[Paul Philco322]

[Image: https://mail.google.com/mail/u/0?ui=2&ik...5bc62c1&zw]I have been listening to this Stewart Warner this morning, a bit of an awkward looker but sounds great, my wife asked if it was FM it sounds so nice. It has a phase inversion circuit for the large speaker and I struggle to understand that concept at times but it sounds good. 6 tubes and Slug tuning, 1946 year of manufacture. It will be playing most of today. Paul B.

[morzh]

Paul

Your image does not show up.

A radio from 1946, they should've added the FM band.

[MrFixr55]

Hi Pholks,

Paul, what do you mean by phase invertor? These are usually used only with Push Pull output stages. I pulled up the Nostalgia Air schematic God bless them and the service that they provide to this hobby, but this schematic is particularly hard to see.

The circuit is rather normal except for using the 6SF7 as an IF and detector and the 6SK7 as a 1st Audio. However, My Zenith 6S52 chassis uses a 6K7 and 6F6 as an audio section and that set sounds particularly good. This set is an AM / SW set and does not have an FM circuit. However, it is inductively tuned, like a car radio of the 50s, 60s and 70s.

[Paul Philco322]

I think I plead a bit confuzzled, in the Riders it states it uses a two stage type of inverse feedback arrangement........so my bad on phase inversion. So what do they mean with two stage inverse feedback arrangement?

Yeah I know no FM, wifes comment though is interesting as she can tell most sets are AM only don't always sound BIG. If she thinks it sounds like FM means I can play it more.

Paul

[RodB]

Paul,

Each stage of a radio inverts the signal 180 degrees from grid to plate and the signal at the cathode is in phase (but, quite often the cathode is at ground potential). So negative feedback can be used just about anywhere in the audio amplifier as long as the source is out of phase with the destination and is typically 2 or 3 stages. The effect is a slight reduction in volume and greatly reduces distortion. Just turn up the volume control a notch.

[Paul Philco322]

Thanks for the explanation, perhaps the lower distortion is why this radio sounds so nice. The 6K6 is the output tube and seems to do the job. I put a Radio Shack AM tunable antenna behind the thing and it sings even on the low power AM stations I enjoy. I have another STewart Warner but it needs some work and is not the same build quality of this one. Stewart Warner made some Firestone branded sets. The 62T16 has a sister Firestone set.

Here is my other Stewart Warner, though it wears the Firestone Badge....


https://www.flickr.com/photos/92577012@N...ed-public/

You may detect on the left a smudgey appearance, the was a hole there and it was rudely plugged I someone planned a mod at some point. I like the dial glass though.

Paul

[RodB]

I'm finishing up the restoration of a Firestone/Stewart Warner right now. I've had it several years and finished the cabinet work some time ago. It's a fair sounding radio and very sensitive.

[Paul Philco322]

What Model do you have there RodB? Got a photo?
Paul

[Paul Philco322]

Been listening to the little red one too. When a Philco Console is just too big.

[Image: https://ci3.googleusercontent.com/mail-i...=s0-l75-ft]

[Arran]

I've noticed that there was this trend towards neo-classical cabinets in that era, some look all right, but others don't do anything for me, like that Firestone Paul linked to. Then again some people don't like the Northern Electric 5200s:

https://www.radiomuseum.org/r/northernel_5200.html

But I like them for the same reason I like the Bush DAC-90 and DAC-90As, they are a nice, clean design, but still unique. I have two 5200s but need to overhaul the chassis. The main issue is that they put the dial lettering on the outside of that plastic window where it should be on the inside, so you have to be careful polishing them.
Regards
Arran

[RodB]

Paul,

Here's a before photo, it's a Firestone S-7397-9. Would the S stand for Stewart Warner?
   

[MrFixr55]

@PaulPhilco, if the Wife likes it, don't ask questions, just enjoy it!

I hafta look at the schematic again, I could not see the negative feedback path, at least not in the amp. I have a Crosley 5C2 which actually uses a "Positive feedback from plate of output via resistor to screen of the previous stage audio amp to increase bass response. it did work.

[Paul Philco322]

https://radioatticarchives.com/radio.htm?radio=13851

Rod-looks like it maybe. Pretty close.....

Paul