EH Scott Radio Enthusiasts

The Fine Things are Always Hand Made

Today I finished putting together the speaker cabinet I have been working on for my 800B. I had decided to go with this approach using a custom enclosure so I could control the response of the design better. I elected to use a new 15 inch woofer, a Dayton Audio DC-380-8 and a Visaton BG13-P from Parts Express. After doing some calculations based on the capabilities of the speakers, I built a cabinet that is a bass reflex and uses a 4 inch diameter port with internal and external flares also from Parts Express. I have the external flare in place but still have to trim the port to correct internal length. I need to visit my friend to take advantage of his band saw to accurately cut that part.

Other items that still have to be done include wiring the drivers to the cross-over network and adding filler for sound deadening. I might use some polyfill as I have heard that fiberglass may cause corrosion over time. To begin with I will leave off any level controls for the mid-tweeter driver. If it turns out to need it I can still add one later.

When I have checked out the speaker with the radio tuner chassis and power supply chassis I can begin work on making a custom cabinet to place the speaker cabinet in plus a record changer.

Here is a picture:

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Joe,

I'd be interested  in your appraisal of the sound of the radio especially the FM. I've had this discussion on these pages in the past in that the FM on the 800B (and RCA Berkshire) was narrow band compared with later quality wide band FM sets. It seems on my 800B and after a careful restoration there can be some distortion of low audio frequencies. I have minimized this with very careful antenna placement. My trusty 1947 Hallicrafters SX-42 (FM) doesn't seem to exhibit this peculiar sound.

Tom 

Tom;

I have not put sweep alignment equipment on the 800B, although I may after I get all the parts replacement done that are needed. Years ago I modified an 800B for a friend and built in a dual channel preamp that used 12AX7 tubes on the radio tuner chassis, clutched treble and bass controls plus a dual clutched volume control. This was way back in the 1970s. I had to build another power amplifier stage (which was not identical to the 6L6 design of the 800B) using the output stage and transformer from a Dynaco power amp and output transformer. The individually adjustable controls for each channel allowed nice balanced sound from both channels. Unfortunately clutched volume and tone controls are no longer being made. The approach allowed me to keep the original appearance of the front controls on the 800B radio tuner chassis. I added a multiplex circuit that was transistorized underneath the FM IF/Audio/Power Supply of the 800B building in a small power supply for the MPX circuit. I added a small MPX indicator lamp on the black portion of the 800B dial that looked like a factory installation when finished. It did involve some extra audio and indicator leads being added back to the radio tuner chassis from the power supply chassis and the extra power supply and power amplifier chassis. It worked quite well. I think the FM Discriminator circuit of the 800B is wider than we might think, otherwise it would not have worked so well.

Has your receiver had its FM circuitry aligned?

Joe

Joe,

I carefully aligned my 800B using the Scott's published service data after my restoration. Most capacitors were replaced as well as several out-of-tolerance resistors. In fact I repeated alignment a few times getting the same results. The FM sounds OK when my dipole antenna is aligned very carefully, but that seems to be critical. I live about 45 miles north of most Philadelphia FM transmitters and most sound clear if the antenna is carefully tweaked. I also restored my RCA Berkshire at the same time and carefully aligned it as well. It can also have the same peculiar sound on continuous low frequency music.

Tom

Tom;

There are many possible issues to deal with when encountering distortion in sound. Multipath signals can cause distortions and be very sensitive to antenna orientation. Also there are many stations these days that are broadcasting with excessive bass boost and signal deviation beyond FCC regulations and getting away with it. There are a number of stations from Dallas and Ft. Worth that are members of the excessive bass boost and excessive deviation gang. Does the bass response and fidelity sound much better when listening to LPs or other sources such as a CD player?

I will admit though that it has been about 40 years since I heard my friend's 800B and I have not heard one since then. I am eager to hear this one as soon as practical.

Joe

Joe,
The audio in general is very good. The problem is distinct to the FM. I had considered multipath being part of the issue. It is telling that the 800B and the RCA Berkshire, both from the same era, sound similar. I think my location and poor FM antennas (simple dipole) contribute greatly. By the way, I modified the treble and bass controls per Norman Braithwaite's suggested changes in the archive on the 800B. The mod is highly effective.

