Old Radio To MP3 Player

Snowman999

Member
I KNOW NOTHING about electronics old or new. But, I do know from watching a youtube video, an old radio can be turned into an MP3 player. Watching the video I'm positive it's too advanced for me to do. But, I do have some questions that perhaps someone might know the answer to.

Here's photos of my old radio which works. I paid a few bucks at an estate sale. I think it was $5. The radio the guy converted did not work.

003.JPG004.JPG

In the video the guy removed most of the guts. He left 2 tubes and the original speaker. Since he removed most of the guts, wouldn't that change the sound going to the speaker? If the person played Big Band music through it, would it sound a little different because most of the tubes are gone?

In my little mind I liken it to listening to vinyl versus CD. I do hear a slight difference.

WOULD IT BE POSSIBLE to do the following (remember I'm a moron. But, it does kind of make sense) If I took the earbuds I use as headphones for my MP3 and removed the earbuds. Took the open wires and attached them to the wiring in the back (which looks to me to be used as an antenna) would I be able to find a frequency that will play the music?

The reason I just don't try it is, the guy in the video spoke about something bad happening if you attached to your MP3 player to the board in the radio. I don't want to do that. But, since I had no idea of what he was talking about in the first place, I could be doing the same thing attaching it to the wiring in the back.
 

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Hey!
First thing's first and that's safety. That looks like it might be a mains powered boyo? If so, it'll gladly kill you so...I'd do nothing until you're 100% certain of the plan, and safety.

Next up, it's always useful to have a schematic if you're going to work on anything like this. Is that something you can get?

You mentioned the guy ripping out a lot of the internals - That sounds normal enough but not strictly necessary
Much of the circuit is going to be the radio tuner then the rest is going to be amplifier.
Quite often the junction between the two is very clear on a schematic either because you know what you're looking at, or because there's already a volume pot right between the two.
In cases where there is an existing volume pot right at the start of the amp portion of the circuit it's pretty simple to disconnect that and take it as your point of entry.

Another option would be to splice a switching jack into the circuit and mount it somewhere on the cabinet so that you can plug in and use it as an amplifier,
but the radio functionality is still preserved.

Maybe stating the obvious here but this radio is going to be mono and your mp3 player will be stereo so you'd need some way of summing L+R also ( or, better yet, get two radios. ;) )
That might be as simple as joining the two but hopefully someone else can tell you that for sure.

If it's something you're interested in but not very confident about consider trying the same thing on a 9v battery radio first.
Even if it's a relatively modern transistor radio the basic idea is still going to be the same and you have the freedom to tinker and play and poke without worrying about any danger.
You might even get a fun portable guitar amp out of it.

Edit : Looks like that might be a field coil speaker - I think that's the right name?
Instead of a fixed permanent magnet, like we'd usually see these days, they used an electromagnet instead and, therefore, require mains power.
Not impossible to use but it's something that would put me off.


...took the open wires and attached them to the wiring in the back (which looks to me to be used as an antenna) would I be able to find a frequency that will play the music?
No, but...
You could just get a little FM transmitter and plug your mp3 player into that, then tune the radio to its frequency.
You get the result you want without any tinkering.

Not 100% sure on the legality of those - I think it might depend on power/range and where you live.
 

Snowman999

Member
Hey!
First thing's first and that's safety. That looks like it might be a mains powered boyo? If so, it'll gladly kill you so...I'd do nothing until you're 100% certain of the plan, and safety.

Next up, it's always useful to have a schematic if you're going to work on anything like this. Is that something you can get?

You mentioned the guy ripping out a lot of the internals - That sounds normal enough but not strictly necessary
Much of the circuit is going to be the radio tuner then the rest is going to be amplifier.
Quite often the junction between the two is very clear on a schematic either because you know what you're looking at, or because there's already a volume pot right between the two.
In cases where there is an existing volume pot right at the start of the amp portion of the circuit it's pretty simple to disconnect that and take it as your point of entry.

