Strange and unusual tuning capacitor

[pwdrive]

I think it was manufactured like that....What can be noticed about the rotor in the center section of the tuning gang in the 1st picture?

Think tracking.

Lawrence.

The clue is that the outer rotor plate, the left hand one, of the high value capacitor of the center section is segmented, that can also be verified by looking at the 2nd picture where that rotor plate now appears on the right hand side, the end of the segment slots can be seen if you magnify the picture.

Lawrence.

[Miguel Lopez]

it's just that some of the rotor and stator vanes on each section have been removed.

I don't think so. The small sub-section has its own terminals for soldering, both up and down the capacitor.

The chassis has six valve holders, all of them octals. No big output transformer. It had just two valves remaining, one of which is a 7A7. Now I don't remember which one was the other, I will see it at home today.

The chassis also has a label in the back, stating that for replacement parts one should contact SEARS, ROEBUK & CO. USA.

Another detail. The dial pointer seems to move vertically in the right hand of the radio

[AlanBeckett]

https://en.wikipedia.org/wiki/Sears

Alan

[pwdrive]

A lot of Sears radios went under the name of Silvertone, my guess is that the radio the tuning gang came from was a broadcast band and shortwave job with selected band spread ranges on shortwave.

Lawrence.

[Hartley118]

Many American radios were built with RF stages for higher sensitivity and hence a better choice of stations for listeners in remote areas. That would account for the 3-gang capacitor.

Bandspread on the short-waves (tuned with those low capacitance sections) would further increase the listener's ability to tune readily into a greater variety of stations and easily return to their favourites.

Martin

[Mike Watterson]

It will be MW + SW.
May or may not have more than one band or bandspread.
There are over 4000 Sears/Silvertone models

Six tubes:
RF preamp, Mixer/Osc, IF, Det/Preamp, Audio out, rectifier. (Most likely as it's 3 gang MW + 3 Gang SW)
OR
Mixer, Osc, Det/Preamp, Audio out, rectifier. (less likely)

I can't find any Silvertone / Sears using 7A7 though, which is Loctal. 6A7 maybe.

e.g. http://www.radiomuseum.org/r/sears_roeb_..._4612.html

[Miguel Lopez]

There are over 4000 Sears/Silvertone models

The valves has the inscription "Silvertone", I remember that.

7A7 though, which is Loctal

You're right, the valve bases are loctals

The other valve that I retrieved is 7C6 or 7A6 (don't remember), I will check at home and maybe I will show some pictures on Thursday as tomorrow I won't be here.

[pwdrive]

The Silvertone 9054 had 6 valves, 7H7, 7Q7, 7A7, 7C6, 7C5 & 7Y4, has broadcast and shortwave but maybe no band spread?

http://radioattic.com/item.htm?radio=0021252

Lawrence.

[pwdrive]

If it's a 9054 then here's the schematic/layout etc, it uses a 6 gang tuning capacitor but so far as I can make out from the schematic no band spread, however the gangs appear to be paired up on broadcast band (band A) and the 1st shortwave band (band B) and from then on (bands C,D & E) three of the gangs seem to not be used, can anyone confirm that from the schematic in the link below?

Sears 9054 manual:

http://www.nostalgiaair.org/pagesbymodel...017876.pdf

EDIT: Tuning ratios (approx):

Band A = 2.96:1
Band B = 2.78:1
Band C = 2.17:1
Band D = 1.56:1
Band E = 1.41:1

Lawrence

[AlanBeckett]

You're a better Man than I am Gunga Din working that out
However, I think you're correct. It seems a bit odd really. The Pyes (39J/H, A39Jh, PE41, PE60 and PE80) simply use the 'Big' Sections for the LW/MW and the 'Small' Sections for SW.

Alan