Which radios are similar to the Sobell 515p?

[Rcokflake]

Two weeks ago I decided to take up radio restoration as a new hobby. I was fed up with the sound from the Blaupunkt Virginia which adorns my kitchen and felt it shouldn't be that hard to put it right. But I didn't want my beloved Blaupunkt suffer from my early attempts and so went online to find a set to practice on. That's why I have a Nordmenda Fidelio.

Then I found this site. It really is an excellent site. So much so that I decided I'd be better off practicing on a British radio. That's how I bought my Ekco CR152F....and the Ekco u159 and the Phillips and the Sobell 515p. Two weeks and I've turned into a collector. And I haven't even switched on my new multi-meter (analogue, but not an Avo-8).

The plan is that once they are restored they'll be presents, with the first target a birthday in January. The deal with my beloved is that I can't buy any more until I've restored a few.

Now, I'm an absolute beginner but I have been lurking around this site and made one or two simple posts. Very impressed. The thing is I've decided to start on the Sobell but there aren't any Sobell 515p in the success stories section. So what I want to know is what radio is it similar to. I'm really only interested in the insides and I'm determined to do a good job. The cabinet is fine.

You'll see from the pictures that it has a good patina of dust although the screws for the back are mismatched so I may find someone else has gotten to it already. The guy in the market told me it worked and it does indeed switch on but other than a reassuring low-level hum I haven't managed to pick up a station on it. Then again I haven't tried it with an aerial yet.

Any ideas?

[paulsherwin]

I think your decision to learn the ropes on a simple low value LW/MW/SW set is spot on. That looks like an early 50s short superhet. At a guess the valve lineup will be ECH42, EBF80 and EL41, with an EZ41 rectifier.

You will certainly need an external aerial to receive anything at all. A few metres of wire connected to the aerial socket will pull in MW stations. A longer aerial is normally needed for LW but as you're in Dublin you're almost next door to the RTE1 LW transmitter on 252kHz so almost anything should pull that in.

It sounds as if this radio is almost ready to go, but you will need to check the circuit voltages and almost certainly change some leaky capacitors. Many people would just change all caps of 0.001uF or larger with a set like this. You will be amazed how the performance improves.

Good luck, Paul

[AlanBeckett]

Service data and circuit
http://www.service-data.com/section.php/7502/1
Alan

[Rcokflake]

Thanks Alan and Paul.

I've downloaded the service data and will wire up an aerial tonight. The valves are an ECH81, and EAF42, an EBC41 an EL 84 and an EZ 40.

[paulsherwin]

That's an unusual valve lineup and indicates that the radio is a full superhet rather than a short superhet. You do find odd mixtures of B8A and B9A valves in the mid 50s. The EAF42 is probably just doing the job of an EF41 with the diodes left unused - there seems to have been a glut of them at one time, making them cheaper than EF41s.

There's a very good chance the radio will work if you connect an aerial, at least after a fashion.

[julie_m]

There is one capacitor you must replace as soon as possible. It's the one connected to the grid of the EL84 (pin 2) and probably will be 10nF / 400V.

If it goes faulty, it can trigger a nasty cascade failure which will ruin the EL84, the output transformer, the speaker, the EZ40 and the power transformer. Just change it.

[Rcokflake]

Paul, I've decided to take your advice and remove all capacitors above 0.001uF. There's no sense in coming on to this site to get advice if I don't then take it. So here are the capacitors in question.

• C2 Aerial coupling 0.003uF Waxed flat
• C13 S.W. osc. Tracker 3,900pF Waxed flat
• C15 S.G. decoupling 200pF brown plastic cylinder
• C17 AGC decoupling 0.05uF brown plastic cylinder
• C18 Pu tone corrector 0.01uF brown plastic cylinder
• C22 AF coupling 0.01uF rolled inside a copper(?) Sheet
• C23 V3 anode decoupling 0.25uF brown plastic cylinder
• C24 HT bypass 0.1uF brown plastic cylinder
• C25 parts tone control 0.005uF brown plastic cylinder
• C26 parts tone control 0.01uF brown plastic cylinder
• C28 A.F. coupling 0.01uF brown plastic cylinder
• C29 H.T. smoothing 32uF blue metal plastic-coated cylinder, (electrolytic?)
• C30 H.T. smoothing 32uF same blue
• C31 Bias decoupling 50uF metal cylinder orange plastic coated
• C32 Tone corrector 0.005uF paper waxed cylinder
• C33 Neg feedback 0.25uF brown plastic cylinder

I've looked at the site's section on replacement capacitors here, but am having difficulty tracking down the correct replacement capacitors on the recommended websites, specifically in getting "yellow LCR metalised polypropylene axial" capacitors on the RC or CPC websites. Now it may be that I'm doing something wrong. I have followed this thread to get to Justradios site here, which seems to have a good selection but would prefer to order from a British supplier (after all, you guys are helping to bail us out).