Another option would be to splice a switching jack into the circuit and mount it somewhere on the cabinet so that you can plug in and use it as an amplifier,
but the radio functionality is still preserved.

Maybe stating the obvious here but this radio is going to be mono and your mp3 player will be stereo so you'd need some way of summing L+R also ( or, better yet, get two radios. ;) )
That might be as simple as joining the two but hopefully someone else can tell you that for sure.

If it's something you're interested in but not very confident about consider trying the same thing on a 9v battery radio first.
Even if it's a relatively modern transistor radio the basic idea is still going to be the same and you have the freedom to tinker and play and poke without worrying about any danger.
You might even get a fun portable guitar amp out of it.

Edit : Looks like that might be a field coil speaker - I think that's the right name?
Instead of a fixed permanent magnet, like we'd usually see these days, they used an electromagnet instead and, therefore, require mains power.
Not impossible to use but it's something that would put me off.



No, but...
You could just get a little FM transmitter and plug your mp3 player into that, then tune the radio to its frequency.
You get the result you want without any tinkering.

Not 100% sure on the legality of those - I think it might depend on power/range and where you live.

THANK YOU! You've reinforced all I was told late last night.

I looked up old radio clubs and found a few. The first thing I was told, I would probably burn my house down if I didn't recap the radio. I only understood the "burning the house down".

I've noted phrases to search for someone in New Jersey who can actually do the work.

After I posted this I thought of the FM transmitter, I had one years ago when I owned an ipod and wanted to use it in the car where I only had a cassette player. It turns out the cassette with the wire worked much better. But, since the radio would be stationary in the house I thought that might work. But, this radio (1934-35 440T, I had no idea) is only AM and Shortwave. So, that wouldn't work.

ONE THING you brought up:
These old swing and Hank Williams Sr recordings (I'd only be playing old music through it) they're still mono even on modern CD pressings? I hope so. If they made them stereo, that would kill my entire idea.
 

Ponder5

Member
I love these projects. Done several.

Have one to do, but the cabinet isn't really spiff. It'll need some cleaning and conditioning.
So the only priority that really matters is *appearance*. That's all.
Someone else might wanna restore the thing. Okay. They could. They get crazy. They go for restoration items like any resto types do. They'll even repackage capacitors to look like the original wax caps by putting a modern cap in the paper tube and filling it with yellow wax. I kid you not!
I am not such a resto guy.
And if you are not either, then all you care about is how it looks. Clean it up. New coat of wax. Maybe first see if there's any varnish or woodwork to do.

Then you gut everything. None of it is useful or competitive with anything you'll get today. Field coil speak? Ditch it. Sell it on ebay to the cork sniffers. If it's just the exact right one, they might give you something for it (after a thousand questions). Tube amps? Ditto (though the amps will bring bupkis).

Now you have a nice blank canvas to strap in all the goodies you desire. Parts Express is your friend.
Mount another speaker. Heck, mount 6 or 8 more speakers of various sizes. It's just some screws and maybe a cutout or two.
You could even take the front 4 knobs and exchange them for rotary encoders soldered into a controller.

Now if ALL you want is a 3.5mm plug to attach your iPod to, well, it's gonna be a lotta trouble. First things first, you gotta make sure the thing works. If it doesn't work right now, someone is gonna have to fix it. Then SOMEONE has to go in and run a tap for your jack. Or, like i say, gut the thing and put in a small stereo system.

If you're dead set on going mono, most modern recording collapse to mono pretty well.

These are fun. Just remember: unless you're going back to showroom new, exactly restored, you're gonna be stepping on someone's toes - that includes any aux inputs. So decide which way you wanna go and have FUN!
 

ecc83

Well-known member
I can only give advice WRT to UK and some EU radios.

