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 Post subject: Re: EH Scott Imperial High Fidelity Receiver (new acquisitio
PostPosted: Nov Wed 08, 2017 6:54 pm 
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phlogiston wrote:
Good job!


Thanks Russ kind of you to say. When you did your restoration of the Stratosphere you used molded resistors. How did you find their performance characteristics to be? I will almost certainly be doing more of the same in the RF section on this unit and would love to hear. Link below for anyone interested.
https://www.russoldradios.com/blog/into-the-stratosphere

Cheers.

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 Post subject: Re: EH Scott Imperial High Fidelity Receiver (new acquisitio
PostPosted: Nov Wed 08, 2017 11:14 pm 
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I have never had a problem with one of the molded resistors in a circuit that is working properly. Actually only one melted, but that circuit had real problems.

I usually use 3 or 4W wire wound resistors even in the 1/4W (original rating) sizes that are less than 1K ohms and film types over 1K also putting as high wattage of resistor as I can fit in the 1/2W, 1W and 2 W packages. You might not want to use WW types in some RF circuits, so change them out to film or other types. Heat has always been my first concern.

Otherwise, no issues at all.

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 Post subject: Re: EH Scott Imperial High Fidelity Receiver (new acquisitio
PostPosted: Nov Fri 10, 2017 5:53 am 
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Finally time to have a look at the RF chassis.

So made a box just like the PS box so the chassis is held firmly in place. The opening in the top of the box needs to be 22" wide and a minimum of 13.5" deep. 13.5" is barely enough just so you know.

Anyhow here is the initial survey. Lets start with the top side chrome.
Attachment:
RF chassis top chrome.jpg
RF chassis top chrome.jpg [ 85.69 KiB | Viewed 483 times ]

Pretty good shape!

full bottom side image.
Attachment:
RF chassis full.jpg
RF chassis full.jpg [ 103.64 KiB | Viewed 483 times ]


3 part series for closer inspection
Attachment:
RF chassis left.jpg
RF chassis left.jpg [ 76.26 KiB | Viewed 483 times ]

Attachment:
RF chassis center.jpg
RF chassis center.jpg [ 102.6 KiB | Viewed 483 times ]

Attachment:
RF chassis right.jpg
RF chassis right.jpg [ 92.84 KiB | Viewed 483 times ]


There ya go. There is lots for me to look over yet. Next thing is for me to get the coil turret off of there. I need to make sure it is in the correct position first as apparently the switch can be damaged if this operation isn't done correctly.

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 Post subject: Re: EH Scott Imperial High Fidelity Receiver (new acquisitio
PostPosted: Nov Fri 10, 2017 9:34 am 
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Location: England
Um! most interesting !

What coils are they? Good to see the switching which I guess is underneath.

thanks Gary


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 Post subject: Re: EH Scott Imperial High Fidelity Receiver (new acquisitio
PostPosted: Nov Fri 10, 2017 10:58 am 
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Interesting!

I'm not sure if I remember seeing the underside of an AW23 chassis.
The variable bandwidth linkage is interesting.

I suppose the AW23 came out just after the 1000Z Stratosphere as it uses octal tubes.
I know McDonald make the 1000Z because of Scott, was the 23 Scotts Answer?
Or perhaps it was going to happen anyway regardless of Zenith's effort?

I suspect the latter, but I bet the Philly was influenced by Zenith's big dials.

btw, I like your chassis holders. I've done similar things, but not quite that robust! :D

-Steve

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 Post subject: Re: EH Scott Imperial High Fidelity Receiver (new acquisitio
PostPosted: Nov Fri 10, 2017 6:24 pm 
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Radio Fixer wrote:
Um! most interesting !