As this is not a valuable set and this is my first time out I don't want to spend a fortune but that said I will spend whatever is needed. Any advice welcome.

By the way, I did try out an aerial and got RTE 1 on MW, thanks.

[ppppenguin]

http://www.vintage-radio.com/downloa...ster-axial.gif is a good start. Then type the codes into the RS site to get this sort of thing:

http://uk.rs-online.com/web/search/s...854347&x=0&y=0

This is an excellent range of caps.

Don't forget that modern preferred values are 10, 22, 47 with 15, 33, 68 also often available. So for example you replace 0.05uF with 47nF.

The first 3 caps on your list are not likely to need replacement. Leave well alone for now as C13 especially can affect alignment.

I really hope you haven't actually removed all those caps. Strongly recommend that you replace caps 1 or 2 at a time, testing the set between replacements. Then you will know when you have made a mistake, which is something we all do.

[Rcokflake]

Thanks pppenguin. Will check out those sites.

haven't removed anything and won't be doing anything without checking here first.

[Rcokflake]

Okay, this thread has little relationship with the original question but thanks for bearing with me.
I've checked out the sites as suggested and marked off caps 1-3. Assuming its okay to replace a 50uF cap with a 47uF, and a 0.25uF cap with a 0.22 one, that still leaves me with two 0.005uF caps, one a standard brown plastic cylinder and one a waxed paper capacitor which I know from reading other posts I really should replace.

And I haven't even gotten started on the resistors yet.

Just got my Ekco u159 through the post this morning and picked up a Roberts R606 in need of a lot of love which I'm keen to move onto once I've learned the ropes.

[Station X]

Replace 0.005uF with 0.0047uF or 4.7nF.

[paulsherwin]

The standard value for 0.005uF is 0.0047uF or 4.7nF. As it's the tone correction capacitor you'll probably need a 1kV part. Alternatively you could omit it altogether, which will make the radio sound brighter. Some people prefer a brighter sound than was normal in the 50s.

You don't need to buy specific types of capacitors for this job. Of course, some will fit better or look better, but any modern plastic film capacitor of the right value and voltage rating will be fine. The values have quite a bit of leeway too, though as a beginner it's best to stick as close to the original values as possible.

The caps that you describe as 'plastic' are almost certainly the dreaded Hunts Mouldseals, which are actually paper caps with a resin coating. They don't last well and you are right to change them.

Don't change any resistors without a good reason. Even if the values have drifted there's usually enough tolerance in the circuit for the radio to work perfectly well. Just check the circuit voltages once you've changed the caps and investigate any that are significantly out.

[Rcokflake]

Thanks Paul. Can I bypass both 4.7nF caps by replacing with a piece of wire?

[ppppenguin]

Originally Posted by Rcokflake

Thanks Paul. Can I bypass both 4.7nF caps by replacing with a piece of wire?

No! If you are going to leave out a cap, such as the tone correction cap, just remove it. Some caps can't be removed but I don't think there's any case where you can short out a cap.

[Rcokflake]

Thanks PPPenguin. And can I leave out both?

[ppppenguin]

I don't have the circuit diagram to hand so I can't say. Paul Sherwin has already said you can leave out the tone corrector.

[paulsherwin]

No! You can leave out the tone correction cap across the output transformer (C32 in your list.) The earlier cap of the same value appears to be part of the tone control arrangement and if you omit that the radio won't work properly.

Given your level of expertise, I think it would be better not to make any circuit modifications at all. You can experiment when your understanding of circuit operation has improved.

[Rcokflake]

Thank you and your advice re not making circuit changes is fair enough. For the benefit of other beginners who may find this thread useful in future I'm attaching photos of the circuit, including, in order, the mouldseals which I mistakenly described as "plastic", the flat wax capacitors, one of the metal capacitors, the and the wax-paper capacitor.