Elpico Vintage Car Radio MP3 Input

The conversion of the Elpico unknown model car radio is complete, the quality of MP3 audio played back through the audio stages is pretty good actually.

Here is a better picture of the beast.

Laughable British technology,and how cheap can we make them engineering, note the beautiful alignment of the push buttons and the slot in the front panel that they come through. I wonder if the term elcrapo came from this stuff, we used to use it to refer to cheap and nasty electronics like elcheapo too.
The radio had several problems the aerial cable was fatigued and broken where it entered the case, the braid was frayed internally with strands hanging just a millimeter or so from and internal screen which is at +12Volts.
The Band Change switch was noisy as expected and responded to a clean up. This revealed the real cause of scratchiness and intermittently going dead. Tapping the radio or just touching the RF/Mixer AF117 Transistor brought it back to life. All the AF117’s have been ‘flashed’ at some time I suspect, they all bear scratch marks on their cans. I replaced the offending one with an AF239, OK its not now as original but neither is adding an MP3 input.
The life of these radios with original transistors must be limited as even brand new replacement old stock transistor, of which I should have a few in my loft, will exhibit the tin whisker growth short circuits which cause these problems, if they don’t they soon will. In fact the car radios which used AF117’s started the problems very early in use, more so I think than the Transistor Portable Radios, temperature variations I wonder.

Here are the internal connections.

Using a switched 3.5mm Stereo Socket we can change from Radio reception to MP3 input by inserting the plug from the MP3 headphone output. The 120 Ohm resistors combine the stereo L and R channels for the mono radio, the 22uF capacitor shown was the original idea to provide isolation from any DC potentials, with the unknown factors of what will get plugged in I opted for extra precaution and used a 0.47uF non polarised capacitor in each lead.

The Jack Socket connections.

The Elpico radio has an internal switch which enables the radio to run on +ve or -ve Earth vehicles. The actual radio circuitry is positive earth so the screen of the lead must not be connected to the earthy end of the Volume Control. There are several places and PCB tracks which are connected to the radio case, connecting the screen there is fine for +ve or -ve Earth cars.

The Volume control connections.

The socket and components need to be mounted in a small preferably screened metal box, where do you get one of those theses days, make it.

The input socket for the MP3 Player.

Elpico Vintage Car Radio

This is a real long shot. There is a picture of an Elpico all Transistor Car Radio on the web, that is as near as I can get to any information on the thing.
Edit:- Thinking further about this, the photo below was used by an E-Bay seller toward the end of 2013. It may well be the self same radio, see the lean to the right at the bottom of the cursor, I have cured that.

Elpico photo from the web.

Its a small picture, I will produce a better ones because I have one here. Its a ‘little’ job I have taken on. It has no Model or Serial numbers on it. I would like to know what model it is. They say Google is your friend, well it aint often if your subject is any different from what the masses are enthusing about. I have searched a few times for this thing and the photo is as near as we get.

I used to work on these things when they were new-ish. Nostalgia in box? Yes I could almost draw the circuit from memory and certainly list the common faults.
Memory is a funny thing though, a car radio in those days was not cheap. It wasn’t my department but we used to fit car radios too, that’s how I got to drive the first E Type Jaguar in town just after the owner took delivery.
My house was being built at the time and I turned up for a check on the builders in the E Type with the radio fitter, the road test you see.
The Radio that went in the E Type was better than the Elpico admittedly, a Pye but not that much better.

Elpico front view.

I was shocked by the experience of going inside the Elpico, such flimsy poor construction, front and back panels held by a couple of tiny self tapping screws that by now rattle like loose teeth in their holes. AF117’s Mixer and IF’s, AC127 / AC128 drivers, single AD149 PA. Audio Transformer shoe horned in at an angle mounted behind the rear panel, reluctance tuning with a dial cord and pointer that runs jumping and scraping along the edge of a piece of white plastic, (the scale backing).
Paxolin PCB with tracks that carry the audio looping all the round the board from one side, at the detector, to the volume control at the opposite end then from front to back and half way round again to the pre amp stage.
Well thank goodness radio and electronics has come a long way since then.

Elpico rear view.

My ‘little’ job is to fit an MP3 input to the Elpico which will be in a Vintage car, seems they do that a lot.
So not wishing to re invent the wheel I did the Google search, there is a little general information but not a lot, all linked with Vintage Car Groups. What a lot they are, they tear apart the best information I have found because he said use a 3.5mm Jack Socket and added 1/8 I think, this apparently makes him a total idiot. Why do people have to be so rude even if they are ignorant.
Thing is the poor guy is French, the Vintage Car Group is American, he knows that maybe they use imperial measurements for Jack Plugs.

Then the clever boys come in:-
Its dangerous there will be voltages on the top of the Volume control which could destroy your MP3 player.
So says another add a .5MFD cap to isolate it.
That’s no good chirps in a guy who knows, it will block the DC and the MP3 player will not be able to charge when its connected.
Another guy who says he is an ‘Audio Technician’ but admits he knows nothing about the circuits inside, knows that input levels will either be Microphone or Line, connect too high a level to the input and the speakers will be destroyed and smoke will rise, fuses will blow.
Yes comes a comment you need to use resistors in that case.
Another genius knows that resistors only work on DC and Audio is AC so you have to use transformers, they are available with switchable values in boxes.
Another guy thinks its time to attack the poor fellow who originated the information again, “the information and drawings are probably useless to people who read this blog”.
Best to let a firm do it says another, its only 100$.

Too true welders and de-cokers should keep their fingers out of radios.

Elpico PCB and front panel view.

Time to invent the wheel I feel, although I can’t really see the point of listening to an Ipod in mono via a Germanium Transistor audio hiss generator that gets hot passing quiescent current.

I will follow this up with the mod done and a picture of the radio reassembled.