What coils are they? Good to see the switching which I guess is underneath.

thanks Gary


Gary - ask and you shall receive.
So as a starter here is the functional description of the RF section from the technical service bulletin for this beastie.
Attachment:
RF section function desc.jpg
RF section function desc.jpg [ 53.8 KiB | Viewed 463 times ]


Next up an image from the same technical service bulletin which has the coil turret with a parts description.
Attachment:
RF coil turret diagram.jpg
RF coil turret diagram.jpg [ 128.06 KiB | Viewed 463 times ]


Finally, a snippet from "Scott Radio News - November 1935" which shows both the wave change and the wave change switch.
Attachment:
RF wave change coils and switch.jpg
RF wave change coils and switch.jpg [ 62.33 KiB | Viewed 463 times ]


Neat piece of engineering!

Reading back through this monstrously long thread now to see if I can answer Steve's question above. I think I am going to need to put a table of contents on this bad boy at the beginning for anyone who discovers it later. :D

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 Post subject: Re: EH Scott Imperial High Fidelity Receiver (new acquisitio
PostPosted: Nov Fri 10, 2017 6:45 pm 
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azenithnut wrote:
Interesting!

I'm not sure if I remember seeing the underside of an AW23 chassis.
The variable bandwidth linkage is interesting.

I suppose the AW23 came out just after the 1000Z Stratosphere as it uses octal tubes.
I know McDonald make the 1000Z because of Scott, was the 23 Scotts Answer?
Or perhaps it was going to happen anyway regardless of Zenith's effort?

I suspect the latter, but I bet the Philly was influenced by Zenith's big dials.

btw, I like your chassis holders. I've done similar things, but not quite that robust! :D

-Steve


Hiya Steve. Right so looking through the EH Scott radio collectors guide - 2nd edition there are a couple of dates in there.

Variation 1 of AW23 chassis (5 knob) was introduced in March '35
The example I have is of this variation and at the very top of the standard broadcast band there is a marking which reads...
"Experimental High Fidelity Station" in itsy bitsy lettering. I am curious if the same is true of the 7 knob version. Chime in peanut gallery.

Variation 2 of AW23 chassis (7 knob) was introduced in March '36

Thanks for the recommendation on getting hold of this book BTW.

In EH Scott the dean of DX by Marvin Hobbs the first appearance of the AW23 is pegged at May '35. There is no mention of when the 7 knob version came about. There is also a section on competitors for Scott which mentions Lincoln, McMurdo-Silver, Fischer and Midwest but no mention of Zenith at all.

My guess on the 2 month disparity is about Scott advertising a couple of months ahead of when it actually came to market. Dave P or Norman probably have more accurate information to add on this.

If you really wanted to get timeline information you would probably have to throw a Zenith expert and a Scott expert with a pile of documentation into a room and see what comes out the other side.

Thanks for the compliment on the holder. This chassis is weird as it has capacitors running through holes from bottom to top and it is going to be worked on while on its top, bottom, and sides so rectangular frame it is. If I ever have to store or move this bad boy components will go right back onto the frames and be crated.

Cheers.

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 Post subject: Re: EH Scott Imperial High Fidelity Receiver (new acquisitio
PostPosted: Nov Fri 10, 2017 6:48 pm 
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Thanks for that. A fascinating chassis to get stuck into. Lets hope the switch wafers are not too worn. Always a major concern for me as there is little that can be done about them.

Now going to get my Scott book out again and have a read...

Gary


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 Post subject: Re: EH Scott Imperial High Fidelity Receiver (new acquisitio
PostPosted: Nov Fri 10, 2017 6:59 pm 
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Radio Fixer wrote:
Thanks for that. A fascinating chassis to get stuck into. Lets hope the switch wafers are not too worn. Always a major concern for me as there is little that can be done about them.

Now going to get my Scott book out again and have a read...

Gary


Sure Gary. Glad I had the data.

Fascinating might not be the word I would choose at this moment. All right, it is actually fascinating but whoever was in there before me has made this a really heavy lift to get looking original again. It isn't just the capacitor sleeves. Some of the caps have been replaced with ceramic discs and some of the wire is just ganky and incorrect. Will see how this goes. I am probably going to need some really good imaging from other Scott collectors.