First of all SAFETY! As Mr S said, mains V kills. In UK we had the ghastly "AC/DC" radio. Deadly things with no isolating mains transformer, if you don't see TWO iron transformers in there, one bigg, one small, walk away. Even if it has a mains traff the very first test isa a proper PAT especially the high voltage earth leakage test. Assuming it passes PAT my MO would be...

Strip out ALL the Cs and Rs and just leave the valveholders and transformers. You can loose at least two valves although I would also ditch the valve rectifier, and the heater wiring (but I would rewire as balanced. I hate hum!)

You would keep the output valve* and the triode/detector but if short of gain or, you wanted to fit T&B controls, keep one IF Pentode strapped as a triode for more gain (might then make a decent shredder!)

I have often thought of having a crack at this. I refurbed an old record player for daughter a couple of years ago. I have fixed more old radios and TVs than some of you have had hot lunches!

*A 'safe' was to do this is a total rip out then fit an amp module (look at "Vellmann" modules) and power it from a wall rat.
Also, removing some valves takes a few watts heater load off the ole traff. If fitting a sstate rectifier make sure the new caps are rated for the OFF LOAD extra volts! Engergized speakers? Yes not going to be nice sounding, v old but the coil was often part of the HT smoothing circuit so that need recalculating.

Dave.
 

ecc83

Well-known member
I have caught the bug! My daughter's partner is into retro kit, wanted an old telly a few months ago till I pointed out it was bloody dangerous, CRT neck exposed!
I have bought Marconi T42A radio for £20 and am in the process of gutting it down to mains and OP traffs and valve bases. Uses an EL84 op bottle (hole in it! but I have spares) so should be pretty pokey when done as the Silcon rects I shall fit will give more HT than the suspect EZ80. I just hope the existing mains traff is safe, no leak mains winding to chassis on a meter but not put 230V anywhere yet!

Not quite decided on circuit topology yet but I already have bought a Bluetooth reciever so I want him to be able to balance that against a guitar. Oh yes! Has a huge (for the time) 280x 120mm speaker just hope it is ok as I cannot find anything elese that drops in.

Will keep you all 'in the loop'.

Dave.
 

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Snowman999

Member
I have caught the bug! My daughter's partner is into retro kit, wanted an old telly a few months ago till I pointed out it was bloody dangerous, CRT neck exposed!
I have bought Marconi T42A radio for £20 and am in the process of gutting it down to mains and OP traffs and valve bases. Uses an EL84 op bottle (hole in it! but I have spares) so should be pretty pokey when done as the Silcon rects I shall fit will give more HT than the suspect EZ80. I just hope the existing mains traff is safe, no leak mains winding to chassis on a meter but not put 230V anywhere yet!

Not quite decided on circuit topology yet but I already have bought a Bluetooth reciever so I want him to be able to balance that against a guitar. Oh yes! Has a huge (for the time) 280x 120mm speaker just hope it is ok as I cannot find anything elese that drops in.

Will keep you all 'in the loop'.

Dave.
Did you ever do anything with this?

My radio is sitting at the place we'll eventually be moving to. One day...
 

ecc83

Well-known member
Did you ever do anything with this?

My radio is sitting at the place we'll eventually be moving to. One day...
Yes, but I have not finished it. Something of a saga and the work was interrupted by two funerals. I shall put the work process in some sort of order and post it soon. I wanted a totally valved device but the OP stage I was not happy with...other problems ensued. Will post more soon.

Dave.
 

ecc83

Well-known member
Attached is a short account of my 'progress'. One safety feature not mentioned was a 470uF capacitor in the output stage. I was surprised at how good the original elliptical speaker sounded and so did not want to risk its destruction if the amp decided to latch up to pos or neg rail!
Bare bones account I know (missed out a LOT of bad words!) so do ask for specifics if you want.

Dave.
 

ecc83

Well-known member
First off, although mains transformer was in good shape the OPT was O/C primary, fortunately (I thought!) I had a 'Midget Output Transformer”. Whacked it in with an ECC83 driver. Poorly sound.





