Sky chief USA radio

[Goldieoldie]

I found an old thread

https://www.vintage-radio.net/forum/...d.php?t=120024

It’s very similar to my radio
He says one side of the mains goes to the heater chain and the other goes to the on/off
switch which then connects to the wiper of the volume control !
I’ve checked mine and it’s the same !
It looks original
Surely this can’t be right ?
I think the wiper should go to chassis ?
I de soldered the lugs to see if there was a wire that had been chopped off but no
Bit of a mystery !

[Goldieoldie]

Pics

[vinrads]

Hi I think you need to draw the circuit ,won't be to hard it's a simple trf , loos like there should be a wire from the switch to chassis , note this is not a true volume control it controls the gain of the rf stage, that's why it is wired like it is .just a thought remove the pot and look to see if there is an earth connector on the centre tag , like a washer which when fixed touches the chassis , Mick.

[ms660]

With the pot connections disconnected is there continuity between wiper tag and the body of the pot ?

Lawrence.

[Goldieoldie]

Thanks I’ll check the pots wiper connection

[Goldieoldie]

No the wiper is not connected to chassis .

[Goldieoldie]

Circuit from other thread

[ms660]

I've not come across that circuit arrangement before, usually the wiper is connected to chassis/ground.

Lawrence.

[vinrads]

That must be a mistake. so you have 150ma plus going through an aerial coil and a carbon pot Mick.

[G6Tanuki]

I'd say that in th4e diagram shown the connection between the pot-wiper and the switch should also include a connection to the chassis.

In these US budget radios it was quite normal to find the 'volume' control served both as a resistor to load/attenuate the antenna circuit and as a bias-control on the RF-stage. It worked quite well as a way to throttle-back the RF amplification in urban/suburban areas where you could easily be line-of-sight to a number of multi-Kilowatt broadcast transmitters.

"Cross-modulation" was a big issue in the days before the idea of recovering a carrier-derived signal-level voltage and using ot to control variable-Mu amplifiers [a Hazeltine patent in the US] became the norm.

[G6ONEDave]

I've had a chance to look through the copies of the American Rider's Perpetual Trouble Shooters Manual, which are books similar to the Radio Tv Servicing books of the UK Having gone through all 8 volumes that I currently have, the only reference for SKy King are for models A-218, A-219 and A-221, which all use the GT series of valves. They are in volume XI. I am guessing what you require is in volume VII, VIII or VIIII, which I don't have at present. I do have the first six volumes and three others. I am in the process of adding their contents into my service info database but it will take quite a time to complete the task given that to list volume VI took me something like 14 hours to do and contains 1228 pages.

Probably no help at present but hopefully will help in the future.

Good look.

Dave

[clockman]

Asbestos and Line Cords
I think the fear of asbestos in line cords is highly exaggerated if the line cord is in good condition there is no problem. I have two Ferguson 202U radios i have refurbished both with there original line cords and as there is no room inside for any type of mains dropper to be fitted and a mains 120 volt transformer would cost more than the radio i think these scare stories are unfounded? TAB

[Goldieoldie]

Originally Posted by G6ONEDave

I've had a chance to look through the copies of the American Rider's Perpetual Trouble Shooters Manual, which are books similar to the Radio Tv Servicing books of the UK Having gone through all 8 volumes that I currently have, the only reference for SKy King are for models A-218, A-219 and A-221, which all use the GT series of valves. They are in volume XI. I am guessing what you require is in volume VII, VIII or VIIII, which I don't have at present. I do have the first six volumes and three others. I am in the process of adding their contents into my service info database but it will take quite a time to complete the task given that to list volume VI took me something like 14 hours to do and contains 1228 pages.

Probably no help at present but hopefully will help in the future.



Good look.

Dave

Thanks very much for looking Dave
It is in fact a Sky Chief not a Sky King

[G6ONEDave]

What a typo to make, it was Sky Chief that I looked for, full name Sky Chief Radio Corporation, they are between Setchell Carlson inc and Sonora Radio & Television Corporation in volume XI, the book was copyright in 1940.

I do hope to obtain the remaining missing 9 volumes in my collection, as and when finances allow.

Sorry for the typo.

Dave

[Goldieoldie]

No worries thanks again for looking

[usradcoll1]

Originally Posted by Goldieoldie

No worries thanks again for looking

The wiper and the mains switch definitely goes to chassis ground!
The Riders manuals that cover a set such as that are in volumes, 11,12,13 and 14.
Please don't judge US made receivers by that example!
Dave, USradcoll1. Over 60 years of this nonsense.

[Goldieoldie]

Yes I think the wiper does go to chassis which would be logical .
The strange thing is there is no evidence of this as shown in my pics.
What’s also interesting an old posting here says his radio is the same !
I wonder if the wiper is connected to chassis internally but has failed ?
Would be interesting to get the circuit to confirm this

[Goldieoldie]

I’ve had some success.It’s now working but not a lot of sensitivity
I striped down the regen/ volume pot and the wiper should go to chassis !
Unfortunately there are no markings on the pot and the track has had it so can’t measure it .
I tried a 1 Meg which only worked at max ,just taking it off the end stop caused it to emit no volume
I’ve bodged it by using the pot as a volume control in the normal manner into the input of the output valve .It works well !
Any thoughts on the circuitry at the front end ,is it missing something ?
Circuit in post 27

[G6Tanuki]

I would say a 10K or 25KOhm pot would make more sense.

[Goldieoldie]

I tried a 47 k which was worse .I think anything attenuates the aerial coil