Cheers.

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 Post subject: Re: EH Scott Imperial High Fidelity Receiver (new acquisitio
PostPosted: Nov Fri 10, 2017 7:24 pm 
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Thanks for the response. I won't go off topic any further. I apologize for that.
This is about your AW23, nothing more.

EDIT I will link this wonderful article by Martin Blankinship about how the 1000Z came to be.

https://www.hlara.org/news/radiogram/ra ... 007-12.pdf

Clearly Scott was a big influence.

-Steve

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Radio Interests
-Zenith
-Sparton
-Pre-War FM
Consoles and floor models, the bigger, the better!


Last edited by azenithnut on Nov Fri 10, 2017 8:36 pm, edited 1 time in total.

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 Post subject: Re: EH Scott Imperial High Fidelity Receiver (new acquisitio
PostPosted: Nov Fri 10, 2017 7:46 pm 
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azenithnut wrote:
Thanks for the response. I won't go off topic any further. I apologize for that.
This is about your AW23, nothing more.

-Steve

Steve

Absolutely not a problem at all. It would be REALLY interesting to know what all of the principles in these businesses were thinking and absorbing to create their designs. That would be an excellent project to pull together all of the information from various experts while the information is still there to be had. Sort of a master timeline. Have been really enjoying Rodney's thread on the Setchell Carlson Jet.

Another interesting tid bit from the Dean of DX book...
Murray Clay became the head engineer at Scott in 1934 through 1938. His designs were 3 of the high fidelity receivers (one of which is the design I am working on). Apparently for a couple of years prior to joining Scott laboratories Murray Clay was working in the RCA license laboratory. This lab worked on application and testing of the effectiveness of RCA patented technologies. There is lots and lots of interesting information out there.

Usually this information is sort of corralled into its own thread by people interested in one particular brand / make or another. It would be really interesting to have a master time line of what was going on. NOT VOLUNTEERING have too much work as it is.

Cheers.

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 Post subject: Re: EH Scott Imperial High Fidelity Receiver (new acquisitio
PostPosted: Nov Sat 11, 2017 7:07 pm 
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Well looked at the Dean book again and studied the schema.

My understanding is that the RF and Osc coils are on the turret and switched underneath by propriety contacts, possibly still excellent. But I don't know where the antenna coils are switched? My guess is by ganged wafer switches which maybe shown in one of your images?. Could be again a Scott build and so still better than most.

But the reality is its going to sit most of the time on the BC band.

To me you were really lucky with the cabinet as I look again through this most enjoyable Post. One of the nicest, not to ornate and very stylish. Shame that Scott wasn't into better dials for such up market radios. Have to hand it to the Commander (and others) that it must have been a big selling point when seeing demo's in store. Really like the dial on my 7A28A and what is it? just a few very cheap to do coloured bands on the rear of the dial.

Gary


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 Post subject: Re: EH Scott Imperial High Fidelity Receiver (new acquisitio
PostPosted: Nov Sat 11, 2017 7:34 pm 
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The antenna switch primary is the wafer located immediately behind the front apron. The secondary is located above the chassis in the middle coil shield.

Norman

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 Post subject: Re: EH Scott Imperial High Fidelity Receiver (new acquisitio
PostPosted: Nov Sat 11, 2017 8:06 pm 
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Hi Norman. Thanks for the additional information. So after seeing the initial chassis survey do you still think I should attempt to make it look original? I could alternately go through this chassis and make sure that every single component is dead on specification. The problem with this approach would be loss of many original components.

Thoughts?

