Sobell 516

[ekcopyephilips]

Hi all

I am just starting to look at a Sobell 516 table radio. Ive downloaded the trader sheet from this wonderfull site, but im a tad confused. My radio doesnt seem to be wired up as per circuit diagram for the 516.

I think also in the past someone has had a go at the chassis as there is some evidence of wires bieng snipped, on the photo of the Tx one can see a green wire soldered to a tag and evidence of a red wire once bieng soldered there too, if you look above the Tx you can also see an earth point on the chassis with more evidence of a green wire bieng snipped off. Ive scoured the chassis but cannot see where anything might be missing or drastically changed. Could this have been an error made in its manufacture ?

Im also baffled by the on/off vol pot. on the middle tag was soldered two capacitors in series, both 0.1uF 1000v, with nothing connected to where the wires are twisted together.

Im really confused, have i actually got a 516 chassis or have i got a 516 cabinet and back with a different sobell chassis inside ? there are no marking to identify any chassis type.

Id really welcome any help with this one.

Regards

Mike Burton

[Steve_P]

Be on your guard, sir! The phantom's been here....

The on/off switch is disconnected and the volume control is disconnected. Check the mains transformer and connect it so that the On/Off control switches the live pin of the mains.

Replace those two caps with a 0.01uF, connect up that last wire and make sure any others are out of the way/insulated. Those which you don't need can be cut back at the end of the restoration.

I don't often say use a variac, but here I think you should. Make sure the AC is there on the valve bases and on the anode pins of V5. Then put V5 in and see if the HT comes up.

Take it from there, but carefully. I have assumed it is the 516AC by the way.

Cheers,

Steve P.

[ekcopyephilips]

Hi steve,

ill certainly be carefull with this one. The really odd thing is that the live of that dodgy rubber mains cable was soldered to the on/off switch. Thats what made me look more carefully at it, as i was of the understanding that the neutral was usually switched in days gone by.

[Nickthedentist]

Originally Posted by ekcopyephilips

Hi The really odd thing is that the live of that dodgy rubber mains cable was soldered to the on/off switch. Thats what made me look more carefully at it, as i was of the understanding that the neutral was usually switched in days gone by.

Not sure about that, I don't think there was any definite pattern - other than the live was not always necessarily switched.

Looking at the diagram, one side of the mains goes to the transformer via a SP switch, the other to the voltage selector. It makes sense to connect the (touchable) voltage selector to N rather than L

As Steve says, some bodger has been there. I don't think it was a manufacturing defect or anything like that. Volume controls are commonly "got-at" as they usually need replacement during the life of the set.

Does the diagram tie-up in most respsects? If so, I'd try and get things back to how they once were. With a bit of thought, I think it may be easier than you fear.

It's a shame that there are no under-chassis component layout diagrams in the service data. If you have Paul's CD/DVD, look at the 518TG too as the chassis layout seems very similar.

Nick

[Steve_P]

Modern safety standards, Nick. Do you want a set that's Off but Live?

Cheers,

Steve P.

[Nickthedentist]

Hi Steve,

Sorry for being unclear. I fully appreciate that, and agree with you.

But I have seen many old sets where the manufacturer's only concern re. mains polarity was keeping the live side off the exposed voltage selector.

All I was trying to say is that the switched-live configuration Mike found may or may not have been original.

Cheers,
Nick

[Steve_P]

No worries - sorry about that. I had my first 'live' experience with a set in a similar state....

Cheers,

Steve P.

[Herald1360]

Is that pot definitely the volume control? A pot wired as a variable resistor with some series capacitors may be a top cut tone control- there ARE three connections to the other pot. ON/OFF/tone is not an unheard of combination for controls; you can then leave the volume set at your preferred level all the time!

Just a thought ......

Chris

[Nickthedentist]

Originally Posted by Herald1360

Is that pot definitely the volume control?

Good point, Chris.

On the 518TG sheet, that switched pot is marked TONE

[paulsherwin]

Originally Posted by Nickthedentist

Good point, Chris.

On the 518TG sheet, that switched pot is marked TONE

This was a very common arrangement with radios of that era. The idea was that most people would listen to the radio at the same volume most of the time, so putting the on/off switch on the tone control would reduce the wear on the volume pot with consequent crackles. It's also often necessary to adjust the volume once the set has warmed up if the switch is on that control.

Paul

[Michael Maurice]

Hi Mike,

I've just got in and seen your PM.

This is the set that I restored last Nov/December.

I can confirm that on the set I restored, the On/Off switch was switching live and the pot was for the Tone control.

When I restored my set, I reformed the smoothing capacitors with a device similar to the one described on this site, I then replaced electrolytics C30 and C33. I replaced all the coupling capacitors between anodes and grids, Checked a few resistors to make sure they were ok and that was it, switched on and after a few seconds a hum, a bit of tuning and i was rewarded with sound!

I hope this helps you. Please feel free to ask me if you need further help.

[ekcopyephilips]

hi all

yup i can confirm that this is indeed an on/off and tone control.

thanks for the replys so far, ill do a bit more investigation and post some pics as i progress.

Mike