. Guess I was supposed to dicker. He asked me if I wanted it and when I said yeah, he said they'd give me 10% off.

Do they perform very well after restoring?

There's a cracked corner in the glass dial. I'm hoping I can make it hardly noticible with some water clear epoxy.

John

Reece · #2 04-13-2009, 11:30 AM

Not familiar with that particular set but from NostalgiaAir schematic, it's a typical AA5. However, it has a larger than usual wooden cabinet and a 5" speaker, so will sound a bit better than the average plastic kitchen radio. If you don't care about originality, and if there's room in the cabinet, you might be able to squeeze a larger speaker in there: 6", 8", or 5 x 7" would give better bass. The cabinet doesn't look too bad so maybe one of the "restorer" products would work without a complete stripdown. Those "inlaid" strips might be photofinish printed paper, so you'd want to inspect them carefully with a magnifying glass before proceeding. Any solvent or cleaner might take them off or dissolve the printed finish. Might have to work around them, mask them off with blue or green tape first.
Reece

jeyurkon · #3 04-13-2009, 12:39 PM

Hi Reece,

An AA5 with six tubes. I could never figure out what to call it.

You're right about the inlay. It's a photo tape on top of the wood. The finish isn't too bad. I might try a restorer product like you mentioned.

I haven't opened it up yet but by peeking in through the back it appears that the speaker has been replaced once. I think there is room for a higher quality speaker like you suggest.

I'm not going for complete originality. I will completely recap it and use safety caps where appropriate. The speaker can't be seen anyhow.

But, in the interest of some basic originality, were these small wooden sets usually shiny or have a satin finish? I saw a post on arf saying that they were shiny. I kind of prefer satin.

John

Jeffhs · #4 04-14-2009, 10:15 AM

I just looked at the schematic of your set and found an RF amplifier stage directly ahead of the antenna. Many table sets of this vintage had RF stages, as not every city or town in which these radios were used had local AM radio stations. Because of this, the sets had to be built for long-distance reception, and were often used with outdoor antennas in fringe areas. Yours should work very well for AM DXing, although with only one IF stage it may have issues with separating powerful stations on the dial, say 1100 and 1110 kHz, especially if one station is 50kW and the other is much weaker.

I second the suggestion as to putting a larger speaker in the cabinet. If the radio sounds good with a 5-inch speaker, replacing it with a 5x7 or even an 8-incher will improve the audio quality quite a bit, especially in the bass range. The cabinet looks as if it should accomodate up to an 8-inch speaker, so I'd say go for it. The improvement in the sound quality will be well worth the effort.

jeyurkon · #5 04-14-2009, 11:48 PM

Thanks for all the feedback on the speaker issue. I'll see what I can fit in to it.

The RF stage might be helpful to me. I listen to WBBM in Chicago at night, which is a bit far from Bath Michigan.

I often use my GE AA5 or my Silvertone 6002, which is a Noblitt-Sparks 4 tube. When reception gets bad I use my HQ-160. The Noblitt-Sparks is amazingly sensitive. It truely has one IF stage.

I'm not sure how to count them in the Sonora. There are two IF transformer but only one IF amp. I think I'd call it two IF stages. It's basically an AA6. I guess I'll see what the local station does to me when I get it working.

John

Reece · #6 04-16-2009, 11:24 AM

Whoops, I mistyped: obviously has 6 tubes so is an AA6. It has only one IF stage, with separate input and output IF transformers. It ought to be plenty useful for DX when recapped and aligned. Keep us informed with some pix along the way!

Reece

jeyurkon · #7 04-16-2009, 12:42 PM

I haven't started working on it yet, but I did discover that a larger speaker won't fit. The current 5" speaker almost hits the tuning pulley.

If I tried to put in a higher quality speaker I'd need to change the output transformer. The current speaker has a 2.6 Ohm impedance. That'd be a bit difficult to find.

