Sphere Signal Generator....... Help!

[LastTemplar]

Hi,

first off i'd like to thank Dragonfly for all his help with this item, he found the only information i have seen so far on this unit.

So i'd like to get it working, i should possibly say working correctly as it does seem to do something however it's not exactly fully functioning

The unit has a date of around 1949 according to the info Dragonfly found, so it uses valves!

These appear to be working and light up, much more than that i don't know about those.

So when opperated it appears to put out a signal only when set to the force and audio position on the MicroVolt switch.
The scope patterns are poor, you can seen some sort of modulated signal, you can attenuate the signal aswell as adjust the frequency on the display.
this is when it is set on RF, you patterns like like those seen from a modulated signal if you monitored a transmission with a scope.

On Af you get a wave form of sorts but it is very messy, you can vary it to some degree on the scope.

On the frequency counter not much unless on force and audio then it is nowhere near the frequency on the dial.
On Rf set to around 27.500 MHz you can eventually find the signal produced by the Rf generator on a Rig the signal moves the needle maybe 3db with some hiss but no tone can be heard.

My guess is the capacitors are probably duff but i don't have any replacements or any way of testing the valves.

I have no Circuit diagram i am hoping that all these Sig Gens of this time period are similar?

So any ideas or input welcomed, i will add some pictures to try and illustrate what i am seeing incase it helps

I've started drawing a basic circuit diagram of what i can see and it is here



Here we are set to Force and Audio rf modulated signal.



Here it's set to Rf CW and force and audio



Here the attenuator has been turned up and the signal reads bigger



MicroVolts x1000 setting


Here we are set to Af Force and audio Modulated



Af Cw with force and Audio


A look inside the Sphere...
caps and transformer board


Rear of the Microvolt switch im guessing somekind of diode on the resistor pack but what is the white thing at the top?


Large cap


The Switches as per diagram Rf/Af, CW/Mod and Band



Attenuator switch


Mains Transformer


Tansformer and Valve 1

Valve 2


The Frequency coils


im guessing those white adjusters are some sort of variable resistor?

Thanks

Sean

[cjay]

It's really a case of just going through the resistors and capacitors because carbon resistors like that go high resistance with age and heat, the caps are also likely to be knackered.

The white adjusters I think are compression capacitors, they're variable.

The 'diodes' on the back of the microvolt switch I think are also capacitors, picofarad range.

Nice retro piece of kit, there are mailing lists and forums out there who may be able to help with more info.

[Mattylad]

Try asking for info at http://www.vintage-radio.net/forum

And don't just replace caps will nilly, if you want to keep it maintaining it's look then you need to remove the inside of the wax tube caps and put a modern cap inside then reseal it.

I'll see what info I can find when I get more time.

[cjay]

What he said, if you want to keep it 'retro' then you can reuse the body of the old caps to house a modern replacement.

There's a few examples on the net of how that's done.

[Mattylad]

TBH these days a small SMT signal generator could be hidden inside the big silver cap & no one would be the wiser lol

Goggle does bring up a lot of celestial stuff.
Also http://www.thevalvepage.com/testeq/sphere/75/75.htm

[LastTemplar]

Thats the page Dragonfly found thanks Mattylad...

so the brown devices between the switch terminals we think might also be caps? These don't look to be in the best condition having a slightly melted looking appearence.
would that not make the switch shorted? the top one the little white thing i can see that as a cap, the way the others are wired joins each terminal together so i thought they might be diodes so that each position adds in another resistor?
ie
1 resistor gives x1000 Mv
2 resistors gives x100 mV
3 resistors give x10 Mv
4 Resistors give x1 Mv
the other white lets call that a capacitor probably controls force and audio stting at 1 volt with a tone maybe? i dont know

https://www.flickr.com/photos/92466887@ ... 3725641056 Link to my flickr album for bigger pics

[wardster]

How long had this been stood for before you powered it up to the mains?

[LastTemplar]

it had been powered up before i got it so not long a few days a week maybe.

I'm going to build a DDS sig gen when i get around to it but time etc projects already started and so on....

i'm sure the first time it powered up there was more happening and better control of the wave form

[Mattylad]

Asking at http://antiqueradios.com/ may help too.