Rebuilding an old radio

[silver ghost]

I have been thinking about how an old radio could be improved or even remade and still keep the old look and functions as much as possible. Has anyone made a classic radio or amplifier using the old circuit schematics? Replacing parts with new and better ones might improve sound.

It is a few years ago now, but I heard and old radio ethusiast talk about how many old radios suffer from signal interferances and distortions because of the standard of parts used back then and bad insulation. What if we made an effort to improve on the old radio from scartch by covering chassis with an insulating plastic film to replace with new and improved parts when possible?

It is a daunting task, but I guess not too far from making and designing new modern valve amplifiers. I have noticed the EL34 tube is used in both old and current amplifiers.

[joebog1]

Its fairly easy, silver ghost. BUT not so simple to do. If you follow the circuit diagram and replace a part with a modern part, it will undoubtably be "better".
BUT that is subjective, because by better can mean many things.
AFTER you "rebuild " a radio it will need realigning ( that means tuning all the inside parts ) and set up the operating conditions to do what the origional designer made. It requires some test equipment at a minimum, and a knowledge of modern parts versus old parts.

IF you have an old radio and want to rebuild or refurbish it, its maybe better to ask directly about the radio you want to rebuild. You may ask here, I think, and receive much information and advice.
REMEMBER too, there are not so many radio stations in todays modern world. Yes there are some, but not what it used to be.
Plus the digital world has destroyed or distorted much of the wavebands where radio was once supreme.

Best regards
Joe

[silver ghost]

I have a 1930s Swedish Radio in mind, I like the look of it. I had it in for repair once, but the expert in the shop told me it was in bad condition and not possible to replace a part. It might be a canidate for modificaton. I rather build a similar valve type circuit than modify the exterior case to fit a DAB radio. So far it is an open project in planning stage. I may find another radio suitable for the purpose, but it is a bit of a hunt.

[joebog1]

Please show us the Swedish radio. There are a few Swedes here in this forum that would be willing to help I think. To begin, we need to know what brand of radio, and any details that you might have that are directly related to this radio.
Can you take some pictures?. Ideally, from iside AND outside. From underneath the chassi that contains the parts?.

If you need help to post pictures there are instructions in our help section. If you have trouble understanding those instructions, you can ask directions here, and somebody will help you for sure.

Regards
Joe

[stevehertz]

At the end of the day, any AM radio has its limitations, AM was never high fidelity and the best components in the world will not make it so. Perhaps quieter, more selective, sensitive etc. Just my opinion, best of luck with the project though.

[Herald1360]

The most distortion producing parts of a '30s radio are likely to be the loudspeaker and (if any) audio interstage transformers. Any other parts still in satisfactory electrical condition would not have much effect on the sound.

[Silicon]

The 'Expert in the shop' probably knows that the type of repair/restorations that vintage radio enthusiasts do are very time consuming and sometimes require a variety of skills.

Some 1930's radios can sound very good if there is a good signal strength and no local interference.

If you do decide to modify the radio, please allow future owners the opportunity to change it back to its original circuit.

[Silicon]

Some experts claim that radios using the standard diode detector could easily be upgraded to an infinite impedance detector for improved fidelity.

[kalee20]

I've certainly found the Infinite Impedance detector very good! I made a superhet last year using one.

To be honest, the diode detector ought to be good - the two drawbacks in the 'traditional' diode detector are (1) the AC load on the diode is less than the DC load and this causes distortion above a certain modulation depth; and (2) when AVC is derived from the same diode (or an alternative diode in the classic double-diode circuit) there is additional distortion when the modulation envelope cuts across the AVC delay.

The OP's post- I stripped down to bare chassis and rebuild an Ever Ready portable this year, using all-new components, rewinding the output transformer, etc. although it works, it's never going to be as good as a redesigned unit, with maybe an extra couple of valves. But that's not the spirit of the post!

[Silicon]

The radio enthusiasts that talked about bad insulation and poor components may have been referring to waxed paper capacitors.

We usually replace them with polyester or polypropylene insulated capacitors.

Rubber insulated wiring can become brittle and crack.
In 1930's radios, Electrolytic capacitors usually need to be replaced. The valves are often OK.

[silver ghost]

Very interesting replies from you all. If I remember correcetly, the guy in the work shop said it was a lot of work to be done with the radio, and the main issue had something to do with a "voltage bridge", where you could move a metal part to points along a half moon dial. The dial had a number of different voltages to choose from. He had problems with finding a replacement for it. However, he wanted the radio if I didn't anymore.

Give me a couple of days, and I shall do what I can to take pictures.

The reason I started thinking along these lines was a guy I knew a few years ago. He had built a stereo amplifier after a Mullard 5-20 scematics. It was far from the latest build, but the sound impressed me. I think he payed less than £1000 for all parts, and built it himself. He told me the reason the sound quality was good, was he had managed to get good parts. There were many amplifiers that would do better in comparison, but they tend to cost more than he could spend on it. He also said, that a lot of old tube radios and stereo systems would sound better with the parts we have available today.

