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How can I Scavenge/Salvage a crystal+audio transformer from an old radio (or anything!) for an AM transmitter project? Answered

Hi! My name's Bashu, I'm 18. My electronics skills are pretty feeble but I think I'm trying to get a better idea about how they work.. by making projects! old homeschooler reflex.

So my brother has an old 1982 lovable Toyota Tercel named Humphrey. Humphrey was passed on to my brother the way God or Toyota made him.. with an AM radio. This is pretty rad if we want to hear Chinese/Spanish/Italian radio jockeys (they have really nice vocal rhythms), except usually we don't for some reason.

So I wanted to make an AM transmitter. I found a project on here.

Looks pretty simple. Requires an approx 1 mhz crystal and an 8-1000 ohm audio transformer, which I was prepared to buy, except then I heard about salvaging them from cheep radios! VERY EXCITED WAS I! I love reusing old things that were once very incredible (taking songs out of the air? Magic) and would otherwise go to the dump.

Alors, I bought an old clock-radio from a thrift-store, opened it up and looked inside, and realised I had no freakin' idea what the crystal or audio transformer would look like.

I then decided to enlist the help of the only community I thought would know. You! My question is, if I wanted to find a 1 Mhz Crystal and a 8 into 1000 ohm audio transformer, without buying them, where would I be likely to be able to salvage them, and what will they look like? Pictures of the radio I bought and opened up are attached, in case they are on there and easily spottable. I don't mind digging. Thank you very much for any advice you have!

I am also thinking it would be really cool to have an instructable dedicated to salvaging components from various equipment. I found a wiki on it, but it's somewhat incomplete and has no photos whatsoever.


Before attempting to actually the question of where to find these components, the 1.000 MHz crystal, and the 8 into 1000 ohm audio transformer, I am going to mention a few things that might want to know.

Packaged Crystal Oscillator vs. Just Plain Crystal

You might be confused as to the difference between a packaged crystal oscillator, and  a just plain crystal.   The instuctable you refer to uses a packaged crystal oscillator.  Such a packaged oscillator has, usually, 3 or 4 pins:  two for power (usually  +5V DC) and ground, and a third for the oscillator output.  In contrast a just plain crystal only has 2 pins, and if you have to build the oscillator circuit to go with it.  Obviously the packaged oscillator is the easier way to go.  The following page ( a link into the catalog of a popular surplus monger) shows a packaged crystal oscillator and a just plain crystal side by side:

This retailer, in the Former US, has just the packaged crystal oscillator you are looking for, for 1 USD. 

The AM Radio Band
starts at 0.530 MHz and ends at 1.610 MHz.  So any crystal oscillator you can find in this range will work.  I am guessing that it just so happens  that 1.000 MHz is the most common one in this range that you'll find.

Salvage 1.000 MHz oscillator
I'm trying to think of the last time I saw a 1.000 MHz packaged oscillator in the wild... I think it might have been on some old piece of computer equipment.  Maybe a motherboard, but a really old one, like 286 or 8088 vintage.  Or it might have been an old modem, or something... If you like I'll look through my junk pile and see if I can find it again, if its still there.

Salvage audio transformer
It would likely be something with an 8 ohm speaker(since that's what is usually attached to the 8-ohm side of the transformer), an old answering machine, or some other noise-making toy.... something.

Other ways to get/build an AM transmitter:

Thanks a lot! The explanation about the crystal probably has saved me a lot of brainsweat. Goldmine-elec looks like a pretty neat site, though I am in Canada so shipping requires a big order to be economical.

Really old motherboards, eh? I don't mind slumping around places where old electronics go to die and riffling through old motherboards/modems, as long as I know what I'm looking for. Will they mostly look like the packaged crystal oscillator in the picture?

thanks again.

I looked through my junk pile, and I found crystal oscillators on old motherboards.  Unfortunately none of them were of a frequency in the AM Band (0.530 MHz to 1.610 MHz).  So I can't say for sure where you might find the elusive 1.000 MHz oscillator in the wild, but I still think old computer motherboards or peripherals might be a likely place.

Some pictures are attached.  Most of the crystal oscillators I found were in the tens of MHz. 

First picture is a 286 motherboard with crystal oscillators labeled 16.000, 24.000, and 20.000 MHz.  Second picture is another 286 motherboard with crystal oscillators labeled 36.000, 25.175, 28.322, 42.000, and 1.8432 MHz.  Third picture is an ISA soundcard with a single crystal oscillator labeled 46.61512 MHz.


 COOL stuff! Thanks for the hunt, Sir Jackaloper. I think I know what to look for now!

This might help your hunt for salvageable crystal oscillators in general: http://en.wikipedia.org/wiki/Crystal_oscillator_frequencies

If you're looking for 1 MHz packaged crystal oscillators, I'd check 9600 baud modems, old motherboards, or peripherals that connect via a serial port.


I would look for some 8bit computer cards like for modems I'm looking at one I found and it has a 1.8432mhz crystal like this one http://www.goldmine-elec-products.com/prodinfo.asp?number=X65002 the only difference is mine has the name FOX on it. Happy hunting.


7 years ago

You can easily find it in a Door Bell (esp Parrot sounding). As far as the crystal is concerned, an old pc motherboard has many of them (3-pin).


7 years ago

Instead of a 1000:8 ohm transformer, you can also use a small 120v:12v power transformer. Break open a wall-wart and liberate it. The turns ratio will not be exact, neither does it have to be.

Getting the exact crystal you need is just the luck of the draw.  Some pieces of equipment use exactly what you need but some use 4mhz 9 mhz etc.

Sometimes you can find the crystal very cheaply at surplus stores on the net.  Same thing for the transformer.

The transformer is not quite as important to get the exact value.

The transformer does not actually need to be 1000-8 ohms? right o. I shall try and figure out why that is- you have given me some more things to look into! thanks.