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 Post subject: Re: EH Scott Imperial High Fidelity Receiver (new acquisitio
PostPosted: Nov Sat 11, 2017 10:09 pm 
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If you plan on removing many of the capacitors for testing or replacement, I would recommend rebuilding to original cosmetics. Except for tuned circuits, I would not worry about the components being "dead on spec". If the resistors are within 20 to 25% of the marked value the set will work as intended. The dog bone resistors in the bias divider circuit can be even farther off their marked value and the set will work as intended as long as all are off value by a reasonably similar percentage. I usually leave the bias divider resistors alone if the bias voltages are near correct.

Norman

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 Post subject: Re: EH Scott Imperial High Fidelity Receiver (new acquisitio
PostPosted: Nov Sun 12, 2017 1:12 am 
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I have a whole bag of caps I saved when I rebuilt an AW-23, the owner did not care about the looks under the chassis. If you want them for postage you can have them.


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 Post subject: Re: EH Scott Imperial High Fidelity Receiver (new acquisitio
PostPosted: Nov Sun 12, 2017 10:30 am 
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Norman "apron" is not used in regard to radios over here, its what Mum used to wear when cooking :)

So I have marked up what I think?

Attachment:
AllW 23 top WEB.jpg
AllW 23 top WEB.jpg [ 97.66 KiB | Viewed 362 times ]


I cant guess where the Ant coils primaries are? Perhaps they are beneath the turret?

Seems plenty of schemas for the radio but no layout diagrams.

thanks Gary


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 Post subject: Re: EH Scott Imperial High Fidelity Receiver (new acquisitio
PostPosted: Nov Sun 12, 2017 4:21 pm 
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The antenna coil primary is located between the coil wheel and the bandswitch knob, just behind the vertical front wall of the chassis.

Norman

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 Post subject: Re: EH Scott Imperial High Fidelity Receiver (new acquisitio
PostPosted: Nov Sun 12, 2017 6:42 pm 
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Another snippet from the technical service manual.
Attachment:
RF chassis top diagram.jpg
RF chassis top diagram.jpg [ 139.76 KiB | Viewed 343 times ]

So the coil in the middle appears to be the antenna secondary. <-- maybe not. this might be the primary.

I was getting ready to take off the wave change turret and reading the technical data.
Attachment:
wave band turret removal instructions.jpg
wave band turret removal instructions.jpg [ 128.05 KiB | Viewed 335 times ]


The coil numbered 276 is the red and blue band primary.
There is another coil just to the left of the antenna coil in this image but I cannot make out what it is other than "coil".

Going to start removing covers and storing parts now.

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Last edited by Bosch's Fault on Nov Sun 12, 2017 7:26 pm, edited 1 time in total.

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 Post subject: Re: EH Scott Imperial High Fidelity Receiver (new acquisitio
PostPosted: Nov Sun 12, 2017 7:20 pm 
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The coil in the middle is the broadcast band antenna coil primary and secondary. The primary is located inside the secondary and is not visible. The coil set labeled 276 and 282 x 3 is the shortwave band (all three) antenna coil primary and secondaries. The item labeled 295 to the left of the BCB antenna coil is a mica capacitor. It is not unusual for the BCB antenna coil primary to be open due to lightning. This can be easily checked by connecting an ohm meter across the antenna and ground terminals (antenna and antenna for later receivers set up for a dipole antenna) and checking continuity in each position of the bandswitch. The BCB antenna coil primary should be a few ohms (somewhere under 50, likely well under) and the shortwave band primaries should be very low (near zero ohms). This test can also be used to confirm registration of the antenna coil primary bandswitch which is sometimes out of registration if someone has seriously dinked with the bandswitch in the past (I have encountered this condition once in the past on a "restored" chassis).

I just checked the antenna coil primaries for the early set on my workbench and on an early shortwave antenna coil set in my parts stock. The following resistances were measured:
BCB: 43-ohms
SW1: 1.2-ohms
SW2: 1.4-ohms
SW3: 0.4-ohms

The later AW-23 sets with the dipole antenna setup have a single shortwave antenna coil primary for all three shortwave bands. That primary measures 1.2-ohms.

Norman

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