Tom

Tom;

You may be right about a narrower IF and Detector response in older FM receivers. Even the advent of Muzak and its subcarrier region did not develop until some years later. I recently restored a Silvertone 8127D model which uses Loctal tubes throughout and has a FM front end with a 4-gang tuning capacitor (something not seen again until the advent of the Citation III and Fisher 200-B FM tuners of the early 1960s). It is one of the few tube type receivers I have tried at my location that is able to receive a weak station on alternate frequency to a local relay station running at 10KW only 4.5 miles from my house. It does have the same effect that you noted in that the tuning on the weak station has to be right on target at its center frequency or there is notable distortion in the sound, especially the bass response. This is in mono let alone any consideration of stereo reception.

I will let you know as soon as I am able to get this unit up and running.

Joe

Joe,

Thanks for the note. I'm retired and have been slowly tackling radios in my collection that needed attention. My favorite is a Scott AM-FM Philharmonic. I just finished recapping and alignment and I'm really pleased with the results. It's great fun to see how good we can make radios of the past perform in 2017. On shortwave, this set is at least as sensitive as my National 183-D. Selectivity and adjacent channel issues is another story, but overall it's amazingly good and great fun to listen to. The 183-D has crystal selectivity and dual conversion.

Tom

Tom;

That Philharmonic is certainly a beautiful chassis! I saw one at Larry Lindsey's house last year and they are true beauties!

Your National 183-D is a great communications receiver. I have a friend in North Dallas who has one he is restoring. I have a Hallicrafters SX-25, which like your National, has a crystal IF filter as well as some other wider choices for shortwave listening and regular AM broadcast band reception.

I was looking through some E H Scott modifications and see that later they recommended adding a 10kHz whistle filter to the audio circuits to combat heterodyne whine introduced by close adjacent AM stations. I disagree with the way it was implemented. They placed it in the audio output stages where it is in circuit regardless of what function is selected on the front panel. In my opinion, it should have only been added in the AM circuitry so that it would not affect phonograph or FM operation.

My first old radio to restore was a Philco 40-201 which has type 42 push-pull outputs. It has a unique rotatable AM loop antenna that has an added electro-static shield. It helps eliminate static interference from car ignition, neon lights and electric motors with sparks jumping inside. Philco only used that design in 1940 which was developed and patented by William H. Grimditch, their chief engineer. They dropped it and GE and Detrola later used it in hotel/motel pay to listen radios. Unfortunately the SW band on that radio is not too useful as the thumb-wheel tuning control is far too coarse in action and tuning in a shortwave broadcast is quite touchy. There is no comparison to the 116 series of Philco receivers in the middle 1930s which had vernier tuning on SW and variable IF selectivity for a number of years.

Joe

Tom;

One of the ways that IF response can be sharpened or broadened is by using resistors either in series with or in parallel with existing IF coils. Note the way the sharp versus wide IF selectivity is handled in the 800B AM and SW IF circuitry. It would be interesting to do an alignment of the 800B FM IF circuits using a Sound Technology or other recent superior test equipment that allows alignment while looking at the end result distortion. It is possible that a better result could be obtained by that approach. Alternatively judicious use of swamping resistors across the IF coils could broaden IF response. It could at the same time reduce sensitivity some as such measures may also reduce circuit gain. It is possible that a happy medium could be arrived at though. Even an approach to slight stagger tuning could be used. Sweep alignment would be needed for that technique.

The Silvertone unit I mentioned was their top unit right after the war. Like RCA they only made about 500 of them. The company that made them was Continental Radio which was based in New York at the time. The sets sold in Sears stores for just under $500 which was quite a sum at the time. Like the Scott, it was peak aligned except for the discriminator circuit for which they recommended sweep plus an oscilloscope to view the resulting S-curve. It was possible to use a voltmeter though and look for equal displacement either side of the 10.7mHz center frequency.

Joe

Joe,

Very interesting indeed. I'll be interested in your results (the pressure is on!) after your 800B restoration. I do remember the alignment of the discriminator was extremely touchy, not allowing for any variability. The Silvertone you mentioned looks very interesting. There is some info and pictures on line.

Tom

Most recent activity on that model on Antique Radio forum was by myself and Darren Garansi. He had the same model and he and I shared restoration thoughts and parts. I still have some items on mine to finish. There is not much information around on the wire recorders that they used. I had to get rubber drive pulleys rebuilt by TheVoiceofMusic.com I could not have done it without them. The record changer was unique to that model too.

You can see some pictures and information on it at:

http://s1213.photobucket.com/user/rubal182jhn/library/Silvertone%20...

Joe

Thanks for sharing that, Joe. I seem to remember seeing the Silvertone show up on Ebay in the past. It looks like even the output tubes were loctal and the wire recorder was probably unique to this unit. I had a Webster-Chicago wire recorder when I as young. A strange device.

Tom

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