Hi, I do radio repairs on old equipment including radios (as a long time hobby) but 99% of the time I repair solid state only (for now).
One idea (perhaps a question) regarding old mechanical switches used in vintage radios kept lingering in my mind for quite some time.
The Question is: how can I get rid of the old (multiple-contact switches) and replace them with something like logic IC’s or something to eliminate the noise problems that inevitably occur (to any old analogue radio) because of the worn out or tarnished silver coated contacts.
I recently came across an old radio in particular that I would like to use (as a sacrificial radio) in trying to find/build a type of circuitry that would achieve such thing.
I’m talking about an old (1974-ish) radio that is entirely made with discrete germanium transistors and is called <<OKEAN 205>> and it is from the old “SOVIET ERA” It has been produced by a factory in LATVIA (eastern Europe) I really like the look of this radio.
Has been given to me as a gift (recently). It has Long wave, Medium wave, FM band and 5 separate SHORT WAVE bands.
The materials and components used in this particular radio are NOT Great! and would be (for sure) a massive restauration process for sure.
Now, the radio is still kind of “willing to work” but has a massive problem with the switches used to change the radio bands and to be honest no amount of cleaning would actually solve this problem. I’ve tried cleaning them (at first) with a vast variety of chemicals, tried springing the contacts a little etc. So I finally concluded that I would like to go ahead with the idea of making a circuit that would get rid of the switches for ever and (for good !!!).
So the idea of still trying to clean them has now been long abandoned! (I really don’t want to go back to it)
From the technicality point of view the radio has a big main (massive) rotary switch that contains many little PCBs inside it, one PCB for each band. and each PCB has up to 14 springy contacts on them that slide (to make contact) to a set of permanently fixed contacts. So at any one time UP to 14 contacts will be employed depending of which radio band you’re in.
So the idea is to still keep the rotary switch “KNOB” as a dummy with a little switch attached to it so when rotated it would give an impulse to the new switching circuitry telling it to switch bands as you rotate the Knob.
NOTE: I am not interested in presenting the radio as original as possible but in a proper functionality side of things it is intended for personal use and not for resale!
Now, has anyone know how it can be done or perhaps has already done it in the past please?
It is something I’m not familiar with and any directions, suggestions are of course highly appreciated.
It would be nice if this can be achieved with some type of old TTL/CMOS ICs something like the 74 series or something perhaps some reed relays (the IC style)
Perhaps there could be some kind of a specialized ICs that can do it ?
What I don’t want to get to do is having to deal with microcontrollers such as Arduino’s, STM’s, or Pi’s because they are simply noise generators and try to avoid them all together and on top of that is the programming side of things that am “not too keen on” to be honest.
So again, is anybody out there that have some pointers or perhaps knows of some youtube videos explaining the above matter ?
Two pictures of that radio and a part schematic diagram of what I’m trying to do (for your edification) below:
It sounds a great project, but if your coming away from a selector switch. The next best thing will be a rotary encoder or touch sensitive switch. Both of these will require a microcontroller to interrupt what response is required and then process this info. A relay board would take up quite a bit of space or you could use optocouplers. But this way is going to require some programming to be done. YouTube could help you with this skill, so it wouldn’t cost you much to learn, just the price of the hardware. I wish I could help you more, but you now have a few things to think about.
Woodb180
@brian-wood Tnx. for your input. Will have a look @ what you said .
I too first thought of an encoder, but again that is complicated and not your preferred route. It would be nice to learn arduino as I have one, just not the programming side of that (only the slightest idea and that was long ago). Integrated wise would be a challenge I feel. MC would probably think up something pretty quick.
Radios + Tubes + Scopes + Cars= Nothing better!
@radtekman Hi, programming can be learned even though is not an easy task to do. To learn programming takes a number of months perhaps years. It all depends of how deep you wanna go. Certain aspects of programming are really hard to grasp and implement such as the Interrupts concept etc. I can already do ” some” programming but only simple stuff such as: blinking LEDs, or timers or temperature reading etc.
Now going back to the original subject. I try not to use microcontrollers simply because it is known that they are noisy (because of the clock frequency employed) and other PWM going on etc. and we talking about a sensitive radio receiver here with a limited enclosure space.
But the truth to the fact is I don’t really know for sure and that is the reason I am inclined to believe that the best solution would be some plain old LOGIC ICs. or…..perhaps some kind of specialized IC that is purposely made for such things. Again, I really don’t know. This is a gray area for me but willing to learn how it can be achieved.
Is it really worth the time and the effort for this particular radio? Most likely NOT!. However, from the learning experience point of view it is well worth the effort (well…it is to me anyways)
@ovi4 Yes I am the same way. I have done super basic stuff while watching a tutorial. I want to build stuff more complicated but that is holding me back right now. Just need to look around for resources to use, it has been sitting on the shelf for a while now.
I feel like with shielding and filtering it shouldn’t be impossible. Luckily, based on what it is doing, there shouldn’t need to be PWM.
Exactly, the experiment is worth trying just to know. If it works then it opens up possibilities for other stuff, if not we proved it didn’t.
Radios + Tubes + Scopes + Cars= Nothing better!