John

Hemingray · #8 04-16-2009, 06:07 PM

by AA6, (and it being AM from the looks of it), does it have an extra 12SK7/12BA6?

jeyurkon · #9 04-16-2009, 11:58 PM

Quote:

Originally Posted by Hemingray

by AA6, (and it being AM from the looks of it), does it have an extra 12SK7/12BA6?

O.K. I was a little confused. I picked up a photofact for an RDU-209. The Riders on Nostalgiaair for an RDAU looks identical, but is different internally. I do have the RDAU-209.

The lineup is:

12SK7 RF Amp
12SA7 Converter
12SK7 IF
12SQ7 Diode-Audio
35L6GT Output
35Z5GT Rectifier

John

Reece · #10 04-17-2009, 05:49 PM

If you're measuring the resistance of the speaker with an ohmmeter, that's not the same as impedance. Resistance will be lower than impedance. It's probably a 3.2 or 4 ohm impedance speaker. Anything between 3.2 and 8 ohms would work. An 8 ohm speaker would be just a trifle lower in volume than a 4 ohm, at the same volume control setting, which would be remedied in all practicality by just turning up the volume a little more. A new output xfrmr. would not be needed. Of course you're looking at the insides and I'm not, but maybe a larger speaker could be mounted differently from the way the original one is. Just a thought.
Reece

peverett · #11 04-17-2009, 06:46 PM

Before going to all the trouble of changing speakers-remember that we are talking about an AM radio here. With all the static on the AM band these days, I am not sure changing speakers is worth the effort. Also remember the main content of AM these days(at least in my area)-sports, talking heads, etc. Not much music.

My opinion would be to only change the speaker if something is wrong with the original. I might re-consider for a FM set or if I was planning to broadcast a local AM signal from a CD player for example.

jeyurkon · #12 04-18-2009, 12:15 PM

Quote:

Originally Posted by Reece

If you're measuring the resistance of the speaker with an ohmmeter, that's not the same as impedance. Resistance will be lower than impedance. It's probably a 3.2 or 4 ohm impedance speaker. Anything between 3.2 and 8 ohms would work. An 8 ohm speaker would be just a trifle lower in volume than a 4 ohm, at the same volume control setting, which would be remedied in all practicality by just turning up the volume a little more. A new output xfrmr. would not be needed. Of course you're looking at the insides and I'm not, but maybe a larger speaker could be mounted differently from the way the original one is. Just a thought.
Reece

I'm going by the Sam's Photofact. I did a double take when I saw it. They list the impedance as 2.6 ohms. I thought it was a typo but then for the output transformer they show an impedance of 2.6 ohms and a DC resistance of 0.55 ohms.

A 3.2 ohm speaker would still work fine. Maybe just a little less loud.

To put a larger speaker in I could possibly extend the control shafts to move the chassis back. Then shorten the brackets between the back panel/loop antenna to keep it in the same position.

Right now I don't think it's worth the effort. I'll keep it as is unless I don't like the sound. Cleaning, fixing the dial, and recapping will come first. Mouse urine covers everything and the variable tuning cap is rusty on top because of it.

The speaker looks brand new, but it has the original part number and is mounted by the magnet yoke so it must be original. I don't know how it survived the attack of mice.

John

Tony V · #13 04-17-2009, 08:41 PM

That Sonora has an Ingraham designed cabinet which are favorites among alot of collectors.
-Tony

jeyurkon · #14 04-18-2009, 12:19 PM

Quote:

Originally Posted by Tony V

That Sonora has an Ingraham designed cabinet which are favorites among alot of collectors.
-Tony

I guess I'd better do a decent restoration on the cabinet then or I'll have a lot of collectors on my case!

I tried "Googling" Ingraham and Sonora and didn't find much except for items for sale. Do you have any links to information on Ingraham?

John

peverett · #15 04-18-2009, 03:27 PM

I actually also have one of these radios(unrestored as of now). Luckily, mine was not the victim of a mouse attack.

One note of caution-I think the two bands of different grain wood on either side of the radio are decals. If you just strip the radio, they will come off.

Before attempting to re-finish the radio, I would ask around about how to handle these.