The traff had a max current rating of 30mA and the HT was high at around 400V due to solid state recs. Sound on music seemed 'gritty' and nowhere the volume it should have been. A plea put out on the 'fretboard' forum got me an RS (OEP) Universal transformer from a great chap ICBM. I messed with that for some time, trying various ratios but still could not get a volume or sound quality I was happy with. Reluctantly I decided to go for a solid sate PA. I had an old Maplin “200W” kit amp I had built yonks ago. They really only put 50W, maybe 70 at a push into 4 Ohms and since I would be running it on a much lower, 25 0 25V supply, maybe 12W tops?





That amp plus a TL072 pre amp gave me good, hi fi sound for the Bth side of the build but I still needed a high Z input stage for guitar so I decided to investigate 'starvation' low voltage valve circuits. Worked well. An ECC83 run from just 20V DC gave more than enough gain and just a hint of 'crunch' when pushed. (I shall be doing more experiments with these stages when time and energy permits)





Problem. Hum. This was caused by the current demand of the heater supply. 150MA at 12V. I spent a lot of time trying to fix this but have eventually decided to replace the valve stage with another TL072. I am confident that with more time, money and application I could have fixed the hum problem but just got a bit pissed off with the whole thing.





So, I just have to fit the HZ pre and tidy things up, see to cosmetics. Hope to deliver in about a week but don't hold yer breaths!
 

rob aylestone

Well-known member
I'm going to skip the safety stuff - it's perfectly true that kit with large transformers and big capacitors can hurt, but with a simple test meter, things can be worth experimenting with - and learning too while doing it.

In virtually all the old valve/tube kit the volume control signified the start of the audio section - so audio invariably came in on the centre of the three volume pot solder pads. One of the others is connected to ground/chassis and the other is the output to the amp. It meant you could connect your guitar, synth, or even sometimes a microphone using the ground and the opposite solder pad - a quick connection - often just a twist before I learned to solder - and you had an amp. My first electric guitar went this way into an old radiogram that had a medium/long wave radio my mum and dad didn't use. The output had a transformer and my little test meter said no volts, so I connected that to all sorts. The input terminals said lots of volts - so connections there were avoided. After your first shock, you develop a safety protection thing. Prod with the meter before touching. Make sure the grounds are connected - they save lives. Your body even becomes a signal injector. with your finger on the screwdriver, you can trace the path from that volume pot and discover which bits do the tone adjustments. You can therefore find the pre-eq and post-eq path and send things in or out. You learn what parts of the circuit can hurt and what can't. You discover that the High Tension side that feeds the Valves/tubes hurst quite a bit, so you don't prod valve bases with your fingers.

Experimentation like this, without the internet and the library real builds skills, but shocks can easily be gained by prodding in the wrong place. This is dangerous. Nowadays the idea of building a radio in school as a project with valves would be banned instantly but a teachers saying "how many Volts?". My physics teacher didn't say this at all - he said "but how many Amps?" Volts Jolts but Mils Kills was his favourite phrase and he was right. After education my first few weeks as a radio engineer passed on a few extra tricks from the older engineers. Keep it away from your heart boy - was one phrase I heard from one of the grumpy old men. The idea that when you have to work on a live radio, you would stick your right elbow on the metal case and then if your right finger touched something live - it would go in through your finger and out through your elbow - making you whip your finger away without the path going through your chest on it's way out of your damp wet leather solder shoes. By today's standards, a crude and unacceptable process. Now maybe we'd wear nytryl gloves, but when we started doing sensitive solid state work in computers we would ground ourselves with a wrist strap. I always imagined getting your finger stuck on a live pin and the strap preventing you breaking the circuit - it never happened of course.