I am not experienced at all, just interested and trying to get some where with this old radio.

[Hybrid tellies]

Its a personal and can be a controversial subject, so here goes.

Rebuilding or redesigning any radio is ok for some. But what you will be destroying the very characteristics of the original design. You might as well go and buy a new radio or design one from scratch using the latest modern tech such as the new generation Si chips.
On this forum its all about repairing and sticking to the original circuit diagram. Yes you have to change out leaky or crumbling capacitors with new ones but the values should be the same. For transistors its finding suitable replacements for know problem transistors but you are still keeping to or as near as possible to the original design.

[stevehertz]

Originally Posted by Hybrid tellies

Its a personal and can be a controversial subject, so here goes.

Rebuilding or redesigning any radio is ok for some. But what you will be destroying the very characteristics of the original design. You might as well go and buy a new radio or design one from scratch using the latest modern tech such as the new generation Si chips.
On this forum its all about repairing and sticking to the original circuit diagram. Yes you have to change out leaky or crumbling capacitors with new ones but the values should be the same. For transistors its finding suitable replacements for know problem transistors but you are still keeping to or as near as possible to the original design.

i wasn't aware of that rule!

On a purely personal basis I don't see any real point in the exercise - as I've said above - but I accept that we're all different and this is simply a project that the OP has a passion to undertake and clearly will find it interesting to do, and good luck to him I say. I think we often place too much store on 'originality' when firstly, that is up to the owner of the set and secondly, more often than not we're not talking about rare, valuable items, they're mass produced radios most of which yield a value of a few tens of pounds, so no harm done unless one is being ultra purist about the issue. Obviously I wouldn't agree with 'modernising' a rare, valuable set, but even then if you want to (say) change a cap value for more treble, then it's not the end of the world and is easily reservable.

[silver ghost]

Well, I was planning on sticking to the original chassis and knobs. I know there will be a lot of replacement wiring, soldering and parts. In my mind the original circuit diagram would be point of venture, and any improvment in sound and parts replaced I would accept. Nothing like this is made any more with all the DAB technology taking over. As it is, this is a radio a repair guy told me was too far gone to be able to save it, but looking at what others have restored and documented on the web, I think there still might be hope.

[newlite4]

There is very little in the vintage radio arena that cannot be repaired, most parts are available for most sets. The repair guy that you saw obviously has to make a profit so decided that the set was uneconomic to repair since the time involved and the cost of sourcing parts would make the job too expensive for the customer. Fortunately, many enthusiasts are prepared to take on this work and are undaunted by the task.
Neil

[silver ghost]

This is a very close model, if not exact.

[joebog1]

Assuming yours in in good condition, it should not be too difficalt to rebuild. If you want to keep it origional inside it will take some time to do. It does have a quite complex selection of wave bands.
You need to find the circuit diagram at least, or perhaps there was a service manual available.

JOe

[McMurdo]

I assume the OP means a radio reconstruction or replica, rather than a completely new design?
If the former, I'd be worried about making transformers and coils, I think the manufacturers of yesteryear had honed their mass production by the late 30's for example and had reached a good level of cost vs performance.

If the latter, I wouldn't bother, if quality and performance are what you're after, I'd stick to a more modern design from the 80's or 90's.

But I suspect you meant the former....unless you mean a restoration using the best parts available over and above what's there already?

[Hybrid tellies]

Originally Posted by stevehertz

i wasn't aware of that rule!

On a purely personal basis I don't see any real point in the exercise - as I've said above - but I accept that we're all different and this is simply a project that the OP has a passion to undertake and clearly will find it interesting to do, and good luck to him I say. I think we often place too much store on 'originality' when firstly, that is up to the owner of the set and secondly, more often than not we're not talking about rare, valuable items, they're mass produced radios most of which yield a value of a few tens of pounds, so no harm done unless one is being ultra purist about the issue. Obviously I wouldn't agree with 'modernising' a rare, valuable set, but even then if you want to (say) change a cap value for more treble, then it's not the end of the world and is easily reservable.

I don't think it's a rule and it's up to you as the owner of the radio to do what you want with it. But personally it goes against the grain of what we are about which is the repair restoration and preservation of these older radios.

Building a new radio from scratch is possible these days especially using the latest Arduinos raspberries alongside modern DSP Chips from Silicon Labs such as the Si4734 etc. I have seen some really good builds but it's totally different to what we are doing with more vintage technology.

[Cobaltblue]

As it's your radio you get to do what you like.

However these sets can outlast us and they are still being destroyed and lost through accident, lack of interest and poor storage.

I like to think I am less the owner more the Custodian so that future generations can still touch these things and use them rather than just see a few pictures.

Cheers

Mike T