If you have a working old bit of kit - there's no reason not to try connecting things. You soon discover that level matching is important - distortion or really low volume being the two ends of the success scale, but in all my years I never caused a single fault doing this kind of thing. Loads of nasty full volume hums and buzzes, but feeding a speaker output into a tape recorder line input was usually successful as long as you turned everything right down before trying it. At worst you got distortion and hums. Nothing nastier ever happened. Kids today get told not to experiment. That's so sad because experiments are how you learn the really useful stuff.

We get people now almost paranoid - about stupidly simple things. They want to plug X into Y, and before trying it, spend hours on the forums, waiting for answers - and we all know internet advice is crazily unreliable. I just had a few cables with connectors on one end and bar wires on the other. You twisted the grounds together then tried the others at random and when it worked, you wrapped a bit of tape around it. Job done!
 

ecc83

Well-known member
Yea verily Rob. I despair at the lack of 'experimental enterprise' in the budding recordist! Now, many might argue that it is not as easy to 'dabble' in electronics as it was in our teenage years? I would dispute that. Certainly keep away from valve voltages* but you can now buy super safe DC supplies for peanuts. Get a modest solder station, some stripboard and a few 'lucky bag' components (or a Vellemann kit) and for around $100 you are setup. NOTHING like that in our day.

* As mentioned, I intend to investigate V low V valve circuits at some time. Watch this space.

Dave.
 

Snowman999

Member
I just want to say, reading these response, I'm LOST.

I'm going to find someone in PA who can change the caps. I just hope it doesn't lose the original sound.
 

ecc83

Well-known member
I just want to say, reading these response, I'm LOST.

I'm going to find someone in PA who can change the caps. I just hope it doesn't lose the original sound.
Don't give up on us yet! Ask specific questions and I shall do my best to answer them. Changing the coupling caps may not change the original sound but then what is the point.

A cap followed by a resistor to ground is a 'High Pass Filter' and is usually configured to pass the whole audio band down to some pre determined frequency, usually 20Hz* at which f it will be 3dB (1.414 times) down on the mid band response. Doubling the cap value will roughly halve the 3dB f, i.e. 10Hz...anything you want down there?

* Electrolytic capacitors have a very wide tolerance, + or - 20% or worse so the ACTUAL LF response is a bit lap of gods.

Dave.
 

Snowman999

Member
Don't give up on us yet! Ask specific questions and I shall do my best to answer them. Changing the coupling caps may not change the original sound but then what is the point.

A cap followed by a resistor to ground is a 'High Pass Filter' and is usually configured to pass the whole audio band down to some pre determined frequency, usually 20Hz* at which f it will be 3dB (1.414 times) down on the mid band response. Doubling the cap value will roughly halve the 3dB f, i.e. 10Hz...anything you want down there?

* Electrolytic capacitors have a very wide tolerance, + or - 20% or worse so the ACTUAL LF response is a bit lap of gods.

Dave.
I've been told by many that old caps can catch fire. I'd prefer not to burn down the town house we'll be moving to, it's already made of garbage. I say that, because we live in a 1924 Tudor that's a "real" house. I see these McMansions being put up, and they're made of pressed wood. Which is tad amount to having a house made by Ikea.

I really want to hear old swing music through a radio that people would have listened to it through when it was new. The old radio might not have as good a sound. But, hopefully it'll be truer to what the public heard way back when. I will sit there sipping my glass of brandy while listening to Dorsey, Armstrong, Miller, and all the rest. I have a nice collection of big band music. Plus a ton of old time radio comedies. The complete Hank Williams Sr (which radios were a little different. But, it would be cool to hear him through that speaker.)

I just picked up at a flea market the complete recordings of Glenn Miller 13 discs for $2. Two of my prized collections are from Edith Piaf. Between the two I have all of her recordings minus two or three. Each set is 20 CDs, you'd think you'd get it all between 40 discs. But, somehow they managed to omit these. Maybe they're lost. She did only record about 320 songs.
 

ecc83

Well-known member
In 60 years in electronics I have never had a capacitor catch fire! Explode and punch its way through 4mm of pretty tough Bakelite yes but no fire. But to the 'vintage radio' sound...More than 90% of the sound quality of the old radios was, IMHO down to the speaker and the small (acoustically) cabinet. I was fortunate that the rather big for the time approx 14x10cm speaker in my radio was in good order and sounds remarkably good with a pleasant 'false' bass. Do not be swayed by arguments about 'old valve tone', yes, has some validity with guitar amps but not for radios that were trying to be of good quality.

So, unless you are well versed in high voltage valve techniques, forget 'em! Try to find a plywood, not plastic cased radio and get one as large as you can. You will just have to take a chance that the speaker is OK but of course check it's there and not obviously damaged.
A modest, ~4W transistor amp module such as the Velleman K4007 "7W" unit will give enough level but not endanger the old woofer. The amp might have enough sensitivity to be driven from whatever source you will be using but Vs make a range of pre amp/tone control modules.

Power. SMPSUs are very good and very cheap and you want a 15-16V unit with an amp output. If you are up to some mains wiring you could of course install a suitable transformer and regulator supply.

If you want to have a go I would be happy to help you with the project.

Dave.
 

Snowman999

Member
In 60 years in electronics I have never had a capacitor catch fire! Explode and punch its way through 4mm of pretty tough Bakelite yes but no fire. But to the 'vintage radio' sound...More than 90% of the sound quality of the old radios was, IMHO down to the speaker and the small (acoustically) cabinet. I was fortunate that the rather big for the time approx 14x10cm speaker in my radio was in good order and sounds remarkably good with a pleasant 'false' bass. Do not be swayed by arguments about 'old valve tone', yes, has some validity with guitar amps but not for radios that were trying to be of good quality.

So, unless you are well versed in high voltage valve techniques, forget 'em! Try to find a plywood, not plastic cased radio and get one as large as you can. You will just have to take a chance that the speaker is OK but of course check it's there and not obviously damaged.
A modest, ~4W transistor amp module such as the Velleman K4007 "7W" unit will give enough level but not endanger the old woofer. The amp might have enough sensitivity to be driven from whatever source you will be using but Vs make a range of pre amp/tone control modules.

Power. SMPSUs are very good and very cheap and you want a 15-16V unit with an amp output. If you are up to some mains wiring you could of course install a suitable transformer and regulator supply.

If you want to have a go I would be happy to help you with the project.

Dave.
THANK YOU! Once we're in the new place and settled, I'm going to work on it. I just have so much more that has to be done. Just to eventually live there. Karen's mom has a townhouse filled with things, and she hasn't touched it. So, our stuff is in bins, and her mom's stuff is in the same place. She's been gone since September.

This is what I own. It works. I need to get the am transmitter, which I found on etsy for $80. You're the first person who told me the caps can't catch fire. The woman said, if I remind her, she'll send me the cap replacements. I used it for about a half hour or so when I first bought it. One station came in.

If a cap was going to explode, would it happen when you turn it on, or after a while when everything heats up (If it heats up)?

1627014454581.png
 

ecc83

Well-known member
"If a cap was going to explode, would it happen when you turn it on, or after a while when everything heats up (If it heats up)?"

DON'T TURN IT ON FFS! Yes the caps could go bang once the valve rectifier heated up and they would then make a g'dawful mess (actually, in a radio that old they might be waxed paper not electrolytic) What do you want to do with the radio? If getting it working 'as was' I would say you are on an expensive hiding to nothing. Strip it out and build a valve amp in there? Doable, especially if you bought a 5W 'Champ' kit say. The easiest option is to strip it down to a bare chassis and fit a solid state amp in there.

Looks lovely tho'but! Just to add, that image is pretty low res' and small. I would like to see better images, especially the rear of the chassis. Make and model number please.

Dave.
 
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